By PAUL HETZLER
As far as tree health is concerned, the optimal pruning season is the six weeks or so before buds open. We still have ample time to prune, as spring appears to be in no hurry to get here. Pruning is both a skill and an art, and must be learned in that order. Proper equipment and a few guidelines are needed to master the skill; the art will come with experience.
If you had to shovel the driveway with a spatula, you’d soon despair, especially this winter. By the same token, pruning with cheap tools is agony. A high-quality hand saw and bypass-type hand pruners are essential, and a good lopper is a welcome bonus. Good tools will last lifetimes, and you’ll be amazed at the difference they make. Unless you’re near an urban center, though, you’ll probably have to order online—just search for “arborist pruning tools.”
Trees and threes seem to go together. You might say pruning starts in “3-D,” because removing dead, damaged and diseased branches is the first order of business. When it comes to live healthy wood, no more than one-third of the branches should be removed during any pruning cycle, which is typically three years for shade trees. Young trees can tolerate heavier pruning, while older ones need a light touch.
Once the 3-Ds are out of the way it’s usually easier to see what else needs attention. If you find crossing and rubbing branches, take the less desirable of the two. Whenever possible, favor wide branch-to-trunk attachments over narrow ones, which are more prone to breakage. In most cases, branches are pruned back to the trunk, although sometimes pruning back to a side branch is preferred for aesthetic reasons. When doing so, make sure that side branch is at least one-third the diameter of the branch you remove.
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 the upper canopy actually get so hot they can no longer photosynthesize. But the shaded lower branches are able to still carry on essential tree business until things cool down for the leaves up top.
Obviously, maples will “bleed” if pruned now. While the loss of sugars is not considered significant, you may want to prune maple (and butternut, birch 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 problems. For trees, mostly.
“Prune the branch, not the trunk.” This statement, ridiculous on its face, is important. At the base of most branches is a swollen area called a branch collar, which produces fungicides (seriously). The branch collar is part of the trunk and should never be cut. In other words, flush cuts are bad.
In the past, pruning cuts were painted over with various compounds, but research has shown that coated wounds never fare better than uncoated ones. In fact, many times they actually decay faster and more extensively than untreated wounds. To the best of my knowledge, though, people-cuts can still be treated with Band-Aids. Keep some of those on hand—good pruning tools are really sharp.
Paul Hetzler is a forester and Cornell Cooperative Extension of St. Lawrence County horticulture and natural resources educator.