February 13, 2010

1 - It is still not recommended to top trees.

Yard and Garden - February 13, 2010


It has been a long time since you wrote an article about not topping trees. I have seen many topped trees lately. Is it OK to top trees now?

- G. W.



No! Do Not Top Trees! You are correct that I haven't written about this for a while, so it is time to write again. Some people may not have heard of the damage that topping does to trees, so your question is a service to those people.

Topping trees continues to be something to avoid. Yet, some people continue to top their trees, or hire people to top their trees. They are perpetrating a permanent injury on the tree. Topped trees cannot protect themselves from entry and spread of decomposing fungi that attach the wood. This results in rotting of the center of the tree and greatly increases the chances of branch loss (falling on you, your car, or the roof of your house) and the chances for catastrophic tree failure. The whole tree may break at a weak point in the trunk due to these fungi that have entered the tree at the point of the topping cut.

A topping cut is a cut in which the trunk of the tree, or a major branch is cut without regard to the location of the branches below the cut. In addition to the entry of disease organisms, these cuts often stimulate the tree to produce branches from adventitious buds formed just below the topping cut. These branches are poorly attached to the tree and more likely to experience branch failure (breaking out off the tree) than branches that were formed in the normal manner (adventitious means abnormal). These branches form a cluster of branches trying to undo what the improper pruning has done to the tree. This "witches broom-like" growth is unattractive and the production of these branches causes the tree to draw from its stored food reserves to produce this new growth. That further reduces the ability of the tree to resist diseases and insects.

When a tree has been topped, it looks like the homeowner has "gotten his money's worth", but in fact, he has gotten the opposite. His tree will be weakened, perhaps dying within a few years. The dangers from falling branches or the tree falling over has been increased and his property and life may now be at risk. We Do Not recommend topping of trees!

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

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