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Retrenchment Pruning Can Extend the Life of Mature Trees

Written by John Sepulveda, Certified Arborist WI-1454A, and August Hoppe, President Hoppe Tree Service, Certified Arborist WI-0477A

Retrenchment is a pruning strategy for mature trees that are declining in health due to decay, dieback, or damage to the crown. Mature trees reach a point in their canopy growth that they cannot grow past or support. The purpose of retrenchment is to grow a new crown below the current one that is at a reduced height. The resulting tree form is shorter and never reaches the original heights, but the tree is still alive and growing. Similar to how regular pruning is an ongoing process, retrenchment pruning mimics a natural process but is done in a controlled fashion by humans.

Retrenchment pruning can extend the life of mature urban trees.

Retrenchment can be a good strategy for homeowners who don’t want to lose a heritage tree that may have great sentimental value to them. It is possible to get many more years or even decades of further life with the tree since reducing wind load and stress is the number one way to reduce and prevent storm damage and breakage in trees.

This method of preservation also challenges the ideology that declining trees needed to be removed immediately. In urban areas, trees that are declining are often removed due to safety concerns, but in certain settings it is a viable strategy. With a little bit of time and careful pruning it is possible to try and keep trees around for longer than we usually do in the U.S. In Europe, retrenchment is a common practice.

Here are answers to frequently asked questions about retrenchment:

Q: When would you want to consider retrenchment pruning?

A: Retrenchment is done when your tree has grown old and the tips of the tree begin to die. This dieback occurs naturally, but we can help it along. The pruning is done in a phased manner. First, the reduction of upper crown branches is done while maintaining as much leaf area as possible for photosynthesis, while limiting further stress on the tree. The new lower canopy forms through development of epicormic shoots or adventitious buds, which are grown from buds underneath the bark that respond to stressors and shoot tip loss. The process can take a few years as the lower growth is allowed to develop and form good attachments to the tree. The reduction of the upper crown can progress every three to five years without causing topping.

Q: Are some trees better candidates for retrenchment than others?

A: This can be done with all sorts of species, but is typically done with larger trees with heavy limbs and taller heights, especially when they are in a position that could cause property damage. Silver maples and boxelders are two examples. Both are fast-growing larger trees that are susceptible to decay and breakage. Retrenchment pruning often works very well for them. It is sometimes done with smaller trees, but this often becomes an aesthetic type of pruning rather than a safety pruning.

Q: Is retrenchment something Hoppe Tree Service ever recommends?

A: Yes, we recommend it all the time. Often is it tied in with weight reduction of longer, larger limbs to make the trees more stout and able to hold up better against snow, ice and wind.

We take a holistic approach to caring for trees at Hoppe. Every tree and situation is different. Some cases will also require additional support with cables and/or tree health treatments such as fertilization or growth regulators. Growth regulators are effective because they will slow the vegetative growth of a larger tree, allowing the tree to reallocate its resources into fine absorbing roots and resiliency.

Q: Why is retrenchment becoming more popular in the U.S.?

A: It hasn’t been that common the past because some people believe that retrenchment pruning is too closely aligned to topping of trees. Topping is a poor practice: The pruning cuts are arbitrary and leave the tree more prone to decay, disease and insect damage, which can reduce the tree’s life span. On the other hand, retrenchment pruning is surgical, done with thought and artistic flair. It is gaining in popularity as more and more people want to save large old trees and preserve them for as long as possible.

If you are concerned about the health of your trees, give us a call at 414.257.2111 or request a quote. One of our certified arborists can come out to diagnose potential issues and consult with you on solutions to preserve the beauty and longevity of trees in your yard.

Since 1972, Hoppe Tree Service has been taking care of people and their trees. Join us as we celebrate 50 years of service to great customers in southeastern Wisconsin.

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