Looking around East Texas this year, you will no doubt see trees that are pruned in several ways. How a tree is pruned will greatly affect the growth form, vigor, and stability of the tree. Two common types of pruning are thinning out and topping. Topping is not a recommended practice. In fact, some refer to it as “the Texas Chain Saw Massacre.”
Thinning out is also known as selective cutting or drop-crotching. It involves complete removal of a branch back to the main stem or to another lateral branch to the point of origin. Thinning conforms to the tree’s natural branching habit and results in a more open tree, emphasizing the branch’s internal structure. Thinning also strengthens the tree by forcing diameter growth of the remaining branches.
Topping is a more severe type of pruning and consists of cutting the top of a tree in a “flat-top” or “snowball-cone” shape. With topping, effects will be far more negative. Numerous new shoots will develop rapidly, producing many fast-growing, succulent sprouts. The tree will appear bushy, and the new shoots will generally form more structurally weak junctures with the main branch of the limb. Branches will tend to angle up very closely to the tree trunk, producing weak crotches. Topping trees vastly reduces the number of leaves they have, thereby limiting the trees’ ability to produce food energy through photosynthesis. This, in turn, can make them susceptible to attack by insects and disease. It can result in early death. In addition, topping produces large pruning cuts that are slower to heal and more vulnerable to decay.
An ideal ornamental tree shape is a straight tapered trunk with scaffold branches coming from the trunk. The most structurally sound branches are those that come out at wide angles from the trunk. By keeping in mind a general structural framework for trees that encourages strong growth, the trees will be better able to withstand adverse weather and environment conditions.
Linda Billings, Smith County Master Gardener
Texas AgriLife Extension Service