Retrenchment Pruning

What is Retrenchment Pruning?

The purpose of retrenchment is to modify the canopy 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. Its ecological benefits along with a plethora of other features can be enjoyed as the trees ‘useful life expectancy’ is greatly prolonged.

This type of pruning aims to reduce the mass of or remove potentially hazardous branches overhanging your boundary or asset that have;

A high risk of failure e.g. excessive end weight, defects, dead dying and diseased
If they were to fail, would have a significant impact on your assets, human life etc leading to an unnecessary financial expense
Aesthetic reasons can contribute, but are not often the main reason to do so

Retrenchment pruning mimics the tree’s natural process of senescence by selectively reducing the canopy before the tree does so.

We commonly also adopt this method of pruning to compensate for root loss in ‘Tree Protection Zones’ on development sites. It also greatly lowers the risk of whole tree failure post construction if root mass is disturbed during construction activities.

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 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.

Retrenchment Pruning for Veteran Tree Management

Veteran trees naturally reach a point in their canopy growth when they cannot grow past or support the physical weight. We commonly also adopt this method of pruning to compensate for root loss in ‘Tree Protection Zones’ on development sites. It also greatly lowers the risk of whole tree failure post construction if root mass is disturbed during construction activities.

Retrenchment pruning mimics the tree’s natural process of senescence by selectively reducing the canopy before the tree does so. As a result, large branch failures become more prevalent. Overmature trees are also more susceptible to large branch failure in large storm events, highlighting the importance of adopting this technique in the urban area to prolong the life of our valuable veteran trees.

Retrenchment FAQs:

Are some trees better candidates for retrenchment than others?

This can be done with all sorts of species, but is typically done with larger trees, especially when they are in a position that could cause property damage.

Our beloved Eucalyptus are a great example as they are fast-growing larger trees that are susceptible to decay and large branch failure. 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.

Why is retrenchment becoming more popular?

It hasn’t been that common in the past because some people believe that retrenchment pruning is too closely aligned to topping or lopping of trees.

Topping or lopping 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 (especially with Council) as more and more people want to save large old trees and preserve them for as long as possible.

Is retrenchment something that Skys the Limit Trees ever recommends?

Most often we do in response for ‘Arboricultural Impact Assessments’ recommendations to balance the impacts of development, whilst retaining trees to adhere to local government regulations.

When would you want to consider retrenchment pruning?

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.

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.

Contact us today to learn more about our Retrenchment Pruning Services.

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