Types of Pruning for Trees

Pruning a tree is a ‘double edged sword’. We want to remove a branch or limb, but in doing so we are going to be hurting  (wounding) the tree and removing the trees ability to produce food for its-self. Pruning is also something that we want to do and not something the tree necessarily ‘needs’. Unless there are structural problems that we need to do in order to fix a defect. Pruning of a tree is not ‘needed’ in order for the tree to be healthy.

First, I want to start with defining the term pruning and why I use pruning and not trimming. Trimming is the indiscriminate removal of something (i.e. you get your hedges or hair ‘trimmed’). Pruning is the specific removal of something at a specific point. This is extremely important when dealing with trees. Tree compartmentalize. That means that they kind of grow in sections and deal with wounds, decay, or disease in sections. So if a wound is made (branch cut) in a spot where the tree cannot compartmentalize, that wood will be open to disease, decay or other problems (stress) that will ultimately hurt the tree. However, if the wound is made where the tree can grow to close off, (compartmentalize) the wound, the chances of decay, disease, or excessive stress will be greatly reduced. For that reason, we prune trees at specific places and use different standardized types of pruning to ensure the tree can handle the stress of the wounding and thus ultimately live a longer and stronger life.

There are 4 main types of pruning as defined by the American National Standards Institue A300 Pruning Standards for Arboriculture: Clean, Thin, Raise, or Reduce. Additionally, in any case where pruning is going to be done to a tree, the type and specifications of that pruning should be described with specific tasks (goals) in mind. For example, if I am going to raise a canopy on a tree, I will describe that I will prune all major limbs off a tree that raise the canopy to a specific height and not just that I will canopy raise a tree. Otherwise, the work can get out of hand or the results not met because clear definitions and goals where not described. And if that is the case, I’m just trimming…

To clean a tree (often call canopy or crown clean) is to remove and branches or parts of the tree that might be disease, broken or dead. This is also often referred to as deadwooding. Often time with this type of pruning I will describe that I will remove all dead branches 2 inches in dameter and larger. Of course, if the customer wants something larger or small, we can define that size.

Thinning is when selective branches are removed to reduce the density of live branches in a canopy. I am not a fan of thinning unless it’s a situation where I am removing excessive epicormic growth because of stress or storm damage sprouting. If the tree is healthy and growing normally, thinning is rarely necessary or beneficial to the tree.

Raising a canopy or tree crown is the most common form of tree pruning. Its what you do when you prune off branches so you don’t get whacked in the face while mowing. Again, when canopy raising is done we provide specifics as to what clearance or height to remove to. Canopy raising should also be done slowly as the tree grows starting when the tree is young until it reaches maturity. Raising the canopy on a large mature tree can be very stressful on the tree and create such large wounds that the tree may never be able to close off those wounds. Finally with canopy raising, there should be a clear objective in where or what the lowest permanent branch will be on the tree. On young trees, this may be a small branch 20 feet off the ground, but once its defined a plan can be created in order to slowly prune to meet that height over time as the tree grows. Smaller pruning wounds are always desirable.

Crown reduction is when the height of a tree or large limb must be reduced. This is another type of pruning that must be done carefully. Crown or canopy reduction is still essentially ‘topping’ of a tree, and we all know how bad that can be. However, there are times when the reduction of a canopy is warranted and necessary to help the tree recover from stress or disease or to reduce the risk of failure in an old mature tree. But, reducing the height of a tree of unwarranted reasons will only cause problems. The most common and best used situation of reduction pruning is when its done to young trees with structural problems. This is also referred to as structural pruning. For example, reducing one side of a tree with co-dominant stems so that it has only one central leader to dominate the canopy.

Tree pruning should be a carefully planned project. Follow these standardized types of pruning and proper pruning techniques and you and your trees will be happy. Whether you are going to prune your tree or hire a professional to do the pruning, make sure you have a specific goal in mind for the results. Just cutting a tree for the sake of cutting it does not do you or the tree any favors.