Topping accelerates shoot growth and promotes branches that are weakly attached to stubs rather than anchored from within the limb. Topping not only makes trees more likely to break in a windstorm, it also hurts the health of the tree, Clatterbuck said. The root system of a topped tree also dies back. If there aren't enough leaves to make food to sustain the present root system, the roots will die back, he said. In addition, bark suddenly exposed to full sun may be burned, damaged, killed, or it may develop disease cankers.
Unhealed wounds increase the chance of insect attacks and fungal decay.
These enter through the wound and spread throughout the tree. If a tree has to be pruned every five years, the forester said, the tree is too large for the site and you should replace it with a smaller tree. Ask if tree services are members of the International Society of Arborculture or the National Arborist Association. Help is as close as your computer. Teresa Avery, a graduate student in horticultural information sciences at The University of Tennessee in Knoxville, studies helpful Web sites related to gardening.