While traveling around our community, I've noticed several home landscapes that have mature trees topped. Despite more than 25 years of seminars and handouts, topping continues to be a common practice. Topping is perhaps the most harmful tree pruning practice known.

What is topping? Accord to the International Society of Arboriculture (ISA) - "topping is the indiscriminate cutting back of tree branches to stubs or lateral branches that are not large enough to assume the terminal role. Other names for topping include 'heading,' 'tipping,' 'hat-racking,' and 'rounding over'."

Most homeowners resort to topping to reduce the size of a tree because the tree has outgrown the property. Some feel tall trees are hazardous to their home or adjoining property. Topping, however will make a tree more hazardous in the long run.

Topping stresses trees.  Topping often removes 50-100% of the leaf-bearing crown of a tree. The leaves are the "food factories" of a tree and this can temporarily starve a tree. Severe pruning triggers the survival mechanism of the tree which forces rapid growth of multiple shoots below each cut. The tree needs to put out a new crop of leaves as soon as possible. The new shoots grow very quickly, as much as 20 feet in one year, in some species. Remember the reason most homeowners top their trees is to reduce hazardous conditions; however, now the trees are more susceptible to damage, especially in windy conditions.

A stressed tree is more vulnerable to insect and disease infestations. Large, open pruning wounds expose the sapwood and heartwood to attack. The tree may lack sufficient energy to chemically "defend" the wounds against invasion. Some insects are actually attracted to stressed trees by chemical signals. (ISA)

Topping Causes Decay: Trees should be cut just beyond the branch collar. If the tree is healthy and the wound isn't too large, the natural healing process will occur to close the wound. When multiple cuts are made, decay organisms begin to move down through the branches and can lead to eventual death of the tree.

Topping Can Lead to Sunburn: "Branches within a tree's crown produce thousands of leaves to absorb sunlight. When the leaves are removed, the remaining branches and trunk are suddenly exposed to high levels of light and heat. The result may be sunburn of the tissues beneath the bark. This can lead to cankers, bark splitting and death of some branches." (ISA)

Topping Makes Trees Ugly: The natural branching structure of the many varieties of trees is a biological wonder. Topping destroys the natural form of a tree. Without the leaves a topped tree looks disfigured. When the leaves appear in the spring it appears to be a ball of foliage without the graceful appearance it should exhibit A tree that has been topped can never fully regain its natural form.

Topping is Expensive: The cost of topping a tree is not limited to the initial pruning. If the tree survives, it will require pruning again within a few years. Continual pruning will be needed to keep the tree at the desired height. If storm damage occurs, there will be the added expense of cleanup. If the tree dies it will have to be removed. Topping is a high maintenance pruning practice.

Alternatives to Topping: There are times when a tree must be reduced in height or spread. Providing clearance for utility lines or storm damage. There are recommended techniques for doing this. "If practical, branches should be removed back to their point of origin. If a branch must be shortened, it should be cut back to a lateral that is large enough to assume the terminal role. A rule of thumb for this is to cut back to a lateral that is at least 1/3 the diameter of the limb being removed. This method of branch reduction helps to preserve the natural form of the tree." (ISA)

Hiring an Arborist: Pruning large trees can be dangerous. If pruning involves working above the ground, or using power equipment, it is best to hire a professional arborist. An arborist can determine what type of pruning is necessary to improve the health, appearance and safety of your trees. A professional arborist can provide the services of a trained crew, with all of the required safety equipment and liability insurance. There are a variety of things to consider when selecting an arborist:

Membership in professional organizations; proof of insurance; a list of references (Don't hesitate to check.); avoid using the services of any tree company that advertises topping; avoid services who use climbing spikes to prune trees.

Thanks to the International Society of Arboriculture (ISA) for the information in this article. They are a non-profit organization supporting tree care research around the world and dedicated to the care and preservation of shade and ornamental trees. For further information, contact: ISA, P.O. Box 3129, Champaign, IL 61826-3129, USA. http://www.isa-arbor.com.

Read other articles about trees & tree care