One source of winter injury is a heaving in clayey soils which exposes roots of small and newly transplanted plants. This may be remedied by applying a ground mulch of straw litter or manure over the entire area immediately around the trees and covering the area of root growth. Another source is premature activity of the sap, due to the warmth of the sun's rays. If the ground is frozen hard and deep, and sun and severe winds strike evergreen plants they will "scorch" or dry out because sap cannot flow from the roots to take the place of that evaporated. Many evergreens which are exposed to severe winter conditions are in reality killed during the months of January and February; but the damage done does not become evident until time for spring growth to begin during the months of April and early May. If the evergreens which have been killed during the winter months in the nursery are dug and shipped to owners of estates at a time prior to spring growth and prior to a time when it is possible for a nurseryman to determine whether or not the plant is in a normal growing condition, plants killed in this manner (because of the lack of winter protection) do not show the injury until the growing season, at which time, with the beginning of warm growing weather, the leaves turn brown. Conditions of this kind often follow a severe winter. During a severe winter in which successive freezing and thawing conditions are a common occurrence evergreens are apt to be seriously damaged. Under such conditions it is the heat which causes the worst injury to the evergreens during these winter months and, as commonly believed, this is not injury due to excessive cold. A succession of extremely cold nights and warm thawing conditions during the day causes excessive evaporation from the leaves which, as heretofore mentioned, cannot be replaced through the dormant root system, the soil surrounding which has not been sufficiently warmed to excite growth. This evaporation may be stopped by shelter fences or by wrapping the plants with straw "overcoats." Care should be taken, however, to avoid wrapping too tightly, or injury to the plant will result from heating of foliage. Boxwood hedges also, particularly when young, should be covered to prevent winter injury in sections of the country where the temperature may fall as low as zero during the winter months. Such hedges may be boxed, or they may be banked with cornstalks or coarse litter and also with evergreen boughs. One of the best protections for boxwood hedges (as well as broad-leaved evergreens) is to be certain that they have a thorough soaking, especially during a dry fall, immediately before the freezing weather begins.
Mice often injure plants, and where this occurs mulching should be delayed until cooler weather, when the rodents will have nested elsewhere. Poisoning may be resorted to by placing poisoned wheat in drain tiles among the mulch. Mice and rabbits will gnaw certain shrubs and fruit trees, such as quinces, spireas, forsythias, etc. Such plants should be protected, especially the first year, by tar paper or burlap if mice are present. Wrapping should begin slightly below the surface of the ground at the base of the tree, and extend to a height of two feet. The author is advised on good authority that where there is excessive danger that the base of certain shrubs and fruit trees will be gnawed by mice and rabbits, an excellent method of protection is that of mulching these hedges with coal ashes to a depth of three to four inches around the immediate base of the plant. The gritty condition of this material is evidently objectionable to rabbits and mice and its use has saved a number of valuable hedge plants.
Perennials - Winter Protection of. Perennials should have a good mulch of well-rotted manure, straw, leaves, etc., applied just before freezing weather, in a late fall, and at the beginning of freezing weather in an early fall. In reality, it is not as essential, as we often assume it to be, that perennial borders, regardless of the material they contain or the type of soil in which the perennials are planted, should be mulched during the winter months. There are hundreds of gardens which pass through the winter without any protection whatsoever being given to the plants. These gardens are not, however, those which are developed on clay loam soil. The general feeling is that plants are mulched and given this winter protection because otherwise they would not be hardy. Quite to the contrary, most of these perennials are hardy, and as a matter of fact it is rarely possible that any amount of mulching such as is ordinarily provided for the garden can make any perennial hardy which is not by nature perfectly hardy in the climatic and exposed condition where it is growing. Every person who is responsible for the mulching of a perennial garden should use only a loose texture of material for mulching purposes. When mulching perennials place stakes beside small plants and those which begin growth late in the spring. This will prevent any loss when the mulch is spaded in or removed in the spring. Perennials with persistent leaves should not be mulched with anything which will mat down. This applies to foxgloves, hollyhocks, sweet williams, and violas. Cornstalks and leaves which drop late are best for such a mulch. Boxes filled with leaves may be inverted over plants; but when this is done the top should be watertight or damage may follow. Some tender plants such as pansies and snapdragons may be carried over the winter if a heavy mulch is applied before freezing weather appears.
Bulbs and Lilies - Winter Protection of. Eremurus and the tenderest lilies should be protected by a mound of ashes which will help shed water and retain an even temperature. All bulbs should be mulched with leaves, manure, or litter. If bulbs are planted in the heavier types of soil it is quite necessary to cover the crown with a good mulch which will maintain in the ground a more even temperature and will lessen the possibility of injury to the bulbs because of sudden fluctuations of temperature (freezing and thawing conditions), which cause heaving of the soil. It should be borne in mind that bulbs start growth very early in the spring. If the mulch is left on the surface of the ground until after the bulbs have started growth, especially in a sunny exposure, then the bulbs become spindly and strong plants and flowers do not develop. In the planting of crocuses late in the fall it is advisable to cover the ground immediately with some fresh straw manure which will keep the temperature of the ground from becoming too cold until after the bulbs have developed slight root growth.
Vines - Winter Protection of. Vines and various climbers, such as climbing roses or trained fruit trees, when growing against a southern or western wall, should be protected by burlap from the winter and early spring sun, which may cause growth to start too soon. Very tender vines, such as jasmine and some clematises and roses, can best be taken down and buried, especially where local climatic conditions or exposures are severe. When plants are so treated they should be allowed to lie on the ground for ten days or two weeks after they have been uncovered in the spring. This allows the canes time to harden-off.
Roses - Winter Protection of. Hybrid Teas and Hybrid Perpet-uals in most winters can be safely carried over by hilling up the soil about the plants to a height of six or eight inches, thus covering the lowest six buds, and then covering the plants with hardwood leaves eighteen to twenty-four inches deep. The leaves should be held in place with cornstalks or brush to prevent their being blown away. A three or four inch blanket of stable manure may be applied before the leaves are used and a windbreak of boughs of pine or fir trees, or cornstalks may be substituted for the leaves if manure is used. Cultivation should be stopped in September to discourage late growth, but the plants should be thoroughly soaked with water in October, just before hilling them up. This protection should be removed piecemeal in the spring, to gradually harden-off the plants.
Standard roses may be protected by laying them on the ground and treating them as tender vines. This is the most satisfactory method. They may also be wrapped with straw and burlap, or boxed, with a filling of leaves within the box. The safest method in severe exposures is that of burying them.
Rhododendrons - Winter Protection of. Rhododendrons, other broad-leaved evergreens and, to a certain extent, all other evergreens, are apt to be scalded in winter by the morning sun shining through the coating of ice or snow upon the leaves, unless they are shielded. They should be mulched also during both winter and summer. The mulching of rhododendrons for summer is done for the purpose of providing a thin layer of leaf mold which will produce as nearly as possible the natural conditions of the undisturbed soil in the woods and fields where rhododendrons grow. Mulching for winter protection is effected by banking the plants with a deep layer of leaves. These leaves prevent excessive freezing and possible heaving of the soil around the roots. Rhododendrons are further protected by building a screen of evergreen boughs or of cornstalks entirely around the plantation, but especially on the exposed side. A portion of the leaves used in the winter mulch can be left when the mulch is removed in the spring. Under no conditions should an attempt be made to spade this mulch of leaves into the ground in the spring. It may be loosened slightly with a fork, but because this plant has its roots so near the surface the ground around the roots, below the natural surface, should not be disturbed.
Trees and Shrubs - Winter Protection of. When mulching trees care should be taken to extend the mulch out as far as the roots extend, or at least as far as the ends of the branches extend. Most of the Japanese flowering peaches, cherries, etc., need a four-inch root mulch every winter in severe climates. Boxbushes, many other evergreens, and some deciduous material should be tied in winter. This is done to keep the plant from splitting under the weight of the heavy snows. Bands of rye straw or burlap are better than string for tying. Shrubs and trees when planted in groups or plantations, being thus close together, will protect each other to a considerable extent.
When plants are of doubtful hardiness, screens may be erected for protection on the most exposed sides, or completely surrounding the plants. Such screens may be made of poles to which is attached brush or burlap. Another method is to make a screen of boards. Screens are frequently used to protect evergreens, trees, and shrubs. A shed without sides also may be constructed over such plantings. This is done to avoid loss by drip from buildings, or breakage from the weight of snow. Shrubs may be wrapped with straw or burlap, the covering being bound with raffia or twine. A pole is usually placed inside the wrapping to prevent the plant from bending or breaking. It is preferable, however, to plant more hardy types of material, because screens are extremely unsightly unless the plants are in an obscure location.
Lawns - Mulching of. After the first year it is generally not necessary to protect lawns in winter. If a mulch is desired use straw or well-rotted manure old enough so that there is no danger from weed seeds. In the spring the coarse manure should be removed and the finer portions pressed in with a heavy roller. Heavy, coarse manure is apt to suffocate the growing grass and leave bare spots on the lawn.