The following information on windbreaks comes from Five Acres and Independence by M. G. Kains. Five Acres and Independence is also available to purchase in print.
Perhaps on no horticultural question are the “pros” so obstinately pro and the “cons” so stubbornly con as on that of windbreaks. To hear the arguments we might almost suppose that two radically different things were under discussion instead of the same thing—but under different conditions.
Windbreaks are by no means unmixed blessings or unmitigated curses. In their proper places they will do all their enthusiasts claim; but in wrong situations, the reverse. The whole matter simmers down to the local application and the species of trees or shrubs used.
Properly constructed, a windbreak is a wind-B-R-A-K-E, not a wind-stop: it checks the force of wind and thus may gain many advantages, any one of which may be important enough to warrant planting trees or shrubs for that purpose alone. But when a windbreak becomes a wind-S-T-O-P it may become responsible for any or all the damages claimed by its opponents. As the disadvantages are fewer than the advantages let’s discuss them first.
When the trees or shrubs in a windbreak include species which harbor orchard or garden insects or diseases they are certain to prove a menace to domestic plantings. For instance, wild cherry encourages peach borer and tent caterpillar, elms are breeding quarters for canker worms; wild roses foster rose chafer; red cedars are alternate hosts for rust disease of apple and quince. But we don’t need to plant such trees and bushes nor to let them stand if they are already growing in natural woods nearby.
When windbreaks are so close to gardens or orchards that their roots rob the cultivated plants or trees of water and plant food, or when their tops shade these plantings unduly they exceed their jurisdiction; but that is our fault, not theirs. We should not have planted them so close, or should have placed our gardens or orchards farther away.
Sometimes windbreaks may make areas in their lee colder than would be the case without their “protection.” Because of this, damage may accompany spring or fall frosts. In such cases the trouble is usually due to the windbreak being a wind-stop. This condition may be prevented by spacing the trees far enough apart to allow reduced air movement through them, by reducing the number of trees or shrubs already planted, or by pruning out some of the branches.
The claim that windbreaks are wasteful of land is by no means clear cut. Often the land they occupy is worthless for crop production or the advantages to be gained are of far more importance than the quantity of produce that might be gathered from the “waste space.”
Now let’s look at some of the advantages. If the trees and shrubs are conspicuous when in flower or in autumn colors, especially when evergreens are included among them, they have an ornamental as well as a practical use that makes them doubly valuable. In other cases, if we plant shadblow (or juneberry), mulberry, hackberry, highbush cranberry and other fruit and seed bearing trees and shrubs we may attract birds away from our cultivated berries and yet gain all the advantages of their aid in keeping down insects in our gardening and fruit growing.
We may even insure direct profit from our windbreak by adopting the California practice of planting fruit or nut trees or bushes on the margins of the area we seek to protect. In that state English walnuts, almonds, apricots and figs are popular for this purpose; in the East we might use improved varieties of filberts, black walnuts, northern pecans, highbush blueberries, elderberries, raspberries, blackberries, or sugar maples for maple syrup and sugar making.
When a windbreak has become well established before planting the orchard, the fruit trees will grow straight instead of bent or lop-sided, as they often do in windy sections unless staked. It will also lessen the quantity of windfalls and the breakage of branches when loaded with fruit or ice.
During blossoming time the flowers on protected trees are less likely to be blown off than where unprotected and bees are more certain to do the work of pollinating, thus insuring larger quantities of fruit.
Similarly a windbreak facilitates—even insures—work in the orchard under windy conditions, especially in winter when pruning is done, in spring when spraying might be useless or wasteful or inferior because of unchecked wind, and in autumn when late fruit must be harvested.
Windbreaks are also important because they reduce evaporation of water from the soil and transpiration from the crop plants, particularly the leaves. Thus they mitigate the effects of drouth and winter injury which often follow a dry summer and a wet autumn. Because of this they also help the plants make better development and enhance the size and quality of thin skinned fruits such as strawberries, raspberries and blackberries.
The harmful effects of winter are lessened by the retention of leaves and snow on the ground, for in the lee of a windbreak where these collect the ground freezes less deeply than where they are blown away, so the roots of fruit trees, bushes and other plants are less likely to be injured because of their presence.
Along the sea and the Great Lakes shores where sand is often blown for long distances inland, windbreaks have been found particularly useful to check the destruction of crops and the burying of good soil.
A still more important effect: They greatly enhance the physical comfort and noticeably reduce the cost of maintenance of man and animals whose living quarters they shield from winter winds. Houses so protected require less fuel to maintain comfortable temperatures than do adjacent similar ones not so favorably placed; and animals so sheltered need less food to keep them in condition favorable to the production of work, milk, eggs, and flesh.
As a general thing dense plantings are desirable in inland locations because wind coming over large expanses of ground is likely to be colder in winter and hotter and drier in summer than that which passes over a large body of water. Where sea or lake winds prevail the plantings may be more open so as to allow the air to pass through with less check than through dense plantings. Such plantings also avoid the danger of still air which often occurs on the lee side of a sea or lake shore windbreak.
In general, no windbreak planting should be done before a careful study has been made of the local conditions, especially with respect to air drainage—the flowing of cold air from higher to lower levels. This must be assured to prevent cold spots or “pockets.”
For inland plantings the coarser evergreens such as pines, firs, and spruces have special value because they give dense protection near the ground; for seashores and lake shores these trees should be much farther apart but be supplemented by deciduous trees.
Open windbreaks, where needed at all on low lands, are better than dense ones because cold air naturally settles in such areas unless means are provided for draining it away to still lower levels.
Planting should be not less than 50′, preferably 100′, away from the principal area or buildings to be protected. Its influence extends for a distance equal to 20 times its height; that is, trees 30′ tall influence the force of wind for 600′ on the level. On the protected or lee side of a windbreak of 10′ to 30′ is a calm zone where snow drifts during wind-driven storms. Hence the necessity of planting far back from buildings.
The length of the planting will depend upon the area and buildings to be protected. It should extend at least 50′ beyond the last building, or feed lot area. On rectangular farms where length greatly exceeds width and an L-shaped windbreak would be inconvenient, greater protection may be had by extending the planting 100′ to 125′ northerly or westerly beyond the buildings.
Windbreaks need well prepared soil to get a good start. Deep fall plowing and thorough spring discing, especially of heavy soils, are essential. Soils in sod should be plowed early enough in fall to assure rotting of the sod. On light soils the plowed area should be covered with manure both to increase fertility and reduce blowing and drifting of the surface soil in winter and early spring.
Choice and size of trees will depend on type of soil, general region, cost of trees and the primary purpose of protection. The most suitable are conifers. Hardwood trees are not recommended as part of permanent windbreaks, except under special conditions where a snow-trap or temporary protection rather than a high windbreak may be needed for the young conifers.
Conifers should be at least three years old, once transplanted in the nursery; four-year and even five-year transplants are recommended for white spruce, Douglas and balsam fir. Small seedlings or transplants may be used safely but more cultivation will be necessary until they have grown beyond the danger of weed and grass competition. Hardwood trees one or two years old will usually be large enough. Suitable trees may be grouped according to the kinds of soil to which they are adapted: Norway and Scotch pine for light, sandy soils; Douglas fir, white pine, Norway spruce, Chinese elm and red maple for light loams; white spruce, balsam fir, arborvitae, cottonwood, ash and sugar maple for heavy loams and clays.
Two or more species of trees in a windbreak provide a more compact growth of foliage than when only one is used, especially where spruce and arborvitae are used with open-growing white or Norway pines. The possible loss of one species from a future insect or disease epidemic will thus not destroy the windbreak. Russian willow or cottonwood may be used to give early protection while the slower conifers are becoming established in their lee.
Where there is enough space three rows are desirable, otherwise two. For all suitable trees except arborvitae the rows should be 8′ apart and the trees 6′ asunder. For arborvitae they should be 6′ apart and the trees 4′ asunder. On sandy soils where growth will generally be slow the trees should be staggered in the rows; on fertile ones they should be planted in checks because in 12 and 15 years they will crowd at 6′ to 8′. Then by removing each alternate tree in each alternate row the remaining trees will be left in staggered positions at wider spacing.
This method will insure compact growth throughout the life of the windbreak. Where arborvitae is planted, the original spacing should be maintained. Thinning will not be necessary. (Fig. 6.)
Windbreaks depend for their usefulness largely on the care they receive for the first five or six years after planting. Poultry and livestock must be kept out, perhaps by temporary fencing. A mulch of straw, marsh or salt hay or sawdust 2″ deep and 12″ in radius around each tree should be applied within a few weeks of planting. This will hold soil moisture and help to smother weeds. Sod growth around the trees must be prevented.
To avoid heaving by frost, a winter mulch 4″ to 6″ deep of straw with a low percentage of manure should be applied annually until the lowest branches are at least 2′ long. If applied after the ground is frozen and preferably after a light snow is on the ground there will be no danger of mice nesting in it. It should remain on the ground the following summer to add fertility to the soil, prevent evaporation of moisture and smother weeds.
In windbreaks where spruce and white pine are used some summer shade is desirable during the first two years. Sunflowers, having small root systems, will not compete much with the young trees and they have value for chicken feed and silage. One row should be sown for each row of trees. Three or four plants of a single flower variety are enough between trees.
When the windbreak extends easterly-westerly the sunflowers should be planted 18″ south of the trees; in northerly-southerly rows they should be directed in line with the tree rows. Thus the trees will have intermittent sunshine and shade. Conifers in a windbreak should never be pruned: It is desirable to retain those branches that grow near the ground. If trees have enough sunlight they will maintain their foliage throughout most of their lives.