If snow and ice are winter concerns in your area, then fall is the time to begin to prepare your trees for the hard cold season. Evergreens and trees with multiple trunks are at the most risk of winter damage, but it's a good idea to assess all of your trees so you can ensure they can survive winter unscathed.
1. Prune Away Weak Growth
Fall isn't considered the prime time for pruning, simply because trimming at this time can encourage new growth that won't be hardened off by winter cold. The new growth will then be prone to winter damage. You can avoid this by putting off tree trimming until after a few days of frost, but you must complete it before snow and ice arrive.
Begin by trimming out weak growth. This includes damaged branches, as well as branches that have a weak growth pattern. For example, if the crotch angle where the branch grows the tree is greater than 90 degrees—in other words, the branch droops downward—that branch will likely snap when loaded with snow.
2. Shape and Thin Heavy Foliage
When it comes to evergreens, heavy foliage can be a problem. If the snow and ice can build up on top of the foliage, the weight can cause the tree to split open. Trees with multiple trunks, like arborvitae, are at the highest risk. Evergreens with a natural pyramidal shape are less at risk compared to those that must be kept pruned to a more formal shape, such as some hollies.
You can minimize the chances of damage with a good trim. Although heavy thinning is best done in spring, you can lightly thin out a compact crown in fall after a frost. Focus mainly on removing any branches that rub together, since these are more prone to damage and breakage during winter winds. For trees and shrubs that require shaping, opt for a rounded or pyramidal shape so ice and snow don't collect as well. Flat tops will hold more snow, increasing the chances of splitting.
3. Wrap to Avoid Splitting
Splitting is a risk mainly only when it comes to multiple trunk trees or those with dense, trained shapes. For example, your blue spruce or lodgepole pine is typically safe from splitting, but your juniper will be at risk. Tying up the foliage is a great solution. After pruning, your tree service will wrap twine around the tree or shrub so that the branches become compact. Tying in this manner prevents snow loads from forcing the branches apart and splitting the tree. The service may also wrap burlap around the tree if winter burn is a risk.
Contact a residential tree trimming service for more assistance.