Topping trees causes decline

Everyone can relate to that feeling of panic after making a cut and realizing you’ve just ruined the shape of your shrub.
Or perhaps you have ignored a plant’s obvious structure problem because you were afraid or unsure of what pruning action to take.
I continue to see poor pruning decisions throughout the county. The other day after teaching a class on proper pruning techniques, I came home to a neighbor topping their crape myrtles. Why is this bad?
Topping is a term used to describe the practice of indiscriminate removal of a tree’s crown by cutting off large branches and the main stem of a tree, leaving large branch stubs.
Most topping tragedies happen because we want to maintain a plant at a specific height or to keep it from growing too fast. Topping plants or cutting the central leader is fine when you want to make a scrawny shrub broad and full, but it is a nightmare for trees.
Removing the tops of the tree causes it to create several new leaders to replace the ones lost. These leaders compete with each other and compromise the structural integrity of the tree. Trees with one dominant leader are better equipped to handle wind and storms. Also by cutting into thick established wood it can expose the tree to insects and disease.
Although it was once standard practice to make a flush cut when removing a limb, studies show that flush cuts cause extensive trunk decay because the wood that is actually part of the trunk gets cut.
Large branches can be too heavy to hold by hand when pruning, so a three-cut method is recommended. The first cut is made on the underside of the branch about 15 inches away from the trunk and as far up through the branch as possible before the branch weight binds the saw.
The second cut is made downward from the top of the branch about 18 inches from the main trunk to cause the limb to split cleanly between the two cuts without tearing the bark. The remaining stub can then be supported easily with one hand while it is cut from the tree. The final cut should begin on the outside of the branch bark ridge and end just outside of the branch collar swelling on the lower side of the branch.
The branch bark ridge is usually rough, always darker than the surrounding bark, and fairly obvious on most species. The collar is a swollen area at the base of the branch. This region between the branch and the trunk acts as a natural barrier to decay-causing organisms.
Painting wounds with tree wound dressing is no longer recommended. Research has shown that wound dressings do not prevent decay. When exposed to the sun, the protective coating often cracks, allowing moisture to enter and accumulate in pockets between the wood and the wound covering. This situation may be more inviting to wood-rotting organisms than one with no wound cover.

Susan Brown is a horticulture agent with the Brunswick County Extension Service. Call 253-2610 or e-mail susan_brown@ncsu.edu.