Plant Pathology Infobytes

October 28, 1996
Caution! Topping Could Be Hazardous To Your Tree's Health

Mississippi is blessed with many large and graceful shade trees. Beautiful specimens abound and our parks and residential landscapes obviously wouldn't be the same without them. So it's not unusual that County Extension Offices receive many requests for information on ways to help maintain tree health.

There are several recommended practices which will help prolong the life of your trees, such as carrying out a recommended fertility program and removal of diseased and insect infested branches. However, some practices carried out by homeowners aren't so good and could result in more harm than good.

A good example of the type of practice to avoid is tree topping. Topping is the extensive removal or cutting back of large branches in mature trees. The tree is pruned much as a hedge is sheared with the main branches remaining as stubs. Topping is also referred to as heading or dehorning, and the practice can damage trees in the following ways:

* Topping removes much of the tree canopy and limits the tree's food making potential. This leads to depletion of stored food reserves.

* Canopy removal suddenly exposes the bark to the sun's direct rays, often causing scalding or even death of these tissues.

* Topping removes existing buds which would ordinarily produce normal sturdy branches.

* Large branch stubs left from topping seldom heal properly. This leaves the stubs and ultimately the entire tree vulnerable to decay fungi and insect invasion.

* Deteriorating branch stubs, along with weak sucker growth, make topped trees highly vulnerable to wind and ice damage.

* Some tree species, such as oak and maple, do not readily re- sprout. Without the resulting foliage, a bare trunk results and the tree quickly dies.

* Topping disfigures the tree. Unsightly branch stubs, conspicuous pruning cuts and a broom-like growth replaces its natural beauty and form.

Trees should be pruned to remove potentially hazardous dead and diseased branches which may break during ice or wind storms and to prevent branch interference with overhead utility wires. Pruning practices such as selective branch removal should be considered as an alternative to topping.

A less damaging alternative for reducing the tree crown is "thinning-out" which involves removing selected branches by pruning them back to the lower lateral branches. This reduces the tree's height and spread while retaining its natural shape. Pruning cuts are made close to the trunk, leaving only the collar of the removed branch instead of stubs. These pruning cuts heal rapidly and completely.

Thinning-out requires greater skill and time than topping, but it is well worth it. Careful and judicious pruning while the tree is young can eliminate the need for major pruning later on. This can effectively control tree growth and preserve the natural form of the tree without causing serious damage to tree health.

In some circumstances, such as when a large tree is obviously dying from disease, insect invasion, or other factors, it may be better to remove the tree and replace it. Before replanting, consider the potential height and spread of the tree at full maturity. Avoid planting where the tree will eventually interfere with utility lines or other obstacles. Careful planning ahead can often eliminate the necessity of drastic pruning in the future.

If you have questions about tree pruning methods, check with your County Extension Agent or with a licensed tree surgeon.

Note: part of the information used in preparation of this infobyte came from a University of Kentucky Cooperative Extension Service publication.


Written by the late Dr. Frank Killebrew

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