By PAUL HETZLER
So far as tree health is concerned, the optimal pruning time is the six weeks or so before buds open. We should still have ample time to prune, as spring appears to be “on time,” unlike last year when buds burst open in mid-March.
The right tools will make pruning much easier. Much. If you had to shovel the driveway with a spatula, you’d soon despair. By the same token, pruning with cheap, dull, or rusty tools is agony at best. A high-quality hand saw and bypass-type hand pruner are essential. If it’s in your budget, consider buying a good lopper and pole saw as well. These tools will last lifetimes, and you’ll be amazed at the difference they make.
Trees and “threes” seem to go together. Start any pruning job with “3-D.” That is, remove dead, damaged and diseased branches. Next, look for crossing or rubbing branches, and prune off the less desirable of the two. Then, branches that conflict with your needs, whether that be visibility pulling onto the street or clearance for mowing. You can remove a maximum of one-third of the crown during any pruning cycle, typically three years for shade trees. For older and stressed trees, take no more than a quarter per cycle. (This messes up my tidy rule of threes, but it’s important.)
Whenever possible, favor wide branch unions over narrow ones, which are more prone to breakage. Usually it’s best to cut entire branches at the trunk, but for appearance’s sake sometimes it looks better to prune back a large limb to a side branch. The side branch must be at least one-third the diameter of the limb at that juncture.
Another rule is that two-thirds of a tree’s leaf area should be in the lower half of the crown. Lower branches are essential. It seems hard to believe, but on hot summer days the leaves in the upper canopy actually get too hot to photosynthesize. But they shade the lower branches, which carry on essential tree business until the day cools down.
Obviously, maples will “bleed” if pruned now. While the loss of sugars is not considered significant, you may want to prune maple (also butternut and hickory) trees in mid-to late July, the second-best time (tree health-wise) to prune trees. Put away the saw, though, during spring leaf-out and again during fall color—pruning in these times can lead to serious long-term health problems. For trees, mostly.
“Prune the branch, not the trunk.” While ridiculous on its face, this is important. At the base of most branches is a swollen area called a branch collar, which produces fungicides (really). The branch collar is part of the trunk and should never be cut. In other words, flush cuts are bad.
In the past, wounds of all types were painted with various compounds, which made sense, given that we cover our wounds to protect them. Research has shown that coating tree wounds does no good, and in fact often accelerates decay. To the best of my knowledge, though, people-cuts can still be treated with Band-Aids. So keep some on hand—good pruning tools are really sharp.
Paul Hetzler is a forester and a horticulture and natural resources educator for Cornell Cooperative Extension of St. Lawrence County.