PACHYSANDRA
Pachysandra, spurge. Evergreen perennial groundcovers.
Description: Pachysandra terminalis, Japanese pachysandra or Japanese spurge, has oval, glossy, dark green, 1-to 3-inch leaves set in whorls 6 to 8 inches high. Plants have underground creeping stems that spread steadily, producing a thick carpet. In May, white flower clusters appear on stout, fuzzy spikes. Japanese pachysandra has been identified as an invasive species in some areas. Zones 4–9.
P. procumbens, Allegheny spurge, is native to the Southeast. Leaves are coarsely toothed at the ends and mottled with purple. Flowers are white and borne near the ground. Plants are evergreen in the South, semi-evergreen to deciduous in the North, and are a handsome native ground-cover. Zones 5–9.
How to grow: Pachysandras prefer partial shade in rich, moist, slightly acid soil. The plants can adjust to deep shade, but the leaves yellow in full sun. In fall, top-dress the soil with dehydrated manure, or mulch lightly with compost. Rejuvenate old plantings by mowing in spring. Propagate in spring by division or cuttings. Space plants 6 to 12 inches apart.
Landscape uses: Plant pachysandras under shallow-rooted trees or broad-leaved evergreens. Pachysandras are excellent groundcovers for banks, slopes, or any difficult shaded areas. Keep Japanese pachysandra away from wooded areas or other sites where it may spread beyond the garden, because it can compete with populations of native wildflowers.
PAEONIA
Peony. Spring-blooming perennials.
Description: Cultivars of Paeonia lactiflora, common garden or Chinese peony, bear 3-to 8-inch single to double blooms in white, pink, and red shades, many with tufted (and sometimes yellow) centers. Common garden peonies bloom over a 4- to 6-week season above elegant, 4- to 10-inch, glossy, dark green leaves on shrublike plants averaging 3 feet tall and wide. The foliage remains attractive throughout the growing season, often flushing red, purple, or bronze in fall. Two famous fragrant cultivars that have stood the test of time are ‘Festiva Maxima’, a double white flecked with red, and ‘Sarah Bernhardt’, a soft pink double. Zones 2–8. P. officinalis, common peony, bears 4- to 5-inch satiny, vivid purplish red blooms on 1½- to 2-foot mounds of medium green, matte foliage resembling the common garden peony’s. It blooms about a week before the common garden peony. Zones 3–8.
Tree peonies are derived from several species, including P. suffruticosa, P. lutea, and P. delavayi. Unlike herbaceous peonies, tree peonies have woody stems that don’t die back to the ground in winter. The single, semidouble, or double flowers may be up to 10 inches across and come in white, pink, red, salmon, deep purple, yellow, and apricot. The sometimes-fragrant blooms appear in mid-spring on sturdy, well-branched, 4- to 6-foot shrubs with divided dark green leaves. The plants are slow growing, but they can live for decades with a little extra care once established. Zones 3–8; provide winter protection in Zones 3–5.
How to grow: Plant peonies during late summer in the North or early fall in the South. If you wish to increase a favorite plant, divide herbaceous peonies at the same time. (Expect at least a year for the plant to settle in before blooming again.) Peonies prefer a sunny spot (partial shade in the South and for pastel cultivars) with fertile, well-drained soil. They can remain in the same spot for many years, so prepare a roomy planting hole with lots of compost.
Improper planting is a common reason for failure to bloom. For herbaceous peonies, make sure the tips of the pointed, pinkish new shoots, called eyes, are just 1 to 2 inches below the surface of the garden bed. Plant tree peonies with the graft union about 6 inches below the soil surface.
Remove foliage of herbaceous peonies when it dies down after frost. Tree peonies benefit from a light yearly pruning to promote bushy growth; also, remove all suckers from the rootstock. Both kinds of peonies benefit from a layer of mulch the first winter or two after planting. In early spring, feed plants with a balanced organic fertilizer; keep soil evenly moist throughout the growing season. Peonies often flop over from the sheer weight of the blooms or from a heavy rain; to prevent this, use a plant hoop to keep the stems upright, pushing it into the ground as growth emerges in spring. Single-flowered peonies are less likely to flop than those with heavier blooms.
Botrytis blight can cause wilted, blackened leaves and make buds shrivel before opening. Remove wilted parts immediately. Cut stems to ground level after frost blackens leaves. Anthracnose appears as sunken lesions with pink blisters on stems. Pruning off infected areas and thinning stems to improve air circulation will help lessen anthracnose problems. Infection by root knot nematodes can cause plants to wilt, become stunted, and have yellowed or bronzed foliage. Roots may be poorly developed and have tiny galls on them. Dig out and destroy severely infected plants.
Landscape uses: Use as specimens or in small groups in borders. Grow peonies alone in beds or in dramatic sweeps along a lawn, foundation, wall, walk, or driveway, or around a focal point such as a fountain or statue.
PALMS
Palms. Evergreen trees or shrubs.
Description: Approximately 4,000 species of palms are found in the world’s tropical and subtropical regions; palm fruits, oils, and building materials make the palms an economically important family. Eight or nine genera of palms are native to the United States, where they occur mostly in the Southern coastal regions. For palm resources, visit the Web site of Jungle Music Palms & Cycads or the International Palm Society; see Resources on page 672.
Cycas revoluta, Japanese sago palm or simply sago palm, is not a true palm, but is included with palms for practical purposes. It consists of a rosette of stiff, coarse, compound leaves that are a dull dark green and 2 to 7 feet long. Japanese sago palm may develop a trunk after many years but will stay within the range of 3 to 5 feet tall. The plant bears a conelike male flower and a female flower that may eventually bear fruit. Zones 8–11.
Raphidophyllum histrix, needle palm (also called porcupine palm, hedgehog palm, and blue palmetto), forms a low rounded clump with a coarse outline. The 3- to 4-foot-long foliage is blue-green and fanlike, with black needlelike sheaths protruding at the bases of leaves. This palm is hardier than most, tolerating temperatures down to 0°F. Zones 7–11.
Sabal palmetto, cabbage palmetto (also called Carolina palmetto), is a Southeast coastal native that can survive temperatures of 10° to 20°F in its home habitat. Cabbage palmettos reach 80 to 90 feet tall and bear fan-shaped leaves that are 5 to 6 feet long, 7 to 8 feet wide, and deeply divided. Cabbage palmetto is the state tree of both South Carolina (it is featured prominently on the South Carolina state quarter) and Florida. Zones 8–11.
Sabal minor, dwarf palmetto, forms a mounding, coarse-textured rosette of stiff, fanlike, compound leaves growing 3 to 8 feet long. Small whitish flowers appear on stalks in summer, followed by black fruits in autumn. Often found growing in the shade of taller trees, dwarf palmetto grows 3 to 5 feet tall. Zones 8–11.
Serenoa repens, saw palmetto, is similar to dwarf palmetto in many ways. It has olive to blue-green, fan-shaped foliage with coarse serrations along the edges. Large branches (up to 3 feet) of small, fragrant white blossoms appear in summer and are favorites of bees. Berrylike, bluish black fruits provide food for wildlife. Saw palmetto spreads via rhizomes, making it difficult to transplant or remove. Zones 8–11.
Trachycarpus fortunei, windmill palm or Chinese fan palm, has an erect form with a slender trunk and a head of large, fan-shaped leaves of dull dark green. The texture is coarse and bristly from the stiff crown to the fiber-covered trunk. Look for yellow flowers among the foliage and bluish fruits developing afterward. At heights of 15 to 30 feet, windmill palm is a good choice for small spaces, such as courtyards and entryways. It’s also more cold tolerant than most palms, surviving temperatures down to 5°F. Zones 7–11.
Washingtonia filifera, petticoat palm or California fan palm, is a West Coast native that lines streets in southern California and Florida. Petticoat palm, so-named because its persistent foliage hangs down from the crown to form a “petticoat” around the trunk, grows to 50 feet tall in the landscape; fan-shaped gray-green leaves may be 6 feet wide on mature plants. Zones 9–11.
How to grow: Most palms require full sun and fertile, moist, slightly acid soil. Dwarf palmetto is somewhat shade tolerant and often lives beneath a hardwood canopy; cabbage palmetto will also tolerate partial shade. Fertilize lightly in spring and summer. Palms are extremely susceptible to cold injury, so don’t do anything (like heavy or late fertilization) that would cause plants to produce tender new growth in fall. Cold injury is most damaging when it affects the palm’s crown, from which all new growth arises; plants that suffer damage to leaves may look unhealthy but will survive.
Landscape uses: Use low-growing palms for naturalizing, groundcovers, barriers, massed plantings, or foundation plants. Don’t plant sharp-leaved saw palmetto or needle palm in high-traffic or play areas, but consider either for a durable hedge. Use windmill and petticoat palms as focal points. Petticoat palms and cabbage palmettos are good street trees in California and Florida. Beyond the coastlines of the Southeast and Southwest, even hardy palms are limited to container growing in the United States.
PAPAVER
Poppy. Spring-to summer-blooming annuals, biennials, and perennials.
Description: Poppies bear saucer-to bowl-shaped blooms with prominent central knobs. Single, semidouble, and double poppies bloom on long stems above masses of hairy leaves; flower colors include solid shades and combinations of white, pink, red, purple, yellow, and orange. The delightful state flower of California, the annual or tender perennial California poppy, is in an entirely different genus (though also in the poppy family); its botanical name is Eschscholzia californica.
Annual Papaver rhoeas, corn poppy or Flanders poppy, produces 2-inch red blooms on sparse-leaved plants usually reaching 2 feet.
Biennial or short-lived perennial P. nudicaule, Iceland poppy, bears 2- to 6-inch, mostly single, orange, salmon, pink, or white blooms over basal rosettes of gray-green leaves; plants reach 1 to 1½ feet tall. Zones 2–7.
Perennial P. orientale, Oriental poppy, offers dazzling 6- to 10-inch-wide red, scarlet, white, pink, or purple flowers (most with striking black blotches inside) on stems from 2½ to 4 feet above dense, leafy masses. Zones 2–7.
How to grow: All poppies are easy to grow and prefer full sun to very light shade and average to rich, moist but well-drained soil. Direct-sow corn poppies in spring; start Iceland poppies in late summer in the North (fall in the South) for bloom the next year. Allow both to self-sow. Plant container-grown Oriental poppies in spring or in summer after the leaves disappear, which is an ideal time to divide them if necessary. Give Oriental poppies plenty of room in the bed or border—mature plants can take up as much as 3 feet of bed space. Provide light, loose mulch in winter.
Landscape uses: Grow in borders and informal gardens, or enjoy a solid bed or mass of corn or Iceland poppies. Combine Oriental poppies with later-blooming annuals and perennials like asters to fill the large gaps when the poppies go dormant, but leave room for leaves that reemerge in fall. Flowers last a few days in water if cut ends are seared in a flame.
PARSLEY
Petroselinum crispum
Apiaceae
Description: Parsley is a decorative 8- to 18-inch biennial with much-divided leaves. In its second year, it produces small yellow flowers in flat umbels. To some, the leaves have a bitter taste and smell of camphor; most people, however, enjoy the pleasantly pungent flavor.
There are two distinct kinds of parsley available—curly and flat-leaved. Flat-leaved or Italian parsley (Petroselinum crispum var. neapolitanum) has luxuriant, shiny leaves and contains more vitamin C than the curly kind. It also has superior flavor. Curly parsley (P. crispum var. crispum) has ruffled leaves; it is popular in cooking and as a garnish. All parsley contains three times as much vitamin C, weight for weight, as oranges. It is also a fine source of vitamin A and iron. Both types will grow in Zones 3–9, though in zones colder than Zone 5, parsley should be treated as an annual.
How to grow: You can plant parsley outdoors in spring, but since it is slow to germinate (4 to 6 weeks), it’s better to start seeds indoors. In either case, first soak the seeds in warm water for several hours or overnight.
For a reliable supply, sow new parsley plants each year. Although it’s hardy, parsley will flower and die the second year unless you remove the flower stalks. Parsley plants that do flower in the garden will often self-sow. Pot up small plants in fall for indoor use.
Harvesting: Pick leaves as you need them. Freeze chopped or whole parsley in self-sealing bags to keep more of its fresh flavor, or dry them on screens in a food dehydrator or in an oven or microwave.
Uses: You can use parsley to enhance salads as well as main and side dishes, since its flavor combines well with most other culinary herbs and nearly all foods except sweets. It is traditionally one of the French fines herbes used in soups, omelets, and potato dishes; it’s delicious in soups, stews, and pasta sauces; and it is indispensable in Middle Eastern dishes like tabbouleh.
PARSNIP
Pastinaca sativa
Apiaceae
Parsnips are large carrot-shaped roots with a distinctive nutty-sweet taste. They require 100 to 120 days to mature and need a bit of extra soil preparation, but parsnip lovers know they’re worth the effort. Prepare parsnips like carrots—steamed or sliced into soups or stews. For an extra-special treat, try roasted parsnips.
Planting: Parsnip’s cream-colored root grows 8 to 24 inches long, with 2- to 4-inch-wide shoulders. Take extra care in preparing the planting area. Loosen the soil to a depth of 2 feet; remove rocks or clods. Dig in 2 to 3 inches of compost; avoid high-nitrogen materials that can cause forked roots.
In most areas, sow seed ½ to 1 inch deep in spring or early summer. Your goal is for the crop to mature at about the time of your first fall frost. In the South, plant parsnips in fall for a spring harvest. Use only fresh seeds, and soak them for several hours to encourage germination. Even then, germination will be slow and uneven, so sow the seed thickly and mark the rows with a quick-maturing radish crop. Cover the seed with a light material such as vermiculite or fine compost and water gently; keep the soil evenly moist.
Growing guidelines: Keep young plants free of weeds, and use a light mulch to conserve moisture. Parsnips have long roots and tolerate dry conditions, but your crop will be more successful if watered regularly.
Problems: Parsnips are usually problem free. See the Carrot entry for details on controlling problems that do occur.
Harvesting: Harvest roots after a hard frost for the best flavor. Dig and store like carrots, or mulch with a thick layer of hay and leave in the ground over winter, harvesting as needed. Pull the entire crop in early spring before new growth spoils its flavor.
PEA
Pisum sativum
Fabaceae
The crisp texture and sweet taste of fresh peas embodies spring. Ancient peoples foraged for peas in the wild long before they were domesticated. Romans, however, believed fresh green peas were poisonous and had to be dried before they could be eaten. It wasn’t until the time of King Louis XIV of France that a French gardener developed a green-pea hybrid known as petits pois. Fresh peas soon became the rage at the king’s court and thereby quickly gained widespread popularity.
Types: Still a garden favorite, peas are one of the first vegetables that you’ll plant and harvest in spring. There are extra-early, early, mid-season, and late types, taking 7 to 10 weeks to mature. Vining peas need trellises to grow on, while dwarf types need little or no support. Vining peas usually produce a heavier crop than do dwarfs.
Among green—or English—peas, there are wrinkled-seeded types and smooth-seeded types, both of which must be shelled. While wrinkled green peas are sweeter, smooth ones are hardier and better for super-early spring planting and for autumn and winter crops. If you’ve had problems with pea diseases, look for disease-resistant varieties such as ‘Maestro’. If you want to can or freeze peas, choose a variety such as ‘Dakota’ that has a heavy and concentrated pod-setting period.
Snow peas and snap peas have edible pods. Snow peas produce flat pods that you can eat either raw or cooked. Snap peas are eaten either as young flat pods or after the peas have grown and are fat and juicy in the pods. Snow and snap peas are available in both vining and dwarf versions. New varieties of dwarf snow peas such as ‘Snow Sweet’ have pods that stay tender longer than traditional snow peas.
Some edible-podded cultivars have strings running down each pod that you must remove before eating; fortunately, “stringless” cultivars such as ‘Sugar Spring’ have been developed that eliminate this task. Edible-podded peas are perfect for stir-fries and other Oriental dishes.
Field peas or cowpeas—which include black-eyed peas, crowder peas, and cream peas—are, botanically, beans. These plants thrive in areas with long, hot summers. See the Bean entry for information on cultivating these crops.
Planting: Give early peas a sunny spot protected from high winds. Later crops may appreciate partial shade. You can also plant peas in mid to late summer for a fall crop. If possible, sow your fall crop in a spot where tall crops such as corn or pole beans will shade the young plants until the weather cools.
Early peas in particular like raised beds or a sandy loam soil that warms up quickly. Heavier soils, on the other hand, can provide cooler conditions for a late pea crop, but you’ll need to loosen the ground before planting by working in some organic matter. Being legumes, peas supply their own nitrogen, so go easy on fertilizer. Too much nitrogen produces lush foliage but few peas.
Peas don’t transplant well and are very hardy, so there’s no reason to start them indoors. Pea plants can survive frosts but won’t tolerate temperatures over 75°F. In fact, production slows down drastically at 70°F.
Southern gardeners often sow peas in mid to late fall so the seeds will lie dormant through winter and sprout as early as possible for spring harvest. On the West Coast and in Gulf states, you can grow peas as a winter crop. Elsewhere, if the spring growing season is relatively long and cool, plant your peas 4 to 6 weeks before the last frost, when the soil is at least 40°F. For a long harvest season, sow early, mid-season, and late cultivars at the same time, or make successive sowings of one kind at 10-day to 2-week intervals until the middle of May.
When planting peas in an area where legumes haven’t grown before, it may help to treat seeds with an inoculant powder of bacteria, called Rhizobia. This treatment promotes the formation of root nodules, which contain beneficial bacteria that convert the nitrogen in the air into a form usable by plants. To use an inoculant, roll wet seeds in the powder immediately before planting.
Space seeds of bush, or dwarf, peas 1 inch apart in rows 2 feet apart. Bush peas are also good for growing in beds. Sow the seeds of early crops 2 inches deep in light soil or 1 inch deep in heavy soil; make later plantings an inch or two deeper. Thin to 2 to 3 inches apart. This close spacing will allow bush peas to entwine and prop each other up.
Plant vining types in double rows 6 to 8 inches apart on either side of 5- to 6-feet-tall supports made of wire or string, with 3 feet between each double row. The more simple the support, the easier it is to remove the vines at the end of the pea season and reuse it.
Generally speaking, 1 pound of seeds will plant a 100-foot row and should produce around 1 bushel of green peas or 2 bushels of edible pods. Another rough guideline is to raise 40 plants per person. Unused seed is good for 3 years.
To make good use of garden space, interplant peas with radishes, spinach, lettuce, or other early greens. Cucumbers and potatoes are good companion plants, but peas don’t do well when planted near garlic or onions.
Growing guidelines: Providing peas with just the right amount of water is a little tricky. They should never be so waterlogged that the seeds and plants rot, and too much water before the plants flower will reduce yields. On the other hand, don’t let the soil dry out when peas are germinating or blooming or when the pods are swelling. Once the plants are up, they only need about ½ inch of water every week until they start to bloom; at that time, increase their water supply to 1 inch a week until the pods fill out.
Peas growing in good soil need no additional fertilizer. If your soil is not very fertile, you may want to side-dress with compost when the seedlings are about 6 inches tall.
The vines are delicate, so handle them as little as possible. Gently hand pull any weeds near the plants to keep from damaging the pea roots. To reduce weeds and conserve moisture, lay 2 inches of organic mulch once the weather and soil warms. This also helps to keep the roots cool. Soil that becomes too warm can result in peas not setting fruit or can prevent already-formed pods from filling out. Mulch fall crops as soon as they are planted, and add another layer of mulch when the seedlings are 1 to 2 inches tall.
Once a vine quits producing, cut it off at ground level, leaving the nitrogen-rich root nodules in the ground to aid the growth of a following crop, such as brassicas, carrots, beets, or beans. Add the vines to your compost pile, unless they show obvious signs of disease or pest problems.
Problems: Aphids often attack developing vines. For information on controlling these pests, see page 458.
Pea weevils can chew on foliage, especially along the edges of young leaves. They are serious only when they attack young seedlings. Apply Beauveria bassiana as soon as damage is spotted to head off problems.
Thrips—very tiny black or dark brown insects—often hide on the undersides of leaves in dry weather. They cause distorted leaves that eventually die; thrips also spread disease. Control them with an insecticidal soap spray.
See the Animal Pests entry for information on protecting seeds and seedlings from birds.
Crop rotation is one of the best ways to prevent diseases. To avoid persistent problems, don’t grow peas in the same spot more than once every 5 years.
Plant resistant cultivars to avoid Fusarium wilt, which turns plants yellow, then brown, and causes them to shrivel and die.
Root-rot fungi cause water-soaked areas or brown lesions to appear on lower stems and roots of pea plants. Cool, wet, poorly drained soil favors development of rots. To avoid root rot, start seeds indoors in peat pots and wait until the soil is frostless before setting out the plants. Provide good fertility and drainage for strong, rapid growth.
Warm weather brings on powdery mildew, which covers a plant with a downy, white fungal coating that sucks nutrients out of the leaves. Bicarbonate sprays can help to prevent mildew. Destroy seriously affected vines, or place them in sealed containers for disposal with household trash. Avoid powdery mildew by planting resistant cultivars.
Control mosaic virus, which yellows and stunts plants, by getting rid of the aphids that spread it.
Harvesting: Pods are ready to pick about 3 weeks after a plant blossoms, but check frequently to avoid harvesting too late. You should harvest the peas daily to catch them at their prime and to encourage vines to keep producing. If allowed to become ripe and hard, peas lose much of their flavor. Also, their taste and texture are much better if you prepare and eat them immediately after harvesting; the sugar in peas turns to starch within a few hours after picking.
Pick shell and snap peas when they are plump and bright green. Snow-pea pods should be almost flat and barely showing their developing seeds. Cut the pods from the vines with scissors; pulling them off can uproot the vine or shock it into nonproduction.
Preserve any surplus as soon as possible by canning or, preferably, by freezing, which retains that fresh-from-the-garden flavor. To freeze peas, just shell and blanch for 1½ minutes, then cool, drain, pack, and freeze. Snow peas, which are frozen whole, are treated the same way, but don’t forget to string them first if necessary. Peas have a freezer life of about 1 year.
If peas become overripe, shell them and spread them on a flat surface for 3 weeks or until completely dry. Store in airtight containers and use as you would any dried bean.
PEACH
Prunus persica
Rosaceae
There may be no greater pleasure than biting into a peach fresh from the tree. Growing peaches organically can be a challenge, and you’ll need to be content with less-than-perfect fruit. However, the taste will more than make up for any surface imperfection!
These wonderful fuzzy fruits are the same species as nectarines. Only a single gene controls whether a cultivar bears smooth-or fuzzy-skinned fruit.
The Fruit Trees entry covers many important aspects of growing peaches and other tree fruits; refer to it for more information on planting, pruning, and care.
Selecting trees: Most peach trees are self-fertile. One tree will set a good crop.
Select cultivars to match your climate, or see the explanation of chill hours at right for a more exact way to determine which cultivars to plant. Choose disease-resistant peaches when available.
What you plan to do with your harvest will influence your selection. Freestone fruit are easy to separate from the pit and great for fresh eating, but the melting flesh often turns soft when canned. Clingstone fruit hang onto the pit for dear life, but their firm, aromatic flesh is great for cooking and preserving.
Yellow flesh is standard, but white-fleshed peaches are quite tender and equally tasty.
If you have the space for several trees, pick cultivars that will give you a succession of harvests. Just be sure your growing season is long enough for the fruit to mature.
Rootstocks: Peach trees are sold as grafted trees; common rootstocks include ‘Lovell’, ‘Hal-ford’, and ‘Guardian’. ‘Citation’ is a dwarfing rootstock. Where nematodes are severe, try ‘Nemaguard’ rootstock. ‘Siberian C’ rootstock may be a good choice for cold climates where winter temperatures do not fluctuate. If you have warm spells, seedling rootstocks may be less likely to break dormancy prematurely. If you’re planting peach trees for the first time, ask your local extension service for recommendations of the best rootstocks for your region.
Planting: Peaches prefer soil that is well drained and sandy-light on the surface with heavier texture in the subsoil. This keeps the crown and roots dry, helping to prevent disease problems, but still provides a deep reservoir of moisture and nutrients. For best results in any soil, add organic matter and correct any drainage problems before planting. Peaches need a pH of 6.0 to 6.5. Don’t add lime if the pH is 6.2 or higher, since a high level of calcium in the soil reduces absorption of potassium and magnesium by tree roots. Fertilize with compost. Space standard peaches 15 to 20 feet apart, and space dwarfs 12 feet apart.
Peach blossoms are easily damaged by frost. In areas where late-spring frosts are common, avoid planting in frost pockets (see page 242). Instead, choose a site on the upper half of a north-facing slope. A north-facing slope warms slowly, which may delay flowering by as much as 1 to 2 weeks. Planting about 15 feet away from the north side of a building may have the same effect. A thick mulch under the trees will help delay flowering by keeping the soil cool.
CHILL HOURS
Like other tree fruits, peach trees need a period of cold-weather rest or dormancy. The number of hours of cold between 32°F and 45°F needed before a tree breaks dormancy is referred to as chill hours. (Cold below 32°F doesn’t count toward meeting the dormancy require-ment.) Once the number is reached, the tree assumes winter is over, and it starts growing the next warm day. Peaches bloom rapidly once their requirement has been met, which makes them more prone to frost damage than other tree fruits that are slower to burst into bloom.
Call your local extension service to find out how many chill hours your area receives and what cultivars match that requirement. If you choose a cultivar that needs fewer chill hours than you normally receive, it will flower too early and be prone to bud damage. But if you choose one that needs more chill hours, it won’t get enough chilling to stimulate normal bloom.
Peaches ripen best when the sun shines and temperatures hover at about 75°F. If temperatures are consistently cooler, the fruit can develop an astringent flavor or be almost tasteless. Plant your tree in a sheltered location that conserves heat to help the fruit ripen.
Since most peach trees have a maximum productive life of about 12 years, plant replacements periodically. If you plan ahead, you will always have mature trees and fresh fruit. Don’t replant in the same location, though. Viruses and nematodes, which will shorten the life of new trees, may have built up in the soil.
Care: Healthy peaches should grow 1 to 1½ feet a year. If growth is slower or the foliage is a light yellow-green or reddish purple, have the leaves and soil tested for nutrient content, and correct deficiencies. The Soil entry gives specifics on soil testing. In cold climates, fertilize only in early spring so wood can be fully hardened before winter. Mulch with compost or other low-nitrogen organic materials to maximize water and nutrient availability.
Peach trees need even moisture around their roots to produce juicy, succulent fruit. If the weather is dry or the soil is sandy, install drip irrigation over the entire root system out to the drip line. Keep the soil moist, not wet. Mulch to reduce evaporation. See the Drip Irrigation entry for more information.
Sometimes peaches flower when the weather is still too cool for much insect activity. To ensure fruit set, you must take the place of insects and spread pollen from flower to flower. Use a soft brush to dab pollen from one flower onto its neighbor. Hand pollinate newly opened flowers every day, and you’ll have a decent crop.
Frost protection: Winter temperatures of –10°F or lower will kill some or all of the flower buds of most peach cultivars. Some may even suffer cold damage to the wood, branch crotches, or trunk. The closer the cold snap comes to spring flowering time, the more severe the damage will be. Plant cold-tolerant cultivars to minimize losses. Or try letting the tree grow taller than you normally would; the upper boughs may escape frost damage.
If frost is predicted, spray an anti-transpirant the day before for 2° to 3°F of extra protection. Or get up and hose down trees with water just before sunrise.
Pruning: Train peaches to the open center system. This makes an attractive, productive tree that is low and spreading and easy to reach. For instructions, see page 246.
Start training your tree when you plant it. The first few years, prune as needed to shape the tree. After that, prune only to keep the tree fruiting and reasonably small. Prune each year just before the tree breaks dormancy. If canker is a problem or spring frosts are common, prune after flowering to minimize disease problems and ensure that you will have a good crop. Dry weather at pruning discourages canker invasion, and you will be able to prune more or less depending on how many buds survived winter. Heading back new growth now reduces the fruit load and your later thinning chores.
Try central leader training if your trees suffer sunscald, or protect trees by painting the larger branches with diluted white latex paint. In very cool climates, try training your peach tree against a stone or brick wall that reflects sun and radiates heat. For training instructions, see page 245.
No matter what training method you choose, try to minimize the amount of wood you remove the first few years. Rub off unwanted shoots and suckers as soon as they appear during the growing season. Your tree will bear earlier and more heavily if you do.
As the tree gets older, continue to prune each spring for maintenance and renewal. Peaches fruit only on one-year-old-wood. Encourage new growth by cutting off old branches that are no longer productive. Head back new growth by ⅓ to ½ of its length to keep the tree compact. Cut back to just above an outward-facing branch or bud. Heading back also encourages more small side branches, which are the best fruit producers, and keeps the tree from overbearing.
Thinning: Once your tree starts bearing, it may set more fruit than it can handle. Remove some of the green fruit before the pits harden, so the remaining fruit will grow large and sweet and the tree won’t break under the weight of the ripe fruit. Leave one peach every 4 to 6 inches. If you don’t remove enough, prop up heavily laden branches with a forked stick until harvest. Prune and thin harder the next year.
Harvesting: Peach trees bear within 3 years. As peaches ripen, the skin color changes from green to yellow; the flesh slightly gives to the touch when ripe. Hold the fruit gently in your palm and twist it off the branch. Avoid bruising it. You can store ripe peaches for about a week in a refrigerator.
Problems: Peach trees can be plagued by various pests and diseases; the most serious are canker and peach tree borers. Nectarine fruits are even more likely to be attacked by fruit pests than peaches are, perhaps because pests dislike the fuzzy skin on peaches.
Common peach pests include green fruit-worms, two types of peach tree borers, mites, and plum curculios. For descriptions and control methods see page 249. Aphids, Japanese beetles, scale, and tarnished plant bugs can also cause problems; see page 458 for descriptions and controls.
Oriental fruit moths lay eggs on shoots and the larvae bore into the tissue early in the season. Later generations of larvae burrow to the center of fruits to feed. Young fruits exude a gummy substance and often drop prematurely. Control this pest by removing infested shoots and fruit and destroying them. Encourage native parasitic wasps that attack the eggs and larvae.
Fall webworms and tent caterpillars spin webs and munch on leaves. Gypsy moth caterpillars also eat leaves. Destroy webs and caterpillars as soon as you see them. Spray Bt (Bacillus thuringiensis) where they are feeding.
Trees infected by root knot nematodes may have weak growth and yellow leaves. Affected trees won’t bear fruit and will eventually die. If you suspect a nematode problem, ask your local extension office about having your soil tested for nematodes. To avoid nematode problems, don’t replant where peaches have grown previously, solarize soil before planting, and enrich soil with organic matter to encourage natural fungi or apply parasitic nematodes to soil before planting. ‘Nemaguard’ rootstock is resistant to root knot nematode.
Some common diseases of peaches are bacterial leaf spot, brown rot, and perennial canker (also known as valsa and cytospora). See page 249 for descriptions and controls.
Peach leaf curl is a fungal disease that causes leaves to become thick, puckered, and reddish. It’s a common problem in cool, humid areas. Symptoms appear about a month after bloom. Leaves drop soon after. Fruit will look distorted and off color. To prevent peach leaf curl, remove infected leaves and destroy them. Increase air circulation by pruning trees every year when they are dormant. It’s rare for peach leaf curl to become a serious problem, but if it’s threatening to kill off your trees, spray with Bordeaux mix (a blend of copper sulfate and hydrated lime) in fall after leaves drop or in early spring while the trees are still dormant.
Peach scab causes small, olive green spots, usually clustered near the stem end of half-grown fruit about a month after infection. Later the spots turn brown and velvety, and the skin cracks. Twigs and leaves also get peach scab. Remove and destroy infected fruit and clean up fallen leaves and fruit. Weather that is warm and either wet or humid encourages scab. Control as you do brown rot. If you’ve had problems with scab in previous seasons, spray sulfur weekly from the time the first green shows in the buds until the weather becomes dry.
Certain cankers cause wilting or yellowing of new shoots or leaves and can also girdle limbs. Delay routine pruning until after bud break to reduce the chance of infection by canker organisms. Prune out and destroy any gummy cankers on trees whenever you spot them.
Crown gall and crown rot sometimes attack peach trees; providing good drainage helps to avoid these problems. Use a sharp knife to remove galls that form near the soil line.
Virus diseases such as yellows and mosaic may cause leaf distortion, discoloration, and mottling. Buy only certified disease-free stock. Destroy infected trees immediately.
PEANUT
Arachis hypogaea
Fabaceae
Contrary to popular belief, the peanut is not a nut; it is actually a vegetable belonging to the legume family, which includes peas and beans. These tropical natives of South America require about 120 days to mature, but fortunately they can withstand light spring and fall frosts. ‘Jumbo Virginia’ is a productive variety for home gardens. Although peanuts are generally considered a Southern crop, Northern gardeners can also grow them successfully if they choose early cultivars such as ‘Early Spanish’ and start plants indoors.
Planting: Peanuts need full sun. If you have heavy soil, ensure good drainage by working in enough organic matter to make it loose and friable.
Peanut seeds come in their shells and can be planted hulled or unhulled. If you do shell them, don’t remove the thin, pinkish brown seed coverings, or the seed won’t germinate.
Northern growers should start plants indoors in large peat pots a month before the last frost. Sow seeds 1 inch deep, place in the sunniest spot possible, and water weekly. Transplant seedlings to the garden when the soil warms to between 60° and 70°F. Space transplants 10 inches apart, being careful not to damage or bury the crown.
In the South, plant outdoors around the date of the last expected frost. Space seeds 2 inches deep and 5 inches apart in rows 2 to 3 feet apart. Firm the soil and water well. Thin plants to 10 inches apart.
Growing guidelines: When the plants are about 1 foot tall, hill the earth around the base of each plant. Long, pointed pegs (also called peduncles) grow from faded flowers and then push 1 to 3 inches down into the soil beside the plant. A peanut will form on the end of each peg. Lay down a light mulch, such as straw or grass clippings, to prevent the soil surface from crusting so that the pegs will have no difficulty penetrating the soil.
One inch of water a week is plenty for peanuts. Being legumes, peanuts supply their own nitrogen, so avoid nitrogen-rich fertilizers, which encourage foliage rather than fruits. Well-prepared soil will provide all the nutrients the plants need.
Problems: Peanuts are usually problem free. For aphid controls, see page 458.
Harvesting: The crop is ready to harvest when leaves turn yellow and the peanuts’ inner shells have gold-marked veins, which you can check periodically by pulling out a few nuts from the soil and shelling them. If you wait too long, the pegs will become brittle, and the pods will break off in the ground, making harvesting more difficult. Pull or dig the plants and roots when the soil is moist. Shake off the excess soil, and let plants dry in an airy place until the leaves become crumbly; then remove the pods. Unshelled peanuts, stored in airtight containers, can keep for up to a year.
PEAR
Pyrus communis and its hybrids
Rosaceae
With their glossy leaves and white blossoms, pear trees are a beautiful accent in a home landscape. Plus they produce bushels of delicious fruit, are long-lived, and suffer fewer insect and disease problems than many tree fruits.
Most gardeners are familiar with European pears, including the familiar ‘Bartlett’ and ‘Bosc’ pears. However, Asian pears, which have crisp, juicy, almost round fruits, will also grow well in most parts of the United States and Canada. The Fruit Trees entry covers many important aspects of growing pears and other tree fruits; refer to it for additional information on planting, pruning, and care.
Selecting trees: Pears need cross-pollination to set a good crop. Most European and Asian cultivars pollinate each other. A few cultivars don’t product viable pollen; if you select one, you’ll need to plant three different cultivars to ensure good fruit set. Certain cultivars will not pollinate other specific cultivars. Check pollination requirements before you buy.
European pears are hardy to –20°F, but Asian pears generally are hardy only in Zones 5 and warmer. European and Asian pear varieties have a range of chilling requirements, so check on this when deciding what to grow. (For more information on fruit tree chilling requirements, see page 419.)
Fire blight can be a devastating disease problem in some regions, especially areas with warm, wet spring seasons. ‘Magness’ and ‘Warren’ are resistant to fire blight. ‘Magness’ doesn’t produce viable pollen, so be sure to plant it with two other cultivars. Asian pears seem to be less appealing to pear psylla, another common problem.
Rootstocks: Standard pear trees are grafted onto seedling rootstocks, but they can grow 30 feet tall. Semidwarf and dwarf varieties are easier to care for and harvest. Many dwarf and semi-dwarf pear trees are grafted onto quince rootstock. ‘Old Home × Farmingdale’ rootstock is resistant to fire blight and pear decline and makes a semidwarf tree.
Planting and care: Pear trees are quite winter hardy. They bloom early but tend to be more resistant to frost damage than other fruits. (Opened pear blossoms can be damaged at 26°F.)
Pears will tolerate less-than-perfect drainage but need deep soil. They are vulnerable to water stress, which causes foliage to turn brown and prevents fruits from enlarging. To prevent this, mulch with a thick layer of organic matter out to the drip line, and irrigate deeply if the soil dries out.
Pears prefer a pH of 6.4 to 6.8. If pH is too low, the tree may be more susceptible to fire blight. A healthy pear tree grows 1 to 1½ feet a year. If growth is less, have the foliage tested and correct any deficiencies. The Soil entry gives details on how to get foliage tested. Go easy when fertilizing with nitrogen; it encourages soft new growth that is susceptible to fire blight. If there is too much new growth on the tree, let weeds or grass grow up beneath the tree to consume excess nutrients in the soil.
Pruning: Pear trees grow tall. However, you can keep all the limbs within an arm’s reach of a ladder by training your young tree. How you choose to prune and train your tree will greatly affect its lifespan as well as its ability to produce large crops. Start training as soon as you plant your tree. Be sure to spread the branches, because pears tend to grow up, not out, if left on their own. Minimize pruning, because too much pruning can also stimulate more growth than you want.
If you develop a strong, spreading framework, it will be easier to prune, and the tree will bear earlier. When you do start to prune, prune just before the tree breaks dormancy in spring. Or in locations where pears suffer winter bud damage, prune just after flowering.
Train European pears to a central leader system and Asian pears to an open center system (see the Fruit Trees entry for pruning details). In areas where fire blight is severe, you may want to leave two main trunks as crop insurance.
To minimize fire blight attack on susceptible trees, discourage soft young growth, and make as few cuts as possible. Thin out whole branches rather than heading them back. This will reduce the total number of cuts made and won’t stimulate the growth of soft, highly susceptible side shoots. Snip off any flowers that appear in late spring or summer. They are an easy target for fire blight.
Remove unproductive and disease-susceptible suckers that sprout from the trunk and branches. As the tree gets older, you may want to leave a renewal sucker to replace a limb with 4- or 5-year-old spurs, or one damaged by fire blight. During summer, select a sucker near the base of the branch to be replaced. Spread the crotch so it will develop a good outward angle. Carefully remove the old branch the next spring so the sucker will have room to develop.
Thinning: Pears are likely to set more fruit than they can handle. Fruits will be small, and the heavy fruit load may break branches or prevent flowering the following year if not thinned. A few weeks after the petals fall, remove all but one fruit per cluster. Prop up heavily laden limbs with a forked stick.
Harvesting: Pears bear in 3 to 5 years after planting. Pick European pears before the flesh is fully ripe; the fruit will finish ripening off the vine. To test ripeness, cut a fruit open; dark seeds indicate ripe fruit. Also, if you can pull the fruit stem away from the branch with a slight effort but without tearing the wood, the fruit is prime for harvesting. Store pears at just above 32°F. Many European cultivars store well; hard, late-bearing cultivars store better than earlier cultivars. When you’re ready to eat them, place them in a 60° to 70°F room to soften and sweeten (putting them in a bowl with some bananas will speed their ripening). Pears that won’t ripen may have been in cold storage too long, or the ripening temperature may be too high. If a pear is brown and watery inside, it was harvested too late.
Asian pears are sweetest when allowed to ripen on the tree. Watch for a color change, and taste to decide when they are ripe.
Problems: Apple maggots, codling moths, green fruit worms, mites, and plum curculio can attack pears. For descriptions and control methods, see page 249. Pears also attract aphids, scale, and tarnished plant bugs; see page 458 for descriptions and controls. See the Apple entry for description and control of leafrollers and other leaf-eating caterpillars.
Pear psylla is a major pest in many areas. These tiny sucking insects are nearly invisible to the naked eye. They are often noticed only when the foliage and twigs at the top of pear trees turn black in late summer. The black color is actually a sooty mold that grows in the honeydew produced by the psylla. Left uncontrolled, psylla and sooty mold can reduce fruit production or even kill the tree. Psylla also can infect trees with viruslike diseases, such as pear decline. Native beneficial insects can help keep psylla in check. To prevent psylla problems, spray trees with kaolin clay beginning in spring, and if possible, keep the trees coated by repeat spraying all through the growing season. The psylla don’t like to lay their eggs on sprayed trees, and the clayey coating also irritates psylla nymphs.
Thrips are tiny insects too small to see, but you can see their small dark droppings on leaves. Leaves will appear bleached and wilted, fruit may show scabs or russeting. Predatory mites will control thrips, but if populations are high, spray with insecticidal soap.
Pearslugs are the small sluglike larvae of sawflies. They eat leaf tissue but leave a skeleton of veins behind. Hand pick, wash them off leaves with a strong water spray, or spray with insecticidal soap.
Fire blight, a bacterial disease that affects many fruit trees, is especially severe on pears. It can rapidly kill a susceptible tree or orchard in humid conditions. The sooty mold that goes with psylla can also look like fire blight. Sooty mold wipes off; fire blight doesn’t. For control measures, see page 249. Pear trees also suffer from cedar apple rust; see the Apple entry for description and controls.
Pseudomonas blight symptoms resemble fire blight, but it thrives in cool fall conditions when fire blight is less common. Control as for fire blight.
Pear scab looks much like apple scab. See the Apple entry for description and controls.
Fabraea leaf spot causes small, round, dark spots with purple margins. Leaves turn yellow and drop. Fruits develop dark, sunken spots and may be misshapen. If many leaves drop, trees are weakened, and future crops are reduced. Clean up fallen leaves each winter. If leaf spot has been a problem in the past, spray copper just before the blossoms open and again after the petals fall off.
Many viral diseases affect pears, causing leaf or fruit distortion and discoloration. Buy certified virus-free stock, and control insects such as aphids, which may transmit viruses.
PELARGONIUM
Pelargonium × hortorum, zonal geranium, garden geranium. Tender perennials grown as annuals or houseplants.
Description: Flower colors include white, pink, rose, red, scarlet, purple, and orange shades, plus starred, edged, banded, and dotted patterns of two or more colors. Pick from single (fivepetalled) or double forms resembling rosebuds, tulips, cactus flowers, or carnations. The rounded flower clusters may be very dense or quite open and airy, measuring 1 to 6 inches across. Geraniums normally grow 1 to 2 feet in a single season. Smaller sizes include miniature (3 to 5 inches), dwarf (6 to 8 inches), and semidwarf (8 to 10 inches). Upright, mounded, and cascading habits are available. The soft and fuzzy, rounded, scalloped, or fingered leaves can grow from ½ to 5 inches wide. Leaves may be all green, chartreuse and maroon, banded in dark green, or green combined with one or more shades of white, red, yellow, chartreuse, or brown.
Pelargonium peltatum, ivy geranium, brings color to window boxes and baskets throughout summer and fall. Clusters of white, red, pink, salmon, lavender, and purple flowers bloom profusely on trailing stems above shiny, scalloped, ivy-shaped leaves. Some of the many cultivars have variegated leaves, including ‘Crocodile’, with unusual yellow-netted leaves. Plants can grow 2 to 5 feet in a season. There are also more-compact hybrids between the ivy and garden (zonal) geranium.
Ivy geraniums are excellent hanging-basket plants. You can also grow them in the traditional window box, in a raised planter, or as a flowering groundcover.
P. × domesticum, Martha Washington or regal geraniums, are the glamour queens of the genus. They take the spotlight in cooler regions, where their 6-inch clusters of azalea-like flowers bloom profusely in white, pink, red, lavender, burgundy, salmon, violet, and bicolors. Rounded leaves up to 8 inches wide grow thickly on mounded 1- to 2-foot plants.
Spectacular in beds, regal geraniums also make great houseplants and dazzling standards. If you live where summers are hot, you can still enjoy these beauties as spring pot plants, discarding them after bloom.
How to grow: Buy blooming plants of cutting-grown cultivars from a nursery; try to buy locally grown cultivars that are suitable for your region, especially in the humid South. Or sow seeds in February for plants that will bloom by summer. Plant out after all danger of frost is past. Most prefer full sun, but shade variegated cultivars from the hottest afternoon sun to prevent leaf browning. Geraniums adapt to most well-drained soils with average moisture, although they prefer sandy loam. Avoid high-nitrogen fertilizers, which encourage leaf growth at the expense of flowers, unless you’re growing cultivars such as ‘Vancouver Centennial’ or ‘Crystal Palace Gem’ for their fabulous foliage. Pinch the tips of plants that are reluctant to branch on their own to avoid tall, leggy plants with leaves and flowers only toward the top. In late summer, root 4- to 5-inch cuttings in clean sand, or dig up your favorites and pot them before frost.
Scented Geraniums
Although not as colorful as zonal geraniums, scented geraniums (Pelargonium spp.) also deserve a place in your garden. A few of them have attractive blooms, producing small clusters of pink, white, or lavender flowers, but they’re really grown for their fragrant foliage. Leaf form varies from tiny ½-inch rounded leaves to 6-inch oaklike giants, but all release their powerful aromas with a gentle rub. Habit ranges from loose, spreading plants to strong bushes reaching 4 feet or more.
Scented geraniums require much the same care as zonal geraniums, but don’t overfeed them or the fragrance won’t be as strong. They grow well in pots of loose, well-drained soil, and their scented foliage makes them ideal houseplants. Grow them in your flower borders for a green accent, or show them off in an herb or kitchen garden. Both flowers and foliage are edible and can be used fresh or dried in herb teas.
There are many, many scented geraniums available. The list here is only a small sample.
| NAME | FRAGRANCE |
| Pelargonium crispum | Lemon |
| P. denticulatum | Pine |
| P. fragrans | Nutmeg |
| P. graveolens | Rose |
| P. ✕ nervosum | Lime |
| P. odoratissimum | Apple |
| P. scabrum | Apricot |
| P. tomentosum | Peppermint |
Hybrids between these and other species have given rise to many cultivars, among them ‘Grey Lady Plymouth’, with rose-scented, gray-green leaves edged in white; ‘Mabel Gray’, with an intense lemon fragrance and sharply lobed leaves; and ‘Prince Rupert Variegated’, bearing small, cream-and white-variegated lemony foliage.
Buy ivy geraniums in bloom to set in sunny spots but provide afternoon shade in summer. Water container plants frequently, but don’t let them stand in water. Use a rich, well-drained potting mix and feed monthly with liquid organic fertilizer. Pinch back for more flowers.
Set purchased regal geranium plants in a sunny, cool spot with good, slightly alkaline soil. They require plenty of water while in bloom. Treat them as true annuals and discard at season’s end, or take cuttings or pot up plants to bring indoors for winter.
Landscape uses: Mass geraniums in beds of their own, or use them to brighten a mixed border. Geraniums in containers will light up a deck, patio, or sunny porch; if you use them in a sitting area, choose plants with attractively colored foliage as well as showy flowers for double the viewing pleasure. Use ivy geraniums in hanging baskets. Plants may live for years in pots, and look especially handsome if trained into standards. (For more information on creating standards, see page 315.) Fill a window box with a single color or a mixture, and add splashes of color to slightly shaded corners or areas under tall trees with variegated types.
PENSTEMON
Penstemon, beardtongue. Late-spring-to summer-blooming perennials; wildflowers.
Description: Penstemons produce clusters of tubular flowers with scalloped tips and a fuzzy area (beard) inside the throat. Flowers range from white to pink, red, scarlet, orange, wine, and indigo. They bloom at the ends of creeping or 1- to 3-foot upright stems bearing pointed, often evergreen leaves. Zones 3–9, depending on the species. Many penstemons are common wildflowers in the West; only a few species are native to the eastern United States. The best bet for Eastern gardens is the white-flowered Penstemon digitalis, foxglove penstemon, and its cultivars, such as ‘Husker Red’, which has deep red foliage and pink flowers. Unlike other penstemons, it thrives in moist soil. Zones 4–8.
How to grow: Plant or divide in spring in sunny, average, very well-drained soil. Provide partial shade in warmer areas. Mulch with gravel or other inorganic material; organic matter holds too much moisture and will rot the crowns. Divide clumps every 4 to 6 years to maintain vigor.
Landscape uses: Use penstemons as a filler in borders and beds and in rock gardens.
PEONY
See Paeonia
PEPPER
Capsicum annuum var. annuum
Solanaceae
Pepper choices—ranging from crispy sweet to fiery hot, from big and blocky to long and skinny—increase each year. This native American vegetable is second only to tomatoes as a garden favorite, and it needs much the same care. Peppers are also ideal for spot planting around the garden. The brilliant colors of the mature fruit are especially attractive in flower beds and in container plantings.
New varieties of bell peppers are released every year, in mature colors ranging from bright red to orange to white, purple, and nearly black. If you’ve had past problems with diseases such as tobacco mosaic virus or bacterial spot, choose disease-resistant varieties.
Planting: Choose a site with full sun for your pepper plot. Don’t plant peppers where tomatoes or eggplants grew previously, because all three are members of the nightshade family and are subject to similar diseases. Make sure the soil drains well; standing water encourages root rot.
Garden centers offer a good variety of transplants, but the choices are greater when you grow peppers from seed. Pepper roots don’t like to be disturbed, so plant them indoors in peat pots two months before the last frost date, sowing three seeds to a pot. Maintain the soil temperature at 75°F, and keep the seedlings moist, but not wet. Provide at least 5 hours of strong sunlight a day, or ideally, keep the plants under lights for 12 or more hours daily. Once the seedlings are 2 to 3 inches tall, thin them by leaving the strongest plant in each pot and cutting the others off at soil level.
Seedlings are ready for the garden when they are 4 to 6 inches tall. Before moving the young plants to the garden, harden them off for about a week. Peppers are very susceptible to transplant “shock,” which can interrupt growth for weeks. To avoid shocking the plants, make sure the soil temperature is at least 60°F before transplanting; this usually occurs 2 to 3 weeks after the last frost. Transplant on a cloudy day or in the evening to reduce the danger of sun scorch; if this is not possible, provide temporary shade for the transplanted seedlings.
When buying transplants, look for ones with strong stems and dark green leaves. Pass up those that already have tiny fruits on them, because such plants won’t produce well. Peppers take at least 2 months from the time the plants are set out to the time they produce fruit, so short-season growers should select early-maturing cultivars.
Space transplants about 1½ feet apart in rows at least 2 feet apart, keeping in mind that most hot-pepper cultivars need less room than sweet ones. If the plot is exposed to winds, stake the plants, but put these supports in place before transplanting the seedlings to keep from damaging roots. To deter cutworms, place a cardboard collar around each stem, pushing it at least an inch into the ground. If the weather turns chilly and rainy, protect young plants with hotcaps.
Growing guidelines: Evenly moist soil is essential to good growth, so spread a thick but light mulch, such as straw or grass clippings, around the plants. Water deeply during dry spells to encourage deep root development. Lack of water can produce bitter-tasting peppers. To avoid damaging the roots, gently pull any invading weeds by hand.
Although peppers are tropical plants, temperatures over 90°F often cause blossoms to drop and plants to wilt. To avoid this problem, plan your garden so taller plants will shade the peppers during the hottest part of the day. If you plant peppers in properly prepared soil, fertilizing usually isn’t necessary. Pale leaves and slow growth, however, are a sign that the plants need a feeding of liquid fertilizer, such as fish emulsion or compost tea. See the Compost entry for instructions for making compost tea.
Problems: Since sprays of ground-up hot peppers can deter insects, it’s logical that pests don’t usually bother pepper plants. There are, however, a few exceptions. The pepper weevil, a ⅛-inch-long, brass-colored beetle with a brown or black snout, and its ¼-inch-long larva, a white worm with a beige head, chew holes in blossoms and buds, causing misshapen and discolored fruits. It’s a common pest across the southern United States. Prevent damage by keeping the garden free of crop debris. Hand pick any weevils you spot on the plants.
Other occasional pests include aphids, Colorado potato beetles, flea beetles, hornworms, and cutworms. See page 458 for information on these insect pests and how to control them.
Crop rotation and resistant cultivars are your best defense against most pepper diseases. Here are some common diseases to watch for:
Anthracnose infection causes dark, sunken, soft, and watery spots on fruits.
Bacterial spot appears as small, yellow-green raised spots on young leaves and dark spots with light-colored centers on older leaves.
Early blight appears as dark spots on leaves and stems; infected leaves eventually die.
Verticillium wilt appears first on lower leaves, which turn yellow and wilt.
Mosaic—the most serious disease—is a viral infection that mottles the leaves of young plants with dark and light splotches and eventually causes them to curl and wrinkle. Later on, mosaic can cause fruits to become bumpy and bitter.
See the Plant Diseases and Disorders entry for more information on some of these diseases and control measures.
Harvesting: Most sweet peppers become even sweeter when mature as they turn from green to bright red, yellow, or orange—or even brown or purple. Mature hot peppers offer an even greater variety of rainbow colors, often on the same plant, and achieve their best flavor when fully grown. Early in the season, however, it’s best to harvest peppers before they ripen to encourage the plant to keep bearing; a mature fruit can signal a plant to stop production.
Always cut (don’t pull) peppers from the plant. Pick all the fruit when a frost is predicted, or pull plants up by the roots and hang them in a dry, cool place indoors for the fruit to ripen more fully. To preserve, freeze peppers (without blanching), or dry hot types.
PERENNIALS
Perennials are part of our lives, even if we’re not flower gardeners. Most of us grew up with day-lilies, irises, and peonies in our yards or neighborhoods, and perennials like astilbes and hostas are familiar faces too. But many less-well-known perennials have an exotic mystique: We may admire them, but we’re not sure we’d know what to do with them in our own gardens.
Technically speaking, most plants grown in the garden are perennial, if you count every plant that lives more than a year, including trees and shrubs. But to most gardeners, a perennial is a plant that lives and flowers for more than one season but dies to the ground each winter.
Many perennials—including peonies (Paeonia spp.), Oriental poppies (Papaver orientalis), and daylilies (Hemerocallis spp.)—are long-lived. Others, like coreopsis and columbines (Aquilegia spp.), may bloom just a few years before disappearing, but they are prolific seeders, and new seedlings keep coming back just like their longer-lived cousins. Most popular perennials fall somewhere between the two extremes, and will reappear year after year with reassuring regularity.
Landscaping with Perennials
Perennials are all-purpose plants—you can grow them wherever you garden and in any part of your garden. There’s a perennial to fit almost any spot in the landscape, and with a little planning, it’s possible to have them in bloom throughout the frost-free months. In addition to the endless variety of sizes, shapes, colors, and plant habits, there are perennials for nearly any cultural condition your garden has to offer.
Most perennials prefer loamy soil with even moisture and full sun. Gardeners who have these conditions to offer have the widest selection of plants from which to choose. However, if you have a shaded site, there are dozens of perennials for you, too, such as those listed on page 432. For ideas for other types of sites, see the lists on pages 433 and 437 as well.
Perennials add beauty, permanence, and seasonal rhythm to any landscape. Their yearly growth and flowering cycles are fun to follow—it’s always exciting to see the first peonies pushing out of the ground in April or the asters braving another November day. Look at your property and think about where you could add perennials. There are a number of ways to use perennials effectively in your yard.
Shade gardens: Turn problem shady sites where lawn grass won’t grow, such as under trees or between buildings, into an asset by creating a shade garden. Many perennials tolerate shade, but remember that shade plants often have brief periods of bloom. For the most successful shade garden, you should count on the plants’ foliage to carry the garden through the seasons. The most engaging shade gardens rely on combinations of large-, medium-, and small-leaved plants with different leaf textures. For example, try mixing ferns with variegated hostas, astilbes, Virginia bluebells (Mertensia virginica), and shade-tolerant groundcovers like Allegheny foam-flower (Tiarella cordifolia) and creeping phlox (Phlox stolonifera) to create a diverse mix of size, foliage, and texture.
Bog and water gardens: If you have a low area that’s always wet, you know that fighting to grow grass there is a losing battle. Instead, turn that boggy patch into a perennial bog or water garden. Some perennials will even grow with their roots submerged in the shallows. For more on making a bog or water garden, see the Water Gardens entry.
Rock gardens: If you have a rock wall that edges a bank or a dry, stony slope in full sun, you have a perfect site for a rock garden. A host of plants thrive in poor soil and relentless sunshine, including yarrows, sedums, and hens-and-chicks. For more on rock gardening, see the Rock Gardens entry. (For a design featuring a rock garden, see page 638.)
Containers: To add color and excitement to a deck, patio, balcony, or entryway, try perennials in containers. Mix several perennials together, combine them with annuals, or plant just a single perennial per container. Try a daylily in a half barrel in a sunny spot or hostas with variegated foliage in a shady one. Remember, containers dry out quickly, so choose plants that tolerate some dryness for best results. For more ideas, see the Container Gardening entry.
Perennial plant of the year: Every year, the Perennial Plant Association (PPA), the professional organization for the promotion of perennial plants, announces the winner of its Perennial Plant of the Year competition. The PPA is composed of nurserymen, perennial plant breeders, educators, landscape and garden designers, and others with a serious interest in perennial plants. Each year, the membership nominates the plants they feel deserve the honor of being named Perennial Plant of the Year, based on such criteria as consistency, low maintenance, ornamental value in multiple seasons, pest and disease resistance, wide adaptability to a range of climatic conditions, easy propagation, and wide availability. What this means is that gardeners can count on the winning perennials to perform well in their gardens, wherever they live, with minimal care.
KEY WORDS Perennials
Perennial plant. A plant that flowers and sets seed for two or more seasons. Short-lived perennials like coreopsis and columbines may live 3 to 5 years. Long-lived perennials like peonies may live 100 years or more.
Tender perennial. A perennial plant from tropical or subtropical regions that can’t be overwintered outside, except in subtropical regions such as Florida and Southern California. Often grown as annuals, tender perennials include zonal geraniums, wax begonias, cannas, and coleus.
Hardy perennial. A perennial plant that tolerates frost. Hardy perennials vary in the degree of cold that they can tolerate, however, so make sure a plant is hardy in your zone before you buy it.
Herbaceous perennial. A perennial plant that dies back to the ground at the end of each growing season. Most garden perennials fall into this category.
Semiwoody perennial. A perennial plant that forms woody stems but is much less substantial than a shrub. Examples include lavender, Russian sage, and some of the thymes.
Woody perennial. A perennial plant such as a shrub or tree that does not die down to the ground each year. Gardeners generally refer to these as “woody plants.”
You can’t go wrong by adding these great perennials to your garden. You’ll find more information on the Perennial Plant of the Year program on the Internet; see Resources on page 672 for the address.
Designing Beds and Borders
Designing with perennials may seem overwhelming, since there are so many to choose from. Just take your design one step at a time. Chances are, your growing conditions are right for only a fraction of what’s available. Let your moisture, soil, and light conditions guide you in choosing plants. For example, if you have a garden bed in full sun that tends toward dry soil, cross off shade-and moisture-loving perennials like hostas and ferns from your list. Instead, put in plants that like full sun and don’t like wet feet, like daylilies and ornamental grasses. And don’t forget to choose only plants that are hardy in your area. For information on combining perennials to create a lush bed or border, see the Garden Design entry.
Planting Perennials
Because perennials live a long time, it’s important to get them off to a good start. Proper soil preparation and care at planting time will be well rewarded.
Soil preparation: The majority of perennials commonly grown in beds or borders require evenly moist, humus-rich soil of pH 5.5 to 6.5. A complete soil analysis from your local extension office or a soil-testing lab will give you a starting point. For more on soils and do-it-yourself soil tests, see the Soil entry.
Best Perennials for Shade
There are dozens of choice perennials to brighten a shady site. Most prefer woodland conditions: rich, moist, well-drained soil and cool temperatures. Many plants in this list grow well in partial shade. Plants that tolerate deep shade include species of Actaea, Brunnera, Epimedium, Heuchera, Hosta, Mertensia, Polygonatum, and Pulmonaria. Plant name is followed by bloom time and color.
Aconitum spp. (monkshoods): summer to early fall; blue
Actaea spp., formerly Cimicifuga spp., (bugbanes): summer to fall; white
Aquilegia spp. (columbines): spring to early summer; all colors, bicolors
Astilbe spp. (astilbes): late spring to summer; red, pink, white, purple
Bergenia spp. (bergenias): early spring; rose, pink, purple, white
Brunnera macrophylla (Siberian bugloss): spring; light blue
Dicentra spp. (bleeding hearts): spring; rose pink, white
Epimedium spp. (epimediums): spring; pink, red, yellow, white
Helleborus spp. (hellebores): early spring; white, rose, green, purple
Heuchera spp. (heucheras, coral bells): spring to summer; pink, red, white, green
× Heucherella tiarelloides (foamy bells): spring and summer; pink, white, cream
Hosta spp. (hostas): early to late summer; violet, lilac, white
Mertensia virginica (Virginia bluebells): spring; blue, white
Polemonium spp. (Jacob’s ladders): spring to summer; blue, pink, white, yellow
Polygonatum spp. (Solomon’s seals): spring; white, greenish white
Pulmonaria spp. (lungworts): spring; purple-blue, blue, red
Tiarella cordifolia (tiarella, foamflower): spring; white, pink
Dig deep when you prepare your perennial bed. Plants’ roots will be able to penetrate the friable soil easily, creating a strong, vigorous root system. Water and nutrients will also move easily through the soil, and the bed won’t dry out as fast. As a result, your plants will thrive. Have any necessary soil amendments and organic fertilizers on hand before you start, and add them to the bed once you’ve worked it.
Turn the soil evenly to a shovel’s depth at planting time. Thoroughly incorporate appropriate soil amendments and fertilizer as required. Break up all clods and smooth out the bed before planting. For soil preparation techniques see the Soil entry. If your soil is particularly bad or you’d like to avoid the effort involved in digging a garden, try techniques outlined in the Raised Bed Gardening entry.
Perennials with Striking Foliage
Most perennials bloom for only a few weeks, so it makes sense to think about what they’ll look like the rest of the season. These dual-purpose perennials have especially interesting foliage when not in flower. Try species of Ajuga, Asarum, Bergenia, Epimedium, Hosta, Lamium, Liriope, Saxifraga, Sedum, Sempervivum, Stachys, and Tiarella for three-season interest, and don’t forget ferns and ornamental grasses. Plant name is followed by foliage interest.
Acanthus spp. (bear’s-breeches): shiny; lobed or heart-shaped; spiny
Ajuga reptans (ajuga): striking variegations and colors, including gray, green, pink, and purple
Alchemilla mollis (lady’s-mantle): maple-like; chartreuse
Artemisia spp. (artemisias): ferny; silver or gray; aromatic
Asarum spp. (wild ginger): leathery; glossy or matte; dark green
Bergenia spp. (bergenias): glossy; evergreen; burgundy fall color
Heuchera spp. (alumroots): maplelike; dark purple, silver, reddish, green, often with contrasting veins
Hosta spp. (hostas): smooth; puckered; variegated; green, blue-gray, chartreuse, yellow, cream, white
Houttuynia cordata (houttuynia): heart-shaped; shiny; variegated forms
Lamium spp. (lamiums): green-, yellow-, white-variegated
Polygonatum odoratum (Solomon’s seal): long, graceful shoots; variegated forms
Pulmonaria spp. (lungworts): dark green; gray-or silver-spotted
Rodgersia spp. (rodgersias): huge; maple-like or buckeyelike; bronze
Saxifraga stolonifera (strawberry geranium): silver-veined; reddish undersides
Sedum spp. (sedums): fleshy; many colors; variegated forms
Sempervivum spp. (hens-and-chicks): fleshy rosettes; some red-or purple-tinged
Stachys byzantina (lamb’s-ears): white, gray green, yellow; velvety
Tiarella cordifolia (Allegheny foamflower): maplelike; green with red or purple veining; evergreen
Yucca spp. (yuccas): sharply pointed; large; evergreen; variegated forms
Planting: Plant perennials any time the soil is workable. Spring and fall are best for most plants. If plants arrive before you are ready to plant them, be sure to care for them properly until you can get them in the ground.
Planting is easy in freshly turned soil. Choose an overcast day whenever possible. Avoid planting during the heat of the day. Place container- grown plants out on the soil according to your design. To remove the plants, invert containers and knock the bottom of the pot with your trowel while keeping one hand spread over the soil on top so the plant doesn’t fall to the ground and snap off. The plant should fall out easily. The roots will be tightly intertwined. It’s vital to loosen the roots—by pulling them apart or even cutting four slashes, one down each side of the root mass—so they’ll spread strongly through the soil when planted out. Clip any roots that are bent, broken, or circling. Make sure you place the crown of the plant at the same depth at which it grew in the pot.
Perennials for the North
These perennials flourish in the cooler summers of Northern zones and withstand cold winters to Zone 3. Species of Campanula, Delphinium, Hemerocallis, Papaver, Penstemon, Phlox, Primula, and Veronica are hardy to Zone 2. Many of these same plants will grow as far south as Zone 9, but only a few prosper under hot, humid conditions. Plant name is followed by bloom time and color.
Achillea spp. (yarrows): spring to summer; yellow, white, red, terra-cotta, pink, purple, cream
Actaea racemosa, formerly Cimicifuga racemosa, (black snakeroot): late summer; white
Aquilegia spp. (columbines): spring to early summer; all colors, bicolors
Campanula spp. (bellflowers): spring to summer; blue, white, purple
Delphinium spp. (delphiniums): summer; blue, red, violet, white
Dianthus spp. (pinks): spring; pink, red, white, yellow
Dicentra spp. (bleeding hearts): spring; rose pink, white
Gypsophila spp. (baby’s-breath): summer; white, pink
Hemerocallis spp. (daylilies): spring to summer; all colors except blue
Hosta spp. (hostas): early to late summer; violet, lilac, white
Iris spp. (irises): spring to summer; all colors, bicolors
Papaver orientale (Oriental poppy): early summer; scarlet, pink, white, purple
Penstemon barbatus (common beard-tongue): spring; pink, white
Phlox spp. (phlox): early spring to summer; pink, white, blue
Primula spp. (primroses): spring; all colors
Rudbeckia spp. (coneflowers): summer; yellow
Sedum spp. (sedums): spring to fall; yellow, pink, white
Thermopsis spp. (false lupines): spring; yellow
Veronica spp. (veronicas, speedwells): spring to summer; blue, white, pink
Planting bareroot perennials and transplants requires more care. Inspect the roots carefully and prune off any irregularities. Dig a hole large enough to accommodate the full spread of the roots. Build a mound with tapering sides in the center of the hole. Spread the roots of fibrous-rooted plants evenly over the mound and rest the crown of the plant at its apex. Check to be sure that the crown will end up just below the soil surface. Build up the mound to raise the crown if necessary. Do not plant too deeply!
Perennials for the South
These perennials stand up to the heat and humidity of Southern summers, although most benefit from partial shade in the hottest months. Species of Achillea, Baptisia, Boltonia, Coreopsis, Echinacea, Helianthus, Hemerocallis, Hibiscus, Iris, Rudbeckia, and Verbena will tolerate full Southern sun. Plant name is followed by bloom time and color.
Achillea spp. (yarrows): spring to summer; yellow, white, red, terra-cotta, pink, cream, purple
Asclepias tuberosa (butterfly weed): summer; orange, yellow, red
Baptisia spp. (baptisias): spring to summer; blue, white, yellow, purple
Boltonia asteroides (boltonia): late summer; white, purple, pink
Coreopsis spp. (coreopsis): spring to summer; yellow, red, pink, bicolors
Echinacea spp. (purple coneflowers): summer; mauve, white, yellow, orange, pink
Helianthus spp. (perennial sunflowers): late summer to fall; yellow
Hemerocallis spp. (daylilies): spring to summer; all colors except blue
Hibiscus moscheutos (common rose mallow): summer; white, pink, red
Hosta spp. (hostas): early to late summer; violet, lilac, white
Iris spp. (irises): early spring to summer; all colors, bicolors
Liatris spp. (gayfeathers): summer; mauve
Liriope muscari (liriope, blue lilyturf): late summer; lilac, white
Platycodon grandiflorus (balloon flower): summer; blue, white
Rudbeckia spp. (coneflowers): summer; yellow
Salvia spp. (sages): summer to fall; all colors
Sedum spp. (sedums): spring to fall; yellow, pink, white
Verbena spp. (verbenas): spring to summer; red, pink, purple
Veronica spp. (speedwells): spring to summer; blue, white, pink
Position rhizomes such as those of iris at or just below the soil surface, depending on the species. Spread the roots evenly over a mound of soil as described above. Spread tuberous roots like those of daylilies evenly in a similar fashion. Fill in the planting hole with soil, then firm it down and add more soil if necessary before you water the new plant.
Water plants thoroughly after planting so the soil is completely settled around the roots. Give your newly planted perennials a layer of organic mulch to conserve soil moisture. Provide extra water for the first month or so while plants are becoming established.
Best Perennials for Dry Soil
These tough plants tolerate heat and dry soil, making them useful for spots that the hose can’t reach and nice for sunny meadow gardens. Some actually become invasive and weedy in rich, moist soils, while others survive drought but suffer in humid conditions. All prefer well-drained soil. Plant name is followed by bloom time and color.
Achillea spp. (yarrows): spring to summer; yellow, white, red, terra-cotta, pink, purple, cream
Anthemis tinctoria (golden marguerite): summer; yellow, orange
Armeria maritima (common thrift): summer; pink, white
Artemisia spp. (artemisias): summer; gray, white, yellow
Baptisia spp. (baptisias): spring to summer; blue, white, yellow, purple
Coreopsis spp. (coreopsis): spring to summer; yellow, red, pink, bicolors
Dianthus spp. (pinks): spring; pink, red, white, yellow
Echinops ritro (globe thistle): summer; dark blue
Eryngium spp. (sea hollies): summer; blue, silver-blue
Euphorbia spp. (spurge): spring to summer; yellow, red
Gaillardia × grandiflora (blanket flower): summer; red, yellow, bicolors
Hemerocallis spp. (daylilies): spring to summer; all colors except blue
Kniphofia spp. (torch lilies): late spring; red, orange
Liatris scariosa (tall gayfeather): summer; purple, white
Limonium spp. (statice): summer; blue, red, white, lavender
Linum perenne (blue flax): spring; blue
Rudbeckia spp. (coneflowers): summer; yellow
Salvia spp. (salvias): summer to fall; all colors
Scabiosa spp. (scabious): summer; blue, pink, yellow, white
Sedum spp. (sedums): spring to fall; yellow, pink, white
Solidago spp. (goldenrods): late summer to fall; yellow
Stachys spp. (lamb’s ears): spring; purple
Yucca spp. (yuccas): summer; white
Maintaining Your Perennials
Perennials benefit from some regular care throughout the growing season. In return, they’ll reward you with strong growth and vigorous flowering year after year.
Weeding: Weeds compete for water, nutrients, and light, so weeding is a necessary evil. Catch them while they’re small and the task will seem easier. A light mulch of bark or shredded leaves allows water to infiltrate and keeps weeds down. Mulch also helps soil retain water.
Watering: Regular watering is essential. Most plants need 1 inch per week for best growth. Bog and pond plants require a continual supply of water. Dry-soil plants are more tolerant of a low water supply, but during the hottest summer months, even they may need watering. Water all your perennials with a soaker hose where possible. If using above-ground irrigation, avoid watering during the heat of the day when the water evaporates quickly, and mulch to conserve soil moisture and cut down on watering.
Best Perennials for Moist Soil
Grow these perennials if you have a poorly drained or boggy spot in your yard. True to their streamside origins, most prefer at least partial shade and cool nights. Species of Caltha, Chelone, Filipendula, Iris, Lobelia, Lysimachia, Rodgersia, and Thalictrum tolerate full sun, while Hibiscus and Tradescantia demand it. Plant name is followed by bloom time and color.
Actaea spp., formerly Cimicifuga spp., (bugbanes): late summer to fall; white
Aruncus spp. (goat’s beards): late spring; creamy white
Astilbe spp. (astilbes): late spring to summer; red, pink, white, purple
Caltha palustris (marsh marigold): spring; yellow
Chelone glabra (white turtlehead): summer; white with red tinge
Eupatorium spp. (bonesets): late summer to fall; purple, blue, white
Filipendula spp. (meadowsweets): summer; pink, white
Iris ensata (Japanese iris): summer; pink, blue, purple, white
Iris pseudacorus (yellow flag): early summer; yellow
Iris sibirica (Siberian iris): spring; blue, white, purple, wine red, bicolors
Ligularia spp. (ligularias): summer; yellow, orange
Lobelia siphilitica (great blue lobelia): late summer; blue
Mertensia virginica (Virginia bluebells): spring; blue, white
Monarda didyma (bee balm): summer; red, white, pink, purple
Primula japonica (Japanese primrose): late spring; pink, red, white, purple
Rodgersia spp. (rodgersias): late spring to summer; creamy white, red
Thalictrum spp. (meadow rues): summer; lilac, pink, yellow, white
Tradescantia spp. (spiderworts): summer; blue, pink, white, red
Trollius spp. (globeflowers): spring; orange, yellow
Staking: Staking may be necessary for thin-stemmed plants such as coreopsis, yarrow, and garden phlox. Extremely tall plants such as delphiniums require sturdy stakes to keep flower spikes from snapping off. Heavy, mounding flowers like peonies may need hoop supports (circular wire supports set up on legs) to keep their faces out of the mud. You can also stake up a clump of perennials by inserting three or four stakes around the outside of the clump and then winding twine around the stakes. Or circle clumps with twine, then tie the twine to a sturdy stake.
Staking perennials. For clumping perennials such as peonies, pound in four or more stakes around the clump, ideally just after planting or as shoots emerge in spring. Then wrap strings around the stakes; add tiers of string as the plant continues to grow taller and bushier.
Pinching: Pinching keeps plants bushy. Plants like chrysanthemums and asters have a tendency to grow tall and flop. Pinch them once or twice in spring to encourage production of side shoots. Early pinching promotes compact growth without sacrificing bloom.
Thinning: Plants like delphiniums and phlox produce so many stems that the growth becomes crowded and vigor is reduced. Cut out excess stems to increase air circulation and promote larger flowers on the remaining stems.
Disbudding: Disbudding is another technique used to increase flower size. Peonies and chrysanthemums produce many buds around each main bud. Simply pinch off all but the largest bud to improve your floral display.
Deadheading: Removing spent flowers will help promote production of new buds in many plants. Just pinch or cut off faded flowers, or shear bushy plants just below the flower heads if the plant blooms all at once. Some perennials like baptisias and ‘Autumn Joy’ sedum will not rebloom, and their seed heads are decorative. Leave these for winter interest in the garden.
Winterizing: In autumn, begin preparing the perennial garden for winter. Remove dead foliage and old flowers. After the first frost, cut down dead stems and remove other growth that will die to the ground. (Leave ornamental grasses and other plants that add winter interest.) After the ground freezes, protect plants from root damage due to frost heaving with a thick mulch of oak leaves or marsh hay. Evergreen boughs are also good for this purpose. Snow is the best insulator of all, but most of us can’t count on continuous snow cover. Mulching helps keep the ground frozen during periods of warm weather.
A Sunny Perennial Border
This beautiful flower border is a blaze of color from early summer to frost. If you don’t have room to plant an 8' x 20' border, you can narrow down this plant list to create your own design that fits the space you have available.
- New England aster (Aster novae-angliae)
- ‘Autumn Joy’ sedum (Sedum × ‘Autumn Joy’)
- ‘Moonshine’ yarrow (Achillea × ‘Moon-shine’)
- Ozark sundrops (Oenothera missouriensis)
- Spike gayfeather cultivar (Liatris spicata), mauve-flowered
- Garden phlox cultivar (Phlox paniculata)
- purple-flowered
- white-flowered
- Balloon flower (Platycodon grandiflorus)
- Daylily cultivar (Hemerocallis hybrid), yellow-flowered
- Purple coneflower (Echinacea purpurea)
- Peony cultivar (Paeonia lactiflora), white-flowered
- Siberian iris cultivar (Iris sibirica)
- blue-flowered
- purple-flowered
- Columbine cultivar (Aquilegia × hybrida), yellow-flowered
- Blood red cranesbill cultivar (Geranium sanguineum)
- white-flowered
- pink-flowered
- Obedient plant cultivar (Physostegia virginiana), white-flowered
- Baby’s-breath (Gypsophila paniculata)
- Catmint (Nepeta mussinii)
- Switchgrass (Panicum virgatum)
Dividing: Sooner or later, even the slow-growing perennials become crowded and need dividing. Divide plants in spring or fall in the North and in fall in the South. (Some plants such as peonies should only be dug in fall.) Some fast growers like bee balms, chrysanthemums, and asters should be lifted every 2 or 3 years. They have a tendency to die out in the middle, while new growth forms a circle of growth around the old center of the clump. Lift the plants in spring or fall to cut away any old or dead growth. Take advantage of the bare spot to work the soil, adding compost and fertilizer. Replant the rejuvenated clump in the center of the freshly worked planting hole.
SMART SHOPPING
Perennials
Smart shopping begins at home. Make a list of the plants you intend to buy, then stick to it. Buying at a garden center has an advantage: You can see what you’re getting. Many have display gardens where you can see the mature sizes of the plants. The plants will be larger than those available by mail, and they will become established more quickly. But your selection may be limited. Here are some tips to keep in mind when buying plants at garden centers:
- The best selection is available in spring.
- If you want a specific color, buy a named cultivar.
- Avoid plants that are visibly rootbound. Check the root systems of plants that are leggy or disproportionately large in relation to the size of the pot.
- Choose plants with lush, nicely colored foliage and multiple stems. Avoid plants with dry, pale, or shriveled leaves.
- Check for insects on the tops and undersides of leaves and along stems.
- When buying in fall, plants will look rough. Check the root system first. If it is in good shape, the plant is likely to be healthy.
- If you can’t plant immediately, keep containers in the shade and well watered. Check them daily!
Mail-Order Nurseries
Ordering plants from a catalog or Internet supplier requires trust, since you can’t examine the plants until you have purchased them. Start small. Order from a few nurseries at a time until you get the quality you want.
Some nurseries ship in containers; others ship bareroot. If a nursery sells bareroot plants, order them in fall. Some plants such as irises, peonies, and poppies are only available in fall. To get the most from mail ordering:
- Order early for the best selection.
- Specify desired shipping time when ordering.
- Once they arrive, evaluate plants in the same way you would evaluate plants at the garden center.
- Examine bareroot plants for pests and diseases. Check the roots, crowns, and stems for hidden pests.
- If roots on bareroot plants are not plentiful and in good condition, return the plants.
- Rewrap bareroot plants after examination and store in a cool place until you are ready to plant them.
- Before planting, soak roots of bareroot plants in a bucket of water for a minimum of 1 hour.
- Make all claims of substandard or damaged plants to the supplier immediately.
Perennials from Seed
If you have more time and patience than money to spend on your perennials, buying seed is smart shopping. A packet of seed is much cheaper than the equivalent number of purchased plants (or even one plant!). In exchange for a good buy, though, you must be willing to forgo instant gratification. You’ll need to set up a cold frame or nursery bed and care for your seedlings for 2 to 3 years before they reach blooming size. For more on growing from seed, see the Seed Starting and Seed Saving entry.
Lift and pull or cut apart overgrown clumps of irises, daylilies, and hostas. You’ll know a clump is overgrown because it looks crowded, doesn’t have as large or as many blooms as it used to, and may have died out in the center. You may need to separate large clumps with a shovel; see the Division entry for more on this technique. Replant a reasonably sized clump or group of clumps into freshly prepared soil.
Controlling pests and diseases: On the whole, perennials are tough, durable plants, but they’re not completely problem free. The best way to avoid problems is to give plants the conditions they need to thrive. If you plant a moisture-loving bog plant in a dry, windy site, you’re asking for trouble. Poor or inappropriate growing conditions stress plants, and a stressed perennial is more likely to lose the struggle against an invading pest or ailment.
If you know that a perennial is prone to a certain problem, either choose another species or look for a resistant cultivar. Garden phlox (Phlox paniculata), for instance, is mildew prone, and there’s nothing like powdery mildew to ruin the appearance of a plant. The best way to avoid this is to plant cultivars of a similar but mildew-resistant species, wild sweet William (Phlox maculata). If you must have garden phlox or other mildew-prone perennials, choose a mildew-resistant cultivar like ‘David’, ‘Bright Eyes’, or ‘Tracy’s Treasure’. Plant in a sunny site with good air circulation, thin plants to the strongest 4 or 5 shoots so air can circulate in the clump, water from the bottom to keep the foliage dry, and never water at night.
Similarly, when confronted by a pest, start at the low end of the control spectrum rather than rushing for the sprayer. Hand picking insects may not be pleasant, but it’s often effective. A simple soap spray will control most pests. If a pest is a major problem on the same perennial every year, it’s better to replace it with one of the many pest-free perennials rather than waging a time-consuming and discouraging battle again each season. For more on organic pest and disease control techniques, see the Pests entry and the Plant Diseases and Disorders entry.
Propagating Perennials
Time and patience are the only requirements for growing your own perennials. Seeds take longer to produce flowering plants than cuttings, but not all perennials can be grown from cuttings. Of course, you can also propagate by dividing—cutting apart established clumps of perennials.
Seeds: Perennial seeds are available from most major seed companies, although some offer a wider variety than others. Plant societies often have seed exchanges. You can also save seeds of your own plants and trade with friends. Note: Most cultivars cannot be produced from seed. They must be propagated by cuttings or division.
If you leave seed heads of your perennials to mature in the garden, you’ll get self-sown seedlings. Transplant these to appropriate spots or trade them with friends. For more on growing plants from seed, see the Seed Starting and Seed Saving entry.
Cuttings: Cuttings are a quick and easy way to increase perennials. Unlike seed, which produces seedlings genetically different from the parent plants, all cuttings taken from a single plant will be identical to the parent plant.
Take cuttings in late spring or early summer for best results. Cut a 3- to 6-inch section from the stem and strip the leaves off the lower half of the cutting. If the leaves are large, cut them in half. Stick the cuttings in a 1:1 mixture of peat and perlite. Keep them in a high-humidity environment for 1 to 2 weeks or until they are well rooted.
Transplant them to pots or directly into the garden. To learn how to grow cuttings in a nursery bed, see the Nursery Bed entry.
PERMACULTURE
Combining the best of natural landscaping and edible landscaping, permaculture aims for a site that sustains itself and the gardener. The ultimate purpose of permaculture is to develop a site until it meets all the needs of its inhabitants, including food, shelter, fuel, and entertainment. (The word permaculture was coined in the mid-1970s by two Australians, Bill Mollison and David Holmgren.) While it’s the rare home gardener who can follow permaculture principles to the ultimate degree, most can borrow ideas from permaculture to create a new way of landscaping based on production and usefulness.
Gardening and Permaculture
Permaculture emphasizes the use of plants that are native or well adapted to your local area. Plant things you like, but make sure they have a purpose and somehow benefit the landscape. Plants such as fruit trees provide food as well as shade; a patch of bamboo could provide stakes for supporting pole beans and other vining plants. Along with a standard vegetable garden, permaculture gardeners would grow many types of perennial food plants too, such as arrowhead, sorrel, chicory, and asparagus.
Like all gardeners, permaculture enthusiasts love plants for their beauty and fragrance, but they seek out plants that offer practical benefits along with aesthetic satisfaction. Instead of a border of flowering shrubs, for instance, a permaculture site would have a raspberry or blackberry border.
Disease-prone plants such as hybrid tea roses and plants that need lots of watering or other pampering are not good permaculture candidates. Choose a native persimmon tree that doesn’t need spraying and pruning, for example, instead of a high-upkeep peach tree. Consider the natural inclinations of your site along with the needs of its inhabitants, and put as much of your site as possible to use. Work with the materials already on your site, rather than trucking in topsoil or stone. Remember that a permaculture design is never finished, because the plants within a site are always changing.
There is no set formula for developing a permaculture design, but there are practical guidelines. Here are some of them:
Copy nature’s blueprint and enhance it with useful plants and animals. Think of the structure of a forest and try to mimic it with your plantings. A canopy of tall trees will give way to smaller ones, flanked by large and small shrubs and, finally, by the smallest plants. Edge habitats, where trees border open areas, are perfect for fruiting shrubs, such as currants, and for a variety of useful native plants, such as beargrass (Xerophyllum tenax), which is used for weaving baskets. Mimicking these natural patterns provides for the greatest diversity of plants.
Stack plants into guilds. A guild includes plants with compatible roots and canopies that might be stacked in layers to form an edge. As you learn more about your site, you’ll discover groups of plants that work well together. For example, pines, dogwoods, and wild blueberries form a guild for acid soil.
Make use of native plants and others adapted to the site. Plan for diversity.
Divide your yard into zones based on use. Place heavily used features, such as an herb garden, in the most accessible zones.
Identify microclimates in your yard and use them appropriately. Cold, shady corners, windswept places in full sun, and other microclimates present unique opportunities. For instance, try sun-loving herbs like creeping thyme on rocky outcroppings; plant elderberries in poorly drained spots.
Permaculture designers are now working to conceptualize and create whole communities that embody permaculture concepts. If permaculture intrigues you, there’s a wealth of opportunities to learn more about it through books, Web sites, and hands-on courses; see Resources on page 672 for examples.
PERSIMMON
Diospyros kaki (Asian); D. virginiana (American)
Ebenaceae
Persimmons are attractive trees with large, leathery leaves that turn bright colors in fall. The bright orange fruit often hangs on the branches long after the leaves drop. Persimmon fruit can be very astringent before the fruit is mushy ripe, but some cultivars can be enjoyed while firm.
Selecting trees: American persimmons are hardy to –25°F, bear small fruit, and grow to 40 feet. Most bear better crops if you have two trees. Buy named cultivars for reliable fruit. ‘Meader’ has only female flowers and bears seedless fruit if not cross-pollinated. Asian persimmons are hardy to 0°F, bear large fruit, and grow to 30 feet, and most are self-pollinating. Buy young persimmon trees, because older trees have long taproots and don’t transplant well. Also check whether you are buying an astringent or non-astringent cultivar.
Planting and care: Persimmons bloom late and usually avoid frost damage. They tolerate a wide range of soils but perform best in fertile, well-drained soil. Give Asian persimmons a sheltered location. Space trees 20 feet apart to avoid crowding. Persimmons need little fertilizer. A thick organic mulch will conserve water and supply plenty of nitrogen for new growth. Refer to the Fruit Trees entry for additional information on planting and care.
Pruning: Persimmons require only light pruning, but if you want to keep them small, prune each spring before bud break. Train your tree to a central leader as shown on page 244. Cut back long shoots to an outward-facing bud or branch. Spread new scaffolds when they are young to make them strong and to reduce upward growth. Persimmons flower on the current season’s wood. Encourage new growth by cutting out old branches periodically and allowing new ones to replace them. Head back long branches to encourage side branches.
Persimmons produce a lot of root suckers. If not removed, they will form a dark, crowded thicket. Discourage suckers by spreading a thick layer of organic mulch such as compost over the root zone. Avoid cultivating or tramping over the roots, and remove suckers whenever you see them.
Thinning: Young trees may drop immature fruit. However, if an older tree continues to drop fruit, the tree is probably suffering from some kind of stress. Check nutrient levels, winter temperatures, and the severity of your pruning. On Asian cultivars, you may need to hand thin to encourage larger fruits; American cultivars bear only small fruit.
Problems: Persimmons are reasonably pest free in the home garden. They can be troubled by scale and borers, and by persimmon psylla and citrus mealybug in the South. See the Pear entry for information on psylla; see pages 249 and 458 for controls for other pests. In areas where persimmon wilt is a problem, plant Asian cultivars, which are resistant. Paint the trunk and main branches with diluted white latex paint to prevent sunscald. If your tree often fruits every other year, you need to thin the fruit more heavily so the tree is not overstressed.
Harvesting: Persimmons mature in mid-fall. Use pruning shears to clip off the ripe fruits when they are still slightly firm. Let astringent cultivars get very soft before eating. Non-astringent cultivars can be eaten while firm. Ripening often coincides with frost, but chilling is not essential for softening and sweetening. Freezing or drying can remove astringency. Or ripen fruit by putting it in a bag with an apple for a few days.
PESTS
From aphids to slugs, pests are an occasional problem in everyone’s garden. On rare occasions, a pest problem escalates from a mild annoyance to an onslaught that can ruin the looks of a flower garden or the harvest from the kitchen garden. The good news is that there are plenty of ingenious and safe methods that organic gardeners can use to outwit insect pests and prevent major problems.
Insects and insectlike creatures aren’t the only pests that can interfere with our gardening efforts, though. Hungry animals and plant diseases are lumped into the pest category as well. You’ll find information about combating animal pests in the Animal Pests entry, and advice for dealing with disease problems in the Plant Diseases and Disorders entry.
The Organic Outlook on Pests
In conventional gardens and landscapes, gardeners often set perfection as the goal, and they use chemical insecticides, fungicides, and herbicides as their tools for ensuring that no leaves ever have holes in them, no weeds appear among the flowers, and no spots or rots ever invade the beds. Organic gardeners have a different outlook. They understand that pests are part of nature’s plan and that, in a well-tended garden, plants will rarely suffer from serious pest problems.
Basic organic gardening practices bring your yard and garden into natural balance. You create a stable system where there are no huge population explosions of pests, but rather a diverse ecosystem where pest populations are regulated naturally. If you take good care of your soil and plants, your garden will be healthier and have fewer problems with insect pests, diseases, and weeds.
Garden Patrol
One of the best ways to minimize pest woes is to keep a watchful eye out for problems. Make it a habit to walk through your garden at least three times a week—daily is best—looking carefully at your plants. The list on page 447 offers suggestions of what to look for on your patrols.
Preventing Pest Problems
As you plant and care for your garden, there are plenty of useful practices you can employ to make it less hospitable to pests, including choosing pest-tolerant plants, keeping plants healthy at all times, minimizing residues that can harbor pests, timing plantings to avoid pests, and planting special plants that attract and shelter beneficial insects (which help control pest insects).
Pest-Tolerant Plants
Plant breeders have made great strides in developing disease-resistant cultivars of food crops, roses, trees, and many other plants, but developing plants that are resistant to insect pests is a bigger challenge. However, some varieties have physical characteristics that make them more or less attractive to pests. For example, corn cultivars with good husk cover are least damaged by corn earworms, and imported cabbageworms rarely trouble purple cabbage and broccoli varieties.
Healthy Plants
Plants grown on fertile soils with adequate water tolerate insect attack better than plants suffering from nutrient deficiency, water stress, crowding, or low light levels. Healthy plants also mount their own chemical defenses against insect pests and diseases faster.
Healthy soil: Healthy soils contain a complex community of soil organisms that are vital to plant health. Mycorrhizal fungi protect fine roots from infections and aid plants in taking up nutrients. Nitrogen-fixing bacteria live symbiotically with roots of legumes, beneficial fungi trap harmful nematodes, and many fungi and bacteria produce antibiotics that suppress pathogens. Nutrient deficiencies and imbalances make plants more attractive to pests. Conversely, overfertilizing with nitrogen can cause soft, lush growth, which is very attractive to sucking pests such as aphids.
Proper moisture: Water-stressed plants are more attractive to pests and more susceptible to diseases. For example, aphids and thrips are more likely to attack wilted plants, while wet, waterlogged soil encourages soilborne diseases. Plants usually grow best when moisture is maintained at a constant level. Most plants need about 1 inch of water per week from rain and/or irrigation while they are actively growing. Learn your plant’s specific likes and dislikes. Some plants have critical times during their development when sufficient water is crucial.
Be sure to water effectively. Apply water to the soil, below mulch if possible. Avoid routinely wetting leaves, because water helps spread many leaf diseases and may burn leaves in full sun. Water thoroughly: A long, slow soak every few days is much better than a short sprinkle every day. For more information on effective watering, see the Watering and Drip Irrigation entries.
Mulches: Mulching saves water, controls weeds, and may add organic matter. It provides pest control by acting as a barrier, preventing soilborne problems from reaching plants, or providing a home for beneficial insects. You can mulch with a variety of organic or inorganic materials. A deep straw mulch in the potato patch can help prevent damage caused by Colorado potato beetles. Reflective aluminum mulch confuses aphids and prevents them from landing on your plants. For more information on what materials to use and how and when to apply them, see the Mulch entry.
Spacing and training: Proper spacing, staking, and pruning can reduce pest problems. Crowded plants are weak and spindly and are more prone to disease and insect problems. Staking keeps plants from coming in contact with soilborne diseases, prevents them from being stepped on or damaged, and increases air movement. Pruning plants increases air movement and makes it easier to spot insects before they become a major problem. Leafy crops can be their own living mulch and suppress weeds if spaced so that the plants just touch at maturity.
Clean Gardening
Keeping the garden clean is a basic principle of preventing pest problems. Don’t bring diseased or infested plants into your garden, and remove pest-ridden plant material from the garden promptly.
The Garden Detective
Plant problems fall into three general categories: insects and animals, disease, and cultural problems (water stress, heat or cold, nutrient imbalances). Symptoms caused by different problems may look remarkably similar. In order to diagnose a problem correctly, you need to investigate a number of possibilities and do some detective work.
- Look at the entire plant and those around it. Is just one plant, or is an entire row affected? Is the whole plant affected, or just part of it? Does it seem to be random, or is there a distinct pattern, such as only new growth that’s affected?
- Check the undersides of leaves and the stems, flowers, and roots for insects, eggs, webs, or damage such as borer holes. Examine the affected areas with a hand lens, looking for tiny insects or fungal growth.
- Collect sample insects and samples of damaged leaves for later identification. Put samples in pill bottles or plastic bags.
- Do some research to identify the pests. The chart on page 663 can help you decide what type of problem you may have. Pest guides and problem-solving garden books can help, too. Some are arranged by plant type and list the common problems for each; see Resources on page 672. Ask knowledgeable gardeners, garden center employees, or extension agents for help, too.
- Once you have identified the problem, find out as much as you can about it. Then develop a plan to control it.
- Some problems are hard to diagnose. Don’t despair; give the plants the best care you can. Plants often recover when conditions improve. But if more plants develop the same symptoms, put your detective hat back on.
Don’t bring in problems: Check all new plants for signs of insects, disease, or hitchhiking weeds. Thoroughly inspect leaves, buds, bark, and if possible, roots. Discard, reject, or treat infested plants. Choose certified disease-free plants and seed when possible. Avoid buying grass or cover-crop seeds that are contaminated with weed seeds, and avoid hay or other mulches that contain weed seeds.
Clean up pest-damaged plants: Pull up diseased plants or prune off damage. Burn them, put them in sealed containers for disposal with household trash, put them in the center of a hot compost pile, or feed them to animals. Picking up and destroying dropped fruit weekly is an effective way to reduce infestations of apple maggots, currant fruit flies, codling moths, and plum curculios.
Clean up crop residues: Good sanitation includes cleaning up all crop residues promptly. Compost them well or turn them under. Cultivating to incorporate crop residues into the soil after harvest kills pests, including corn earworms, European corn borers, and corn rootworms.
Solarizing soil: Another approach to “cleaning” the soil of pest insect eggs and pupae is by using heat from the sun to kill them. This technique of covering soil with clear plastic to raise soil temperature is called soil solarization. It also works for killing some types of nematodes, disease organisms, and weed seeds. To learn more about this technique, turn to page 473.
Animal Helpers
We tend to think of animals and other critters as pests first, but many animals really are a gardener’s friend because they eat insects, rodents, and other garden pests. In summer, a toad can put away 3,000 grubs, slugs, beetles, and other insects every month. A bat can catch 1,000 bugs in one night. You’ll find information on the more lovable beneficial animals in the Bats, Birds, Earthworms, Toads, and beneficial Insects entries. Read on to learn about an unlikely trio of garden helpers: spiders, snakes, and skunks.
All-Star Spiders
Cars, cigarettes, and high-fat diets kill far more people every year in the United States than spiders have in a whole century. Yet more people panic at the sight of a spider than at more legitimate threats.
Actually, spiders are a lot of fun to watch. The gold and black garden spider spins a new web each day, gluing 1,000 to 1,500 connections among strands to form the pattern it has made perfectly since its first try. The spinner eats the old web before making a new one, recycling the silk proteins. As you brush by leaves in the garden, jumping spiders will leap aside in fast, basketball-style arcs.
Most spiders have a trace of venom, but only two spiders in the United States—the black widow and the brown recluse—have enough to injure a human. The female black widow has a glossy black body a little smaller than a garbanzo bean, marked on the underside with a red hourglass. It weaves a small matted web that it rarely leaves. These spiders are placid and bite only if extremely provoked. The bites are painful, but can be treated.
The brown recluse or violin spider lives only in the Southern half of the United States (south of Kansas). Its distinguishing feature is a dark violin-shaped patch on the top of the orangish yellow body segment behind its head. Its bites form deep sores that can linger for months.
To avoid mishaps with either of these spiders, don’t reach with bare hands into dark crevices of woodpiles, tool sheds, and the like. Shake out clothing and towels, especially in rustic cabins or garages, before putting them on or holding them against your body. Avoiding those two unpleasant spiders leaves almost 3,000 species in the United States to enjoy without alarm. Some of these also bite if teased or startled, but they don’t do more damage than a mosquito bite.
Of the 115 species of snakes in North America, only four kinds are poisonous: rattlesnakes, copperheads, coral snakes, and cottonmouths, also called water moccasins. Most of the snakes that find their way to a backyard will only bite if handled or stepped on, and even then the bite is harmless. In fact, garden pests, especially insects and rodents, are the real prey of snakes.
Beneficial backyard snakes include the common garter snake, eastern ribbon snake, western terrestrial garter snake, green or grass snake, and brown snake, all of which eat slugs, snails, and insects. The corn snake, black rat snake, and milk snake eat mice and rats. Most of these beneficial snakes are beautiful, too.
How can you tell if a snake is poisonous? Rattlers, copperheads, and cottonmouths are all thick-bodied snakes with large, triangular heads. A rattlesnake will rattle a warning if threatened. The position of the bands on the red, black, and yellow coral snake tells its story: “Red next to yellow kills a fellow.”
If you don’t like the idea of snakes patrolling your garden, take a few simple precautions. First, don’t mulch your plots. Mulch provides shelter and attracts mice, a favored food. Keep your yard cleaned up and stack wood away from the house: Cordwood, junk, brush piles, and other debris will attract snakes to your yard. So will dog or cat food set outdoors and left unattended.
Skunks Earn Their Stripes
At the turn of the century, hops growers in New York State pushed for regulations protecting, of all things, the skunk. The growers claimed that skunks were controlling the dreaded hop grub. Modern gardeners have been less enthusiastic, since in addition to their offensive odor, skunks dig holes in lawns. Actually, the skunks are digging for grubs of Japanese beetles and other pests.
Skunk texts state that the animals take alarm at menaces within 25 feet and that they can spray accurately at 12 to 15 feet. Yet skunks seem inclined to mind their own business and ignore all but loud, blatant menaces like cars and charging dogs.
The bigger concern with skunks is rabies. They’re the number one carrier of the disease, followed by raccoons. Stay away from skunks that seem disoriented or too bold, and have pets vaccinated.
Timed Planting
Getting the timing right can help your plants fight pests and diseases. Here are some examples:
Seeds planted before the soil has warmed up in spring are more susceptible to disease. Learn the soil temperature each crop requires to germinate, and use a soil thermometer to determine proper planting time.
Some pests have only 1 to 2 generations a year. You can reduce damage by scheduling planting or harvesting times to avoid peak pest populations. For example, to avoid damage from cabbage root maggots, plant radishes so they’ll mature before the first generation of these pests appear, and delay setting out cabbage-family plants until after the first generation has passed.
Rotating the position of crops from year to year in your garden may also help control certain insect pests, especially if you have a very large garden. See the Crop Rotation entry for more details.
Companion Planting
Neat rows or patches of a single crop make ideal places for pests to thrive. Many organic growers interplant two or more crops or combine certain companion plants with a crop to help reduce pest damage.
A few successful plant combinations work by directly repelling or confusing pests, or by changing the microclimate around the crop. Planting cabbage seedlings among taller plants that provide shade helps protect them from flea beetles, which prefer to feed in full sun. Other companion plants attract adult beneficial insects. After eating, the beneficials lay their eggs among the pests on nearby plants. When the predatory offspring hatch, they attack the pests.
Interplanting crops with different harvest dates also makes good use of garden space. One crop is harvested as the second needs more room to spread out and mature. When interplanted with other plants, legumes may help provide them with nitrogen. For more information on what combinations work, see the Companion Planting and Herbs entries.
Biological Controls for Insect Pests
Biological controls are living organisms—insects, animals, parasitic nematodes, and microbes that are predators or parasites of pest insects. Encouraging these naturally occurring helpers in your yard and garden is a nontoxic, non-harmful way to help minimize pest problems. Some biological controls are also available as commercial products you can apply in your garden. Specialty companies also raise some types of beneficial insects, such as lady beetles and aphid midges, for farmers and gardeners to release in their greenhouses, fields, and gardens.
Beneficial Insects and Animals
Conserving and attracting native beneficial insects, birds, and animals is one of the best and most economical ways for gardeners to control pests. In a well-balanced garden, thousands of beneficial species do most of the work of suppressing pests for you. Learn to identify your helpers and find out what they like. Attract and encourage them to stay by providing food and nesting sites. For more information on beneficials, see the beneficial Insects, Birds, Bats, and Toads entries.
Releasing commercially raised beneficial insects can be highly effective in greenhouses and large-scale plantings, but usually isn’t very effective for bringing a specific pest problem in a home garden under control. You’ll be more successful if you create habitats that attract the native beneficial in your area, and let them wrap up your pest problems for you. For more on this, see the beneficial Insects entry and page 6.
Microbial Products
Microbial controls are strains of disease organisms that kill garden pests.
Bt: Some of the most widely sold biological controls in the world are strains of Bacillus thuringiensis (Bt). Bt kills many species of caterpillars, beetles, flies, and mosquitoes. Bacillus thuringiensis bacteria produce crystals and spores that paralyze the digestive tract of certain insect larvae. Bt products are nontoxic to mammals, are specific to the target pest, do not harm beneficial insects, and may be used right up to harvest. There are several Bt varieties. Btk (B.t. var. kurstaki) controls cabbage looper, cabbageworm, tomato horn-worm, fruitworms, European corn borer, and similar larvae. Bti (B.t. var. israelensis) controls mosquitoes, black flies, and fungus gnats. Btsd (B.t. var. san diego) controls small larvae of the Colorado potato beetle. Unfortunately, many Btsd products are manufactured using genetic engineering processes, so they’re not allowable for use by certified organic farmers. Concerned home gardeners may want to avoid these products too. To learn more about genetic engineering and its impact on home gardens, turn to page 25.
Milky disease: Milky disease infects the grubs of the Japanese beetle and its close relatives. The disease is caused by bacteria (Bacillus popilliae and B. lentimorbus) commonly called milky spore bacteria. Once established, milky disease will persist in the soil for many years (not as long in areas with harsh winters).
Spinosad: Spinosad is a microbial product that contains toxins produced by an actinomycete (Saccaropolyspora spinosa), which is a type of bacterium. It controls fire ants, leaf-eating caterpillars, and some other types of pests. It’s a relatively new type of microbial control, and scientists are still studying its effectiveness in controlling different types of pests as well as its possible effects on beneficial insects.
Beauveria bassiana: This is a fungus that can kill aphids, Colorado potato beetles, whiteflies, and other pests. It can also harm beneficial insects. Beauveria bassiana products work best in cool and moist conditions.
Beneficial nematodes: Some nematodes parasitize insect larvae and grubs. They attack an insect and release bacteria that paralyze and kill the insect within 2 to 4 days. The nematode then feeds on the dead insect and reproduces rapidly. About 10 to 20 days later, huge numbers of nematodes leave the dead insect in search of new victims. Their larvae can survive for long periods in the soil, but for the greatest effect, you need to release more each year. Because nematodes perish in sunlight or dry places, they are most useful against pests in soil or hidden locations. Steinernema carpocapsae and Heterorhabditis bacteriophora nematodes are two of the most widely used species. It’s critical to follow package directions precisely when applying nematodes.
Barriers and Traps
Barriers such as floating row covers are among the most effective ways to prevent pest damage because they stop the pests from reaching the crop in the first place, or deter pests from feeding if they do reach the plant.
Traps generally consist of one or more attractive components or lures (usually a color, odor, or shape) and a trapping component (usually sticky glue, a liquid, or a cage). Traps are used in two ways: to catch enough individual insects to prevent significant plant damage, or to monitor the emergence or arrival of a pest.
When using traps to control pests directly, judge their effectiveness by the reduction in plant damage, not just by the number of dead insects in the trap. If damage does not decrease, try other controls. Monitoring traps are useful for timing application of a control product to stop a pest problem quickly.
Homemade Traps
Here are a few simple traps you can make yourself.
Sticky traps: You can make sticky traps from wood, cardboard, or stiff plastic. Paint the base with a coat of primer and two coats of bright yellow or medium blue paint. Coat with a sticky compound using a paintbrush, or spread it on with a knife. Use stiff adhesives like Tanglefoot for large insects, and thinner glues such as Stiky Stuff or STP oil treat-ment for small insects. Scrape off insects and recoat as needed. To make apple maggot traps, paint plastic apple-size balls red and coat them with a sticky substance. Plastic soda bottles make good cherry fruit fly traps—paint the shoulders of the bottle yellow and fill the bottle with lure.
Traps to use with pheromone lures: You can make a simple trap from a 1-quart, plastic ice-cream or yogurt container. Cut three large holes in the upper half of the sides. Paint the lid, or line it with cardboard to shade the lure. Tape a commercial lure to the inside of the lid. Fasten the trap to a sturdy stake. Fill the bottom half of the container with soapy water and snap on the lid, secur-ing the lure inside the trap.
Floating row covers: Floating row covers of spunbonded polypropylene material improve plant growth and extend the growing season. They are also excellent barriers to such insect pests as carrot rust flies, cabbage maggots, flea beetles, and Mexican bean beetles. They also stop aphids and other insects whose feeding transmits plant diseases. In addition, row covers deter some small animals and birds that might feed on crops. For more information on types of row covers and how to work with them, see the Row Covers entry.
Fences and netting: Deny larger animal pests access to your garden riches with fences, barriers, repellents, and scare tactics. See the Animal Pests entry for specific ways to frustrate hungry moochers.
Cutworm collars: These collars fit around transplant stems to protect them from nocturnal cutworm raids. To make collars, cut strips of lightweight cardboard about 8 × 2½ inches, overlap the ends to make a tube, and fasten with tape. Or cut sections of cardboard tube such as the inner tube from a paper-towel or toilet-paper roll to similar dimensions. When transplanting, slip a collar over each plant and press it into the soil around the stem so about half of the collar is below the soil line.
Rootfly barriers: Tar-paper squares are an old-fashioned and effective barrier to cabbage root flies (adult form of the cabbage root maggot), preventing them from laying their eggs around the roots of cabbage-family plants. Cut tar paper into 6- to 8-inch squares and make a small X-shaped cut in the center of each. Slide the square over the plant and flat against the soil, press the center flaps firmly around the stem, and anchor it with pebbles.
You can also make root-fly barriers out of heavy cloth, pieces of old carpeting, or foam rubber.
Tree bands: Tree bands are effective against pests that can’t fly, such as snails, slugs, ants, and gypsy moth caterpillars. Some prevent pests from crossing; others actually trap pests.
Make cloth tree bands from strips of heavy cotton cloth or burlap about 15 inches wide and long enough to form a generous overlap when wrapped around the trunk. Tie the band to the trunk with a string around the middle of the lower half to make a dead end for creatures climbing up the tree. Check daily and destroy any pests trapped in the material.
Make corrugated cardboard tree bands by wrapping long strips around the trunk several times, with the exposed ridges facing in, and tying snugly with string. These bands attract codling-moth caterpillars looking for a sheltered place to spin their cocoons. Check for and destroy cocoons weekly.
Sticky tree bands: Pests get caught on sticky bands when they try to cross them and eventually die. Paint a 3-inch band of sticky compound all the way around the trunk of mature trees, reapplying as needed. Younger trees may be damaged by the compound. Instead, wrap a strip of fabric tightly around the trunk and cover that with a strip of plastic wrap. Apply the sticky compound to the plastic wrap. When the barrier loses effectiveness, replace the plastic.
Copper barriers: Strips of copper sheet metal make an excellent and permanent barrier against slugs and snails. Fasten them around the trunks of trees and shrubs, wrap them around legs or edges of greenhouse benches, or use them to edge garden beds. Be sure that there are no alternate routes over the strips for slugs to get to the plants. Pull or cut back leaning or overhanging weeds and plants.
To install a copper barrier around a garden bed, press the edge of a 3- to 4-inch-wide strip about 1 inch into the soil around the entire perimeter of the bed. Bend the top edge outward at a right angle to form a ½-inch lip. Eliminate slugs from inside the barrier by using slug traps and by leaving the soil bare as long as possible.
Kaolin clay: This very fine clay is sprayed on plants to repel insects. It may also prevent some types of disease organisms from penetrating plant surfaces. It is mixed with water and applied as a spray. It can deter many kinds of leaf-feeding beetles, including flea beetles, cucumber beetles, and Japanese beetles, as well as leafhoppers and thrips.
Dusty barriers: Dusts that have sharp particles, such as a layer of cinders or diatomaceous earth (DE), scratch the protective outer coating of insects and slugs, causing them to die from dehydration. Dusts work best during dry conditions, renew them after a rain.
Keep in mind that these dusts, particularly diatomaceous earth, may kill as many or more beneficial insects than they do pests. DE is a good control for pests like ants in indoor situations, but be very cautious about using it in the garden.
To deter cabbage root maggots from laying eggs, sprinkle wood ashes, DE, or lime in a 6inch-wide ring on the soil surface around cabbage-family transplant stems.
Colored sticky traps: Colored sticky traps are useful to control or monitor a variety of species. Bright blue traps are suitable for monitoring flower thrips numbers; white traps attract tarnished plant bugs, but they also attract beneficial flies, so should be used only early in the season. Yellowish orange traps lure carrot rust flies.
Some Handy Hints
When you’re looking through catalogs or Web sites at all the products available to help prevent and control garden insect pests, don’t forget that one of the best tools for controlling insects is your own hands.
Hand picking insects is an effective, though rather tedious, way to control light or moderate infestations of large, easy-to-see caterpillars, such as tomato hornworms or cabbage loopers. Here are examples of some other pests you can hand pick:
- Dig cutworms out of their daytime hiding place at the base of plants.
- Pick and destroy spinach or beet leaves with leafminer mines.
- Scrape gypsy moths’ egg masses off tree trunks.
- Pry newly hatched corn earworms out of the tips of corn ears before they can get very far into the cob.
Shaking pests from plants is a variation of hand picking and works especially well for heavy beetles, such as Japanese or Colorado potato beetles and plum curculios. Shake or beat them off the foliage onto a sheet of plastic, then pour them into a pail of soapy water. This is especially effective in the early morning when the pests are still sluggish.
Vacuuming is a high-tech version of hand picking that works well for removing adult whiteflies from tomato plants in a greenhouse. Some commercial growers pull giant bug vacuums behind their tractors to suck up pests. You can achieve similar results by using a handheld portable vacuum cleaner to suck up those pesky whiteflies, and try it for leafhoppers, Japanese beetles, and tarnished plant bugs, too. Be sure to dump the insects into soapy water afterward to kill them.
Yellow sticky traps are effective controls for whiteflies, fungus gnats, and imported cabbage-worms. However, they work only as monitors for thrips and aphids.
Apple maggot traps: Red spheres covered with sticky glue attract female apple maggot flies and are often the only control necessary in a home orchard. Starting in mid-June, hang one trap in a dwarf tree and up to six traps in a full-sized tree, renewing the glue every 2 weeks. Some research shows that attaching an apple-scented lure to the trap increases its attractiveness, but not necessarily to the target pest—other related species may gum up the trap instead.
Cherry fruit fly traps: Yellow sticky traps catch cherry fruit flies if a small bottle of equal parts water and household ammonia or a commercial apple maggot lure is hung up with the trap. Hang one trap in each tree or four traps in a small orchard, and renew the sticky glue and the ammonia bait as necessary.
Yellow water traps: Fill a bright yellow pan or tray with water, to which a small amount of liquid soap has been added, to attract and drown aphids. These traps are effective monitors, but not controls. They also attract tiny beneficials; remove the traps if this happens.
Traps with pheromone lures: Pheromones are chemical cues that insects use to communicate with others of their species. Sex pheromones are wafted onto the air by females to attract males, who follow the direction of the odor until they find a mate. Synthetic pheromones are available in long-lasting lures and are widely used in sticky traps to monitor pest populations, especially the various species of moths that attack fruit trees. When enough pheromone traps are used, they can control the population by trapping so many males that a significant portion of the females go unmated and don’t lay eggs.
Commercial lures are long lasting, and many are available in small quantities for home use and can be incorporated into homemade traps. Set out traps about 2 to 3 weeks before the target pest is expected to emerge; one trap is usually enough for a home orchard or garden. Check the traps daily or weekly; follow package directions.
Pheromones can also be used without traps to control pests. When large numbers of pheromone lures are put out, the air becomes saturated with aroma and males can’t locate females to mate. Twist ties impregnated with pheromones are available for controlling oriental fruit moth and other pests.
Food lures: Slugs and snails are attracted to stale beer, spoiled yogurt, or a mixture of yeast and water. Set out the bait in saucers or tuna cans, buried with the lip of the container level with the soil surface, so the pests fall in and drown. Put a cover with holes in it on the trap to keep rain from diluting the beer and to keep large animals from drinking it.
Pheromones
Pheromones are hormonelike chemicals produced and emitted by insects and other animals to communicate with other members of their species. They are highly specific and can attract insects from great distances. Pheromone products are available for many pests, including peach tree borers, codling moths, corn earworms, cabbage loop-ers, apple maggots, and Japanese beetles.
Traps baited with pheromones are used to keep track of specific pest populations. Small capsules containing pheromones are placed inside cardboard traps coated with a sticky material. The species attracted to the pheromone flies into the trap and gets caught in the glue. Gardeners and orchardists may also be able to control certain pests by hanging large numbers of traps. Pheromone lures without traps confuse pests and keep them from finding food or mates.
Food traps: Control onion maggots by planting sprouted or shriveled onions between rows of onion seeds in early spring. The onion maggot flies lay their eggs in the soil nearby, and the maggots burrow into the trap onions. About two weeks after the trap onions sprout, pull and destroy them to prevent the next generation of flies from developing.
If wireworms are a problem for you, you can use a trap to reduce their numbers before you plant. Cut potatoes in half and poke a stick into each to serve as a handle. Bury the pieces of potato in the soil in early spring. Wireworms will be attracted to the trap potatoes; check the traps every few days, and destroy the wireworms or replace the potatoes.
Trap crops: Plants that are more attractive to certain pests than the crop you want to protect are useful as trap crops. For example, dill or lovage lures tomato hornworms away from tomatoes, and early squash is useful to trap pickleworms before late melons are set out. Pull and destroy trap plants as soon as they are infested, or the pests may reproduce on the crop and thus provide a larger pest population.
Sprays and Dusts
In the rare instances when an insect pest could cause serious injury to plants, you may need to use an organic insect-killing product such as insecticidal soap or neem. In some cases, 1 or 2 well-timed applications of a product like spinosad while the first generation of a pest is just emerging can knock back the pest and head off the crisis.
Botanical sprays (sprays that contain plant-derived substances that can kill pests) such as neem break down into more-harmless compounds in a relatively short time. Some sprays and dusts are less toxic than others to beneficial insects and other living things. Note that a number of botanical sprays widely used by organic gardeners decades ago—rotenone, nicotine, ryania, and sabadilla—are no longer recommended because of their toxic effects on people or the environment. Pyrethrin is a botanical spray that’s still in use, although it should be used with caution (see page 460).
Always choose the least toxic but most effective method available. When using commercial products, follow the directions on the label. Caution: Do not mix products together or add activators or boosters unless the label directs you to do so. To be safe when you apply these products, follow these precautions:
Keep all garden sprays and dusts in their original container with product name and instructions.
Store these products tightly closed and away from food and out of reach of children.
Home-Brewed Pest Controls
Organic gardeners have long relied on homemade sprays that are safe to use and easy to prepare. Results aren’t guaranteed, so monitor the plants after treating them.
Garlic oil: Finely chop 10 to 15 garlic cloves and soak in 1 pint of mineral oil for 24 hours. Strain and spray as is, or dilute with water and add a few drops of soap.
Hot-pepper spray: In a blender, blend ½ cup of hot peppers with 2 cups of water. Strain and spray. Caution: Hot peppers burn skin and eyes.
You can also use a combination spray by blending up to 6 cloves of garlic with 1 or two peppers in 1 quart water. Strain the mixture before spraying and use caution to keep the spray off your skin and well away from your face and eyes.
Mix and apply exactly according to directions.
Wear protective clothing when mixing, applying, and cleaning up. This may include a long-sleeved shirt and pants, rubber boots, rubber or other waterproof gloves, goggles, and a dust mask or respirator. Read the label for requirements.
Wash clothing, skin, containers, and sprayers thoroughly when cleaning up.
Stay out of treated areas until spray is dry or dust has settled.
Iron phosphate baits: These are commercial products that kill slugs and snails. Iron phoshate is a mined mineral mixed into a bait such as wheat gluten. While it is very effective at killing slugs and snails, it is not toxic to people or wildlife.
Insecticidal oils: Petroleum and plant oils have long been used to kill eggs and immature stages of insects. Oils block the insect’s supply of oxygen and are especially effective because they spread well over surfaces. Oils may also poison or repel some insects. They break down quickly and are more toxic to pests than to beneficial insects.
Dormant oils are heavy petroleum oils that can be sprayed on dormant orchard trees and ornamental plants to control overwintering stages of mites, scales, aphids, and other insects. Spray a 1 to 3 percent mixture of oil in water when the air temperature is above 40°F. Certain plants such as Japanese maple are very sensitive, and can be severely damaged by dormant oil. It also removes the blue “bloom” from blue spruce, turning it green. Before spraying a whole plant, spray a small area and see if yellowing occurs.
The Safest Way to Spray
Sometimes the most effective control is also the simplest. A strong spray of plain old water from your garden hose can physically injure aphids, leafhoppers, and other delicate pests, and knock them off plants. Spray plants in early morning or late afternoon. If you have problems with diseases that thrive in wet conditions, you may want to choose another control method.
Summer oils, also called superior or supreme oils, are lighter petroleum oils that contain fewer of the impurities that make dormant oils toxic to plants. Spray up to a 2 percent mixture of summer oil and water even on fully leafed-out plants as long as the air temperature is below 85°F and the plants are not drought or heat stressed. Summer oil controls aphids, spider mites, scales, psylla, mealybugs, and some caterpillars. It is slightly toxic to mammals and registered for ornamental and greenhouse use. Oils may cause leaf damage to some plants under certain conditions. Spray a small area and wait a few days. If the plants are unharmed, spray thoroughly.
Vegetable oils provide similar control. Mix 1 cup of cooking oil with 1 tablespoon of liquid soap. Use 2½ teaspoons per cup of water to spray.
Insecticidal soaps: Insecticidal soaps are specially formulated solutions of fatty acids that kill insect pests like aphids, mites, and whiteflies. Insecticidal soap is a contact insecticide that paralyses insects, which then die of starvation. Spray plants every 2 to 3 days for 2 weeks for bad infestations. Mix with soft water. Soaps may damage plants if applied too strongly or if plants are drought or heat stressed. Soaps break down within 1 to 2 weeks.
The Top Ten Garden Insect Pests
The following list of pest descriptions and control measures provides a good starting point for tackling pest control in gardens throughout the United States and Canada. Control solutions are listed in order of environmental friendliness. Botanical sprays, which can have detrimental effects on beneficial insects and other animals, should be used only as a last resort.
| PEST | HOST/RANGE | DAMAGE | CONTROL |
| Aphids (many species). Tiny, pear-shaped; long antennae; two tubes projecting rearward from abdomen. | Most fruits and vegetables, flowers, ornamentals, shade trees. Found throughout North America. | Aphids suck plant sap, causing foliage to distort and leaves to drop; honeydew excreted on leaves supports sooty mold growth; feeding spreads viral diseases. | Wash plants with strong spray of water; encourage native predators and parasites such as aphid midges, lacewings, and lady beetles; when feasible, cover plants with floating row cover; apply hot-pepper or garlic repellent sprays; for severe problems, apply horticultural oil, insecticidal soap, or neem. |
| Cabbage maggot (Delia radicum). Adults: ¼-inch gray flies. Larvae: white, tapering maggots. | Cabbage-family crops. Found throughout North America. | Maggots tunnel in roots, killing plants directly or by creating entryways for disease organisms. | Apply floating row covers; set out transplants through slits in tar-paper squares; avoid first generation by delaying planting; apply parasitic nematodes around roots; burn roots from harvested plants; mound wood ashes or red pepper dust around stems. |
| Caterpillars (many species). Soft, segmented larvae with distinct, harder head capsule; six legs in front, fleshy false legs on rear segments. | Many fruits and vegetables, ornamentals, shade trees. Range varies with species. | Caterpillars chew on leaves or along margins; droppings soil the produce; some tunnel into fruits. | Encourage native predators, parasites; hand pick; apply floating row covers; spray with Bt (Bacillus thuringiensis) or spinosad. |
| PEST | HOST/RANGE | DAMAGE | CONTROL |
| Colorado potato beetle (Leptinotarsa decemlineata). Adults: yellow-orange beetles with 10 black stripes on wing covers. Larvae: orange, hump-backed grubs with black spots along sides. Eggs: yellow ovals, laid in upright clusters. | Potatoes, tomatoes, eggplant, petunias. Found throughout North America. | Beetles defoliate plants, reducing yields or killing young plants. | Apply floating row covers; use deep straw mulches; hand pick; attract native parasites and predators; spray with Beauveria bassiana or spinosad; spray with neem. |
| Cutworms (several species). Fat, 1-inch-long, gray or black segmented larvae; active at night. | Most early vegetable and flower seedlings, transplants. Found throughout North America. | Cutworms chew through stems at ground level; they may completely devour small plants; most damaging in May and June. | Use cutworm collars on transplants; delay planting; hand pick cutworms curled below soil surface; scatter bran baits mixed with Btk (B.t. var. kurstaki) and molasses before planting. |
| Flea beetles (several species). Small, dark beetles that jump like fleas when disturbed. | Most vegetable crops. Found throughout North America. | Adults chew numerous small, round holes in leaves; most damaging to young plants; larvae feed on plant roots. | Apply floating row covers; repel the pests by spraying plants with garlic spray or kaolin clay; for a serious infestation, try repeated sprays of Beauveria bassiana or spinosad. |
| Japanese beetles (Popillia japonica). Adults: metallic bluegreen, ½-inch beetles with bronze wing covers. Larvae: fat, white grubs with brown heads. | Many vegetables and flowers, small fruit. Found in all states east of the Mississippi River. | Adults skeletonize leaves, chew flowers, may completely defoliate plants; larvae feed on lawn and garden plant roots. | Shake beetles from plants in early morning; apply floating row covers; set out baited traps upwind of your garden on two sides and at least 30 feet away; apply milky disease spores or Herterorhabditis nematodes to soil; spray beetles with insecticidal soap. |
| PEST | HOST/RANGE | DAMAGE | CONTROL |
| Mexican bean beetle (Epilachna varivestris). Adults: oval, yellow-brown, ¼-inch beetles with 16 black spots on wing covers. Larvae: fat, dark yellow grubs with long, branched spines. | Cowpeas, lima beans, snap beans, soybeans. Found in most states east of the Mississippi River; also parts of Arizona, Colorado, Nebraska, Texas, Utah. | Adults and larvae chew on leaves from beneath, leaving characteristic lacy appearance; plants defoliated and killed. | Apply floating row covers; plant bush beans early; hand pick; plant soybean trap crop; put out lures to draw spined soldier bugs (predators) to your yard. Spray Beauveria bassiana, insecticidal soap, or neem. |
| Scales (more than 200 species). Adults: females look like hard or soft bumps on stems, leaves, fruit; males are minute flying insects. Larvae: tiny, soft, crawling larvae with threadlike mouthparts. | Many fruits, indoor plants, ornamental shrubs, and trees. Found throughout North America. | All stages suck plant sap, weakening plants. Plants become yellow, drop leaves, and may die. Honeydew is excreted onto foliage and fruit. | Prune out infested plant parts; encourage native predators; scrub scales gently from twigs with soft brush and soapy water, rinse well; apply dormant or summer oil sprays; spray with neem oil. |
| Tarnished plant bug (Lygus lineolaris). Fast-moving, mottled, green or brown bugs, forewings with black-tipped yellow triangles. Nymphs: similar to adults, but wingless. | Many flowers, fruits, vegetables. Found throughout North America. | Adults and nymphs suck plant juices, causing leaf and fruit distortion, wilting, stunting, and tip dieback. | Keep garden weed free in spring. Apply fl oating row covers; encourage native predatory insects; spray young nymphs with Beauveria bassiana or neem. |
Many organic gardeners use 1 to 3 teaspoons of household soap (not detergent) per gallon of water as a garden insecticide.
Neem oil: Neem oil is extracted from the neem tree, Azadirachta indica, native to India. The oil is extracted from seed kernels, leaves, bark, flowers, and wood. Neem oil is a broad-spectrum insect poison, repellent, and feeding deterrent. It also stops or disrupts insect growth and sterilizes some species. Research is ongoing, but neem oil appears to be easy on beneficials and of very low toxicity to mammals.
Neem oil solution can be used as a spray to control many insects and as a soil drench to control soil stages of pests. Spray when the leaves will remain wet for as long as possible.
Sulfur: You can use sulfur to control mites and chiggers. Sulfur is gentle on large predaceous insects but will kill tiny parasitic wasps. See the Plant Diseases and Disorders entry for more details about sulfur.
Pyrethrins: Pyrethrins are derived from the flowers of pyrethrum daisies (Chrysanthemum cinerariifolium and C. coccineum). The dried flowers are finely ground to make an insecticidal dust. Pyrethrins are extracted from the dust and used in sprayable solutions. Pyrethrins attack an insect’s central nervous system, providing the rapid knockdown that gives many gardeners a satisfying feeling of revenge. At low doses, however, insects may detoxify the chemical and recover. Read labels carefully before buying a pyrethrin product. Many of them are synthetic versions of pyrethrins (pyrethroids) or contain synthetic synergists, like piperonyl butoxide (PBO), which may be toxic themselves. Avoid these products. Check labels to be sure you’re getting a plant-derived, organically acceptable product.
Pyrethrins are effective against a broad spectrum of pest insects, including flies, mosquitoes, and chewing and sucking insect pests. You can apply them up to one day before harvest because they break down rapidly in heat and light. Pyrethrins are moderately toxic to mammals and highly toxic to fish and bees. Don’t apply them around ponds, waterways, or plants where bees are active. Apply pyrethrins only as a last resort.
PETUNIA
Garden petunia. Summer-and fall-blooming annuals.
Description: Petunias bear abundant 2- to 4inch, often-fragrant trumpets in white, pink, rose, red, yellow, blue, and purple. Single or double-flowered cultivars may have lacy or starred shapes and ruffled or smooth margins. Most grow upright or mounded to 1 foot tall. Smallish, sticky leaves are unremarkable.
How to grow: Indoors, sow the minute seeds in late winter or early spring for planting out after frost, or choose from the wide selection of bedding plants at garden centers. At 3 to 4 inches, pinch out the centers to promote bushiness, even if the plants are in bloom. Grow petunias in full sun or with some afternoon shade in average soil and moisture. They tolerate drought very well, and pests rarely bother them. Cut the plants back hard in midsummer if they grow tall and straggly, and give them a little extra water and fertilizer. They will bloom again in fall. Take cuttings of favorites and overwinter them indoors in a warm, bright spot.
Landscape uses: Grow petunias in beds, borders, pots, hanging baskets, and window boxes. Let them tumble over rocks or space them out and use them as a groundcover. Small-flowered petunias add a lovely soft touch to the front of the perennial border; they’ll self-sow if flowers are allowed to mature in fall. Petunias will look tired by late summer, so grow them where other plants can take over while they recover.
pH
You’ll often read the recommendation to check soil pH, but what does that really mean? pH is simply a measure of how acid or alkaline a substance is, and soil acidity or alkalinity (soil pH) is important because it influences how easily plants can take up nutrients from the soil. Many gardening books and catalogs list the preferred pH for specific plants. The good news for gardeners is that, with a few exceptions, most plants will tolerate a fairly wide range of soil pH. The diagram below shows how pH values relate to soils.
Nutrient uptake and pH: Plant roots absorb mineral nutrients such as nitrogen and iron when they are dissolved in water. If the soil solution (the mixture of water and nutrients in the soil) is too acid or alkaline, some nutrients won’t dissolve easily, so they won’t be available for uptake by roots.
Most nutrients that plants need can dissolve easily when the pH of the soil solution ranges from 6.0 to 7.5. Below pH 6.0, some nutrients, such as nitrogen, phosphorus, and potassium, are less available. When pH exceeds 7.5, iron, manganese, and phosphorus are less available.
Regional differences: Many environmental factors, including amount of rainfall, vegetation type, and temperature, can affect soil pH. In general, areas with heavy rainfall and forest cover such as the Eastern states and the Pacific Northwest have moderately acid soils. Soils in regions with light rainfall and prairie cover such as the Midwest tend to be near neutral. Droughty areas of the western United States tend to have alkaline soils. However, the pH of cultivated and developed soils often differs from that of native soil, because during construction of homes and other buildings, topsoil is frequently removed and may be replaced by a different type of soil. So your garden soil pH could be different from that of a friend’s garden across town.
The pH scale. The overall pH scale ranges from 1.0 to 14.0, but soils are rarely more acidic than 4.5 or more alkaline than 8.0. Thus, most soils are less acidic than orange juice and less alkaline than baking soda. Some gardeners refer to alkaline soils as “sweet” and acidic soils as “sour.”
Changing pH: Most garden plants grow well in slightly acid to neutral soil (pH 6.0–7.0). Some common exceptions include blueberries, potatoes, azaleas, and rhododendrons, which prefer moderately acid soil. You can make small changes to soil pH by applying soil amendments. However, you’ll have best success if you select plants that are adapted to your soil pH and other soil characteristics. Adding organic matter such as compost to the soil buffers the pH, which means that it tends to bring both acid and alkaline soils closer to neutral.
If you have your soil analyzed by a lab, the lab report will include soil pH. See the Soil entry for information on how to sample your soil and have it tested. You can also test soil pH yourself with a home soil test kit or a portable pH meter. Home kits and portable meters vary in accuracy but can be helpful in assessing the general pH range of your soil.
The quantity of liming or acidifying material needed to change soil pH depends on many factors, including current pH, soil texture, and the type of material. A soil lab report will contain recommendations on types and quantities of amendments to use.
You can spread liming or acidifying materials with a garden spreader or by hand for small areas. If hand spreading, be sure to wear heavy gloves to protect your skin.
Correcting acid soil: If your soil is too acid, you must add alkaline material, a process commonly called liming. The most common liming material is ground limestone. There are two types: calcitic limestone (calcium carbonate) and dolomitic limestone (calcium-magnesium carbonate). In most instances, you’ll use calcitic lime. Apply dolomitic lime only if your soil also has a magnesium deficiency.
Why Is It Called pH?
What does pH stand for, and why is it spelled in that odd way? Thank chemistry for this incomprehensible abbreviation. It stands for “potenz Hydrogen” (“potenz” means “the potential to be”). In chemis-try, the elements of the periodic table—remember that from school?—such as Oxygen and Hydrogen, are capitalized; that’s why it’s pH rather than ph, Ph, or PH. But what does hydrogen—much less the potential of hydrogen—have to do with soil acidity or alkalinity? Well, the activity of hydrogen ions in solution—and soil is actually a solution at the microscopic level—determines the acidity or alkalinity of the solution. Acidic solutions have a high concentration of hydrogen ions; alkaline solutions have a low concentration. This may all seem arcane, but here’s a fun fact: The inven-tor of the pH scale developed it to determine the acid content of his beer!
Ground limestone breaks down slowly in the soil. Apply it to the garden and lawn in fall to allow time for it to act on soil pH before the next growing season. A rule of thumb for slightly acidic soils is to apply 5 pounds of lime per 100 square feet to raise pH by one point. In general, sandy soils will need less limestone to change pH; clay soils will need more.
The amount of lime you must add to correct pH depends not only on your soil type but also on its initial pH. For example, applying 5 pounds of limestone per 100 square feet will raise the pH of a sandy loam soil from 6.0 to 6.5. It would take 10 pounds per 100 square feet to make the same change in silty loam soil. However, if 5.6 was the initial pH of the soil, 8 pounds per 100 square feet would be required for the sandy loam soil, and 16 pounds per 100 square feet for the silty loam soil. There is no simple rule of thumb that applies to all soils. The safest approach to take if you plan to apply limestone is to have your soil tested and follow the lab recommendations.
Applying wood ashes also will raise soil pH. Wood ashes contain up to 70 percent calcium carbonate, as well as potassium, phosphorus, and many trace minerals. Because it has a very fine particle size, wood ash is a fast-acting liming material. Use it with caution, because overapplying it can create serious soil imbalances. Limit applications to 25 pounds per 1,000 square feet, and apply ashes only once every 2 to 3 years in any particular area. At this rate, your soil will get the benefits of the trace minerals without adverse effects on pH.
Correcting alkaline soil: If your soil is too alkaline, add a source of acidity. The most common material to add is powdered elemental sulfur. As a rule of thumb, add 1 pound of sulfur per 100 square feet to lower pH 1 point. But as with lime, the correct amount will depend on your soil type and its initial pH. Testing your soil and following lab recommendations is the best approach if you want to lower the pH of an entire bed or area of your yard.
Mixing peat moss with the soil will also lower pH. Peat moss can be expensive, so it’s generally only a feasible choice for small areas such as flower beds, when planting one or two acid-loving shrubs (such as blueberries), and in container gardens. Peat moss has also been overharvested in many areas; incorporating ample organic matter (such as shredded leaves) is a more environmentally friendly option.
PHLOX
Phlox. Summer-blooming perennials.
Description: Phlox paniculata, garden phlox, enjoys star billing in many summer gardens. Hundreds of 1-inch rounded blooms crowd into massive, roughly pyramidal clusters of white, pink, rose, red, orange, and purple, many with a contrasting “eye” in the center of each bloom. Most have a sweet, light, musty scent, especially during dusk and early evening. Plants form 3- to 4-foot-tall upright mounds with pairs of 3- to 6-inch pointed leaves set at a 90-degree angle to the pair below. To make it easier to combat mildew, the bane of garden phlox, choose mildew-resistant cultivars such as white-flowered ‘David’ or ‘Bright Eyes’, which has pink flowers with crimson eyes. Zones 3–8.
How to grow: Plant or divide phlox in spring or fall in a sunny, well-drained spot with fertile, humus-rich soil. Partial shade may prolong bloom in the South. Phlox are heavy feeders and benefit from a scattering of organic fertilizer in early spring. Water frequently in summer. For best growth and reasonable powdery mildew control, divide every other year into renewed soil, and thin to about 6 shoots per plant. Never grow in airless spots or allow the clumps to become dense. If you do, the result will be a mildewed mess of ratty leaves and small flower heads. Remove flower heads before they drop their seeds to prevent vigorous seedlings (usually in vivid magenta shades) from crowding out their more desirable parents.
More Fine Phlox
Not all phlox are as imposing as garden phlox, but several are just as useful and attractive in the garden. Native wild blue phlox (Phlox divaricata, also called wild sweet William) and creeping phlox (P. stolonifera) both bear a profusion of delicate 1-inch blooms in shades of white, blue, and lavender on thin stems to 1 foot in spring. These gently spread-ing plants give a misty quality to lightly shaded moist woodlands and provide a cheerful contrast to bulbs and perennials in a border. Wild blue phlox is hardy in Zones 3–9, creeping phlox in Zones 2–8. Lowest growing of all is moss pink (P. subulata), which is hardy in Zones 2–9. Myriad ½-inch blooms in white, pink, magenta, and lilac shades hide its spreading 1- to 3-inch mats of dense, needlelike evergreen leaves in spring. They thrive in sun and lean to rich, well-drained soil. Allow them to fill spaces in rock gardens and walls, or let them carpet a steep bank. All of these phlox have many fine cultivars.
Landscape uses: Feature a variety of colors in a border, or tie a planting together with shades of a single color. Phlox look good in a bed or cutting garden. Allow reverted seedlings to naturalize in thin woods or a field.
PICEA
Spruce. Evergreen trees or shrubs.
Description: Large trees that reach heights of 30 to 60 feet in the landscape, spruces are pyramidal to conical in habit, with short stiff needles and drooping cones.
Picea abies, Norway spruce, has horizontal limbs and branchlets that dangle with age. Cones grow 4 to 6 inches long. Norway spruce grows 40 to 60 feet. Zones 2–6.
P. glauca, white spruce, is a native species that becomes spirelike with age and reaches heights of 40 to 60 feet. White spruce has drooping branchlets, four-sided needles, and 2-inch cones. Zones 2–6.
P. mariana, black spruce, another native, is also spirelike with age. It grows 30 to 40 feet tall. Zones 1–6.
P. omorika, Serbian spruce, is a slim-trunked tree of 50 to 60 feet with branches that droop but point upward at the tips. The flattened needles are deep green on top and whitish underneath; cones are 2½ inches long. Zones 4–6.
P. orientalis, Oriental spruce, is a graceful tree that grows 50 to 60 feet tall. Four-sided needles are waxy, deep green, and crowded on branches. Cones are about 3 inches long. Zones 5–7.
P. pungens, Colorado spruce, is a stiffly pyramidal native tree that grows 30 to 60 feet tall in the landscape. The four-sided needles are stiff and prickly; branchlets are yellowish brown and smooth. P. pungens ‘Glauca’ and other cultivars with blue-or silver-green needles are commonly called Colorado blue spruce. Zones 2–6.
How to grow: Spruces need a cool climate and plenty of room. They grow quickly (as much as 1 to 2 feet per year), astounding homeowners with their ability to take up space, especially when they looked so small at planting time. Spruces transplant easily because of their shallow spreading root systems, and even large specimens can be relocated. In addition to space, spruces require evenly moist, well-drained, acid soil and full sun, although they can be grown successfully in clay soils. Most species will tolerate light shade but grow open and untidy looking in heavy shade. To encourage dense growth, prune in spring when new growth is nearly half-developed, removing ½ to ⅔ of the candle of new growth. Spruces generally require little pruning; some species tolerate heavy pruning and can be used to form hedges.
Pests that attack spruces include spider mites, sawflies, spruce gall adelgids, and bagworms. Spider mites often afflict trees that are under drought stress, and infestations tend to appear in very hot, dry weather. Avoid spider mite problems with proper culture—plant trees in cool areas and water deeply in dry weather. Use a strong spray of water to knock spider mites from trees, or spray with an insecticidal soap. Sawfly larvae feed on needles and disfigure trees. See the Pinus entry for sawfly control information.
Spruce gall adelgids are small, aphidlike insects that suck sap from needles, causing a pinecone-or pineapple-shaped gall to form around them at the ends of branches. The galls turn brown and crack open in summer, releasing mature adelgids that lay powdery egg masses near the base of the tree’s buds. Remove and burn spruce galls from the twig tips before the new generation of adelgids emerges. If you can’t take off all the galls, spray with dormant oil before growth begins or with summer oil during the growing season. Don’t use oil sprays on blue spruces—they discolor the foliage. Sprays of insecticidal soap also give control if applied prior to bud break in early spring or timed to coincide with adelgid emergence from galls in July and August.
Bagworms are moth larvae that chew the needles of spruces and many other kinds of evergreens. The bagworms take their name from their ability to spin silken bags, which they stud with bits of needles so that the bags resemble pinecones. Uncontrolled feeding can defoliate evergreens and eventually kill the plants. The larvae use the bag as a shelter. They also pupate in the bags, and adult females lay eggs inside the bags as well. Hand pick and destroy the bags in winter. Spray Btk (Bacillus thuringiensis var. kurstaki) for larvae in spring. Catch adult males in pheromone traps in summer.
Landscape uses: Use spruces as screens, hedges, and windbreaks. Many are attractive trees that work well as focal points in large-scale situations. Use blue spruces with discretion if color harmony is important to you—their strong blues are often hard to combine with other colors in the landscape.
PIERIS
Pieris. Spring-blooming, broad-leaved ever green shrubs.
Description: Pieris floribunda, mountain pieris or fetterbush, is a rounded, spreading shrub that grows to 6 feet tall. This plant bears upright clusters of creamy white flower spikes in spring. Zones 5–7.
P. japonica, Japanese pieris or lily-of-the-valley bush, can reach 10 feet at maturity. Glossy green foliage forms a background for the creamy white, cascading flower clusters. Zones 6–7.
How to grow: Pieris need partial shade and humus-rich, well-drained, evenly moist, well-mulched soil. Prune after flowering to remove dead wood. Remove spent f lowers for good bloom next year. If lace bugs are a problem, control with soap sprays.
Landscape uses: Japanese pieris makes a fine specimen; plant where you can enjoy it at close range. Mountain pieris is a good choice for massed plantings and woodland gardens.
PINUS
Pine. Evergreen trees or shrubs.
Description: Pinus bungeana, lacebark pine, is a multi-trunked tree that reaches 30 to 50 feet in the landscape, becoming flat-topped with age. The bark flakes off, revealing attractive olive, gray, and tan patches. The 4-inch needles grow in bundles of three; the cones are about 3 inches long. Zones 5–7.
P. densiflora, Japanese red pine, has crooked trunks and horizontal branches. This picturesque pine becomes flat-topped with age and attains a mature height of 40 to 60 feet. The 5-inch, blue-green needles grow in bundles of two. The bark is orangish and the cones are about 2 inches long. Zones 5–6.
P. flexilis, limber pine, is pyramidal in youth and flat-topped with age, growing to a height of 30 to 50 feet. The twisted, blue-green, 3-inch needles grow in bundles of five; the cones can be 3 to 10 inches long. This North American native develops deep fissures in its old bark, but its most interesting feature is its rubbery, fun-to-play-with, flexible branches. Zones 5–6.
P. mugo, Swiss mountain pine, is a shrub or small tree that grows 15 to 20 feet tall. Valued for its dwarf cultivars, it has a low, round, bushy habit and 2-inch needles in bundles of two. Zones 3–7.
P. nigra, Austrian pine, becomes massive and picturesque with age. In youth it’s pyramidal, but develops a flat top and gray—almost white—bark with deep fissures forming blocky patterns. It grows 50 to 60 feet tall in the landscape, bearing 6½-inch needles in bundles of two and cones about 3 inches long. Austrian pine is one of the few pines that tolerate urban conditions. Zones 4–6.
P. strobus, Eastern white pine, is soft and graceful in texture, pyramidal in youth, and stout with age. The branches appear in whorls on the trunk, with bluish green 5-inch-long needles in bundles of five. The cones are 4 to 6 inches long. This native evergreen grows 50 to 80 feet tall; it has little tolerance for road deicing salts. Zones 3–6.
P. sylvestris, Scotch pine, is pyramidal in youth and gnarled with age, reaching a mature height of 30 to 60 feet. The bark of the upper trunk flakes off to reveal a colorful orange inner bark that shows through the stiff, twisted, blue-green needles. The 3-inch-long needles are borne in bundles of two. Scotch pine tolerates poor, dry soils and is grown as a Christmas tree in Northern states. Zones 2–6.
P. taeda, loblolly pine, is a fast-growing Southern native that can reach 60 to 90 feet. Its 6- to 10-inch needles are in bundles of three. Older trees have few lower branches; the exposed trunk’s furrowed bark makes a nice background for small trees like dogwoods (Cornus florida). Zones 7–9.
P. thunbergiana, Japanese black pine, is pyramidal in youth, growing irregular, open, and picturesque with age. Its usual mature height in North America is 20 to 30 feet, although in its seaside habitat in its native Japan it grows to 130 feet. The 3- to 4½-inch needles are borne in bundles of two; the bright green, sharply pointed cones are 2½ inches long. Japanese black pine is good for coastal areas because it is resistant to salt spray. Zones 6–7.
P. virginiana, Virginia pine, is a scrubby pine of 15 to 40 feet with paired needles and an irregular branching habit. Virginia pine is not particularly desirable as a landscape plant, but it is a native species and tolerates poor, dry soils and can be used in difficult sites. Zones 5–9.
P. wallichiana, Himalayan white pine, is a pyramidal tree that becomes massive with age. Soft, gray-green needles are 8 inches long and borne in bundles of five; they droop gracefully from the branches. The cones are 6 to 12 inches long; the tree reaches a height of 50 to 80 feet. Zones 5–6.
How to grow: Somewhat more adaptable to poor soil, exposed sites, and urban conditions than firs and spruces, pines prefer full sun, well-drained soil, and plenty of room. Several pest and disease problems trouble pines, but serious damage is usually limited to stressed trees or those found in large plantings such as Christmas tree farms.
Pine needle scales appear as small yellowish white bumps on the needles. A heavy infestation gives branches a snowy look. The scales feed while attached to the needles; eggs mature beneath the scales, and one or two generations of tiny reddish crawlers emerge during the growing season. Infested needles may turn yellow and drop from the tree. Apply dormant oil and lime sulfur spray in late winter before growth begins; spray insecticidal soap or summer oil when crawlers appear in spring and again in early summer.
Sawfly is a name given to several species of nonstinging wasps that insert their eggs into the needles of pines and other evergreens. The larvae emerge to feed on the needles; one generation occurs per year in the North, but as many as three may attack Southern pines. These pests usually eat old foliage first, but severe infestations can defoliate entire trees. Pick off any caterpillars that you can reach, or spray with summer oil or neem.
Pine tip and pine shoot borers are the caterpillars of several species of small moths. Pine tip moth larvae bore into needle and bud bases, killing the shoots. Damaged trees have brown, slightly curled shoot tips. Remove and destroy infested branch tips; apply sprays of Btk (Bacillus thuringiensis var. kurstaki) when caterpillars are visible.
Landscape uses: Grow pines as specimen plants, screens, windbreaks, and hedges. They can make glorious focal points in large-scale situations.
PLANT DISEASES AND DISORDERS
When plants are well nourished and well taken care of, they have a natural ability to resist disease. And since keeping plants healthy is at the heart of organic gardening, disease problems tend to be minor in organic gardens. Organic gardeners feed the soil regularly with compost and organic matter, which keeps disease organisms in check both by producing stronger plants and by encouraging beneficial soil organisms that actually fight against pathogens.
Factors other than diseases can produce diseaselike symptoms, and these problems are called plant disorders. Extreme weather conditions or soil imbalances may be the cause, and, in fact, people are often indirectly the cause of common plant disorders such as salt damage or ozone damage. Choosing plants that are well suited to the site is the best way to prevent many frustrating, costly, and sometimes fatal plant disorders.
KEY WORDS Disease
Pathogen. An organism that causes disease.
Host. A plant or animal that a parasite or pathogen depends on for sustenance.
Spore. A one-or many-celled reproductive unit.
Nematode. A microscopic, unsegmented, threadlike worm; also called an eelworm.
Parasite. An animal or plant that lives in or on and draws nourishment from another organism (the host) without contributing anything toward the host organism’s survival.
Infection. Entry or growth of a disease-causing organism into a host.
Interveinal chlorosis. A condition in which leaf veins remain green while the tissue between veins turns yellow.
Figuring Out What’s Wrong
If a plant in your garden has, say, leaves that are turning yellow or black spots on its fruit, how can you tell what’s causing the problem—an insect, a disease, a nutrient imbalance, or something else?
Start by ruling out insect damage and cultural problems. Inspect the plant carefully, using a magnifying lens. If it’s an insect problem, you can usually find some evidence of the insects on the plants. Review the symptoms of nutrient deficiencies (page 481), and consider recent unusual weather patterns and nearby sources of pollution. See page 663 for more tips on how to detect the cause of garden problems.
If you can rule out insects and cultural problems, then you’ll need to consider diseases or other kinds of disorders. Become familiar with the general types of plant diseases and the common disease problems in your area. Or you can consult books on plant diseases and garden problem solving, which often are organized by plant and list the diseases that each can get (see Resources on page 672). The chart on page 663 may also help you determine whether the symptoms on your plants are due to insects, disease, a plant disorder, or a nutrient imbalance.
A Who’s Who of Plant Pathogens
Microorganisms that can cause diseases include fungi, bacteria, viruses, and pathogenic nematodes.
Fungi: Fungi are primitive plants. They don’t have chlorophyll, the pigment that allows green plants to convert sunlight and air into food. Instead, fungi obtain nutrients by inserting special rootlike structures (called haustoria) into host plants or dead organic matter. Many fungi live on and decompose dead organic materials. These beneficial fungi are an important ally in the garden. Parasitic fungi, on the other hand, are a leading cause of plant disease. Some attack only one species of plants, while others attack a wide array of plants.
Fungi produce tiny spores that are spread by wind, water, insects, and gardeners. Spores germinate to form mycelia—the body of the fungus. Mycelia rarely survive winter, but spores easily survive from season to season.
It’s often easy to spot signs of fungi—mushrooms are the most common example. Often the structures that produce fungal spores look like dots or discolored areas on leaves, stems, or fruit. These structures are one of the best ways to distinguish fungal diseases from other plant problems.
Bacteria: Most bacteria are beneficial—they help to break down dead organic matter. Some, however, cause plant diseases. Bacteria usually reproduce asexually—the cells simply split in half. Bacteria spread via wind, water, insects, garden tools, and gardeners’ hands. Bacterial diseases are usually more difficult to control than fungal diseases, and they spread more quickly than other types of diseases. You need a microscope to see actual bacterial cells, but some of the disease symptoms they cause, such as dark streaks on leaves or stems and bacterial slime are easy to see with the naked eye. (The slime often smells bad, too.)
Nematodes: Nematodes swim freely in the film of moisture surrounding soil particles and plant roots. A few types are barely visible to the naked eye. Many nematodes do not cause plant diseases and are important members of the soil community. In fact, beneficial nematodes often prey on the nematodes that attack plants.
Parasitic nematodes can be very destructive. They lay eggs that hatch into tiny larvae. Larvae molt several times before maturing to adults. Nematodes puncture plant cell walls, inject saliva, and suck out the cell’s contents. Some species move from plant to plant to feed; others attach themselves permanently to one root. They can travel short distances on their own but are spread through the garden by water and on tools or gardeners’ hands.
Viruses: Viruses are so small, they’re difficult to see even with a microscope. Viruses are not complete cells and must be inside living cells of a host in order to reproduce. The symptoms they cause vary widely from distorted growth to mottling of leaves to stunting. Viruses are transmitted by vegetative propagation, in seeds and pollen, and on tools and gardeners’ hands. Viruses are also transmitted by aphids and other insects, mites, nematodes, and parasitic plants.
Natural Defenses against Disease
There may be hundreds of species of disease organisms in your garden soil or living in weeds in and around your yard. However, even though disease-causing organisms are nearly always present, that doesn’t mean that your garden crops and ornamentals will develop a disease. Untold millions of potential diseases never amount to anything, because conditions aren’t favorable for their development.
Plants have intriguing defenses that help protect them from infection. Leaves have a waxy coating called the cuticle that prevents them from staying wet, making it hard for disease-causing organisms to survive. The leaf cuticle may also prevent spore germination and slow the penetration of disease-causing organisms. Leaf hairs trap spores and hold them away from the surface of the leaf. Some leaf hairs actually secrete chemicals that prevent spores from germinating or sticky substances that help catch pathogens and/or the insects that transmit them. Leaves also exude substances that promote the growth of beneficial microorganisms that compete for space with, or are antagonistic to, pathogens.
Plants can also spring to their own defense when pathogens try to invade. For example, some plants can form a corky layer of tissue around the site of attack. Other plants may seal off the diseased part, which then dies along with the disease organisms.
Plants also have natural chemical defenses that repel or damage the pathogens themselves. Some of these defenses are present all the time and some are “turned on” when disease-causing organisms are present.
The discovery of these natural defense mechanisms (and more new discoveries are still being made) has been of great benefit to organic farmers and gardeners, because plant breeders can select for these mechanisms when they’re working to develop disease-resistant cultivars. It also appears that products containing harpin and other plant growth promoters help to prevent disease by triggering plants to turn on their natural chemical defenses.
Preventing Diseases
Most of the time, simple preventive controls will stop disease problems from developing or limit their severity. In a few instances, you may have to resort to spraying substances such as neem or sulfur to prevent a disease from ruining a plant or crop. These substances are considered organic because they derive from natural sources—however they are not innocuous. For example, sulfur can burn plant leaves, and spraying sulfur too often can cause soil imbalances that harm beneficial soil organisms.
Smart Gardening Helps
The smartest way to help prevent disease problems in your garden is simply to take good care of your plants. It also pays to take simple steps that avoid the risk of infection. Some of the most important smart gardening practices to prevent diseases are listed here; see page 474 for more.
Build up soil organic matter content, and correct nutrient imbalances.
In the vegetable garden, interplant crops and use crop rotation if you can (see the Crop Rotation entry).
Some disease problems can be avoided by planting earlier or later than usual.
Prune your plants at the proper time of year and thin out growth as needed throughout the growing season to promote good air circulation around plants.
Put up a barrier against insects such as leafhoppers and cucumber beetles that spread disease by covering crops with row covers from seeding until harvest when possible.
Clean Gardening Helps
Fungi, bacteria, and other pathogens have evolved many ways of surviving cold temperatures or other unfavorable conditions. They may spend winter inside the bodies of insects or in the soil—even in bits of soil clinging to tools stored in a garden shed. Some can survive winter in infected plant debris, seeds, or plant tissue. A few widespread diseases can produce “resting spores” that stay dormant in the soil for years until conditions are right or a host plant is planted in the area.
Many good gardening practices help prevent disease because they prevent disease organisms from overwintering and spreading from place to place during the gardening season. You probably already take some of these steps routinely in your garden.
Choose disease-resistant or tolerant cultivars, and make sure all transplants and seeds you plant are free of disease.
Stay out of your garden when the leaves are wet because disease organisms spread easily in wet conditions.
Avoid damaging plants, as every wound is an opening for disease to enter.
Clean and disinfect tools, hands, and feet regularly, whether you are working with diseased material or not.
Do an annual fall garden cleanup.
Dispose of diseased material throughout the season. Pull up plants or prune off infected portions, and get rid of them by burning, putting them in sealed containers for disposal with household trash, burying them deeply, or putting them in the center of a hot compost pile.
Growth Promoters Help
Going beyond the basics of maintaining healthy plants and a clean garden, you can apply homemade and commercially produced sprays that will make your plants even more resistant to disease problems. These products are different from fungicides, which work by killing fungal spores via toxic or caustic chemicals. Instead, these growth-promoting sprays work by stimulating beneficial microorganisms, and seemingly by triggering plants to turn on their own natural defense systems.
Homemade sprays: Compost tea is one of the homemade sprays that help boost plant defenses. Applying sprays of seaweed extract or comfrey tea may have similar beneficial effects. See the Compost entry for instructions for making compost tea. Make comfrey tea using a similar method, but dilute comfrey tea half-and-half with water before applying. A homemade garlic spray may work by killing spores on plant surfaces. Mix 5 to 10 cloves with 1 pint of water in a blender, strain, and spray on plants.
Harpin: Harpin is a protein that reportedly stimulates plant defense systems, and some commercial products are available with harpin as the active ingredient. It has no reported adverse side effects on plants or the environment, but it has not been listed for use by certified organic growers.
Fighting Disease
For organic gardeners, the two primary ways to fight disease are to take steps to kill spores in the soil or on plant surfaces—before the spores infect roots or leaves. Soil solarization kills many types of disease spores, along with some pests and weed seeds. Applying biocontrol agents to soil or plants can kill or outcompete pathogens. And as a last resort, sulfur and copper sprays will kill spores and in some cases even prevent a disease organism from spreading within a plant.
The more you learn about the common disease problems in your area, the less often you’ll need to resort to using dusts and sprays. Keep records of the disease problems that occur in your garden, or ask fellow gardeners what diseases to expect in your area and when to expect them. This way, you can limit spraying or dusting to those seasons and weather conditions when your plants are most vulnerable to becoming infected.
It’s also important to make sure you know what disease you’re trying to control by applying a spray or dust. If you run into a problem that you can’t identify, submit a fresh plant sample to a diagnostic laboratory or your local extension office for identification.
Always take appropriate safety precautions when applying sprays and dusts; see the Pests entry for guidelines. The following descriptions of disease-control methods and products are arranged from least to most toxic.
Soil Solarization
If an area of your vegetable garden has been troubled by disease, or if you plan to start a new planting of any kind and are concerned about soil-borne diseases, consider solarizing the soil before you plant. You’ll need to plan ahead, because it’s important to solarize soil during the hottest period of the year if you live in the North.
Solarizing is a simple procedure: You tightly cover the soil with clear plastic for 1 to 2 months. This can generate high enough temperatures in the top 6 to 12 inches of soil to kill many disease organisms, nematodes, pest insects, and weed seeds. The beneficial effects seem to last for several seasons. The illustration at right shows how to prepare a bed for solarizing. For even better results, support a second layer of plastic on wire hoops over the covered bed to provide added insulation.
Midsummer is the best time to solarize soil, especially in the North. Cultivate and remove crop residues from the soil, rake it smooth, and water if it is dry. Dig a trench several inches deep around the bed, and spread thin clear plastic film (1 to 4 mils) over the bed. Press the plastic into close contact with the soil, and seal the edges by filling the trench with soil. Leave in place for 1 to 2 months, then remove the plastic.
Biological Controls
Solarization. Covering a bed of moist soil that’s a minimum of 6 feet by 9 feet with clear plastic during sunny, hot weather helps to kill disease spores. A second layer of plastic supported by wire hoops increases effectiveness.
One of the most exciting areas of plant disease research focuses on using naturally occurring bacteria and fungi to fight against plant pathogens. The bacterium Bacillus subtilis kills or out-competes the fungus that causes powdery mildew as well as some other plant pathogens. The fungus Trichoderma harzianum (sold as RootShield) kills the pathogen Rhizoctonia (one of the many fungi that cause damping-off). Trichoderma locates Rhizoctonia by a chemical the pathogen releases, then it attacks the damaging fungi and destroys it. In a study testing biological fungicides on vinca plants, researchers at Clemson University found that greenhouse plants treated with SoilGard (Gliocladium virens) had excellent shoot and root growth and were the equal of those treated with chemical fungicides.
Stress-Free Plants Don’t Get Sick
Plants are more prone to disease problems when conditions are not optimum for the plant, such as when they’re not getting enough water or nutrients. Be on the lookout for factors such as these that may leave your plants open to disease.
Moisture stress: Plants need a steady supply of moisture in the soil for proper growth. Too little and plants wilt. Too much and the roots become stunted from lack of oxygen. Either way, the plants are less able to resist disease-causing organisms.
Nutrient imbalance: It’s easy to understand that a nutrient deficiency can lead to disease, but too much fertilizer can also increase disease problems. For example, too much nitrogen can stimulate young succulent growth that is susceptible to powdery mildew, rusts, and fire blight. Such growth is also susceptible to cold injury, which in turn can lead to other diseases. Nutrient imbalances also cause symptoms that can be mistaken for disease symptoms (see page 481).
Lack of beneficial microorganisms: In a healthy garden environment, the multitude of good microorganisms in the soil and on plant surfaces tends to keep disease organisms in check. The balance, however, can be upset by overtilling, failing to add organic matter, or the improper use of pest-and disease-killing products (even organic ones). When the balance is upset, the disease-causing organisms often bounce back faster than the beneficial organisms that normally keep them in control.
Weather: The climate, weather conditions, and exposure also have major effects on plant growth. Cold injury, sunscald, hail, and wind can injure plant tissues, leaving openings for infection. Too much shade can result in weak growth. High humidity and lack of air movement encourages many plant diseases.
Mechanical damage: Lawnmower damage to bark and other types of injuries weaken plants and, more important, provide openings in a plant’s protective layers. Many diseases gain access to plants through wounds.
Chemical damage: Air pollutants, road salt, and herbicide drift are added insults that can weaken plants and leave them open to disease.
Among the most beneficial root-inhabiting organisms, antibiotic-producing mycorrhizal fungi (sold as BioVam) cover plant roots to protect against pathogens, forming a “fungal mat,” which also increases nutrient-uptake ability.
Barriers
A thorough spray of vegetable or light horticultural oil coats plant surfaces, acting as a barrier to infection. Oils seem to help prevent fungal rusts and mildews. For application rates, see page 456.
Garlic appears to be a fungicide as well as an insecticide. Horsetail (Equisetum arvense) infusion sprayed on plants may help prevent fungal diseases. For more information on making homemade sprays see “Home-Brewed Pest Controls” on page 461.
Bicarbonate Sprays
Commercial products containing potassium bicarbonate (such as GreenCure) and homemade baking soda (sodium bicarbonate) sprays prevent fungal spores from establishing themselves on plants and may even prevent established fungi from continuing to develop. Dissolve 1 teaspoon of baking soda and 1 drop liquid soap in 2 quarts of water, mix well, and spray on plants. A higher concentration isn’t better: If these sprays are too concentrated, they may burn plant foliage.
Neem
An oil extracted from the seeds of the neem tree is an ingredient in many products formulated to kill a wide variety of pest insects. Neem oil also is effective at killing some types of fungal disease spores. For more information on neem, turn to page 457.
Sulfur
Direct contact with sulfur prevents the development of disease organisms. However, it also damages important soil microorganisms and beneficial insects and is moderately toxic to mammals, including humans. Apply sulfur sparingly, and always take appropriate safety precautions.
Both a plain spray mix of elemental sulfur and mixtures of sulfur and other substances are effective preventive fungicides. Powdered sulfur is almost insoluble in water. Wettable sulfur has been finely ground with a wetting agent and is easier to use. Liquid sulfur is the easiest to dissolve. Sulfur also can be applied as a dust or as a fumigant.
Adding lime to sulfur increases its effectiveness as a fungicide. Lime allows the sulfur to penetrate leaves and kill recently germinated disease spores. However, lime sulfur sprays are more likely to damage plant tissue than are plain sulfur sprays. Certified organic growers must follow strict guidelines when using sulfur for disease control.
At temperatures above 85°F, sulfur can injure plant tissues. Combining sulfur and oil also causes damage to growing plants. A combination of oil and lime sulfur can be applied to dormant trees; see the Pests entry for details on oils.
Copper
Copper is a powerful, nonspecific fungicide that kills disease organisms. It damages beneficial soil microorganisms and beneficial insects and is more toxic than sulfur to plants. Repeated applications of any copper product will stunt plants. Copper sulfate is classified as very toxic to humans. Organic gardeners often choose to avoid copper fungicides when possible because of their negative effects on nonpest species.
Copper is available as a powder or liquid. Fixed-copper fungicides are available as dusts or sprayable solutions.
Common Plant Diseases and Disorders
The common names of plant diseases often reflect the type of symptom they cause. If you can identify the symptoms as a blight or wilt, for example, you may be able to successfully take steps to limit the disease, even if you don’t know the specific pathogen causing the infection. The most common garden plant diseases and disorders are described below.
Remember: If you’re considering applying a spray or dust, take time to identify the specific disease problem first so that you apply the appropriate product at the correct time to be effective.
Blights
When plants suffer from blight, leaves or branches suddenly wither, stop growing, and die. Later, plant parts may rot.
Fire blight: This bacterial disease affects apples, pears, fruit trees, roses, and small fruits. Infected shoots wilt and look blackened. For further description and controls, see the Pear entry.
Alternaria blight (early blight): This fungal blight infects ornamental plants, vegetables, fruit trees, and shade trees worldwide. On tomatoes, potatoes, and peppers, it is called early blight. On leaves, brown to black spots form and enlarge, developing concentric rings. Heavily blighted leaves dry up and die as spots grow together. Lower leaves usually show symptoms first. Targetlike, sunken spots will develop on tomato branches and stems. Fruits and potato tubers also develop dark, sunken spots. Alternaria spores are carried by air currents and are common in dust and air everywhere. They are a common cause of hay fever allergies. Alternaria fungi overwinter on infected plant parts and debris, or in or on seeds. Control this disease by planting resistant cultivars and growing your own transplants from disease-free seed. Apply Trichoderma harzianum to the soil just before planting. Promote good air circulation. For early blight, apply potassium bicarbonate (baking soda) sprays starting 2 weeks before the time of year when symptoms would normally first appear. Dispose of infected plants and when possible, use a 3-year rotation.
Phytophthora blight (late blight): Lilacs, rhododendrons, azaleas, and holly infected by Phytophthora fungi suffer dieback of shoots and develop stem cankers. Prune to remove infected branches and to increase air movement.
On peppers, potatoes, and tomatoes, Phytophthora infection is known as late blight. The first symptom is water-soaked spots on the lower leaves. The spots enlarge and are mirrored on the undersurface of the leaf with a white downy growth. Dark-colored blotches penetrate the flesh of tubers. These spots may dry and appear as sunken lesions. During a wet season, plants will rot and die. The pathogen overwinters on infected tubers and in plant debris. Avoid problems by planting only in well-drained soil, and use resistant varieties if possible. For late blight, keep foliage dry as much as possible, and check frequently for symptoms whenever the weather is wet. Preventive sprays of compost tea or Bacillus subtilis may help prevent the disease. Immediately remove and destroy plants infected with late blight; prune off cankered shoots of shrubs. After harvest, remove and destroy all plant debris that may be infected.
Bacterial blight: This bacterial disease is particularly severe on legumes in eastern and southern North America. Foliage and pods display water-soaked spots that dry and drop out. On stems, lesions are long and dark colored. Some spots may ooze a bacterial slime. To control, plant resistant cultivars, remove infected plants, and dispose of plant debris. Use a 3-year rotation and don’t touch plants while they are wet, as you may spread the disease.
Cankers
Cankers usually form on woody stems and may be cracks, sunken areas, or raised areas of dead or abnormal tissue. Sometimes cankers ooze conspicuously. Cankers can girdle shoots or trunks, causing everything above the canker to wilt and die. Blights and diebacks due to cankers look quite similar. Cold-injury symptoms may look like, or lead to the development of, cankers and diebacks.
Cytospora canker: This fungal disease attacks poplars, spruces, and stone fruits. The cankers are circular, discolored areas on the bark. To control, plant resistant trees and cut out branches or trees with cankers.
Nectria canker: This fungus attacks most hardwoods and some vines and shrubs. It is most damaging on maples. Small sunken areas appear on the bark near wounds, and small pink spore-producing structures are formed. It kills twigs and branches and may girdle young trees. Control by limiting pruning cuts and removing diseased branches.
Rots
Rots are diseases that decay roots, stems, wood, flowers, and fruit. Some diseases cause leaves to rot, but those symptoms tend to be described as leaf spots and blights. Rots can be soft and squishy or hard and dry. They are caused by various bacteria and fungi. Many are very active in stored fruits, roots, bulbs, or tubers.
Fruit rots: Grapes infected with black rot turn brown, then harden into small, black, mummified berries. Brown rot of stone fruits causes whole fruit to turn brown and soft. Control fruit rots by planting resistant cultivars, removing and destroying infected fruit, and pruning to increase air movement. Applying compost tea or Bacillus subtilis may help prevent the disease from developing. Sulfur sprays throughout the season can be effective, too, as a last resort.
Root and stem rots: Control these troublesome rots by providing good drainage and good air circulation. Try drenching the soil with beneficial fungi or bacteria. Start cuttings in sterilized mix, and plant only healthy plants. Dispose of all infected plant material. Winter injury may invite problems on woody plants.
Mushroom and wood rots: These rots can damage or kill trees. Some of them form obvious mushrooms or other fungal growths. Cutting out infected areas can provide control. Keep soil well drained, and plant resistant species and cultivars where problems are severe.
Rusts
Rusts are a specific type of fungal disease. Many of them require two different plant species as hosts to complete their life cycle. Typical rust symptoms include a powdery tan to rust-colored coating. Applying neem oil can help prevent rust by killing spores on the leaves.
Asparagus rust: This disease appears as a browning or reddening of the small twigs and needles, and a release of rusty, powdery spores. It overwinters on stalks and infects new shoots as they emerge the following spring. Rust is also carried to other plants by wind. To control, space plants to allow air circulation. Plant resistant cultivars. Remove infected plants and burn them in fall.
Other rusts: Wheat rust, cedar-apple rust, and white pine blister rust require alternate hosts. Wheat rust needs barberry to survive, cedar-apple rust needs both juniper and an apple relative, and white pine blister rust needs a susceptible member of the currant family. Removing the alternate hosts in the area can control outbreaks.
Wilts
Plants wilt when they don’t get enough water. When fungi or bacteria attack or clog a plant’s water-conducting system, they can cause permanent wilting, often followed by the death of all or part of the plant. Wilt symptoms may resemble those of blights.
Stewart’s wilt: This bacterial disease is widespread on sweet corn in eastern North America. It overwinters in flea beetles and infects corn when they begin feeding on its leaves. Infected leaves wilt and may have long streaks with wavy margins. Bacterial slime will ooze out if the stalks or leaves are cut. Plants eventually die or are sufficiently stunted that no ears are produced. To control, plant resistant cultivars and eliminate flea beetles. Destroy infected plants.
Fusarium and Verticillium wilt: These fungal wilts attack a wide range of flowers, vegetables, fruits, and ornamentals. Plants wilt and may turn yellow. To control, plant resistant cultivars. Rotate crops, or do not replant in areas where problems have occurred. If wilt only affects a branch, it may help to cut it out well below the wilt symptoms. Destroy infected branches or plants.
Other Diseases
Anthracnose: Anthracnose, or bird’s-eye spot, is a fungal disease. It causes small dead spots that often have a raised border and a sunken center, and that may have concentric rings of pink and brown.
Bean anthracnose infects beans and other legumes. The symptoms are most obvious on the pods as circular, black, sunken spots that may ooze pink slime and develop red borders as they age. To control, buy disease-free seed, rotate crops, turn under or hot-compost infected plants, and avoid touching plants when they are wet so you won’t spread the disease.
Club root: Club root affects vegetables and flowers in the cabbage family. Plants infected by the fungus wilt during the heat of the day, and older leaves yellow and drop. Roots are distorted and swollen. Avoid club root by choosing resistant cultivars and raising your own seedlings. The fungus has spores that can persist in soil for many years. If you’ve had past club root problems, adjust the soil pH to at least 6.8 before planting susceptible crops.
Damping-off: Damping-off is caused by a variety of soilborne fungi. Seeds rot before they germinate, or seedlings rot at the soil line and fall over. It can be a problem with indoor seedlings and also in garden beds. Prevent damping-off by keeping soil moist, but not waterlogged. Provide good air movement in seed-starting areas. Wait until soil is warm enough for the specific plant before seeding. Sterile seed-starting mix or a mix that includes compost can help prevent problems, too. If you’ve had past problems with this disease, add compost to your soil, and use a product containing Trichoderma harzianum to drench the soil before planting.
Downy mildew: Downy mildews are fungal diseases that attack many fruits, vegetables, flowers, and grasses. The primary symptom is a white to purple, downy growth, usually on the undersides of leaves and along stems, which turns black with age. Upper leaf surfaces have a pale color. Lima bean pods may be covered completely, while leaves are distorted. The disease overwinters on infected plant parts and remains viable in the soil for several years. It is spread by wind, by rain, and in seeds. To control it, buy disease-free seeds and plants, follow a 3-year rotation, and remove and dispose of infected plants. Preventive sprays of bicarbonate may be effective.
Galls: Galls are swollen masses of abnormal tissue. They can be caused by fungi and bacteria as well as certain insects. If you cut open a gall and there is no sign of an insect, suspect disease.
Crown gall is a serious bacterial disease that infects and kills grapes, roses, fruit trees, brambles, shade trees, flowers, and vegetables. Galls are rounded with rough surfaces and are made up of corky tissue. They often occur on the stem near the soil line or graft union but can also form on roots or branches. To control it, buy healthy plants, and reject any suspicious ones. Don’t replant in an area where you have had crown gall. Avoid wounding stems, and disinfect tools between plants when pruning. Remove and destroy infected plants, or cut out galls.
Leaf blisters and curls: Leaf blister and leaf curl are fungal diseases that cause distorted, curled leaves on many trees. Oak leaf blister can defoliate and even kill oak trees. Blisters are yellow bumps on the upper surface of the leaves, with gray depressions on the lower surface. Peach leaf curl attacks peaches and almonds. New leaves are pale or reddish and the midrib doesn’t grow along with the leaves, so the leaves become puckered and curled as they expand. Fruit is damaged, and bad cases can kill the tree. Both diseases are controlled with a single dormant oil spray just before buds begin to swell.
Leaf spots: A vast number of fungi can cause spots on the leaves of plants. Most of them are of little consequence. A typical spot has a definite edge and often has a darker border. When lots of spots are present, they can grow together and become a blight or a blotch.
Blackspot is a common disease on roses. The spots appear on the leaves and are up to ½ inch across with yellow margins. Severe cases cause leaves to drop. To control blackspot, plant resistant cultivars, and destroy all dropped leaves and prunings. Mulch to prevent dirt and spores from being splashed up onto plants. Bicarbonate sprays can be very helpful in preventing leaf spot diseases.
Molds: Molds are characterized by a powdery or woolly appearance on the surface of the infected part.
Gray mold, or botrytis, is a common problem on many fruits and flowers. It thrives in moist conditions and is often seen on dropped flower petals or overripe fruit. It appears as a thick, gray mold or as water-soaked, blighted regions of petals, leaves, or stems. In most cases it first infects dead or dying tissue, so removing faded flowers and blighted buds or shoots will control the problem. Peonies, tulips, and lilies can be severely damaged in wet seasons. Destroy infected material, and space, prune, and support plants to encourage good air movement.
Nematodes: Nematodes themselves are described earlier in this entry. Symptoms of nematode invasion include reduced growth, wilting, and lack of vigor.
Some nematodes cause excessive branching of roots, rotted roots, and enlarged lumps on roots. Other nematodes attack leaves, causing triangular wedges of dead tissue.
Root knot nematodes attack a variety of plant root systems, including most vegetable and ornamental crops. Carrot plants will be stunted, with yellowed leaves, and roots may be distorted. Roots of other plants will have swollen areas. Remember that legumes are supposed to have swellings on their roots that are caused by nitrogen-fixing bacteria.
Prevent nematodes from invading your plants by maintaining your soil organic matter. Plant resistant varieties when possible. Take care not to spread soil from nematode-infested areas to other parts of your garden or yard. Reduce nematode populations by solarizing soil. Use a marigold (Tagetes patula or T. erecta) cover crop to reduce nematodes. Rotate susceptible crops. Adding products containing chitin to the soil can help reduce problems.
Hot-water dips can eradicate nematodes from within roots, bulbs, and the soil on them.
Powdery mildew: Mildews are one of the most widespread and easily recognized fungi. They are common on phlox, lilac, melons, cucumbers, and many other plants. Mildew forms a white to grayish powdery growth, usually on the upper surfaces of leaves. Small black dots appear and produce spores that are blown by wind to infect new plants. Leaves will become brown and shrivel when mildew is extensive. Fruits ripen prematurely and have poor texture and flavor. To control mildews, prune or stake plants to improve air circulation and dispose of infected plants before spores form. Apply bicarbonate sprays to prevent the spread of infection.
Scabs: Scabs are fungal diseases that cause fruits, leaves, and tubers to develop areas of hardened, overgrown, and sometimes cracked tissue. Fruit scab can be a major problem on apples and peaches. Control by disposing of fallen leaves and pruning to increase air movement. If you’ve had past serious problems with scab, ask your local extension service about the best spray schedule for sulfur to control the disease.
Smuts: Smuts are fungal diseases. They are most commonly seen on grasses, grains, and corn. Enlarged galls are soft and spongy when young but change to a dark, powdery mass as they age.
Corn smut can form on kernels, tassels, stalks, and leaves. Smut galls ripen and rupture, releasing spores that travel through the air to infect new plants and overwinter in the soil, awaiting future crops. To control corn smut, select resistant cultivars. Remove and burn galls before they break open, and follow a 4-year rotation.
Viruses: Infected plants often grow slowly and yield poorly. Leaves may cup or twist, and develop mottling, streaking, or ring-shaped spots. Identification is often the elimination of all other possible causes. Professional growers use heat treatments and tissue culture to control viral disease. Purchase certified plants to avoid problems. Control insects that spread viruses. Remove and burn all plants with viral disease to prevent the disease from spreading.
Common Cultural Disorders
Cold injury: Freezing injury can cause death or dieback. Symptoms of cold stress are stunting, yellowing, bud or leaf drop, and stem cracking. Fruit may form a layer of corky tissue or be russeted if exposed to cold when young.
Common Nutrient Deficiency Symptoms in Plants
The plant nutrition problems gardeners most often face are the result of nutrient deficiencies. Some deficiency symptoms are easy to identify, but others can be difficult to distinguish from disease or general stress symptoms. Unfortunately, plants can’t tell us what nutrients they may be lacking, and visual diagnosis of deficiencies is an imprecise art. One helpful tip is to remember that some nutrient deficiencies are likely to appear on new growth first, while others appear first on older plant parts. This table groups deficiency symptoms according to where symptoms are likely to show up first.
| NUTRIENT | DEFICIENCY SYMPTOMS |
| SYMPTOMS APPEAR FIRST ON OLDER OR LOWER LEAVES | |
| Nitrogen | Lower leaves yellow, overall plant light green, growth stunted |
| Phosphorus | Foliage red, purple, or very dark green; growth stunted |
| Potassium | Tips and edges of leaves yellow, then brown; stems weak |
| Magnesium | Interveinal chlorosis, growth stunted |
| Zinc | Interveinal chlorosis, leaves thickened, growth stunted |
| SYMPTOMS APPEAR FIRST ON YOUNGER OR UPPER LEAVES | |
| Calcium | Buds and young leaves die back at tips |
| Iron | Interveinal chlorosis, growth stunted |
| Sulfur | Young leaves light green overall, growth stunted |
| Boron | Young leaves pale green at base and twisted, buds die |
| Copper | Young leaves pale and wilted with brown tips |
| Manganese | Interveinal chlorosis on young leaves with brown spots scattered through leaf |
| Molybdenum | Interveinal chlorosis, growth stunted |
Heat injury: Temperatures that are too high cause sunscald of fruits, leaves, or trunks on the sunny side of the plant. Discoloration, blistering, or a water-soaked and sunken appearance are other symptoms of heat stress.
Moisture imbalance: Plants need a relatively constant supply of water. If they don’t have enough, they will wilt. Long periods of wilting, or repeated wilting, can cause stunting, pale color, and reduced flowering and fruit production. Plant roots also need oxygen. Too much water in the soil damages roots and will cause symptoms like frequent wilting, pale color, root decay, leaf dropping, and lack of vigor.
Wind damage: High winds also take their toll on plant appearance. Silvery discoloration and tattered leaves are symptoms of wind damage.
Salt damage: Ocean spray and road salt, as well as animal urine, can injure plants. Salts can accumulate on leaves, stems, and buds, or build to toxic levels around the roots. Over time, salt burn weakens the entire plant and causes droughtlike symptoms.
Ozone damage: Ozone is a common air pollutant that can cause a wide range of symptoms in susceptible plants, including withered leaves on citrus and grapes and tipburn on conifers. If you confirm that ozone is a common pollutant where you live, your only recourse is to avoid planting sensitive species.
PLANTING
One of the best ways to ensure that plants will thrive is to do a good job planting them. Preparing planting areas thoroughly is time well spent, because it ensures that roots can quickly extend through the soil.
Matching Plant with Site
Before you dig that planting hole or plant those seeds, try to make a good match between the plant and its environment. Learning to know your soil and growing conditions—and using that knowledge to pick the right plants—is just as important as knowing the best planting techniques. So before you plant:
Take a close look at your soil. Is it red clay or deep loam? Waterlogged or sandy or dry? Is it acid or alkaline?
Check the amount of sunlight your site gets. Is it full sun all day or just afternoon sun? Is the shade dappled through the small, shifting leaves of a birch, or deep and heavy, as beneath an evergreen? A tomato plant must have at least 6 hours of direct sunlight daily for good fruit set, but the same amount of sun fades and burns tender fern fronds.
Know your hardiness zone. Your local nurseries and garden centers generally stock only plants that are hardy in your area, but “big box” stores are often less careful in their selections and may sell plants that are not winter hardy in your area. If you shop at these types of outlets or if you do any Internet shopping or mail-order buying, knowing your zone will save you money and disappointment. If you’re not familiar with the concept of hardiness zone, see the Weather and Weather Lore entry for an explanation.
Be aware of seasonal conditions. Is the spot you picked sheltered by a wall or windbreak, or is it exposed to chilling winter wind? Is it low lying and prone to late-spring frost?
Learn the growth rate and size of your plants. Choose a site where they won’t cause problems or overgrow your garden. This is especially important for permanent plants such as trees and shrubs.
Planting by the Moon
Since our ancestors first poked a seed into the ground, astrology has played a role in gardening and farming. Today it’s easy to scoff at people who plant by moon signs and phases, but in truth, we don’t know whether the idea is valid or not. The moon’s position in the sky does appear to influence plant and animal behavior. People who plant and garden by zodiac signs claim they mark the cyclical movement of the planets and are, therefore, good indicators of natural rhythms in the universe.
Even those who don’t believe that planting by signs of the zodiac makes any difference can understand why the sun, moon, and stars were so important to ancient peoples. They were constants in our ancestors’ daily lives. Men and women used the pattern made by the stars’ regular cycles in the heavens as a calendar. Then they saw that crops fared better when planted at certain times than at others. The moon was believed to be the mistress of growth. During a certain period of time (29½ days on average), the moon passed through 12 constellations. This was the zodiac, or circle of animals, also thought to influence plants and planting.
As centuries passed, ancient civilizations learned that some of the celestial objects they had called stars were actually planets. The planets also were given characteristics, and all living things were placed under both the sign of a planet and a zodiac sign. These beliefs gave rise to elaborate systems of gardening, where every task was linked to a certain planet and constellation, ideally when the moon was in a complementary phase.
Enough first-rate farmers and gardeners follow the signs to make us take notice. Maybe they would do just as well if they didn’t garden by the signs. We don’t know. We do know that planting by the moon signs and moon phases does no harm. Why not try an experiment? Plant half your garden by the signs; the other half as you normally would. See for yourself which plot does best. Be fair and let common sense be the overriding factor. Even the most devout “sign planters” take weather and temperature into account before undertaking a gardening project.
For more information about planting by the moon, see Resources on page 672.
Getting Soil in Shape
If you set plants into poorly drained soil, the roots are likely to rot and die. If you plant seeds into poorly drained soil, they may never even germinate. Before you plant a pumpkin seed or a pine tree, be sure that your soil drains well. If drainage is poor, see page 559 for ways to improve it. Or consider growing plants in raised beds. The Raised Bed Gardening entry explains how to make and plant raised beds. For very wet areas, your best bet may be to grow plants that can tolerate wet conditions. See the Water Gardens entry for ideas.
If you till the soil for a vegetable garden or dig a hole for a tree when the soil is too wet, you’ll destroy the soil’s structure. Your soil will compact, causing water to run off or sit in puddles rather than penetrate. Without air, root growth suffers. If your soil is too wet, let it dry before planting. Pick up a handful of soil and squeeze it. If it crumbles, it’s perfect for planting. But if it forms a muddy ball, the soil is too wet for planting.
Most plants pay less attention to pH than gardeners do. If your soil is fertile and well drained and neither extremely acid nor extremely alkaline, most plants will do just fine. But a few popular garden plants are more demanding. Acid-loving azaleas and blueberries, for instance, will do poorly in soil that’s on the alkaline side. If you don’t know the soil pH in an area you plan to plant, it’s a good idea to test it.
Enrich flower and vegetable beds with lots of compost or leaf mold before planting. For more about soil testing and enriching your soil, see the Compost, Cover Crops, Fertilizers, and Soil entries.
Seeds
Plant flowers and vegetables in fertile, well-drained soil that is rich in organic matter. If you’re starting a new garden, prepare the soil by working in plenty of organic matter. Double digging loosens the top 2 feet of the soil, increasing pore space to hold soil and water. For more information on soil preparation techniques, see the Soil entry.
If you must, you can prepare seedbeds with a rotary tiller, but it’s preferable to turn the soil gently with a spade or garden fork instead. If you can dig or till in fall, you’ll be one step ahead come spring. Rake the soil to a fine tilth, breaking up clods and removing stones and weeds.
Check seed packages to find out when to sow and if the plants have any special germination requirements. Some plants, such as peas, prefer cool weather; others, such as corn, will rot if planted before soil warms up. Many will produce flowers or fruit earlier if given a head start indoors or in a cold frame. If you’re interested in starting seeds early, see the Cold Frames and Seed Starting and Seed Saving entries.
Sow seeds thinly to avoid thinning chores later. Sprinkle flower seeds in long single rows for cutting, or broadcast with a flinging motion over a wider area for a free-form display. Plant small vegetable seeds such as lettuce and spinach in rows, or scatter them in a wide band. Plant large flower and vegetable seeds individually, spaced according to package instructions. Vining plants such as melons and cucumbers can be planted in slightly raised mounds called hills, with 3 to 5 seeds per hill.
Cover the seeds with fine soil to a depth 2 to 3 times the diameter—not the length—of the seed. Firm the soil (use the palm of your hand or the back of your hoe) to establish good contact between seed and soil. Some seeds, such as lettuce, petunias, and begonias, must have light to germinate. Lightly press seeds like these onto the surface of moistened soil. (Always read seed packet directions for special germination requirements.)
Always water gently after you plant seeds, taking care not to wash the seeds away. A fine, misty spray is best; you can buy a hose attachment at garden centers and hardware stores. Keep the soil evenly moist until you see stems and leaves popping above the ground.
Bulbs and Herbaceous Perennials
Plant bulbs and perennials in prepared beds that have been enriched with organic matter and have excellent drainage. Bulbs are especially quick to rot in soggy conditions. If you are making a naturalistic bulb planting in a lawn area, add a handful of bonemeal to each planting hole.
Bulbs
Plant bulbs individually, or dig a hole big enough for several bulbs at a time. Even an entire bed can be dug out, then refilled after the bulbs are placed. Dig the planting hole to the depth recommended for each type of bulb, generally 3 to 4 times their widest diameter. When planting bulbs individually, dig holes just slightly wider than the widest diameter of the bulb. Place bulbs pointed-end up in their holes and cover with soil. If you can’t tell which end is up, plant the bulb sideways, and the roots and stems will grow in the proper direction. Firm the soil, and water. If you’re planting in a lawn area for naturalizing, carefully replace plugs of grass atop the holes.
Perennials
Perennials generally are available either bareroot or growing in containers. There’s no time to waste with bareroot perennials—if you can’t plant right away, remove packaging and store roots in moist peat, or heel in the plants in a trench with one vertical and one slanted side, as shown below. For best results with heeling in, uncover the plants and move them to a permanent position while they’re still dormant.
When planting, dig a hole wide enough to allow you to fully spread out the roots and deep enough so the plant is set at the same depth at which it grew previously. Fill soil in around the plant, but avoid burying the crown, from which new shoots will spring. Water thoroughly and mulch. Punch holes in four sides of a cardboard box for ventilation, then upend the box over the newly planted perennial and leave it there for a few days. This blocks light, but allows for some ventilation, and encourages the plant to direct its energies into root growth instead of leaves and stems.
Heeling in. If you can’t plant bareroot perennials, shrubs, or trees right away, keep the roots moist by heeling them in in a spot sheltered from direct sun and wind. Lay the plants against the slanted side of the trench, and cover the roots with soil.
Container-grown perennials are gratifyingly easy to add to the garden. Dig a hole just a bit wider than and the same depth as the pot. To prevent wilting, make a mud puddle of your planting hole by filling it with water. Wait till the water drains away, then fill again. When the water drains the second time, you’re ready to plant.
To remove the plant from the container, hold one hand firmly across the soil surface, with the plant stems between your fingers. Then flip the pot over. With a bit of wiggling and gentle tugging, the pot should slide free. If not, give it some encouragement by smacking the bottom with your trowel. Untangle potbound roots, and set the root ball in the hole. Fill, firm the soil, water once more, and mulch.
Trees and Shrubs
Trees and shrubs represent a sizable investment, and time spent digging and preparing a suitable hole will yield long-term benefits in terms of faster and healthier growth. Keep in mind that although some trees’ roots may go deep, the small but all-important feeder roots grow mainly in the top 6 to 8 inches of soil. For this reason, it’s important to shape the hole to accommodate the feeder roots, sculpting the sides to be widest near the surface.
Plant trees and shrubs at the same depth at which they were previously planted. Look for the dark mark on the plant stem that indicates how deep the plant was grown at the nursery. Checking depth by hauling the tree or shrub in and out of the hole is a lot of wear and tear on you and the plant. Here’s an easier way: Measure from the stem mark to the bottom of the roots or root ball to find out how deep the hole should be. As you dig, check depth now and then by laying a board cross the hole and measuring from the board’s center to the bottom of the hole.
To encourage feeder roots to spread out, prepare a planting site that is shallow and wide, as shown on the opposite page. To loosen ground surrounding the hole, plunge a garden fork in as deep as the tines allow, and wiggle it slightly to break up compacted soil. Repeat every 1 to 1½ feet to a distance of 5 feet or more on all sides.
Settling Them In
Your new trees and shrubs may be bareroot, balled-and-burlapped (B&B), or planted in a container. Many deciduous trees and shrubs, such as apples, maples, lilacs, and roses, are sold as dormant, bareroot plants. Evergreens are usually sold B&B because even when they’re dormant, they have leaves that draw water from the roots. Container-grown plants have roots established in the container (sometimes a little too well established!); these plants are easy to add to your garden, even in full growth.
When planting any tree or shrub, fill the hole with native soil that has not been amended with fertilizer or compost. Otherwise, the roots tend to stay in the cushy, rich, improved soil rather than spreading out into the surrounding soil. For best results, follow these guidelines when planting.
Bareroot plants: As long as you plant bare-root trees or shrubs while the stock is still dormant, your chances of success are good with these generally low-cost plants.
Leave a small cone of undisturbed soil in the center of the hole. Remove any circling, broken, or diseased roots. Spread out the roots over the cone of soil. After settling the plant in the hole, observe it from all angles to be sure it is positioned straight up and down. There’s nothing more frustrating than filling your planting hole and then discovering that the plant is set crookedly. Once you’re sure the plant is positioned properly, add soil gradually. Give the tree or shrub an occasional shake as you refill the hole to sift soil among the roots. Water well and mulch.
Planting Pointers
Take the time for small details when you plant any new tree or shrub. Preparing the root ball, settling the plant properly, mulching, and pruning dead and diseased branches all will contribute to your new plant’s health, beauty, and longevity.
- Dig a planting hole at least twice as wide as the root ball’s diameter.
- Cut or remove ropes around root ball or top of wire basket.
- Peel burlap back from top of root ball.
- Sculpt planting hole sides to be widest near the surface.
- If using support stakes, drive them into soil outside root ball.
- Set tree so that flare of root ball is just above soil level.
- Sit root ball on a small cone of undisturbed soil.
- Spread a 2-inch layer of mulch, keeping mulch away from the crown.
- Prune away diseased, dead, and crossing branches.
- Wrap tree trunk from soil level to lowest branches if damage by animal pests is a concern.
- Cover guy wires with protective material where they encircle the tree.
- Leave guy wires slightly slack.
Balled-and-burlapped plants: It’s best to get balled-and-burlapped (B&B) plants in the ground while they’re dormant, so the roots can get a good start before they have to supply food and water to burgeoning top growth. But the B&B method gives you more leeway; even actively growing trees and shrubs can be held until the weekend for planting.
Don’t Coddle the Roots
Standard tree-planting instructions used to include a recommendation to enrich the soil in planting holes with organic amendments and fertilizers. But recent studies show this can hinder, not help, new trees and shrubs as they adjust to your native soil.
A hole filled with peat moss and rotted manure encourages roots to grow only in the hole instead of branching out into the surrounding soil. These pockets of overly amended soil stay too wet during rainy periods and too dry during drought. This means tree roots can suffocate from too much moisture or can be more prone to wilting during drought. Also, since the roots don’t spread and anchor the plant strongly, it will be more susceptible to windthrow—being toppled during high winds.
Remove binding ropes or twine and all nails. Leave natural burlap in place: It will eventually rot. Slit synthetic wrapping material in several places so roots can penetrate it. Try to keep the root ball intact. If the root ball is in a wire basket, cut off the loops on top to keep them from sticking up through the soil, and snip and remove the top few wires. As with bareroot plants, make sure the plant is set vertically before filling the hole. If the tree is large, have a helper hold it in place as you fill the hole. After every few shovelfuls of dirt, add water to help settle air pockets.
Container-grown plants: Remove any labeling tags to keep the tags or wires from cutting into the stems. Support the plant while you turn it upside down and remove the pot. Even fiber pots of compressed peat or paper are best removed; exposed edges wick away moisture, and the walls slow down root growth.
Snip off dead or sickly roots and use your fingers to comb out any potbound roots. Cut through circling roots. Set plant as deep as it grew before, make sure it’s straight, then fill the hole.
Finishing Touches
Level the soil around the base of the plant. Don’t stomp all the air out of your newly filled hole: Instead of using your feet, tamp the soil with your hands or the back of a hoe to settle it and eliminate air pockets.
Water and mulch: Soak the soil thoroughly after planting. Apply a 2- to 3-inch layer of mulch to retain moisture, keeping it a couple of inches away from the trunk. Make it a habit to water new plants once a week during their first year, especially if rainfall is less than 1 inch per week. By the time you notice wilting or other signs of stress, the roots may already be damaged and it may be too late.
Pruning: You don’t need to prune newly planted trees and shrubs, except to remove branches that are broken, diseased, narrow-angled, or overlapping. If you cut back all the branches, you may actually slow your tree’s or shrub’s establishment, because buds produce chemicals that aid root growth. The exception is young fruit trees, which you must prune promptly if you plan to train them for easier harvesting and care. See the Fruit Trees and Pruning and Training entries for more information.
Wrapping the trunk: A tree wrap protects the trunk from sunscald, nibbling rodents, and lawn mower nicks. Wrap the trunk from the base to the lowest branch, and tie in place. Remove wrapping after no more than a year.
Staking: Stake trees only if they’re located in a windy area or if they’re top-heavy. One or two stakes will hold a small tree, while three stakes may be needed for a large tree. Allow a few inches of slack in the wire or other material that you use to attach the tree to the stake so that the tree can sway a bit in the wind. Remove stakes and attaching materials after 1 year to prevent damage to enlarging stems.
PLATYCODON
Balloon flower. Summer-blooming perennials.
Description: Platycodon grandiflorus, balloon flower, bears inflated, balloonlike buds that open into 2-inch starry bowls of violet-blue, white, or pink, on 1½- to 3-foot plants with attractive 3-inch oval leaves. Dwarf cultivars are available that form tidy mounds only 9 inches tall. Zones 3–8.
How to grow: Set out small or container-grown plants in spring, or divide by carefully separating the fleshy roots before shoots emerge. Plant in a sunny or lightly shaded spot with average to rich, well-drained soil. Balloon flowers come up late in spring; mark their location so you won’t damage them while digging. Stake taller cultivars. Deadhead spent blooms to prolong the bloom season. Plants will self-sow.
Landscape uses: Balloon flowers are beautiful with Rudbeckia ‘Goldsturm’, daylilies (Hemerocallis spp.), and other summer-flowering perennials in beds and borders. Dwarf cultivars make attractive container plants.
PLUM
Prunus spp.
Rosaceae
Plum trees bear greenish, yellow, red, purple, and blue fruit in a wide range of shapes, sizes, and flavors to suit every taste. The Fruit Trees entry covers many important aspects of growing plums; refer to it for more information on planting, pruning, and care.
Selecting trees: Most European plums (Prunus domestica) and damson plums (P. insititia) are partly self-fruitful. They are more hardy (Zones 4–9) and tend to bloom and ripen later than Japanese cultivars. They have a high sugar content and can be dried to make prunes. ‘Castleton’ and ‘Victoria’ are self-fruitful and highly productive.
Most Japanese plums (P. salicina) require cross-pollination. In fact, you may need three compatible cultivars for good crop set because some cultivars don’t produce much pollen. Early-blooming European cultivars may pollinate Japanese cultivars. Japanese plums are less hardy (Zones 6–10) and tend to have larger fruit than European cultivars. Fruits are quite juicy, with a blend of sweet and tart flavor. ‘Beauty’ is self-fruitful; ‘Crimson’ resists black knot and bacterial canker diseases. European/Japanese hybrids, which combine the characters of both types, are available. Choose disease-resistant trees to prevent many common problems.
Many native Prunus species are sold as bush plums. They tend to have small fruit but tolerate drought and hot summers well. Hybrids of plum and cherry or apricot can be fun to try.
Plumcots are a cross between plum and apricot; they require a Japanese plum planted nearby for pollination.
Rootstocks: Trees grafted on ‘Myrobalan’ rootstocks will reach about 20 feet tall. They tend to be hardy and long-lived, resistant to canker and nematodes, and tolerant of clay. Good dwarf and semidwarf rootstocks are available and produce trees as small as 8 feet; ‘Pumiselect’ is a new cold-and drought-tolerant dwarfing rootstock.
Planting and care: Space plum trees 20 to 25 feet apart. Plums don’t compete well with grass in lawns. Spread a thick layer of organic mulch out to the drip line to conserve moisture.
Pruning: Generally, European plums grow upright and Japanese plums spread. Train European types to a central leader as shown on page 245 and Japanese types to an open center as shown on page 246. European plums bear fruit on long-lived spurs in the tree’s interior. Thin suckers and overly thick outer growth to let in sunlight and encourage ripening. Japanese types fruit on older spurs as well as year-old wood. Encourage new growth by pruning off old wood, but leave the still-fruitful inner spurs.
Thinning: Shake limbs to thin or pinch off small, odd-shaped, or overcrowded fruits before the pits harden. Leave 1 to 3 inches between small fruits, 4 to 5 inches between larger ones.
Problems: Plums have many of the same problems as other stone fruits. Expect birds to take their share as well. See the Cherry and Peach entries for common problems. Select resistant trees and prune for good air circulation.
Harvesting: Most plum trees bear in 3 to 4 years from planting. Harvest plums for cooking when they are slightly immature. For fresh eating, let European types grow sweet and soft on the tree. Pick Japanese plums a little early and let ripen indoors. Leave the stems on the fruit and handle as little as possible, and the plums will store better.
POISONOUS PLANTS
Wild mushrooms are a famous example of poisonous plants, and most of us know that some houseplants, such as dieffenbachia, and holiday plant decorations, like mistletoe, are quite toxic. But common backyard plants can also pose a hazard. By learning which plants are poisonous, you can avoid growing them while you have small children, or you can make the garden childproof.
Common plants that are poisonous to touch are usually found in wooded or suburban areas. In the eastern United States and Canada, look out for poison ivy (Rhus toxicodendron) and its cousin, poison sumac (R. vernix). In the western regions of these countries, watch out for poison oak (R. diversiloba). In some areas, you may find stinging nettles (Urtica dioica) in fields, ditches, or open areas. All these plants cause a burning rash, which, in the case of poison ivy, oak, and sumac, can linger and itch for weeks.
Common vegetables with poisonous leaves are potatoes, tomatoes, and rhubarb.
It’s wise to learn which ornamental plants are mildly to fatally poisonous when eaten, too. All parts of autumn crocus (Colchicum autumnale), bittersweet (Celastrus scandens), bleeding hearts (Dicentra spp.), boxwood (Buxus sempervirens), daffodils (Narcissus spp.), English ivy (Hedera helix), flowering tobacco (Nicotiana alata), horse chestnut (Aesculus × carnea), hydrangeas (Hydrangea spp.), mountain laurel (Kalmia latifolia), rhododendrons and azaleas (Rhododendron spp.), and Virginia creeper (Parthenocissus quinquefolia) are poisonous.
Leaves of foxglove (Digitalis purpurea), larkspurs and delphiniums (Delphinium spp.), monkshoods (Aconitum spp.), and oleander (Nerium oleander) are poisonous. Berries of lily-of-the-valley (Convallaria majalis) and hollies (Ilex spp.), hyacinth bulbs (Hyacinthus orientalis), and lupine seeds (Lupinus spp.) are also poisonous.
An excellent resource for identifying poisonous plants is the Handbook of Poisonous and Injurious Plants by Lewis S. Nelson, Richard D. Shih, and Michael J. Balick.
POPPY
See Papaver
PORTULACA
Portulaca, moss rose. All-season annuals.
Description: Portulaca’s 1-inch single or double roselike flowers, in white, pink, red, yellow, orange, or magenta bloom freely on sprawling, 4- to 6-inch mats of succulent, needlelike leaves.
How to grow: Sow seeds directly after the soil warms up, or set out transplants no more than 6 inches apart. Plants thrive in sunny, hot, dry areas with poor soil. Plants self-sow readily, but the flower color may revert to bright magenta.
Landscape uses: Use portulaca as a filler between paving stones and cracks. It also adds color to pots and baskets.
POTATO
Solanum tuberosum
Solanaceae
Growing potatoes is fun as well as practical, thanks to the development of disease-resistant varieties and varieties in a range of colors, shapes, and sizes. Native to the Andes mountains of South America, potatoes thrive in the cool northern half of the United States and the southern half of Canada. Growers in other areas, however, can have successful crops by planting potatoes in very early spring or, in warm regions, in fall or winter for a spring harvest.
Planting: Although you can grow some potato varieties from seed, it’s easier to plant certified, disease-free “seed potatoes” purchased from garden centers or Internet and catalog suppliers. (Potatoes you buy at the grocery store are often chemically treated to prevent the eyes from sprouting.) You’ll need 5 to 8 pounds of potatoes to plant a 100-foot row. Along with standards such as ‘Katahdin’, try some colored potatoes like ‘All Blue’, ‘Rose Gold’, ‘Purple Peruvian’, and ‘Cranberry Red’.
Potatoes need space, sunshine, and fertile, well-drained soil. Acid soil provides good growing conditions and reduces the chance of a common disease called scab.
Plant seed potatoes whole, or cut them into good-sized pieces, each of which should contain 2 or 3 eyes. Cure the cut pieces by spreading them out in a bright, airy place for 24 hours, or until they are slightly dry and the cut areas have hardened. In wet climates, some gardeners take the precaution of dusting seed potatoes with sulfur to help prevent rot.
Plant early cultivars 2 to 3 weeks before the last spring frost or as soon as you can work the soil. Time the planting of late cultivars so they will mature before the first fall frost.
Plant potatoes in rows spaced 3 feet apart. Place the seed pieces 6 inches apart, and cover them with 4 to 5 inches of soil. As the vines grow, hill soil, leaves, straw, or compost over them to keep the developing tubers covered. (When exposed to sunlight, tubers turn green and develop a mildly toxic substance called solanine.) Leaving only a small portion of the growing vines exposed encourages additional root development.
Many growers prefer to plant potatoes in hills. The illustration at right shows potatoes planted in soil hills and mulch mounds. The mulch-planting method is especially good for growing potatoes in containers, such as large barrels. This “dirtless” method makes harvesting extremely clean and easy but can produce a smaller crop of small tubers.
Growing guidelines: Once the plants blossom, stop hilling up the soil, and apply a thick mulch to conserve moisture and keep down weeds. Water deeply during dry spells.
Problems: Climate and growing conditions can create a number of problems. Speckle leaf, a disorder that appears as dark splotches on leaves with sunken areas on the leaf undersides, is apparently caused by too much ozone in the atmosphere. Breeders are developing resistant cultivars. Keeping plants healthy and well cultivated is the best prevention.
Hollow areas in tuber centers are caused by rapid and uneven growth. To prevent this, plant seed potatoes closer together, cut down on watering and fertilizer, and avoid susceptible cultivars.
Potatoes are attractive to several kinds of pests, including aphids, Colorado potato beetles, cutworms, and flea beetles. For control measures, see page 458.
Planting potatoes. Dig furrows about 6 inches deep, space the seed pieces 6 inches apart and hill up the soil around the stems as they grow. Or, spread compost or shredded leaves over the surface of your potato bed, space your seed potatoes evenly over the mulch and top with about a foot of straw or hay.
Other possible pests include blister beetles, leafhoppers, and wireworms. Blister beetles are ¾ inch long, slender, dark-colored insects that feed on leaves; reduce damage by hand picking (be sure to wear gloves to avoid blisters). Thin, wedge-shaped, ¼-inch-long leafhoppers cause leaves to curl and yellow; apply soap spray for control. Wireworms are ½- to ¾-inch-long larvae of the click beetle; these orange “worms” feed on and damage developing tubers. They are more prevalent in newly cultivated areas, so wait a few years after converting a lawn area into garden to plant potatoes there; crop rotation and frequent cultivation can also help, as can wireworm traps like those described on page 455.
An intriguing development in pest control is varieties such as ‘Prince Hairy’ and ‘King Harry.’ These varieties discourage leafhopper and Colorado potato beetles from feeding by virtue of their hairy leaves. The hairs contain sticky fluid that leaks out when hairs are touched, coating the insects with goo.
Avoid most potato diseases by rotating crops, providing good air circulation, keeping the garden clean, selecting resistant cultivars, and planting disease-free seed potatoes. If disease does strike, remove and destroy affected plants. Here are some diseases that might occur:
Black leg, a bacterial infection, begins as yellowing of top foliage and progresses to a black, slimy rot that destroys stems and tubers.
Early blight, also called leaf spot, is a fungus that shows up on leaves as enlarging brown spots that develop concentric rings. The blight eventually spreads to the tubers, reducing yields and creating puckered skins with discolored spots.
Late blight hits crops after they’ve blossomed. It begins with dark, watery spots on leaves and spreads to stems and tubers.
Ring rot is a highly infectious bacterial disease that is not generally obvious above-ground. Underground, it starts with a ⅛-inch ring of decay under a tuber’s skin; eventually the whole interior decays, leaving a shell of firm tissue.
Scab causes rough, corky spots on tubers. It is most commonly a problem in soils that have a near-neutral or alkaline pH or in those that are on the dry side. Keep the pH low and maintain an even moisture level in the soil to avoid scab.
Verticillium wilt turns older leaves yellow and eventually causes the whole plant to wilt and die.
Harvesting: Blossoming plants are a sign that the first “new” potatoes are ready to harvest. Pull aside the earth around the base of plants and gently pick off cooking-sized tubers, which are delicious boiled with the skins on.
Once the foliage starts to wither and die back, the tubers will be fully grown. If the weather is not too warm or wet, they will keep in the ground for several weeks. Dig them up with a spading fork before the first frost. Potatoes that are nicked or bruised during harvesting won’t store well, so eat them as soon as you can. Clean and dry the crop as quickly as possible, but never expose it to sunlight. Store tubers in a dark place at around 40°F.
Note that potatoes with colored flesh often lose that color when cooked in water. To keep red and purple potatoes colorful, try roasting them instead of boiling.
POTENTILLA
Cinquefoil. Spring-and summer-blooming deciduous shrubs.
Description: Potentilla fruticosa, shrubby cinquefoil, is an exceptionally hardy shrub. It has a low, twiggy, rounded form, growing to 2 to 4 feet tall and wide. The compound leaves are a soft gray-green. Lemon yellow, 1-inch flowers cover the plant in late spring, followed by sporadic bloom through summer and into fall. Zones 2–7.
How to grow: Cinquefoil does best with full sun in well-drained soil. Once established, it needs little supplemental watering. Prune in late winter before growth begins.
Landscape uses: Because of its compact size, cinquefoil makes a good foundation plant. It is also effective as a specimen, in mixed borders, or in a massed planting.
PRIMULA
Primrose. Spring-blooming perennials.
Description: Primroses bear rounded, five-petaled flowers in clusters above dense rosettes of paddle-shaped, wrinkled leaves.
Primula × polyantha, polyanthus primrose, practically hides its 6-inch paddlelike leaves in early spring under 8- to 12-inch-tall, dense clusters of 1½-inch blooms in rich shades of white, yellow, red, and blue, many with a distinct yellow eye. Best in Zones 5–7; widely grown as annuals elsewhere.
P. sieboldii, Siebold’s primrose, carries its 1½inch blooms in white, lilac, pink, and magenta-purple shades 8 to 10 inches above spreading masses of scalloped 4-inch leaves that die down in summer. Zones 4–8.
P. vulgaris, English or common primrose, bears yellow, 1-inch, slightly fragrant blooms just above dense rosettes of 3-inch leaves. Zones 4–8.
How to grow: Plant in spring or divide after bloom every 2 to 3 years. Grow in partially shaded, average to fertile, well-drained but moisture-retentive soil enriched with organic matter. They tolerate full sun if the soil remains moist, although common primroses tolerate drier soils than most. Individual plants are usually short-lived, but they self-sow or produce offsets generously. Mulch in summer to retain moisture and in winter to prevent the shallow-rooted plants from being heaved out of the ground by the freezing and thawing of the soil. Hand pick or trap slugs and snails; wash spider mites off plants with a strong spray of water.
Landscape uses: Group primroses along paths, at the edge of borders, and in cottage gardens. Combine with bulbs, ferns, and other spring flowers in a wooded area. Make a late sowing of sweet alyssum to fill bare spots left by dormant Siebold’s primroses.
PRIVET
See Ligustrum
PROPAGATION
Learning to propagate plants—to make new plants from existing ones in your home and gar-den—is one of the most exciting and rewarding aspects of gardening. Many of the methods are easy, and you don’t need fancy or expensive tools. Propagation is cheaper than buying large numbers of plants, so with a little time and effort you can fill your garden quickly at minimal cost. Propagating new plants will keep your house and garden full of vigorous specimens, and you’ll probably have plenty to give away, too!
You can reproduce most plants by several methods. There are two major types of propagation: sexual and asexual. Sexual propagation involves seeds, which are produced by the fusion of male and female reproductive cells. Asexual propagation methods use the vegetative parts of a plant: roots, stems, buds, and leaves. Division, cuttings, layering, budding, and grafting are all asexual methods. Spores (produced by ferns and mosses) may look like seeds, but they are technically asexual structures, because they have a specialized way of forming new plants.
Select a technique by considering the plant you are working with, the materials you have, the season, and the amount of time you are willing to wait for a new plant.
Seeds: Growing from seed is an inexpensive way to produce large numbers of plants. Annuals, biennials, and vegetables are almost always reproduced by seed. You can also grow perennials, shrubs, and trees from seed, although the seedlings they produce may not resemble the parent plants. Raising seeds requires few materials: a container, a growing medium, and seeds. The time to sow seeds depends on the type of plant. For most garden plants, you can sow seeds indoors in late winter or outdoors in spring. Tree, shrub, and many perennial seeds may need a cold period or other treatment before they will germinate. Depending on the type of plant, it could take anywhere from weeks to years to get a garden-sized specimen. For complete information on growing plants from seeds, see the Seed Starting and Seed Saving entry.
Spores: Spores are the reproductive structures of ferns and mosses. To produce new plants, sow these dustlike “seeds” on a sterile medium and cover them to maintain humidity and prevent contamination. Clear plastic shoe boxes or cups are ideal containers for propagation. You can collect spores from your own ferns or buy them from specialty catalogs. You can sow spores whenever they are available. The new plants will be ready for the garden after a period of months or years.
Division: Division is an easy way to produce more plants with almost 100 percent success. This method involves digging up an established plant and separating it into several pieces. Division is used for bulbs and mat-, clump-, or crown-forming plants, including ferns, bamboos, bugleweed, daylilies, and hostas. Single-stemmed plants like trees cannot be divided.
All you’ll need for division is a tool to dig up the plant, and your hands or a sharp implement to separate the pieces. You can divide most plants in either spring or fall. Division produces full-sized plants that can be placed directly in the garden. For more information, see the Division entry.
Cuttings: Cuttings are pieces of leaves, stems, and/or roots that are separated from a parent plant. When placed in the proper conditions, these pieces form new roots and shoots. Stem cuttings are used for a wide range of plants, including geraniums, pachysandra, and coleus. Use root cuttings for perennials such as Oriental poppies (Papaver orientale) or globe thistles (Echinops spp.) and some trees, including goldenrain tree (Koelreuteria paniculata). You can also try leaf petiole cuttings, used for African violets and peperomias, and leaf pieces, used for such plants as gloxinias and snake plant (Sansevieria spp.).
The materials you’ll need depend on the plant and the method you are using. Leaf petiole cuttings of African violets will root in a simple glass of water. You can stick stem and root cuttings in a pot or flat of regular potting soil. A plastic bag or other clear cover will help to maintain high humidity around the cuttings. More complicated structures, such as cold frames and mist boxes, are good for hard-to-root shrub and tree cuttings. Plants reproduced by cuttings can be ready for the garden in a matter of weeks or months. See the Cuttings entry for more details on this method.
Layering: Layering is a way to get stems to root while they are still attached to the parent plant. Some plants produce layers naturally. Strawberries form rooted plantlets on runners; raspberries produce new plants where the stem tips touch the ground. The technique of simple layering involves bending a low-growing stem to ground level and burying a few inches of the stem behind the tip. Simple layering is an easy way to reproduce such plants as camellias, forsythias, and magnolias. To air layer, you shallowly wound a stem a few inches below the tip to stimulate root production, and then wrap moist sphagnum moss around the stem. Covering the moss with a thin sheet of plastic holds in moisture and secures the moss to the stem. Weeping fig trees (Ficus benjamina), corn plants (Dracaena fragrans), and witch hazels (Hamamelis spp.) are all good candidates for air layering.
You don’t need much equipment to try these techniques. A trowel (for digging the trench) is sufficient for simple layering. For air layering, you’ll need sphagnum moss, waterproof tape, a piece of thin plastic, and a knife. Early spring is the best time for simple layering. For outdoor plants, you can set up air layers in spring or late summer. Indoor air layers can be started anytime. It will probably take several months to a year to get a new well-rooted plant. For more information, see the Layering entry.
Grafting: Grafting is a more advanced propagation technique. It involves joining a stem piece of one plant (the scion) to the root system of another plant (the rootstock) in such a way that the parts unite and continue to grow. You can reproduce many types of trees by grafting, including pines (Pinus spp.) and rhododendrons, and even some herbaceous plants, such as cacti. Grafting has several advantages over other propagation methods. It allows you to propagate plants that are difficult to raise from seeds or cuttings. Through grafting, you can produce a plant adapted to your particular needs. Some rootstocks have a dwarfing effect, while others encourage vigorous top growth. They can also provide tolerance to soilborne insects and diseases, or to less-than-perfect soil conditions.
The most important grafting tool is a sharp knife. You may also need string or tape (to keep the graft pieces together) and grafting wax (to prevent water loss and avoid contamination). You’ll have to have suitable rootstocks, too. You can raise your own from seeds or cuttings, or buy them from a specialty catalog or nursery. Spring is the most common time for grafting. Herbaceous plants will join successfully in a few weeks; woody plant grafts usually take a month or two to unite firmly and begin growing. See the Grafting entry for more details on this technique.
Budding: Budding is a particular type of grafting. In this method, you use only a single bud from the desired plant. Budding is commonly used to propagate fruit trees as well as ornamentals, such as hybrid tea roses. For the home gardener, the advantages of budding are similar to those of grafting. In some cases, budding is more successful than grafting because it is easier to get close contact between the bud and the rootstock. Budding also allows you to propagate more plants if you have a limited amount of scion material.
For this technique, you’ll need a sharp knife and some string or tape to secure the bud to the stem. As with grafting, compatible rootstock plants are necessary. Budding is best done in late summer or early fall. Buds inserted at this time will produce new growth the following spring. See the Budding entry for a more complete discussion of this technique.
PRUNING AND TRAINING
Pruning and training are both a science and an art—and probably the least-understood gardening practices. Proper pruning and training bring out the best in each plant. Not only do well-pruned plants produce more and better fruit and flowers, they also are healthier and more vigorous. Pruning and training can improve the health of an ailing plant, make trees stronger and safer, channel growth away from buildings or traffic, and restore a sense of order to an over- planted or overgrown yard.
While pruning and training are most often thought of as techniques used on woody trees, shrubs, and vines, they’re also used to direct the growth of herbaceous plants. Roots can be pruned as well to prepare a plant for transplanting or to encourage the roots of a new plant to branch out into the surrounding soil. The roots of bonsai trees are pruned to restrict growth.
KEY WORDS Pruning and Training
Branch collar. The part of the trunk that helps hold the branch to the trunk, often recognizable as a bulge at the base of the branch.
Branch crotch. The angle where a tree branch meets the trunk or parent stem.
Cane. A long, slender branch that usually originates directly from the roots.
Leader. The main, primary, or tallest shoot of a tree trunk. Trees can be single-leadered or multiple-leadered.
Pinching. Nipping out the end bud of a twig or stem with your fingertips to make the plant more compact and bushy.
Thinning cut. Cutting a limb off at the base, either at ground level or at a branch collar.
Heading cut. Cutting a branch back to a side bud or shoot.
Skirting or limbing up. Pruning off the lower limbs of trees.
Sucker. An upright shoot growing from a root or graft union; also, in common usage, straight, rapid-growing shoots or watersprouts that grow in response to wounding or poor pruning.
Espalier (pronounced is-PAL-yuhr). A fruit tree or an ornamental shrub that is pruned to grow in a flat plane. Although sometimes free standing, an espaliered plant is generally attached to a framework against a wall, and is usually trained in a well-defined pattern.
Topiary. Plants sculpted into sheared geometric shapes or likenesses of animals or people.
Pruning can be used to:
Remove diseased and dead wood.
Encourage branching and bushy growth.
Direct a plant to grow in a particular direction.
Eliminate unattractive, crowded, and congested growth.
Increase the structural strength of a tree or shrub.
Reduce the overall size of a tree or shrub without causing rampant regrowth.
Improve air circulation and reduce disease problems.
Increase flowering and vigor by removing old, nonblooming wood.
Help a newly planted plant become established.
Eliminate reverted growth (such as all-green shoots on an otherwise variegated plant).
Pruning Cuts
Most pruning comes down to making one of two kinds of pruning cuts: thinning cuts and heading cuts.
Thinning cuts: Thinning cuts remove branches totally. They open up a plant but don’t make it shorter. Thinning directs growth into alternate patterns. Use thinning cuts to establish good structure of young trees and shrubs and to allow sunlight and air to reach the interior of a plant. Also use thinning cuts to remove un attractive or unruly branches, branches that block a view, and any stems that rub or cross. Thinning cuts can eliminate sharp crotches and make a plant less likely to break under a heavy snow load.
Making thinning and heading cuts. Make thinning cuts at the branch collar where the branch originates. Avoid a flush cut; leave the branch collar intact, but don’t leave a stub. To make selective heading cuts, cut directly above a bud or side branch that’s pointing in the direction you want the new growth to take.
Heading cuts: Heading cuts shorten plant stems and stimulate latent buds behind the cut to grow, making the plant more dense. Selective heading reduces overall size or height of a plant without changing its natural shape. The plant suffers less stress, and selective heading doesn’t cause vigorous, out-of-control growth the way that nonselective heading does. To make a selective heading cut that will direct plant growth, cut just above a bud or branch that’s pointed in the direction you want the growth to go.
Nonselective heading is the technique used to shape formal hedges and topiary. Pruning encourages growth, and nonselective heading cuts cause a burst of growth from all of the cut stems. Branches are cut back partway along the stem, resulting in rapid, bushy regrowth just below the cut. Nonselective heading is often misapplied—resulting in forlorn lollipop-shaped shrubs or trees that would look more attractive, and would likely be healthier, if pruned to follow their natural form. Selective heading combines the best of thinning and heading, but it can’t be applied to all plants. The older, larger, and woodier the plant, the fewer selective heading cuts should be used.
Pruning Do’s and Don’ts
Proper technique: Prune from the bottom up and, in the case of large plants, from the inside out. Prune out all dead wood first—an important step for health and good looks. Dead wood is easiest to spot in summer because the branches have no green leaves. Also remove diseased and damaged wood.
Next look for a few of the worst rubbing, crossing branches. Leave the best-placed one of any pair. Try to keep branches that head up and out from the center or that fill an otherwise empty space. Step back from the plant you’re working on frequently and look at it from all angles.
Prune to open up center areas and to clean up the base of shrubs. This improves plant health by admitting light and increasing air circulation. It also has a large impact on the beauty of a plant. Depending on what shrub you are pruning, you may want to concentrate on removing excess twiggy growth or removing a few of the older stems that no longer bloom well.
Selectively thin or head back misplaced branches: those that touch the ground, lay upon or crowd other plants, or come too close to the house, windows, and walkways.
Nonselective heading cuts. To trim a hedge or shear branches to a uniform surface, make nonselective heading cuts anywhere on the stem.
Save any heading cuts until the end of a pruning job. Locate the longest, most unruly branch first, follow it down inside the shrub, and cut it off to a side branch or a bud. Remember: Next year’s new growth will be channeled into the bud or side branch you cut above, so choose which way you want growth to go.
Pruning large limbs: A large branch that is sawed from above will tear bark from the trunk as it falls. Use the three-cut method shown below to prevent damage when removing large limbs.
- About 1 foot out from the trunk, cut halfway through the branch from underneath.
- A few inches in from the first cut, saw off the branch from the top.
- Remove the stub by cutting along, but never into, the branch collar. On tight crotches, saw from the bottom up.
Pruning large limbs. Make three cuts in the order shown to safely remove a large limb without causing bark tears.
Pruning mistakes: The most common pruning mistake is to cut back everything in the yard in an ill-fated attempt to make it all smaller again. This actually stimulates an upsurge of messy regrowth, making the final solution more difficult. Tree topping, indiscriminate shearing, and overthinning are the three major forms of “malpruning.” Instead, plan to correct the sizes and shapes of your landscape plants by pruning them properly over the course of several years. If a tree or shrub is simply too large for its site, remember that removing it is one option. You can also hire professionals to transplant even fairly large shrubs or trees that are in the wrong place, so don’t be afraid to ask at your local nursery.
The cure for badly pruned plants is time. Most will reestablish their natural habits given a few years to recover. Rehabilitative pruning can hasten the process and make plants look better. Meticulously prune all dead wood, removing all stubs. Use thinning cuts to simplify tangled branch ends. Take out entire canes. If treelike shrubs have rampantly produced suckers because of heading cuts, slowly remove the worst of them over a period of years. Let the strongest and best- placed suckers grow back into branches. Some plants, including cane growers like weigela, mock orange (Philadelphus spp.), and forsythia, can be radically renovated by cutting them entirely to the ground. In about 3 years they’ll regrow to mature size and bloom again. Many lovely but rampant vines are treated this way to good effect.
Most needled evergreens will not regrow once they are cut back to wood that does not have needles on it. This makes their size difficult to control and radical renovation impossible.
Pruning Timetable
Plan your pruning schedule depending on what you want to accomplish. Removing dead and diseased wood, as well as general thinning can be done in any season. Follow these seasonal guidelines:
Elegant Espalier
An espalier is a fruit tree or shrub trained to grow flat, usually against a wall, supported on a strong lattice, trellis, or wire fence. Wire is easiest and usually the most practical support for fruit trees.
Classic espalier patterns include fan training and a Belgian fence, which has a geometric pattern of crossing branches. In addition to the usual ones, you can also establish an informal pattern to suit a more naturalistic garden and plants that don’t form spurs. Train the branches (or at least the tips) of informal, fruit-bearing espaliers at an angle of at least 30° above the horizontal to encourage branch vigor and flower production.
Plant your young tree about 1 foot away from the framework to allow room for the trunk to expand as it grows. Space it midway between two posts.
Start careful pruning early in the life of the tree, and continue it at regular intervals during the whole life of the espalier. As an espalier gets older, less and less pruning is needed. It may take several years of training to “finish” a pattern.
Balancing the pattern: In general, strive for a balanced pattern by encouraging weaker branches and discouraging branches that are too vigorous. Do this by pruning the strong branches shorter and allowing weaker ones to grow longer. Rub off side buds on the stronger branches right away, but leave the buds on weaker branches. Tie the more vigorous branches frequently and closely to the supports. Leave weaker branches growing freely a little while longer. Remove some leaves from the stronger ones, and remove all fruit from the weaker ones.
Maintenance training: Early in summer, pinch back each lateral branch as soon as it has made 3 to 4 leaves. Also pinch back terminal shoots when they have made a few inches of growth. If a lot of leafy growth occurs as summer progresses, nip out a few shoots entirely.
Throughout the growing season, remove branches that are not growing in the right direction or that are growing out from the framework. Don’t let fruiting spurs develop more closely than 5 to 7 inches apart. When very old spurs bear repeatedly, either prune the spur or thin out the fruit in early summer.
During the dormant season (late winter is better in the North), cut back every lateral branch to 2 to 3 buds. If laterals are close together, remove some to prevent a bunchy look. At the same time, shorten every vertical shoot. If there has been moderate growth (from 4 to 8 inches), just cut back each tip to a healthy-looking side bud. If growth has been vigorous (more than 9 inches), remove up to ⅔ of the shoot. Also cut back the leader if it is growing above the desired height.
Prune evergreen espaliers throughout the growing season. Start early in spring just before growth begins. Remove crowding branches entirely. Cut back terminal shoots to within a few inches of the previous year’s wood.
Spring pruning stimulates the most rapid regrowth, so it’s a good time for heavy pruning. Prune evergreens in spring, but avoid pruning deciduous trees as they leaf out. Prune spring- and early-summer-flowering shrubs such as azaleas and rhododendrons as soon as they finish blooming, so they’ll have time to grow and set new buds during summer.
Cut shrubs that flower in summer or fall on the current season’s growth back in spring as buds begin to swell. This includes Russian sage (Perovskia atriplicifolia) and bluebeard (Caryopteris × clandonnensis).
Summer pruning has a less stimulating effect on growth. Hot or dry weather is extremely stressful for plants, so avoid heavy pruning. This is a good time to tidy up plants and to remove suckers and watersprouts.
In mid-to-late fall, make only thinning cuts. Heading cuts made late in the season can stimulate soft new growth that is easily damaged in fall freezes. Don’t prune plants during the period when their leaves are falling.
Late winter is the traditional time to prune dormant plants; leaves have dropped and it’s easy to see plant form. Winter pruning stimulates growth, but the results are delayed until spring. This is a good time to prune trees as well as apples and other fruit trees, brambles, grapes, roses, and shrubs that form flowers on the current year’s wood.
Good Tools for Good Cuts
Choose pruning tools that cut cleanly and easily. Keep the cutting edges sharp. You’ll probably need only three pruning tools: pruning shears for stems and twigs, lopping shears for branches that are finger-size and larger, and a pruning saw for larger branches and crowded areas.
Pruning shears are available in two types. Anvil pruners cut with a sharp blade that closes against a metal plate, or anvil; bypass pruners work like scissors. A leather holster for your shears is a wise investment.
Lopping shears have long handles that extend your reach and give you leverage for more cutting strength. A small rubber shock absorber is a welcome addition on some models. Folding pruning saws fit nicely into a back pocket, but you’ll have more blade choices if you buy a non-folding saw. One feature to look for is a blade that cuts on both the push and the pull strokes, making it easier to cut in close quarters. Pole pruners can be used for overhead work. The pruning head can consist of either a saw or a cord-operated hook-type shear, or a combination of the two. You may find hedge shears useful for keeping formal hedges neat.
PRUNUS
Ornamental cherry, plum, almond. Deciduous or evergreen spring-flowering trees or shrubs.
Description: Many members of this genus produce edible fruit; you’ll find more information in the Cherry, Peach, and Plum entries.
Prunus cerasifera, Myrobalan plum, is a deciduous shrub or small tree with a rounded, spreading habit and a mature height of 15 to 25 feet. Pale to deep pink flowers precede the leaves, which are purple on most cultivars. Zones 4–8.
P. glandulosa, dwarf flowering almond, is a diminutive shrub of 3 to 5 feet with slender twigs and a delicate, open branching habit. Single or double, pink or white flowers appear before the leaves in early to mid-spring. Zones 4–8.
P. laurocerasus, cherry-laurel, is an evergreen shrub that bears white flowers in early to mid-spring. Leaves are shiny and leathery; fruits are black. Zones 6–8.
P. serrulata, Japanese flowering cherry, grows 20 to 25 feet tall and is vase-shaped; single or double blooms are white to pink. Zones 5–7.
P. subhirtella, Higan cherry, grows 25 feet tall and bears pale to deep pink single or double flowers before leaves appear. Zones 5–9.
How to grow: Except for the cherry-laurels (which prefer shade), most species need full sun and well-drained soil. Protect the thin bark from lawnmower injuries. Prune after flowering. P. cerasifera and P. laurocerasus have been identified as invasive in some states.
Landscape uses: Most tree cherries make fine focal points or groupings in a sunny area. Cherry-laurels work well in shade individually or grouped. Most Prunus attract birds.
PUMPKIN
See Squash
PURPLE CONEFLOWER
See Echinacea
PYRACANTHA
Pyracantha, firethorn. Spring-blooming evergreen or semi-evergreen shrubs.
Description: Pyracantha coccinea, scarlet fire-thorn, is an upright, irregular, spiny shrub reaching 15 feet tall. It has oval, 1 to 1½-inch, dark to medium green leaves, clusters of small white flowers in spring, and showy orange-red berries that persist through fall. Zones 6–8.
How to grow: Provide full sun and good drainage. In Southern climates, site fire-thorns where air circulation will be good; in the North, site them out of the winter wind. Once established, they need little supplemental water. Prune diligently to remove watersprouts and suckers and to maintain shape. A neglected fire-thorn is soon out of control. Once overgrown, it is difficult to coax back to size without some awkward pruning cuts.
Landscape uses: Scarlet firethorn makes an attractive espalier—its flowers and berries are set off by a wall or trellis. You can also use firethorn as a hedge; it makes a nearly impenetrable barrier. Plant it to attract berry-eating birds in winter. In the Pacific Northwest, plants may become invasive because birds eat and spread the seeds.
PYRUS
Pear. Spring-flowering deciduous trees.
Description: Members of this genus produce edible fruit; you’ll find more information in the Pear entry.
Pyrus calleryana, callery pear, is familiar in city landscapes because its cultivar ‘Bradford’ has been widely planted as a street tree. This popular cultivar, which has escaped cultivation and is considered invasive in some states because birds eat and spread the seeds, is pyramidal when young and rounded with maturity, with a dense crown. It attains a mature height in the range of 25 to 40 feet. Its winter buds are a woolly buff color, and its white, malodorous flowers appear in early to mid-spring before the leaves, which are a shiny dark green. Spectacular fall leaf colors of reds, russets, oranges, and yellow are reliable most years, especially in the North. Small (½-inch), round pears appear in fall. Zones 5–8.
How to grow: Provide full sun and good drainage. Pears can have serious problems with fire blight, a bacterial disease, during wet summers. Watch for branches forming fire blight’s distinctive “shepherd’s crooks” at their tips following warm, wet weather during periods of rapid growth. ‘Bradford’ shows good resistance to fire blight, but like many other callery pears, it has naturally narrow (and therefore weak) crotch angles that often break under the weight of mature (perhaps snow-laden) branches. Instead of planting ‘Bradford’, choose other flowering trees such as serviceberry (Amelanchier spp.), white redbud, and Carolina silverbell (Halesia tetraptera).
Landscape uses: Callery pears look nice when massed or as a focal point, especially for an early splash of white flowers. Their tolerance of urban conditions, combined with abundant flowers, attractive foliage, and availability of small- to mid-sized cultivars, makes them a common sight (some would say too common) along the sidewalks of many American cities.