Assess Your Trees Before Pruning

Late November to mid-February is pruning time, but before pruning the trees yourself or trolling the advertisements looking for arborists, stand back and assess what — if anything —  needs to be pruned. Too often, homeowners prune because someone came to the door and offered.

Pruning is done for three main reasons: safety, tree health and appearance. Notice that appearance is last. I’d rather not list it at all because it’s subjective, not objective. Still, it’s a frequently mentioned reason.

The motive for safety is poor branch structure. Narrow branch junctions, called branch crotches, that are V-shaped are extremely weak and should be removed, especially if two or more of the branches are of equal diameters. Think Arizona ashes or hackberries. Long branches that have been repeatedly stripped of their lateral branches are also very weak and should be shortened or removed completely.

Tree health is the second motive for pruning. Everyone can see the “3-D” branches — dead, diseased and dying — that need pruning. But other concerns for tree health are food production and disease. By food production, I mean photosynthesis. The objective of tree leaves is simply to produce the most food possible. Sometimes an overzealous homeowner or ignorant tree trimmer will prune what the tree needs most: leaves. Loss of foliage results in loss of food reserves that fight against disease. The national standard is never to remove more than 25 percent of the canopy during one year.

To prevent disease, remember three things: you should be able to see some sky through the canopy, never cut through the branch collar and always paint oak wounds.

What is a branch collar you ask? The collar is a zone of specialized cells and chemicals that reduces the potential for decay and disease. The collar is the donut-shaped ring at the junction where two branches or trunks connect. As for painting a wound, that is done to prevent oak wilt in oaks. So if it’s an elm, ash, sycamore or pecan tree, it’s not necessary. But for oak trees, paint the wounds!

Pruning a tree is a major task. A homeowner spends most of his or her landscape budget on this single task. Before spending a lot of money and time, remember this: pruning is not mandatory. (No elves or dwarves are doing it in the forest.) But if you wish to have your tree live a long, healthy life in an urban environment, then pruning once every three to seven years is vital.

Picture of Mark Peterson
Mark Peterson
Mark A. Peterson was a conservation project coordinator for San Antonio Water System before retiring. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you're likely to find him hiking San Antonio's wilderness parks or expounding on the virtues of geography and history to his friends.
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