Winter can be harsh on everyone and everything but it is extremely hard on newly planted evergreens. Since evergreens, both needle and broadleaf, maintain live foliage through the winter, the foliage continues to lose moisture even when frozen. Long, cold periods with drying winds can dehydrate these new plants. Plants in new subdivisions are even more prone to being dehydrated through the winter than those planted in neighborhoods with many mature plants.

Sudden warm spells when the ground is still frozen, can also be a problem. During these warm spells, the needles of evergreens respond to the warmth by opening their pores. This lets water evaporate, but the roots are only able to draw limited water from the frozen ground. When the roots cannot keep up with the demand, the needles will turn brown and die. Twigs and buds on the ends become brittle and snap easily when bent.

Winter kill or winter desiccation is the term most commonly used to describe plants that are killed or otherwise damaged during the winter months for no apparent reason and it is a common occurrence on plants, especially evergreens. This damage is generally not noticed until spring. The symptoms often include the needles browning either on part of the plant or even the whole plant. In severe cases the needles will turn reddish-brown, and the bark may split or crack, which ultimately leads to the death of the plant. If an evergreen has suffered winter injury, wait until mid-spring before pruning out injured foliage.

The cause of all of this unexpected damage is simply a result of a temperature/water imbalance. As we all know plants transpire water through their foliage and as this moisture leaves the plant, it is constantly being replenished by the roots, which take in water. During the winter months plants go dormant, neither taking in water nor transpiring it. However in the late winter/early spring months when the ground is still frozen and the days begin to become sunny and warm, leaves begin to transpire sporadically. If the ground is still frozen, the roots cannot replace the moisture loss as readily, resulting in damage to the plant, most noticeable in its foliage. If the area is especially windswept, the effects of desiccation are accelerated. Nearly all evergreens are susceptible to winter desiccation.

So what can we do this time of year to help protect our plants? There are several things that you can do to help your evergreens survive the winter weather. The first thing would be to consider applying an anti-desiccant/ anti-transpirant. These products come under several different names such as Wilt-pruf, Vapor Guard and Transfilm. They create a waxy coating on the foliage which reduces water loss during warm and windy winter days. This practice can help considerably if it is done properly.

The product can be sprayed in late winter/early spring when the temperatures allow it, generally 40 degrees. Since most of our winter-burn actually occurs in March when the temperatures are above freezing but the soil is still frozen, the product will need to be reapplied during our spring thaw. You will also want to make sure that both sides of the needle surface as well as the trunk and stems are covered thoroughly and that it is done early enough in the day, preferably a sunny day, so that the material can dry properly.

The use of this material will seal the plant and reduce excessive amounts of moisture from being lost due to transpiration on those warm, sunny winter days. Make sure that you read and follow the label recommendations when applying these chemicals. Some anti-desiccant/anti-transpirant can become phytotoxic and do more damage to the plant then winter-burn.

The second thing is to provide additional protection for your plants by screening them with some type of material such as burlap or lath fencing to break the winter winds. This can help immensely, but in many instances it can be rather unsightly looking, especially if it is done in a hodge-podge manner. Use sturdy stakes that are a couple of feet longer than the plant is high. Place the stakes in the ground before the ground freezes.

You can either use a ‘V’-shaped screen or a flat screen depending on how many evergreens were planted. To shield your plants, simply place stakes around the plant or plants (at least on the windward side) and nail, staple or tie material like burlap or wire fencing to the stakes. Both fencing and burlap can be purchased in rolls. Whatever you do, never use plastic. Plastic not only stops all air circulation around the plant, but on a warm, sunny day your plants may end up cooking.

Some evergreens such as arborvitae and Alberta dwarf spruce are very susceptible to winterburn and even winter-kill when exposed to winter sun and wind.  To prevent this desiccation injury, and splitting under heavy snow loading, these evergreens can be wrapped with burlap and tied with twine.  Obviously this does not lend itself to an attractive winter display but it does increase winter survival. The wrap should be removed in early April.

Don’t forget about protecting your trees from rabbits and mice. Rabbits and mice may begin to nibble on newly planted trees and shrubs this time of year. Protect young trees by putting plastic tree guards around the bottom of their trunks. Make sure the tree guards go high enough - over the snow line. (I always remove them in the spring because it looks better and then I don't have the problem of the guards trapping moisture against the bark in the summer and attracting insects.)

If rabbits are a big problem in your area, winter care of trees and shrubs should include putting chicken wire cages around the plants they find most tasty. You can also prevent rabbit and rodent damage by using a pest repellent spray that can be applied on lower trunks, branches and stems. These products generally have to be reapplied after wet weather.

Although plant cold hardiness and winter injury are common concerns associated with our winters, appropriate plant selection, selecting the proper site, proper cultural practices, and preventive maintenance will significantly reduce or prevent severe injury or loss of landscape plants. Even though plants respond differently to winter stress and each winter provides a different set of stressful conditions, plants possess a remarkable ability to withstand extremely severe winter conditions. Our winters should not discourage planting of traditional or new plant species.