Q: Now is the time of year when most property owners are considering pruning their trees. Removing unwanted branches improperly and at the wrong time of the year can stress and damage the tree. When and how should trees be trimmed?
A: The best time of the year to prune trees is in the fall after the leaves have fallen from the tree. Most of the energy that the tree has produced over the year has been sent down to the roots for storage, so removal of unwanted branches will have a lesser impact on the health of the tree. When removing a branch, make sure not to cut into the branch collar (tissues where the branch meets the trunk), and don’t remove more than one-third of the live crown of the tree.
The USDA Forest Service has a pamphlet that describes proper pruning techniques. It is available on their website at http://www.na.fs.fed.us/spfo/pubs/howtos/ht_prune/prun001.htm.
– Bill Glesener, DNR forester