Arboricultural Services of Northcoast Tree Care - Pruning

Pruning is the practice of removing dead and/or living branches and roots from a tree.   There can be both positive and negative aspects to pruning. To maximize the good part, it is important that pruning be done in accordance with current professional standards (see Technical Resources below).  These are based on a modern understanding of tree biology.

Perhaps the most critical part of pruning is how a pruning cut is made.  Pruning is indeed a wounding process.  Attention to tree anatomy and how branches are shed helps to explain the best methods for reducing the potential for injury to the tree.

In general, removal of smaller parts is better than larger parts.  Minimizing the amount of living tissue removed is always a consideration.  The time of year may be important for certain pruning applications.  All pruning should take into account the overall health of the tree prior to taking place.  We segregate pruning treatments into the five following types.

1. Crown Cleaning:  Removal of dead, dying, diseased and broken parts.  This can be done for safety, tree health or aesthetic reasons.  It applies to both young and mature trees and shrubs.
2. Crown Thinning:  Removal of living parts beyond #1.  Thinning is done to reduce tree density.  This may be done to lighten branch load or accentuate an aesthetic feature.  Young trees can withstand a greater amount of thinning than mature trees. 
3. Crown Reduction:  This is performed to make the entire tree (or a portion of) smaller.  Younger trees usually can withstand this treatment better than mature trees.  Certain types of trees take this treatment better than others.  Severe reduction (topping) is almost always harmful to all kinds of trees. 
4. Crown Raising:  This is a form of reduction in that it removes the lower parts (limbs).  It is commonly done over roads, walkways and buildings.   This is best applied as a tree grows into a space, rather than waiting until after it is large.  Excessive raising can present structural problems.
5. Crown Restoration:  This applies to trees that have been mispruned in their past or have suffered some other form of traumatic injury.  Sometimes it is possible to restructure them so that they regain a more normal condition.  This can take several operations spread out over many years.

This is a blue oak in Ukiah before pruning.

This is the same tree after a cleaning and thinning.  Like a good haircut, there is very little noticeable difference from afar.

In the foreground is the amount of material removed from the pruned tree.

These trees were “topped”.  This is a drastic form of pruning. It is not recommended unless the tree is to be removed in the near future.

These trees were also topped.  The branches that grow at or near the top cuts are called “sprouts”.  Typically, sprouts are not strongly attached to the top cuts.  After a couple of years, wood decay usually occurs in the top cuts.

Topping is not only injurious but costly.

Overthinning is another way to remove an excessive amount of live crown. Trees that are overthinned tend to suffer broken branches.

When motorized equipment is not available or able to access a tree, climbing is needed. The tools needed to climb trees are relatively few and simple. Nevertheless, they must be in good condition to perform safe operations.

There are several methods for safe and efficient climbing. The climber in this picture has thrown his rope into the tree and now climbs the rope. There are several variations on this theme. All of these are preferred to climbing up the trunk with “spikes” (or “gaffs”).

The dark stained area in the wood of these tree samples illustrates the internal effects of climbing spike wounds. This discolored wood is now dead and the wounds can allow the entry of certain insects and pathogens into the tree. (photo courtesy of Shigo and Trees, Associates)

Pruning is a wounding treatment. In order to minimize the negative aspects of wounding, it is critical that proper cuts are made. Good cuts can only be made when the climber gets into the right position. Once there, the next step is knowing what a proper cut is. (There is detailed discussion of this in the Tree Biology subsection of Tree Science on this website).

Arboircultural Services Menu

Inspections & Evaluation
Cabling & Bracing
Root Care
Technical Resources