Almonds, hazelnuts, pecans, and walnuts contribute to heart health because they’re low in saturated fat and high in mono- and polyunsaturated fats. Nuts are also packed with nutrients including fiber, zinc, protein, magnesium, and phosphorus. Thus more people are racing squirrels to nut trees each fall and finding ways to keep their attics and garages squirrel-proof, so that they can store their nut caches safely.
Most nut trees grow far too big for a small backyard, but some make satisfactory shade trees. The demand for homegrown nuts has spurred a search for better strains, and growers continue to develop new varieties of bigger, better-flavored, and easier-to-crack nuts.
Commercial growers have planted nuts like the walnut, filbert, pecan, and almond for centuries. As a result, these nuts have the most named varieties in cultivation. Only in recent years has a serious attempt been made to improve black walnut, butternut, hickory, and chestnut trees. Beech trees have been developed that produce larger nuts. Research has produced trees that are more disease resistant and some that are suited to growing in areas where previously nuts could not be grown.
Q Should I prune a nut tree when I plant it?
A If you buy a container-grown nut tree, it won’t need pruning at planting time; just untangle its roots. Bare-root trees were probably pruned before shipping, so prune only broken roots. If you must, shorten overly long roots, but leave the taproot as long as possible.
SEE ALSO: Planting Trees, page 78.
Q When should I prune a nut tree?
A Always do major pruning when the tree is dormant. Nut trees in a forest tend to grow straight and tall. Their lower limbs gradually die as the trees reach higher for the sun. In the open, many varieties of large nut trees spread out, and their limbs grow oddly. Sometimes the limbs grow straight up, forming a second top, or they may grow straight out.
Q Should I treat nut trees as shade trees or fruit trees when I prune them?
A That depends on the trees you choose, their natural habit, your location, and their usage in your yard. If you’re growing a small nut tree such as an almond, prune it much as you would a fruit tree (see How to Shape Fruit Trees, pages 224–225). Easterners prune the filbert into a large bush; on the West Coast folks prune it as a small tree.
Most nuts, such as pecans and walnuts, grow on large trees. If you inherit one that’s full-grown, treat it the same as a mature shade tree. If you plant a new one, train it to grow with a strong central leader (see Training Shade Trees, page 80). Sooner or later, you will have to give up and let the tree grow as crotchy and limby as it wants, but keep after it for as long as you can.
Q I have some wonderful old nut trees that shade my house all summer. Can I prune them without ruining their canopies?
A Prune large nut trees for the same reason that you would prune a shade tree — to remove dead or injured limbs. Prune off limbs that weaken the tree. Extra-long, heavy, horizontal limbs put a great strain on any tree and will probably eventually split off, so you should remove them early on. Also, take out limbs at acute angles to the trunk, particularly ones that form crotches at 45 degrees or less. Although home growers don’t usually prune to increase nut yields, commercial orchardists boost production by cutting out old wood and thinning out the branches to allow in more light.
If you need to cut off heavy limbs for any reason, do it in stages, as shown on pages 62–63. Never seal cuts or cavities with tree dressing or paint. If you remove the branch properly at the branch collar, the tree itself will seal the wound.
Q I planted a pair of almond trees a year ago. How should I prune them?
A The almond (Prunus dulcis) is a member of the rose family, as are the plum, peach, and other stone-fruit trees, and it closely resembles them in its growth habit. different varieties grow in different shapes — some are low and bushy and others are more upright. Your pruning should conform to your tree’s natural growth habit. If you care for it properly, your almond will produce for 50 years or more.
Almonds are usually pruned during dormancy, though some California almond growers achieve good results pruning in fall. Train the young tree into an open or modified leader form (see How to Shape Fruit Trees, pages 224–225). Avoid unnecessary pruning, as that will stimulate extra leaf growth and delay bearing.
Q Do mature almond trees need much pruning?
A Almonds bear nuts on short, stubby spurs. These trees need little pruning, and yields may decrease if you prune too much. Prune to let sunlight penetrate the branches, just as you would a fruit tree.
Q Can I grow American chestnuts, or were they all destroyed by blight?
A American chestnut (Castanea dentata) has a naturally spreading vase-shaped habit. Sadly, most of these trees succumbed to the chestnut blight that swept the country in the early 1900s. The few trees that survived have been propagated and crossed with imported, blight-resistant types, so there are now several varieties of chestnut available. None is entirely blight-proof, but some are quite resistant.
Q I like chestnut trees, but the American hybrids are too big for my lot. Can pruning keep them small?
A If you don’t have enough space or simply prefer a smaller tree, consider the widely planted Chinese chestnut (Castanea mollissima), which grows 35 to 40 feet high. Chinese chestnut resists blight and produces nuts that are tasty but less sweet than the American species. As with most nut trees, you need to plant two cultivars for pollination.
Q I just planted a pair of Chinese chestnuts. What’s the best way to prune them?
A For both Chinese and hybrid chestnuts, guide the tree to a modified central leader (see How to Shape Fruit Trees, pages 224–225) with a balanced branch formation. Keep the trunk clear of branches up to a height of 8 feet, never removing more than 25 percent of the crown at one time, preferably less. As the tree matures, the shape of the crown may be hard to maintain as aging branches spread and droop. Bearing trees need little pruning.
Q When should I prune my chestnut trees?
A Chestnuts don’t need annual pruning, but if yours need some work, it’s best to prune when the trees are dormant, not in spring or summer.
Q I have a small garden. Are there any nuts I can grow?
A Filberts and hazelnuts (Corylus spp.) stay small, so they suit the home garden better than most nut trees. They range from the small native American hazelnut (C. avelana) to improved and named varieties of the European filbert, the only member of the species cultivated to any extent. Choose either a self-pollinated filbert like ‘Winkler’ or plant two cultivars to assure cross-pollination. Unlike many nut trees, the filbert lacks a deep-growing taproot, so it is much easier to transplant.
You can start new plants from seeds or via layers. To layer, bend over a low branch and cover the middle section with soil so that it can root. Because filberts are easily propagated in this way, they are seldom grafted.
Q When should I prune my filbert?
A Prune when dormant, from late fall to early spring.
Q I bought a grafted filbert. Should it be pruned differently from filberts grown on their own roots?
A If you have a grafted tree, be especially careful to prune away all the suckers growing around the bottom of the main stem so they won’t crowd out the good part of the tree. Prune most of the suckers growing from the roots of a non-grafted tree also, to keep the tree from getting too bushy.
Q Do mature filberts require pruning?
A Mature filberts need pruning mostly to keep them in shape and to let more light into the tree. Cut out some old branches when dormant, and new ones will replace them.
Q How do I prune my filbert?
A Filberts are usually grown as shrubs or large bushes, except in the West, where they are pruned into a tree form with a single main stem. If you are growing your filbert as a bush, keep it pruned to five or six main stems so it won’t become too wide and unmanageable.
Q My neighbor says I can dig a couple of hickory seedlings from the back of his property. Are they easy to transplant?
A The hickory family is native to the central part of North America and includes the shagbark (Carya ovata), mockernut (C. tomentosa), pignut (C. glabra), and shellbark (C. laciniosa), as well as pecan (C. illinoinensis). Some hickories are ornamental and some (pecan, shagbark, and shellbark) produce high-quality nuts.
To anchor a tree this size, nature equips hickory with a long taproot that develops early in life. Thus, planting or moving even a small tree is not easy. When starting a new tree, unless you want to try one of the hybrids, plant it where you want it to grow so you won’t have to move it later. Never prune the taproot, and take special care to keep it safe during planting.
Q When’s the best time to prune a hickory?
A Prune when the tree is dormant so you can see its form and to lessen chances of disease transmission.
Q Can you give me some guidelines for pruning hickories?
A Train to a central leader, and remove crossed branches. Remove the lower limbs as the young trees grow, so that by the time they are 15 feet tall, none will be closer than 6 to 8 feet from the ground. If growing your trees for lumber, prune higher as a tree continues to grow.
Pruning mature hickories is not usually necessary or practical because of their great height (up to 100 feet). They tend to grow upright, and have a naturally strong central leader.
SEE ALSO: Training Shade Trees, page 80.
Q What do I need to know to grow pecans?
A Pecan (Carya illinoinensis), one of the best-known edible hickories, is native to the central and southeastern United States, but you can find suitable cultivars for most parts of the country. Although primarily a commercial nut, it also grows extensively on farms and in backyard gardens. Some newer pecan varieties are smaller and less upright their native relatives, making them more suitable for the home garden. A few are self-fertile, and thus don’t need a second tree for pollination.
Pecans have long, deep taproots, and they need the same care you’d give any of the hickories when you’re planting the small trees. Never cut or bend the taproot during the moving process. Plant at least two, preferably three, cultivars for maximum yield.
Q How do I prune the young pecan tree I just planted?
A Train in its early years so it will grow with a strong central leader. Make sure branches are well spaced with strong connections to the trunk and no bark wedged between them. Because of pest, disease, and structural issues, these are high-maintenance trees that may need some professional care. Although you can do light pruning when needed, do major pruning, such as the removal of lower or damaged limbs, only when the tree is dormant.
Prune away a few bottom limbs each year, until it has 6 to 8 feet of branch-free lower trunk. If you grow a disease-resistant cultivar, this may be the only pruning a backyard tree will ever need.
Q Is there much difference between butternut and black walnut trees?
A These North American members of the walnut family are valued for their nuts and their lumber. They look so much alike when they’re young that it’s difficult to tell them apart, but their nuts look very different. Although the butternut (Juglans cinerea) is hardier than the black walnut (J. nigra), both grow well throughout most of the eastern United States and southern Canada.
Both butternut and black walnut trees have very strong wood, so they need less pruning than most trees. The unusual crotches that insist on growing may be less hazardous to the trees’ health than they would be on weaker trees.
Q Which method should I use to train my new black walnut tree?
A Train it to grow with a strong central leader for its first few years. The terminal bud is easily damaged by weather, and if this happens, two or three sprouts will grow. Don’t let the tree grow into a bush — keep pinching and snipping it into one main trunk for as long as possible.
Don’t wait until the tree is fully grown to start cutting off the bottom limbs. Large wounds don’t close well, and the trunk will permanently show a scar.
If you are growing the tree for its nuts, site it 30 to 40 feet from other trees. If you are growing your tree for lumber, it’s especially important to grow it with a strong central leader, so that you’ll have logs that are straight and free of large limbs.
SEE ALSO: Training Shade Trees, page 80.
Q How should I prune mature butternuts and black walnuts?
A As the trees grow taller, prune off a few of the lower branches each year. Spread major pruning over several years, always leaving at least twice as much branched area as you have limb-free trunk. Never reduce the leaf space by more than 25 percent in any year.
Q I eat lots of walnuts and want to grow some trees in my yard. Which type should I grow?
A Although black walnut trees are native to eastern North America, English walnuts are the commercial walnut that you buy at the store. Persian walnut (Juglans regia) is the true name of the common or English walnut, which arrived in the colonies on English ships. Actually, the cool climate of the British Isles is not at all suitable for the culture of the Persian walnut, because it needs continuous warmth to grow well. Since the introduction of the Carpathian strain of Persian walnut from Poland (Juglans regia var. carpathian), these trees grow in home gardens all over the country and are no longer restricted to the more temperate West Coast. Careful breeding and seed selection are slowly extending the growing region into the northern states and southern Canada. If you’re buying new walnut trees, ask about the growth and bearing habits of your cultivar so you’ll know how to prune them.
Most walnuts in commercial groves — and even some of those growing in backyard gardens — are grafted, often onto black walnut seedlings. It’s easy to see a difference in the bark below and above the graft on these trees. To grow just one tree, buy a self-fruitful cultivar such as ‘Colby’ or ‘Hansen’.
DISEASE ALERT
The survival of butternut in North America is at risk from butternut canker, Sirococcus clavigignenti-juglandacearum, a fungal disease spread during the growing season by wind and splashing rain. Another butternut fungus, Melanconis juglandis, produces secondary infections that cause branch dieback but not cankers. To minimize risk of disease, prune butternut minimally and only when dormant. Make sure the tree surface is dry before cutting, and sterilize pruning tools before and after each cut.
Q My English walnut needs some pruning. When is the best time?
A Walnuts bleed heavily when pruned in late winter to early spring. That bleeding will not hurt the tree, but if you find it unsightly, prune in late fall after leaf drop or wait until summer.
Q Does my new English walnut need any special care?
A The bark of young walnut trees sunscalds so easily that you should whitewash the trunk of a newly planted tree or cover it with tree wrap for the first few years.
Q How do I prune a young English walnut?
A Remove suckers growing from the base (below the graft); they’re not the nut you want, plus they look unattractive and sap energy from the tree. Some walnut hybrids bear such heavy crops of nuts that you should prune them to grow with a modified central leader to encourage wide, sturdy crotches. It’s also important to remove all branches to about 8 feet above the ground as soon as the tree is tall enough to permit this safely. Prune off competing suckers.
Q How do I prune a mature English walnut?
A A mature walnut needs occasional pruning to let more light into the interior of the tree. Cut out some old, unproductive wood and let new, young branches replace it. Prune off sagging branches hindering the tree’s development.
In later years, some varieties — ‘Mayette’, for instance — tend to be of such spreading growth that an open-center method of pruning is best (see How to Shape Fruit Trees, pages 224–225). Commercial growers who plant walnuts in large orchards prune them so that they can harvest the nuts with a mechanical shaker. Most homeowners shake the tree themselves, so tree shape isn’t as important.