Many property owners like to top their trees to make them look sleek and clean. They think it is a healthy thing to do and will keep the tree growing nicely. While this is true for some trees, there are several reasons we should not top trees.
Trees have evolved over the years to grow at a rate where the food production of the crown (the leafy part of the tree) can nourish the tree down through the limbs, trunk, and roots. If you prune too much of the crown, you can easily cut off too much, throwing off the crown to root ratio, and reduce the ability of the tree to produce enough food to survive. You can potentially starve the tree to death, or, at the very least weaken it, reducing growth and rendering it vulnerable to disease. A good rule of thumb is that cutting over one quarter off the crown will be too much.
The tree's crown acts as an umbrella to the sun's rays. Much the same way as a human's body works, if you cut too much of the top layer off the tree, leaves, branches, and bark underneath it are now exposed to much more sun than they are used to and will burn. The same thing can happen to trees and plant surrounding the tree that might be used to the shade it provides.
When you cut a tree branch, you leave a stub that is now vulnerable to disease and insects. Depending on the diameter of the remaining branch, the tree may not be able to close it in a timely manner. A tree has natural defenses to insects and disease and cutting them off too much can render the tree defenseless.
Cutting the tree too low might result in weaker limbs. If the tree has to replace the limbs instead of letting the cut branch grow, the resulting replacement branch is always weaker. Rotting at the end of the limbs will make the situation a lot worse.
If the purpose of topping a tree is to limit its growth, the result may have the opposite effect. When you cut a branch, the tree often will grow sprouts to replace them. These growth sprouts grow at a much faster rate than the original branches. You might, sooner than later, find your tree taller than when you started.
A topped tree, even if it looks good immediately, will always be a disfigured tree. If it grows to replace the cut leaves and branches, it never develops the same way. The inconsistent growth will eventually be noticeable and you will never be able to restore it to normal.
Some trees will not tolerate topping at all. The result could be certain death so make sure if you insist on try it, you at least determine if the species is tolerant.
The cost of topping a tree may be very steep. While it is easier and less expensive to hire someone for topping a tree as opposed to strategically pruning it, the hidden costs may be staggering. If it disfigures the tree, your property value may be substantially reduced. If the tree dies, the cost of removing it may be high. A weaker tree resulting from topping may necessitate more future maintenance than a healthier one would.
