Topping Trees Not Recommended

1.Q. The trees in my yard are getting too large. A tree pruning service told me that the trees should be topped. What should I do?

A. The first thing you should do is get another tree pruning service. Many people have the misconception that cutting the main branches of a tree back to stubs in an effort to reduce the height is the proper way to prune. In reality, the cutting of a tree back to stubs permanently disfigures and actually weakens a tree.

There are some tree service companies that promote and practice this drastic form of "pruning." Apparently, a short tree is thought to be safer and healthier than a tall tree regardless of how the result is attained. In fact, topping a tree in this manner is one of the worst things man can do to trees.

In addition to the unsightly appearance, topping directly results in several other problems for trees, the most severe being internal decay. When a branch is correctly pruned at its point of attachment to the trunk just outside of the branch collar and the branch bark ridge, internal decay is usually stopped from progressing into the trunk by a barrier inside the collar. Also, a correct cut results in more rapid wound closure by callus tissue so that the bark's continuity is eventually re-established. Branch stubs produced by topping harbor decay fungi which eventually break down the barrier in the collar and then proceed into the trunk. Whenever a cut is made in the main leader by topping, there is nothing to prevent decay from developing in the trunk. The tree may be structurally weakened and its useful life span reduced. Other adverse effects of topping are:

  • Topping removes a major portion of a tree's leaves which are necessary for the production of carbohydrates.
  • Once-shaded bark in the canopy becomes scalded by exposure to direct sunlight.
  • Stubs are likely to attract wood-boring insects.
  • Stubbing stimulates the development of watersprouts just below the cut. These shoots grow rapidly, causing a topped tree to grow back to its original height faster and denser than a properly pruned tree. The watersprouts are also weakly attached and are easily broken off in storms.
If the height of a tree has to be reduced because of storm damage or interference with electrical wires, it can be correctly done by a method called crown reduction or drop crotch pruning. The procedure involves the removal of a main leader or main branch at the point of attachment of a lateral branch. The final cut should be parallel to the lateral branch bark ridge without cutting into the bark ridge. The lateral branch should be at least one-third the size of the branch or leader that is being removed.

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