Horticulture News: Tree topping dangerous for trees and even people

By Adam Leonberger, Published:

It has been a rough year for trees and shrubs. Other agents and I have received a lot of calls of trees, shrubs and perennials killed by the harsh winter. Not only did we experience extremely cold temperatures for this region, but two big cold snaps likely caused a great deal of damage and death as well.

If homeowners haven’t seen any new growth from the base of the plant by now, the shrubs are most likely dead and could be removed.

Just as damaging to trees is tree topping. Topping is the drastic removal or cutting back of tree branches to stubs or lateral branches in large, mature trees. Topping is one of the most harmful tree pruning practices.

Over the last 25 years or so, there has been an effort by certified arborists, extension agents, tree specialists and others knowledgeable about trees to educate the public as to why topping is not an acceptable practice.

The most common reason for topping trees given by homeowners and those who practice topping is to reduce the size of a tree. Homeowners often feel their trees have become too large for their property or fear tall trees may pose a hazard. Some people believe it is acceptable because “we have always done it this way” or they see this example in their neighborhood and believe because a trusted neighbor does this, it must be OK. In fact, topping will make a tree more hazardous over the long term.

Tree can ‘starve’

Topping often removes 50 to 100 percent of the leaves of the tree. Because leaves are the food factories of a tree (the process called photosynthesis), removing them can temporarily starve a tree.

The severity of the pruning triggers a type of survival mechanism. The tree activates growing points and buds that have been inactive, forcing the rapid growth of multiple shoots below each topping cut. The tree must put out a new crop of leaves as soon as possible in order to continue the manufacture of “food.” If a tree does not have the stored energy reserves to do so, it will be seriously weakened and most likely will die prematurely.

A stressed tree is more susceptible to insect and disease infestations. Large, open pruning wounds expose the inner wood of the tree, called sapwood and heartwood, to attacks. The tree cannot close or heal the large wounds effectively.

The tree also may lack sufficient energy to chemically defend the wounds against invasion, and some insects are actually attracted to the chemical signals trees release. Tree topping actually causes decay in the wood, and ultimately leads to the death of the tree.

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 sun and heat. The result may be actual sunburn of the tissues beneath the bark, which can lead to cankers, bark splitting and death of some branches.

The newly produced shoots or limbs of a topped tree grow quickly. These shoots are prone to breaking, especially during wind or ice build up. The irony of topping is that while the reason of the procedure was to reduce the tree’s height to make it safer, the tree has been made more hazardous than before.

The natural branching structure of a tree is amazing and beautiful. Tree canopies form various shapes and growth habits, all with the same goal of presenting their leaves to the sun. Topping removes the ends of the branches, usually leaving ugly stubs.

Topping almost always destroys the natural form of a tree. The tree appears disfigured and mutilated during the months where there is not a full canopy of leaves to hide the damage. A topped tree almost never regains its natural, beautiful growth habit and form.

Can be expensive

The cost of topping a tree over time is expensive. The tree will either need to be pruned back again, or storm damage will have to be cleaned up. When the tree dies an early death, it will have to be removed.

There is another hidden cost to topping that few homeowners realize. Healthy, well-maintained trees can add 10 to 20 percent to the value of a property, according to the International Society of Arboriculture (ISA). Disfigured, topped trees are considered an impending expense to a new homeowner, and cause a reduction in property value. There is also the potential liability issue to the homeowner, since topped trees are prone to breaking and usually are considered hazardous.

Sometimes a tree must be reduced in height or spread. Providing clearance for utility lines is an example. There are appropriate, recommended techniques for doing so. These methods help to preserve the natural form of the tree and reduce possible problems.

However, if large cuts are necessary, the tree may not be able to heal the wounds. Sometimes the best solution is to remove the tree and replace it with a species that is more appropriate in size for the site. Planning ahead before planting is the best practice.

It is always best to hire a professional, ISA certified arborist. A certified arborist can determine the type of pruning that is necessary to improve the health, appearance and safety of your trees.

Avoid using the services of any tree company that advertises topping as a service. Knowledgeable arborists know that topping is harmful to trees and is not an accepted practice. You can find a list of certified arborist or verify an arborist credentials by visiting http://www.isa-arbor.com/findanarborist/arboristsearch.aspx.

For more information on this and other horticultural issues, contact the Franklin County Extension Office at 502-695-9035 or Adam.Leonberger@uky.edu.

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