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Winter Protection and Mulching

REASONS FOR WINTER PROTECTION. Winter protection is necessary under the following conditions: First-When a plant is removed from its natural habitat to one more severe; Second-When plants are not sufficiently hardy to withstand the new climatic conditions or exposures; Third-When it is desirable to retain ground moisture during the winter for planting on exposed places, mounds and banks. Fourth -When plants (especially evergreens) are transplanted into a stiff clay soil under climatic conditions where they will be subjected to considerable freezing and thawing and it becomes necessary to protect them against heaving; Fifth-When plants, especially rhododendrons and other evergreens, must be protected against wind and sun which cause so much damage on account of excessive evaporation of moisture from the leaves at a time when no moisture is being taken into the plant through the root system. Continued, steady cold and a permanent covering of snow are generally sufficient to tide a plant through the severest part of winter, but an open winter, followed by severe cold, or the alternate freezing and thawing in spring, will work havoc. Mulching, therefore, is equally important, not only to control sudden changes in temperature in extreme weather, but also to maintain a cool, even temperature in early spring.

One of the common impressions in connection with mulching for purposes of winter protection is that plants are really being protected against extreme cold. Nothing could be farther from the truth. It is not possible to protect plants against freezing conditions, especially during the cold winters of our north when frost enters the soil to a depth of two to three feet. Under such conditions no normal depth of mulch consisting of rotted leaves or manure could keep frost out of the soil surrounding the roots of the plants. The real reason then is a different reason from that of being a desire to ward off a freezing condition. It is the desire not of warding off the cold but of preventing abnormal evaporation of moisture from the IOI leaves and especially from the lower part of such plants as the roses which are particularly sensitive to this type of evaporation. It is for this reason that plants which do not have well-ripened wood like the golden bell and certain varieties of the deutzia are subject to injury because of this evaporation. Other plants like the bush honeysuckle and lilacs which succeed in developing thoroughly ripened wood before winter approaches do not suffer so much. There are two important sources of injury (outside of the gnawing by animals) which can cause plants to be injured during the winter months and as a protection against which mulching is necessary. The first is abnormal evaporation from the roots and stems of plants that are in exposed situations, and the second a liability of being heaved from the ground where a clay loam soil is subjected to violent changes of freezing and thawing. It is for this same reason that standard roses and climbing roses are frequently lost during the winter months because they are protected by a thin covering of straw, and evaporation is allowed to continue, when, in reality, they should be taken down and buried in soil which remains moist throughout the winter months and thus protects the stems against evaporation.

SOURCES OF WINTER INJURY, AND REMEDIES. 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.