During the winter, extremes of temperature, as well as excess water or periods of cold drought, can be particularly stressful for trees. Preparing your trees for winter, and taking care of them during the coldest months, will help your trees stay healthy and minimize the damage that colder temperatures can cause.

Preparing for winter

One of the best ways of preparing your trees-and your garden-for winter is to choose species that cope well with the types of weather you typically experience. If you live in a particularly cold area, choose tree species that can cope with that weather. Whether or not your trees are well suited for your climate, preparation before winter sets in will help them stay healthy over the cold months.

• Treat any damage caused to your trees promptly, well before winter sets in. If your trees are healthy before the weather gets colder they'll have a much better chance of withstanding extreme temperatures.

• In the fall, apply fertilizer that promotes root growth rather than leaf growth, even if your trees are evergreens. At this point they will not be putting forth new growth until the spring, and will depend more heavily on a healthy root system for food over the winter as well as for new spring growth. Be sure to apply fertilizer only when the tree has entered the dormancy phase.

• Avoid quick-release nitrogen fertilizers-organic fertilizers are particularly effective at promoting root growth without stimulating branch or leaf growth during winter.

• Water trees well in the fall, with particular care if your area is prone to winter drought. The area of ground beneath the branches of the tree should be soaked thoroughly for several hours, once in September and once in late October, before the ground freezes.

• Lay at least five inches of mulch around the base of trees to prevent moisture loss and limit temperature fluctuation. Leave a gap between the mulch layer and the base of the tree-this will help discourage mice.

Pruning

Pruning should be done to keep your trees healthy, and to remove any branches that may cause damage to your home, power lines or other structures if they should break during a storm. Prune in the fall as normal, only after your trees have become dormant. Avoid pruning until you are positive that the tree has become dormant, as pruning too early may encourage new growth that will be particularly vulnerable during the winter. Pruning may also be done in early winter, and if you are pruning to correct your tree's shape this is often the most advantageous time to do so. However, harsh pruning should be avoided during the fall and winter.

When pruning fruit trees, remove any shriveled fruit that still remains on the branches, and remove old fruit from the ground, too. This is a good time to check for signs of disease, as well. If you have any diseased trees, prune the diseased growth, and use disinfectant between each cut. Disinfect your tools well in between treating each tree to prevent the spread of disease, and destroy infected branches and leaves rather than composting them.

Snow and Ice Damage

Fast-growing trees such as silver maples, willows and birches have brittle wood that is vulnerable to ice damage and stress caused by extreme temperatures. Extreme variations in temperature can cause the wood layer beneath bark to crack. While there is little that can be done to prevent this type of damage occurring, young trees can be wrapped to help provide some protection from temperature extremes.

If you live in an area where ice storms or heavy snowfalls are common, the lower branches of trees can be propped up with supports to prevent breakage caused by the weight of snow and ice. Heavy falls of snow can be brushed off lower branches with a stiff-bristled broom, however thick layers of ice should not be removed, as this may cause breakage.

Additional Tips

• Apply rodent repellant to the bases of trees in the fall to discourage pests.

• Check your trees for signs of rodent damage occasionally during winter and use baits or traps if necessary.

• Wrap young trees before winter to protect from rodent damage. Young bark is most vulnerable and most attractive to pests.

• Young trees can be protected with windbreaks or supporting posts if necessary.

• Evergreens are particularly vulnerable to drying out over winter, and will usually require watering in a dry winter to prevent browning of leaves in the spring.

• Check your trees during spring for signs of winter damage and treat as quickly as possible to keep them healthy.