Few operations connected with gardening are more misunderstood than that of providing protection for winter. Someone has remarked that attempts at winter protection injure more plants than they benefit.
This is somewhat exaggerated, but not so much as might be supposed. The basic reason winter protection often fails to protect, or results in injury, is that the remedy is applied without any previous study of the causes of injury against which protection is sought.
These causes are numerous, and methods effective against one form of injury may merely serve to aggravate another.
Freezing
Let’s look at the most common form: freezing, extremely cold temperatures or the particular plant in question.
Why does the same plant – a rose of a particular variety for example – come through the winter unscathed in one garden, while in another in the same vicinity it may be severely injured or killed outright?
Plant Condition
As it goes into winter, a plant’s condition and health have a great deal to do with the degree of cold it can successfully withstand.
It is an established Scientific fact that the more “free water” there is in the stems and branches, the greater the likelihood of freezing injury. Therefore, free water is present in maximum amount when growth is succulent or unripened. While this is true with roses, it applies to all types of plants.
The first step in protection against freezing is to have all wood, particularly all new growth, as well-ripened and hard as possible before the plants go into winter. Heavy feeding, especially with any high nitrogen fertilizer, should be withheld before freezing is anticipated during the month or two.
Excess Moisture
Too much moisture is another factor likely to result in late, soft growth. Restrict late-season watering to amounts sufficient only to prevent drying out of the soil. If copious late rains arrive, the gardener should pay attention to surface drainage to ensure that any surplus runs off as rapidly as possible.
With this preliminary precaution taken to assure well-ripened growth, the next step in winter protection against freezing is to provide a winter overcoat of some sort. This should cover at least the base of the plant, if not all of it.
Do not forget the plant must breathe. Too heavy or too tight a covering often proves worse than none at all. The objective should be to keep the patient warm and dry, never wet and cold.
A heavy mulch of any material that is likely to get wet and soggy is dangerous. Mulches of the latter type – heavy barnyard manure or “soft” leaves such as those of maples – will pack down into a soggy mass that freezes into a cake of ice, and remains wet and cold even during periods when they thaw out.
In the case of individual plants, oak leaves, pine needles and similar light materials, held in place by a cylinder of chicken wire supported by two or three light stakes, make ideal overcoating. Modern insulating materials that come in the form of strips, bats or flakes, afford effective protection.
When To Apply Protection
The time to apply any protection against cold is also important. Ideally, it is best to be put in place just before the first hard frost. Applied too soon it may delay the desired ripening of the new growth.
But, on the other hand, applied too late it may fail in its purpose. The first sudden severe cold snap may cause more injury than the same temperature would later on. Had it been preceded by a series of minor chills, causing a gradual hardening off of the wood.
Exercise care in removing the winter protection in spring. If done too early, an unexpected late frost may result in damaged plants. On the other hand, tender new growth that cannot withstand even the lightest frost may have started if left until too late.
Dehydration
Dehydration, the drying out of foliage and/or bark, is frequently the cause of injury for which cold temperatures arc assumed to be the
cause. Dehydration is probably the number-two killer in winter fatalities, just as surely as it is the number-one killer in transplanting operations. Often low temperatures and dehydration work hand in hand to accomplish nefarious results.
Fortunately, we now have materials like Wilt-Pruf, which can be sprayed on plants to form a thin film over bark and foliage that effectively cuts down moisture loss through transpiration and evaporation.
Though originally developed as an aid in transplanting, it is equally effective in reducing moisture loss and consequent sunburn and scald during winter, especially on young conifers and on such broad-leaved evergreens as pieris holly and laurel.
Although Wilt-pruf has never received the sensational publicity accorded some of the miracle products offered to gardeners, it is one of the most valuable garden aids that has appeared.
Time Tested Protections
The time-honored protections against winter winds and too intense sunshine have been shade and a wind barrier. Do not make the mistake of assuming that plants requiring such protection must be completely covered.
We have frequently seen plants severely injured due to being tightly bundled up, on the assumption that if some protection is desirable, much more must be better. We have found a winter windbreak formed of 2″ by 2″-inch stakes, connected by a 1″ by 2″-inch rail at the top to form a support for extra heavy burlap bags, to be very satisfactory.
Such a fence can be put up and taken down very quickly and requires little room for storage. This type of enclosure left open at the top but partly filled with pine needles, oak leaves, or dry straw, has proved most effective in carrying our collection of English and hybrid hollies through the winter in prime condition – even in a very exposed location.
Breaking
Breaking. Winter damage from high winds, ice storms, and heavy snows is often serious and even disastrous. Little can be done to protect full-grown trees. Their fate is pretty much in the hands of the storm gods. With small trees, and especially with decorative evergreens of moderate size, much can be done.
Occasionally, large trees such as elms, maples, beeches, and even sturdy oaks have double or multiple trunks which, under heavy stress, maybe fatally split. Here the danger must be anticipated, and the protection – in the form of bolts or ringbolts and chains – provided in advance. In most cases, this is work for the tree surgeon.
Small evergreens, likely to be damaged by snow or ice, may be storm proofed by tying up endangered branches to form a pyramidal unit, so that wet snow or ice lodging in them cannot spread and tear them apart. Always the endangering load of snow or ice should be knocked off just as soon as possible. Every hour makes a difference.
Some trees, such as birches, can spring back into their natural positions even after a severe ice storm, but others cannot recover so readily. Therefore, any broken branches should be immediately removed and the wounds – if more than a couple of inches in diameter – treated with tree wound paint.
Heaving
Heaving – caused by alternate freezing and thawing – often works havoc in beds of seedlings or among plants that have been set out in the fall and are not yet securely anchored. It usually occurs late in winter or early spring.
The best protection is to keep the ground frozen using very thorough mulching, best applied after the soil is well frozen. This is true even of small plants being wintered over in a frame, as the mulch helps keep the ground frozen and prevents too early growth in spring.
Drowning
Plants need not be submerged to drown. Soggy wet soil, particularly if it forms a compact crust, may effectively shut out air from the roots.
Seedlings, and such plants as rhizomatous iris and many chrysanthemums, arc subject to such damage. Prevention consists in providing perfect drainage. This is readily done by using raised beds and avoiding the use of any heavy, water-retaining mulch.
FGR-1158 – F. F. Rockwell