Although late winter and spring is the typical time for major tree pruning, some pruning can be done in the fall after a frost has begun to force the trees into dormancy. Thinning out a landscape tree's crown before winter weather arrives can make it better able to survive the rigors of the upcoming season without damage. 

1. Crossed Branches

Branches that are crossed and rubbing together are the ones most likely to break off during a winter storm. Strong summer growth can lead to lots of crossed branches at the end of the season. Thinning out the rubbing branches so there is plenty of room in the crown for movement without friction issues will reduce winter damages.

2. Poor Air Circulation

Mildew and other fungal diseases are more common in a tree crown with poor air circulation. Branch damage and breakage are also more common, as poor airflow and weak sun exposure also lead to weaker branches. Thinning out up to a third of the small branches can open up the crown for better airflow. A less dense crown will also collect less snow and ice. This is important since heavy snow loads can cause branches to break or trees to topple over.

3. Weak Growth Patterns

Another issue with overly dense crowns is that the new branches may not develop the best growth patterns. Branches that droop downward too much, for example, are more likely to bend to the ground with a heavy snow load. Ideally, the angle at which a branch joins a trunk or leader should be between 90 and about 45 degrees, and angling somewhat upward is ideal. 

4. Waterspout Removal

Water spouts are fast-growing branches that grow vertically from the top of other branches. A rash of waterspout growth often follows a heavy spring or summer pruning. These branches are weak and more prone to breaking, so it is a smart idea to have them trimmed off before winter arrives. Similar growth, called suckers, can occur around the base of the trunk, and these should also be cut away.

5. Damaged Wood

Any wood that has severe damage from pests, diseases, or injury will be at risk of breaking off during a winter storm. Further, pests or diseases could continue to spread even while the tree is dormant. Pruning out damaged wood keeps a tree healthy and protects your family from injury due to a falling branch.

Contact a tree service if your landscape trees could benefit from thorough crown thinning.