Sometimes trees that are perfect for the space that they inhabit when planted simply become too big for that space when they reach maturity. So we end up with the difficult decision of what to do about them. Can we train them to fit into their space with pruning? Or are we just trying to fit a buzzard into a birdcage?
Pruning trees to fit into spaces is an acceptable practice for some trees because of their high tolerance for pruning, and their ability to heal and adapt to the alternate forms that we may impose upon them. Indeed, some trees such as fruit trees and dwarf hybrids tend to thrive when pruned correctly. So it is sometimes completely appropriate to manage a tree’s size and form to fit in the space that is available.
Some trees, however, do not tolerate pruning for the purpose of size management or reduction. Trees such as Oak, Hickory, Poplar, Ash, Elm , and most Maples are somewhat programmed by nature to reach their full natural size. When we interfere with their growth by pruning, we cause problems that will eventually lead to sickly, weak, and hazardous mature trees. In these cases it is much better to simply replace the tree when it overgrows its space with a specimen more suited for that space. It may seem somehow callous or dismissive to take this approach, but if we look at what can happen when we try to force a large tree in a small space the logic becomes clear.
Too often we see in urban settings trees that are given “haircuts” to stop their encroachment on pedestrian walkways, buildings, utility lines, and lines of sight. Pruning cuts are made all across the canopy at points on the main leaders or stems for the purpose of a uniform and symmetrical size reduction. This is commonly referred to as “topping” or “crown reduction.”
The re-growth of branches that results from this kind of pruning, although at first glance may appear to be robust and green, eventually reveals the fatal flaw of the method. The attachment of new branches that sprout from cuts on a primary trunk or leader is very weak and prone to failure. Worse yet, the cut on the leader does not ever completely heal. So the result is a cavity of decaying wood at a point that is supporting the weight of quickly growing, weakly attached limbs. The result is a progression of upper canopy limb failures.
So the quick and easy haircut from the bucket truck, although it may seem to solve the problem, will most often result in major problems in the future.
To help with your decision about size management of your trees, talk to a certified arborist. Consultation is often free, and even if you pay for it the benefits will surely outweigh the eventual cost of poor pruning practices.
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