Training Pruning

Training pruning can eliminate structural defects that often result in storm-damaged trees. All photos courtesy of the author.

Storm damage is the ultimate opportunity for arborists to play Monday morning quarterback. Whether it’s our mistake when a client’s tree breaks or we are called to a new property to clean up the mess, there are the inevitable would haves, could haves or should haves. “I wish I had removed that tree.” “If only they had had their trees inspected.” “It should have been pruned and cabled.”

It’s humbling when it’s on our watch. It’s always a balance when we want to both preserve trees and minimize risk. It’s almost worse when you get the panicked call from a client saying, “You were right, I should have listened,” as they look out the window at the damage. No one wants that call.

So, what is the best way to abate storm damage? To go back in time, of course. Wouldn’t that be nice? Obviously, to take action before the tree fails. Being proactive is always best, but you can’t win them all.

Training pruning can eliminate a lot of structural defects. Weak branch attachments seem to be the most common cause of storm damage.

One simple way to decrease some storm damage is to prune trees when they are young.

Training pruning can eliminate a lot of structural defects. Weak branch attachments seem to be the most common cause of storm damage. These branches can easily be eliminated or shortened to create a better long-term structure. The ideal time to prune is after a small tree has been established for at least two years. You can prune a young tree before it is planted, but it’s preferable for it to have a developed root system, which is usually after the tree has been in the ground for a year or two. The smaller the tree, the better; 1- to 2.5-inch caliper is best.

Training pruning of a tupelo before … …and after

The idea of working on the tree when it is young and small is that you are less likely to damage the tree. The pruning wounds are small and the tree is growing rapidly and can overcome the wounding quickly. Think of an 8-year-old breaking his arm compared to a 60-year-old. Who will recover faster?

So often we find structural defects in middle-aged or mature trees, and we are limited as to what we can do. You can shorten branches and install cables, but you should not remove the branch if it’s greater than 12 inches in diameter. At best you will destroy the tree’s shape and, worse, you could create a cavity. It is very difficult for an older tree to close this size wound.

You want to work close to the trunk of a young tree, starting at the top. The most important thing is to have one central lead at the top and eliminate codominant stems. So often you see a healthy tree with a nice shape that grows well, only to then split apart due to a V-shaped branch union or included bark. That is why this type of pruning is especially important for medium- to large-tree species. If these defects are not removed, as the trees grow exponentially larger, they put more weight and stress onto that bad branch attachment.

If you cannot remove entire branches, you can shorten those branches. As a result, the central leader will grow faster, becoming taller and shading the lower branches. This allows the central leader to be dominant and eliminates multiple stems growing larger, which can lead to splitting and catastrophic storm damage.

The classic example is Callery pear. They were planted everywhere in the Northeast in the 1980s. They performed well until they reached a certain size and then broke apart. There are other tree species that, like these ornamental pears, are predisposed to bad branch attachments, but every species will have some.

So often we find structural defects in middle-aged or mature trees, and we are limited as to what we can do.

As you move down the spine of the tree from the top, you want to continue to remove these bad branch unions back to the trunk preferably, but at least shorten them to reduce the fulcrum. As you work your way down, be thoughtful about spacing the branches in a logical manner and be careful not to remove too many branches. Mentally “grow” the tree into the future to get an idea of which branches might be temporary or long-term structural branches. Although a good training pruning is more about the future structure of the tree than what it looks like when you are done, you don’t want to damage the tree by over-pruning.

Most of the time with a small tree you can create a great structure with one pruning. Sometimes you may need to do what’s most important now and come back another time for additional work, usually in a couple of years, after the tree has recovered from the initial pruning.

Again, like most arboricultural practices, being proactive is always best. Proper training pruning is the ultimate way to be proactive. It’s almost as good as going back in time.

David M. Anderson, Certified Treecare Safety Professional (CTSP) and a Massachusetts certified arborist, is a manager with Mayer Tree Service, Inc., a 28-year TCIA member company based in Essex, Massachusetts.

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