One of the most destructive tree pruning practices is "topping," the drastic removal of large branches in mature trees. It removes all parts of a tree above a certain height without considering its structure or health. Topping leaves large, open wounds, increasing the tree's susceptibility to disease and decay; causes immediate injury to the tree; and ultimately results in early failure or death of the tree. Furthermore, topping of trees is prohibited by the Gwinnett County buffer, landscape and tree ordinance.
Topping is often done to reduce the size of a tree. However, topping is not an acceptable method of reducing tree height and tree hazards. In fact, in the long run, topping can increase tree hazards.
Topping can cause significant stress in trees. It removes more than 50 percent of the leaf-bearing crown of the tree. The leaves are the food factories of trees, and the loss of so many leads to starvation. Severe pruning causes the tree to produce latent buds that lead to the growth of multiple shoots below each cut. The rapid growth is an attempt to replace its missing leaf area so it can manufacture food for the trunk and roots. The loss of energy reserves can seriously weaken or kill the tree. Normal branches develop in sockets of overlapping wood tissues, but these new shoots are anchored to only to the outermost layers of the parent branches. The new shoots can grow 20 feet or more a year and are more prone to breaking.
A tree that has been topped is more susceptible to insect and disease infestations. Severe pruning may interfere with the tree's ability to chemically defend the wounded areas against invasion. Some insects are actually attracted to chemical signals released by trees.
Cutting a limb between lateral branches creates wounded stubs the tree may not be able to heal, causing the exposed wood tissues to decay. The leaves absorb much of the sunlight hitting the tree. However, topping removes many leaves, exposing the remaining branches and trunk to high levels of light and heat. The tissues beneath the bark can be sunburned, leading to cankers, bark splitting and death of some branches.
Topping causes the trees to have an ugly appearance by removing the ends of the branches and leaving stubs. It destroys the natural form of a tree. A topped tree can never regain its natural form.
Topping can be expensive in the long run. If the tree survives, it will have to be pruned again in a few years. If it does not survive, it will have to be removed. Topping also can reduce property values. Ugly, topped trees are considered an impending expense in property value assessments. The trees are more prone to breaking and can be a significant hazard.
Plant the right tree in the right space. Each species of tree has different height, width and spacing needs. Matching your tree selection with the site conditions - proximity to other trees, buildings or above-ground utilities - will prevent problems before they occur.
When a tree must be reduced in height, the branches should be cut back to their point of origin. To shorten a branch, cut back to a lateral branch large enough to assume the terminal role that is at least one-third the diameter of the limb being removed.
Do not confuse tree topping with proper tree pruning. A topped tree is noticeable due to the destruction of the tree's natural shape. A properly pruned tree often appears as if no work has been done at all. With proper pruning, an arborist will spend time carefully selecting and removing branches to retain the tree's natural shape and beauty.
Remember, topping is not only harmful to the tree and its appearance; it is also against the law in Gwinnett County.
Timothy Daly is an agricultural and natural resource agent with the Gwinnett County Extension Service. He can be reached at 678-377-4010 or firstname.lastname@example.org.