The Farm Windbreak
Its Planning and Planting
by F.B. Trenk
Extension Service of the College of Agriculture
The University of Wisconsin, Madison
A 40 Year Vision of Wisconsin Windbreaks
In 1894, F.H. King of the Wisconsin College of Agriculture wrote a bulletin on the destructive effects of winds and methods of protection. Here are some of the observations he made:
“…it seems very evident that the wooded lands which are now being so largely cut away in order to increase the acreage for potatoes ought, in part, to be preserved. Where the clearing is done it ought certainly, for the present at least, to be done in strips north and south, leaving belts as windbreaks to stop the drifting and to make surer a crop of the all important clover… well developed windbreaks offer a very material protection if properly disposed… certainly the influence of those (trees) now standing ought to be observed with great care and the destruction of them which is now going on ought to be stayed…”
To grow a windbreak successfully:
• choose the best location;
• prepare the soil properly;
• choose the right trees;
• space the trees most effectively; and
• give the young trees the most helpful conditions for growth.
The planting of a windbreak has been regarded too frequently as a job for spring, whereas much of the work needs to be done in late summer or early fall for the best survival and growth of the trees.
Some windbreaks have failed because of the wrong selection of trees or because of the very location of the break. The full benefits of other windbreaks have been delayed many years, although a moderate amount of cultivation and fertilization would have made them serviceable much earlier.
There is more to windbreak planting than just manual labor, and that is a carefully made plan which must precede the setting out of the trees.
PLANNING THE WINDBREAK
Once established, the windbreak will use the land for a long time, and protect a very definite section of the farm yard. Hence, it is important to select the site carefully. Of first importance are its location with reference to prevailing winter winds, and the distance of the windbreak from the objects to be protected. The distance from farm buildings may be governed somewhat by present development and use of the land.
Our most severe winter storms are driven, most generally, by north and northwest winds. Such winds also are accompanied by lower temperatures in winter. To break the force of such winds, then, and to reduce the blowing and drifting of snow, the windbreak should, preferably, be partly to the north, and partly to the west of the farmstead. An L-shaped windbreak offers the most protection.
In counties adjacent to Lake Michigan, this arrangement will probably be reversed. Many of the most severe storms in winter come from the east, and in localities where these occur, part of the windbreak should be planted to the east of the home and farm buildings.
How Near the Buildings?
The windbreak should be at least 50 feet, and preferably 100 feet away from the principal area or buildings to be protected. Experiments in the Great Plains states show that a windbreak has an influence for the horizontal distance equal to 20 times the height of the break. For example trees 30 feet in height influence the force of wind for 600 feet on the level. Planting trees 100 feet from the nearest building, then, is well within the range of protection.
On the leeward or protected side of a windbreak, for a distance of 10 to 30 feet there is a zone of calm where large drifts of snow accumulate during wind-driven snow storms. For this reason, it is necessary to plant from 15 to 30 feet back from the farm buildings.
The length of the windbreak will be determined by the size of the group of buildings. It should extend at least 50 feet beyond the last building or feed lot area to be protected. On the rectangular-shaped farms where the length greatly exceeds width, and an L-shaped windbreak would not be convenient, greater protection may be had by extending the windbreak 100 or 125 feet beyond the buildings in a northerly or westerly direction, depending upon the arrangement of the buildings.
Preparing the Soil
Windbreak trees should never be planted in sod, or in loose, recently plowed garden or field soil. Heavy soils, and soils covered with sod should be plowed in late summer or early fall. Sod turned over in late summer will be sufficiently rotted by spring to be easily torn up by discing before planting. If the soil where the trees are to be planted has been deeply plowed, and is relatively loose, it should be packed by rolling or cultipacking. Trees planted in loose soil, freshly plowed, commonly show a high loss during the first season due largely to the supply of capillary moisture having been cut off in the loose soil. Rolling or packing the soil restores this capillary contact with moisture in the subsoil.
Light or sandy soils which are plowed or disced in the fall should be covered with some organic material such as well rotted manure, during the winter months. This will increase the fertility of the soil, which is always desirable to hasten tree growth, and it will also reduce soil and soil moisture losses caused by blowing and drifting of the surface soil during the winter and early spring months.
The Choice and Size of Trees
The choice and size of trees for the windbreak will depend on type of soil, general region of the state, cost of the trees, and the primary purpose of protection.
Conifers Are Preferred
The most suitable windbreak trees are white spruce, Norway spruce, Douglas fir, white pine, Norway pine, jack pine and arbor vitae (white cedar). (All of these kinds of trees may be secured from nurseries in this and adjoining states. A few of these species may be obtained as transplants from the state forest nursery to be used in special windbreak demonstrations, conducted under the direction of the county agricultural agent. The species generally available at the state nursery are white spruce, Norway spruce, white pine, Norway pine, and Scotch pine.) These it will be observed, are all conifers, or as they are frequently called, evergreens. The hardwood, or broad-leafed trees are not recommended as part of the permanent windbreak, except under special conditions where a snow trap or temporary protection for a young coniferous windbreak may be needed rather than a high, winter break. The native cottonwood, Chinese elm, Russia willow, and native white ash and red maple serve well where quick growth and only moderate protection are desired.
Conifers should be at least three years old, once transplanted in the nursery; and 4-year or even 5-year old transplants are recommended with such trees as white spruce, and Douglas fir. Smaller seedlings or transplants may be safely used, but more cultivation will be necessary for several years until the trees have grown beyond the danger of severe weed and grass competition. Hardwood trees, one or two years old, will usually be sufficiently large enough.
Suitable windbreak trees may be grouped according to the kinds of soil to which they are adapted:
Light sandy soils: Norway pine – Scotch pine – Russian willow
Light loam soils: Douglas fir – White pine – Norway spruce – Chinese elm – Red maple
Heavy loams and clay: Cottonwood – White spruce – Ash – Arbor vitae (white cedar) – Red maple
Where a windbreak is needed simply as a snow trap around a feed lot, a closely spaced row of Russian willow, white ash, cottonwood, white cedar or jack pine will serve the purpose. A high shrub such as Siberian pea or lilac will do equally as well.
Shrubs or trees planted for the purpose of serving as a snow trap should be about 40 feet to the windward of the area to be protected.
Mixing and Spacing of Trees
Using two or more species of trees in a windbreak has two advantages: a more compact growth of foliage may be obtained especially where spruce or arbor vitae are used with the open-growing white or Norway pines and the possible loss of one species from a future insect or disease epidemic will not destroy the windbreak. The faster growing Russian willow or the cottonwood may be used to give early protection while the slower conifers are becoming established on the leeward side of them.
At least two rows of trees are recommended, and where there is enough room, three rows are desirable. For all species of trees suitable for a windbreak, except white cedar, the rows should be eight feet apart and the trees six feet apart in the rows. For white cedar, the rows should be six feet apart, and the trees four feet apart in the rows. On very light, sandy soils, where growth will generally be slow, the trees should be staggered in the rows (sometimes called “mismatched”), instead of being planted opposite each other, as in check rows.
On the more fertile soils, however, the trees should be planted in check rows, because in 12 to 15 years they will be too crowded at a spacing of 6 by 8 feet. By removing every other tree in each row when the windbreak is 12 to 15 years of age, a staggered or alternate spacing will be obtained, and the trees will then have a 10 foot by 12 foot spacing. This insures a very compact growth of trees throughout the life of the windbreak. Where white cedar is used, however, the original spacing of four feet by six feet should be maintained, and thinning out will be unnecessary.
Two rows of Norway or white spruce and one row of white pine make an excellent combination for a three row windbreak on heavy or moderately heavy soils. In this combination the white pine should be the middle row, with one row of spruce to the windward and one row of spruce to the leeward.
The spruce trees carry their branches nearer to the ground when growing near the open, and thus more effectively stop the filtering of wind that would otherwise go under the more open-growing pine. In addition, they will aid in deflecting the currents of wind upward. On light soils, and in places where rust spreading currants and gooseberries occur, Norway pine should be substituted for white pine, on very stony land, Scotch pine may be substituted for the spruce.
Where faster growing hardwood trees such as Russian willow or red maple are used to serve as a protection for the rows of conifers, the space between the conifers and the hardwood row should be 14 to 16 feet. This will permit a full development of the conifers, without competition from either roots or shade of the hardwoods.
Shelterbelts for Fields
A relatively narrow belt of trees may be as useful in protecting a field from loss of surface soil through wind action, as in protecting the farm buildings and the farmstead from snow and driving winds. Rows of trees planted for this purpose are termed shelterbelts. Much soil fertility is lost each year from light sandy soils in central Wisconsin due to strong winds disturbing the soil and causing the familiar “dust storms.” Belts of trees, two rows, and preferably three rows wide, so planted as to block the course of prevailing winds in large open areas, have proven effective in protecting alfalfa fields and newly-seeded grain from being “blasted” by the sand.
Shelterbelts planted a quarter mile apart, or on “forty” lines, either in a north-south or east-west direction, will not interfere with cultivating and cropping the fields, and they must be at least this close together to be effective. In areas subject to unusually severe wind erosion, two shelterbelts to each 40 acres are advisable. This may mean a complete rearrangement of the fields, but it is an effective way to prevent permanently the loss of soil, soil fertility and crops from destructive wind action.
The several species of pine trees – Scotch pine, Norway pine, white pine, and jack pine – are most suitable for shelterbelts. A single row of trees will give some protection, but for the purpose of producing the tallest trees possible, thereby increasing the effectiveness of the shelterbelt over a greater distance, three rows are recommended. The center row of trees in a three row shelterbelt is stimulated by the rows on each side to make greater height growth in obtaining necessary sunlight. The side rows produce a greater growth of side limbs, because there is no competition for sunlight, and these side limbs, prevent wind from blowing under the trees. There is obtained, through the planting of three rows, the greatest height and the greatest density of foliage possible, for the species of trees used, on each type of soil.
This spacing of trees in the shelterbelt is the same as for the windbreak, rows eight feet apart, with trees six feet apart in the rows. Instead of being placed opposite each other, however, they are spaced alternately when planted, since no later thinning out of the shelterbelt is required.
What Trees to Use
A combination well adapted for light soils of moderate fertility and moisture is Scotch pine and Norway pine. In this combination the Norway pine should be in the center row. On very light soils, from which much of the surface soil and humus has been blown away, a combination of jack and Scotch pine is recommended, the jack pine to be in the center row. Sometimes a belt of old oak trees has served as a shelterbelt, but needs to be replaced with conifers. White pine is adapted to growing under shade, and should be used under these conditions. A suitable combination for underplanting an old oak hedge would be two rows of white pine, with a center row of Scotch or Norway pine. The oak should be removed within five years after planting the pine. If the oak is allowed to remain longer, the pines will not make a normal growth, and may become deformed as a result of too much shade or indirect sunlight.
Soil preparation should be the same as for windbreaks. Recently plowed soil needs to be well-packed before planting the trees. On fields that have had a grain or inter-tilled crop within two years, planting the trees in the bottom of a shallow furrow is a good practice. Cultivation several times a season for the first five years is necessary to prevent sod from growing around the trees.
Sod will generally be found under oak trees in the old oak hedge, and if it is not possible to plow shallow furrows in the sod for planting, each planting spot should be separately “scalped”; that is, two square feet of sod should be peeled from each planting spot.
A shelterbelt may serve the purpose of posts in stringing a fence, if one-inch boards are first nailed to the trees, and the wires are stapled to the board. As the tree gradually increases in diameter, the board will be slowly forced outward, drawing the nail with it. The tree is not injured, and the wires never become embedded in the wood. This is known as “jacketing” trees for a fence line.
PLANTING THE WINDBREAK
The average windbreak will be too large to permit the purchase of expensive balled and burlapped trees. The more economical nursery stock, which does not have a ball of earth attached, is generally packed in wet moss, and shipped either in crates or burlap bundles. When trees are kept packed in this way too long, they are subject to two very serious types of injury – over-heating and drying – but both can be avoided if the person who receives them will immediately loosen the crate or bundle, drench the moss with cold water, and keep the partly opened crate or bundle in a cool darkened place, until the trees are ready for planting.
Final Soil Preparation
After the spring discing of the windbreak planting area, and immediately before the trees are planted, the soil area should have a final working with a spring or spike tooth harrow. After harrowing, the exact location of the rows should be determined upon, and the place for each tree in the rows should be marked. Straight rows and careful, accurate spacing of trees in the rows are highly desirable. A binder twine line for keeping good alignment of trees is recommended, and a 6-foot measuring stick should be used to insure accurate spacing of the trees. The trees in the second row planted will, of course, be set opposite the trees in the first row in order to obtain check-row planting except in sandy regions where pine are used, in alternate spacing.
Setting Out the Trees
The actual date for planting a windbreak varies, of course, depending upon the region of the state, how early or late the season may be, and the local weather. For the southern half of the state, windbreaks should be set out between April 20 and May 15. In the northern half of the state, planting dates will range from May 1 to May 25.
The survival of trees in a windbreak is influenced very largely by keeping the roots moist at all times; and by thorough packing of soil around the roots of the trees during planting.
It may be desirable to hold the trees three or four days after they are received, if soil conditions are dangerously dry, and there are forecasts of cloudy or rainy weather. When trees are carried about during the planting operation, the roots must be kept moist, and protected from exposure to wind and sun. The roots of tree seedlings are destroyed much more quickly by exposure to the air than are the roots of such plants as strawberries, tomatoes, or berry bushes.
A triangular-shaped hole, with one wall vertical, should be prepared to hold the full root system of the tree. The roots should be so distributed against the vertical wall of the hole that they will be in a natural position, and the tree may be planted about one-half inch deeper than it grew in the nursery. Watering of the roots as the soil is filled in, especially if the soil is at all moist, is not necessary but the soil must be thoroughly packed as it is placed in the hole.
After the trees are planted, it is advisable to place a thin mulch of loose soil on the packed soil surrounding the tree to prevent drying and possible backing of the soil.
Care After Planting
The ultimate usefulness of a windbreak will depend very largely on the care it receives for five or six years after planting. Poultry and livestock must be kept out. This may mean the building of a temporary fence, but young conifers cannot withstand the browsing or trampling of livestock, or the inevitable dusting holes which develop where poultry are allowed to run.
A summer mulch, which may consist of straw, marsh hay or sawdust should be applied within a few weeks after the trees are planted. This mulch need be only two inches deep, for a distance of not over one foot in radius around the tree. This mulch will serve a double purpose, hold soil moisture and help to smother out grass and weeds. Preventing the growth of sod around the trees is most important in promoting good tree growth.
A winter mulch, consisting of straw, with a low percentage of well-rotted-manure, is highly important, if damage from frost heaving during the winter and in the spring is to be avoided. This mulch should be from four to six inches deep, applied for a radius of two feet around each tree. If applied after the ground is frozen, and preferably where there is a light snow on the ground, there will be no danger of mice nesting in it. The winter mulch should be allowed to remain on the ground the following summer. By slowly decomposing, it adds to the fertility of the soil, prevents evaporation of soil moisture, and smothers out weeds and grass. A winter mulch should be applied annually, until the lower branches of the trees are at least two feet long. When they attain this size, the trees are beginning to develop their own mulch.
Cultivation for five to eight years after planting has been found to produce more rapid growth and a denser foliage. This has been especially noticeable in cultivated shelterbelts on sandy soils.
In windbreaks where spruce and white pine are used, some summer shade is essential. A very economical type of shade can be obtained through the planting of sunflowers. This plant has a very small root system, and does not offer much competition to the young trees. The sunflowers have value at the end of the season either for chicken feed or for ensilage. It is recommended that one row of sunflowers be planted for each row of trees. Three or four plants of the single flower variety, planted between each tree, are sufficient.
When the windbreak rows are in an easterly-westerly direction, the row of sunflowers should be planted 18 inches south of the row of trees. For rows of trees in a northerly-southerly direction, the sunflowers should be planted directly in line with the tree row. By this arrangement, the trees will be furnished intermittent sunshine and shade – a very favorable condition for tree growth. It would be well to furnish this partial shade through the second summer after planting.
Conifers in a windbreak should never be pruned. It is desirable to maintain those branches which grow near the ground, and if they have sufficient sunlight, they will maintain their foliage throughout most of the life of the tree.