I wish that this chapter could have a title like “Mulching Fruits: A Month-by-Month Calendar.” Unfortunately, seasons and climates vary so much throughout North America that such an approach would be inaccurate and confusing to many people. We will have to be content with general descriptions of what to do in spring, summer, autumn, and winter.
As the snow starts to melt during those first warm, sunny days of spring, gardeners everywhere start champing at the bit. This is the season for restraint. Because most fruits are perennial plants already in place, it is easy to jump the gun on a day with 60°F temperatures. Think about other things if you can. Try to remind yourself that there aren’t many things to worry about in the garden itself just yet. Loosen mulch where it has been crushed by snow, if you like, but don’t remove it too early. Spring is a good time to scout around and see what you can scavenge in the way of mulching materials.
Early spring is the time to plow, spade, or rototill winter mulch into seedbeds where you will be planting your annual plants. Don’t remulch perennial fruits until at least two weeks after the average date of the last killing frost, whenever that may be where you live. Give the earth plenty of time to warm up.
By mid-April here in Vermont we are just beginning to remove winter mulch from the perennials, about three or four weeks after the snow has left our valleys. This date probably will be earlier where you are. Remember: Removing too much mulch from perennial plants too early does not help the soil and the roots to warm up. It may warm it for a few hours, but after the next hard freeze and subsequent thaw (and we have plenty of those in late April and May) plants may be frost-heaved right out of the ground and die of root exposure.
Move protective mulch away from plants gradually and let it lie off to the side, but within easy reach. Take off one thin layer at a time, waiting several days before you remove the next layer. This painfully slow process gives your plants a chance to harden.
Josephine Nuese, in her book The Country Garden (Scribners, 1970), says,
“Don’t whip off winter protection until the soil beneath the plant has thawed out. Strong March winds and strong March sun, both dehydrating, can drain the essential moisture which the still frozen roots can’t replace. Don’t be misled by shallow surface thawing. If you poke down with a stick and can feel ice, leave the mulch.”
As much as anything else, mulch should be kept on so the roots and tender shoots won’t grow too soon and get nipped by frost. If it’s possible, remove the final layer of mulch on a cloudy day so that any young shoots that have started are not blasted suddenly by brilliant sunshine. Once the winter mulch is off completely, leave it off for several days, or even a couple of weeks, before you start to mulch again.
In the late spring start mulching again, to conserve moisture and control weeds before they get a head start. This is a good time to fertilize around fruit trees and berry bushes by adding some sort of feeding mulch, which will contribute humus and nourish the plants. Nitrogen-rich grass clippings usually abound at this time. Use them, but dry them first. Mulch far enough away from your fruit trees — out at least to the drip line (that’s the outer perimeter of the tree if you are looking straight down on it) — so you can be sure your mulch is doing some good directly over the tiny feeder roots.
Summer is the time when mulching should start to pay dividends. During hot spells, roots should thrive in the weedless, cool, moist ground under mulch. You do nothing now except have a look every now and again and renew the mulch wherever weeds show signs of getting the upper hand. Pull any weeds that show up.
Be crafty about choosing materials for summer mulching. Because your fruits will not be tilled, it becomes particularly important to encourage earthworms into your perennial beds in order for your soil to get some aeration. Avoid using mulches like sawdust, pine needles, and redwood by-products, because earthworms don’t like them. A continuous mulch around thick-stemmed shrubs and trees should be a coarse, heavy material that allows plenty of water through, but that is not going to decay too rapidly (it should last for several years). Topdress through the mulch with fertilizer whenever it seems appropriate.
One thing to look out for: There is danger of crown rot in small fruits — strawberries, for example — during the early summer months. If there have been especially heavy rains, postpone your mulching until the soil no longer is waterlogged. Do not allow mulches — especially peat moss, manure, compost, spent hops, or ground corncobs — to touch the bases of your plants. Leave mulch-free circles around the stems several inches in diameter. The idea here is to permit the soil to stay dry and open to the air around the immediate area of the plant.
Mulch should be maintained in a young or dwarf fruit orchard throughout the summer. Organic gardener and farmer Chuck Pendergast, in his book Introduction to Organic Gardening (Nash Publishing, 1971), reports:
“In early fruit orcharding, the practice was to let the trees go to grass. In other words, the land surrounding the trees in an orchard was not cultivated and plant life was allowed to establish itself there. Year after year, this resulted in a gradual building-up of the sod. The more time it has, the tighter sod will become. Eventually there was a conflict between the grasses covering the ground around the trees and the trees, which were being deprived of necessary quantities of water. Hence the practice of keeping the land in an orchard free from growth began.
The immediate results of this practice were favorable. The trees’ health and yield improved. . . . As it is hard to prevent cover grasses from becoming detrimental once they become established, mulching is now a widespread practice in orcharding. . . . We’ve learned smothering and put it to wise use.”
The longer the perennial’s roots can stay at work in the fall, the better — up to a point. Late mulching can prolong a plant’s growing season because it provides a buffer zone against frost. Roots will continue to grow in soil as long as moisture is still available there. When the soil water freezes and is unavailable to roots, they stop. Increase your mulch volume gradually for a while to insulate the soil and to prevent early freezing of soil moisture.
Once the frost has been on the pumpkin more than a couple of times, your plants probably should be given a hardening-off period similar to the one you gave them in the spring. Remove the mulch gradually until the plants are obviously dormant and the ground is frozen.
By now you should be collecting materials for winter mulching. Maybe you will want to cut evergreen boughs. They do a great job of holding snow (which is a superb mulch) in places where it might otherwise be blown away. After harvest time, push mulch back away from fruit trees, leaving an open space around the trunks. If you anticipate that a winter rodent problem will develop in berry bushes, grapes, or dwarf fruit trees if mulched with seedy materials, don’t forget that you can wrap wire mesh, hardware cloth, or plastic protectors around trunks and berry canes.
Fall is the best time to make use of your chopper by grinding up plant residues for future use as mulch. Use your rototiller, if you have one, for sheet-composting leaves between rows. Till in the summer mulch, too.
Should winter mulching of perennials be done before or after the ground is frozen? This has been a source of much controversy and confusion in mulching circles. Don’t be confused: Remember, this chapter has to do with perennial fruits. Mulch your annual beds early — before frost really has settled into the soil — so that earthworms and beneficial microorganisms can stay at work longer during the cold months.
That makes sense for annuals, you might be saying. But what about perennials? Do they need winter mulching?
I have made a study of this — a cursory one, at least. I asked the question, “Why does Mother Nature arrange to have her trees drop their leaves, and then later see to it that a heavy blanket of snow insulates the ground even more? Can winter mulching then be a bad thing?”
Some would still argue that a garden should be left naked and exposed for the winter. John and Helen Philbrick have written:
“Mulch should not be left on over the winter because it prevents the beneficial action of the frost in the earth. Moisture should not be hindered from ‘coming and going’ during the seasons of snow and ice. If protective mulch is in such a condition that it will break down during the winter and become part of the topsoil, it may be left. But the home gardener should study this subject carefully and be sure he knows exactly what he is doing and why he is doing it.”
I would argue that your garden, especially your perennials, should have winter mulch. Winter mulch keeps winter soil frozen — even during thaws. Winter moisture and frost ought to be allowed to penetrate the soil before you lay down a heavy winter mulch. Then, if the mulch keeps the frost in, the plants cannot be “heaved” out of the ground when the soil expands and contracts on alternately freezing and thawing days.
Winter mulch protects perennial foliage from drying winds and too-bright winter sunshine. It prevents the absorption of heat in the spring and doesn’t allow anything to grow until after the last killing frost when finally it is removed. The initial question (in case you’ve forgotten): Should winter mulching of perennials be done before or after the ground is frozen? The answer: after.
Last question: How much winter mulch is enough? I suppose that it is possible to smother plants under too much winter mulch. One approach to the problem might be to find out from your local bureau of the United States Weather Service the average frost depth in your area. Then roughly estimate how deep your plants’ roots are. Once you know this, you might find that Dr. D. E. Pfeiffer provides a clue. In John and Helen Philbrick’s Gardening for Health & Nutrition, he is quoted as saying, “Winter mulch does the same thing that snow does: It insulates the soil to the same depth as the height of the mulch. If there is a three-foot snowfall, the effect of the snow reaches down to a depth of three feet. A mulch acts in the same way . . .” This doesn’t mean that you have to mulch to a level equivalent to the bottom of the frost level. That would mean as much as 4 feet of mulch in Vermont! It only means that you should mulch to a height that is a little greater than your perennial plants’ roots are deep — that is, if the frost level where you live goes below that point.
Without mulch. Alternate freezing and thawing can heave plants out of the ground, causing root damage.
With mulch. Evergreen boughs anchor snow and offer fine winter protection for perennial plants.
I am going to cheat a little here and lump all tree fruits together. I couldn’t find anything to justify treating peaches differently from pears, or cherries differently from apples. I did find mulching to be highly recommended for fruit trees. As with other plants, mulching will help regulate soil moisture and soil temperature, control weeds, and improve the soil structure. An additional benefit to mulching around your fruit trees is that a nice, soft bed of straw or leaf mulch will cushion fruits that drop from the tree.
One real danger when mulching fruit trees is the threat of rodent damage. Rodents have a particular taste for fruit trees and, as I said earlier, mulched trees are even more enticing. Be sure to leave a space of several inches between your mulch and the base of the tree and use a tree guard.
Straw, hay, grass clippings, and sawdust are excellent choices for fruit trees. These break down relatively fast and have to be replenished. Woody mulches or coarsely ground corncobs, which last anywhere from three to five years, may involve less work. If you decide to use these longer-lasting mulches, don’t forget that your trees still should be fertilized once a year or so. Black plastic can also be spread around the base of the trees in the spring to control weeds, but pick it up before late fall to eliminate potential nesting sites for mice.
Organic mulches can be applied to a depth of 6 inches. They will decompose to about half that thickness and you may have to add more. The mulch should be kept at or near that 6-inch depth for good weed control. If it will look all right, apply the mulch out from the tree trunk to slightly beyond the spread of the branches. This gives those falling fruits a larger target and protects more of the root area.
W. H. Thies says that organic mulching can make the difference between a successful strawberry planting and an abysmal failure. He may be overdramatizing a little, but mulch can be very helpful. The nicest thing about mulching strawberries is that the mulch keeps the fruit clean.
Strawberries can be mulched right after planting. Chopped hay or straw is most frequently used. Some like to use sawdust or grass clippings. Apply 3 inches of straw and only 1 inch of sawdust or grass. Be careful not to cover the strawberry leaves with the mulch. A lot of folks are using black plastic around their strawberries. Of course, this is better applied before planting.
Winter mulching is essential to successful strawberry growing. It not only prevents heaving, which breaks roots, but protects the vulnerable crown of each plant, which is in real danger in temperatures below 10°F. The plants should be protected by several inches of mulch whenever temperatures stay below 20°F for any extended period of time.
Don’t mulch your strawberry plants before that — early mulching can do more harm than not mulching at all. Covering your plants too soon will block sunlight from the leaves and halt photosynthesis. This will prevent the plants from producing and storing enough carbohydrates to get through the winter.
Straw is generally the mulch of choice for winter protection, but some work at Cornell University shows that row covers might also do the trick. Marvin Pritts, assistant professor with Cornell University’s Pomology Department, explains that row covers have a few advantages over straw: “Unlike straw, they are lightweight, easy to handle, weed-free, and do not delay bloom. Some are even biodegradable. In addition, they allow light to penetrate in the spring, resulting in higher yield.”
Pritts recommends removing the row covers before the plants start flowering, or they may block pollination and increase the plants’ susceptibility to botrytis fruit rot.
If you use one of the organic mulches, uncover the plants in late spring, when the new growth is about 2 inches long. Again, don’t be overanxious. An early spring frost can nip off uncovered strawberry flowers, and you’ll end up with fewer berries. As you remove the mulch, put half of it in the pathways between rows and leave the other half for the plants to grow through.
Don’t mulch to heavily, or new growth may not be able to push through a thick layer.
Mulch raspberries and blackberries almost immediately after planting to improve yields and lessen cold injury. I use chopped hay or leaves or a combination of the two. Sawdust, wood chips, shavings, dried chopped cornstalks, and poultry litter can also be tried. Apply 3 or 4 inches to the row or over the entire soil surface. Be alert for nitrogen deficiencies.
Mulching blueberries can be a tricky thing. Some argue that they should not be mulched at all unless there is good soil drainage. Overmulching can make blueberries more susceptible to diseases. Other authorities admit that blueberries are apt to ripen later if they are mulched, but claim that higher yield is the end result.
Sawdust and chopped cornstalks are excellent mulches for blueberries. Although some sawdust mulches may make soil slightly more acidic, this would not hurt the blueberries. They seem to do best in a soil with a pH of 4.5 to 5.0, so they should never need lime. This means they can stand a permanent mulch, anywhere from 4 to 6 inches, of pine needles, peat moss, oak leaves, beech leaves, or other mulch that releases acid seepage. Black plastic, neither sweet nor sour, works well on blueberries, too.
These two small fruits have experienced a resurgence in popularity in recent years. Both will benefit from mulch’s ability to keep soil temperatures down and moisture levels up. Just about any organic mulch will function around currants and gooseberries — straw, leaves, aged manure, sawdust, or whatever. Lay down 2 or 3 inches of these mulches while planting your bushes and replenish annually.