Probably the most common reason to trim or prune a tree is to remove branches that are in the way of something. Maybe satellite reception is poor due an obstructing limb, or a view is obstructed, a light is covered, a branch is rubbing a building, etc. When pruning to mitigate these issues, we are most often removing live limbs from a tree. When we do this we should take care to make cuts that will heal and leave a proper terminal branch to the leader that is cut. It is not acceptable to simply cut at a convenient place that achieves the clearance that we are seeking. In fact, cutting at improper points on a branch will often encourage the overgrowth of “water sprouts” that will soon make the clearance or obstruction worse than when we began. Guidelines for pruning cuts are outlined in ANSI z133 and the ISA at treesaregood.org and should be followed by anyone who does this work.

There has been much research data shared and discussed that supports the idea that it is most beneficial to prune trees of all species in the dormant season (winter). So most practicing arborists will agree that winter is the best time to prune. There are many reasons for this, but since there is such an overwhelming consensus on the matter I think this discussion should be more about how the trees should be pruned.