How can I help my trees survive winter?

October 18, 2007

Jerry Naiser

Certified Arborist (ISA), Certified Oak Wilt Arborist (Texas Forestry Service), Texas Department of Agriculture Certified, Structural Pest Control Board Certified, Texas Master Gardner.

Will your trees survive the snow, ice, winter cold and winter sun? There are several short-term and long-term steps you can take to ensure your plants’ survival or lessen potential damage.

Winter conditions cause more damage to trees that are stressed, so one key to preventing damage is preventing stress by keeping your trees in good health year-round.

The first protection you can offer for your trees is to site them in a good location depending on the weather in your area. Certain areas in the home landscape have different climatic conditions from their surroundings. These areas, known as microclimates, should be understood and used for planting appropriate trees. A professional nursery operator or technician can help you choose the best tree and the ideal location to plant that tree around your house.

In winter, the ground around the root system of the plant or tree freezes, stopping or slowing the circulation of water in the tree. Evergreens are at greater risk, since they hold their needles in the winter. The needles lose moisture to the atmosphere as well as to the plant itself. However, since the root system is frozen, the plant is not able to replenish the lost moisture, which makes the leaves dry out and fall off. To minimize the effects of winter drying, high-value evergreens can be treated with an anti-desiccant (usually a wax-like substance) that holds moisture in the leaves.

When the sun shines brightly on a cold winter day, it may heat up the bark of a tree to a temperature which stimulates cellular activity. As soon as the sun’s rays are blocked, the bark temperature drops quickly, rupturing and killing the active cells. This causes "sunscald," the symptoms of which are elongated, sunken, dried or cracked areas of dead bark, generally on the south side of the tree. Sunscald is most common on young, recently transplanted, tin-barked trees, so selecting a protected planting site can reduce the chance of sunscald.

Sunscald of young, thin barked trees can be prevented by wrapping the trunk with a commercial tree wrap, plastic tree guard or light-colored material that reflects the sun and reduces the temperature changes in the bark.

Some multi-stemmed trees and shrubs can be cabled together so that the extra weight of snow or ice can be shared by all the stems. It is best to hire a professional technician for selective thinning or cabling.

Mulch around the tree produces a year-round benefit because it increases the microbial activity and fertility of the soil underneath it; therefore, it is a good practice for reducing tree stress and keeping it healthy. Mulch has the added benefit of acting as insulation between the root system and the outside climate. This helps retain moisture in the root system and reduce the fluctuation of soil temperature.