It’s that time of year when large trees often get “topped” because people consider them to be unsafe. 

More often than not, an un-trained tree trimmer armed with a power saw is hired to do the work and doesn’t stop until all that remains is a trunk with a multitude of sawed off branches. Some people think this is an acceptable pruning practice. Often referred to as stubbing, or heading back, it completely disfigures trees by amputating their entire crown. This senseless and abusive form of tree mutilation is not recommended. 

Topping trees compromises the tree’s health, longevity, aesthetics and property value. By comparison properly pruned trees increase in value each year. 

When trees are topped, the new shoots that form near the pruning cut are weakly attached and prone to breakage as they grow larger and heavier. This fact often makes topped trees more hazardous than before pruning. Consequently, topped trees need to be pruned more frequently to maintain safety. At best, topping is a temporary solution for over-sized trees. Topped trees often grow back to their original height faster than trees that have been properly pruned (thinned). Furthermore, the resultant foliage is denser and therefore less wind resistant.

There are times when reducing tree height is necessary or desirable. The best way to do this is by thinning. This involves removing selected branches by pruning each to a lower lateral branch or to the trunk. This will reduce height and spread while retaining natural shape. Bark damage from sudden exposure to direct sunlight is also minimized because less of the tree’s canopy is removed. Make pruning cuts close to the trunk, leaving the branch collar intact. Thinning cuts are inconspicuous and they close over rapidly and completely with little or no decay. The proliferation of unsightly and weakly attached shoots is not a problem when trees are thinned. Although thinning requires greater skill and usually takes longer than topping, in the long run, it’s more cost effective.

When thinning cuts can’t provide adequate clearance or height reduction, it is better to remove the tree and replace it with one that has a smaller growth form. Select a replacement tree after considering its potential height and spread at maturity, and its adaptability to the planting site. Avoid planting trees where they will eventually interfere with utility lines or other obstacles. With careful planning, the majority of future tree problems due to size can be avoided. 

QUESTION: We have several old trees in our landscape that we think need pruning, but are not sure where to begin. Can you provide some guidelines?

ANSWER: Remember, not all mature trees need to be pruned. Some only require pruning every five to 10 years. Mature trees should only be pruned for specific purposes and in a manner that protects and preserves the tree’s natural form. When a vigorous branch is cut from a tree, part of the tree’s ability to produce food is removed and a wound is created where decay organisms may enter.

Pruning should focus on maintaining tree structure, shape, health and safety. The International Society of Arboriculture recommends the following types of pruning:

Crown cleaning — removes dead, dying, diseased, crowded, weakly attached or low-vigor branches and water sprouts.

Crown thinning — selectively removes branches to increase light penetration and air movement and reduces the weight of heavy limbs.

Crown raising — removes lower branches to provide clearance for buildings , vehicles, pedestrians and signs.

Crown reduction — reduces the size and spread of crowns using reduction and thinning cuts, resulting in fewer sprouts than heading or stub cuts, and maintaining the structural integrity and natural shape of the tree.

Crown restoration — improves the structure and appearance of trees that have been storm damaged or deformed by heading or stub cuts.

A qualified and reputable person or company should be hired to perform tree work — not an individual with a chain saw trying to make a fast buck. It is very difficult, if not impossible to repair damage that has been done by poor pruning. In tree work, the old adage “you get what you pay for” is usually true. More trees are killed or ruined each year from improper pruning than by pests.

WSU has a great publication with detailed information on how to prune ornamental trees. You can obtain a copy of EB 1619 Pruning Landscape Trees by dialing 800-723-1763. You can also order a copy online at: http://pubs.wsu.edu. Cost is $4.50 plus tax, shipping and handling.

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