Caring for Trees in Winter

By Nancy Penrose

Although trees go dormant in the winter, temperature changes can still cause tree stress. Even trees that are native to the region can become damaged from the cold, temperature variations and storms. Landscape and privacy trees can be particularly vulnerable if they are exposed and isolated.

During the winter, temperatures can fluctuate dramatically. Daylight hours, when the sun is out and generating heat, are much warmer than nighttime, when the cold air can freeze even big trees.

This fluctuation in temperature can rupture tree bark cells and cause cracking (also called frost cracking) between the outer bark and inner wood. In most cases, the tree will repair any damage that occurs. However, too much cracking can lead to permanent damage.

One way to prevent cracking, especially with younger trees, is to wrap the bark in a fabric blanket. The blanket will provide the insulation the tree needs from cold weather. The tree can also breathe through a fabric blanket, which will also let in light and moisture.

Any late growth on trees can also be damaged by the cold because the growth is not fully established. If ice crystals start forming, they can damage the cell walls of new growth, which can cause die off. One way to prevent this type of tree stress is to wait until the tree has become dormant before pruning and to use fertilizer with low amounts of nitrogen.

The best way to prevent branches from breaking during storms or from winter snow, is with good pruning during the fall. Using a wooden frame to blanket the tree can also prevent breakage.

Mulching can also prevent extreme temperature fluctuations and the loss of moisture. The mulch acts as an insulator for the soil around the tree as well as the tree’s roots. It also slows down water loss. The best time to mulch is after the ground freezes to prevent rodents from making the mulch their home.

Sometimes winter sun and wind can cause leaves to dry, especially broadleaf evergreens. Use an anti-desiccant to minimize moisture loss.

The bark of young trees may also need to be protected from rodents and other animals. During the winter, tree bark is a source of food for mice and rabbits. You can protect your tree bark with plastic tree guards, chicken wire and paint-on repellents.

Here are some other tips that can help your trees survive the winter:

-Keep trees well-pruned and watered during the fall

-Remove any irrigation bags before the ground starts freezing

-Gently remove any snow that accumulates on the branches

-Never break ice from branches. Instead, connect your garden hose to hot water faucet and rinse the ice away. Be careful not to scald the tree with the water.

-Inspect and prune your trees during their winter dormancy. It will be easier to see the tree’s branch structure and any potential problems. Pruning will also help prevent the spread of disease.

A tree arborist can give you more valuable advice on how to protect your trees during the winter. If you are planning on buying big trees, including maple trees, pine trees, spruce or cedar, make sure you consult a big tree transplanting and sales company as your first step. Professional tree nurserys will know what types of trees are best for your landscape needs.

Nancy Penrose is owner of Big Trees Inc. ( in Snohomish, WA, one of the largest Seattle tree nurseries (see inventory at, specializing in tree transplanting. See our video at