Large Branch Pruning

pruning large branchesQuestion: My neighbor recently pruned some branches off his tree and left stubs several inches long. Two branches snapped while pruning and pulled off a section of bark from the trunk below the branch. I suggested that he prune off the stubs as close as possible to the trunk so they would heal better. What do you suggest as the best way to remove tree branches? Should the wounds created by the torn bark be painted? Is this a good time to prune?

Answer: Yes, now is an excellent time to prune most trees and shrubs. However, I prefer to wait until March to prune fruit trees. They may be more subject to winter damage if pruned in the fall. Spring flowering shrubs should not be pruned until after they bloom. Flower buds are already set for next spring and pruning now would remove many flower buds.

You are correct in advising your neighbor to remove the stubs. However, making cuts as close to the trunk as possible is not the best practice. As branches grow larger on a tree, they grow over the tissue of the enlarging trunk or mother branch from which they originated. This creates a bulge where the branch is connected. Collar is a very descriptive word for this bulge because it reminds you of a shirt collar around a neck. Once a branch has become an inch or more in diameter, this collar becomes very evident.

In a natural forest there are many trees growing close together. As the lower branches become shaded, they are naturally sloughed off by the tree. A special layer of tissue is developed by the tree as the branch dies to protect it from disease and insect attack. In a landscape, lower branches have plenty of light, so they are not removed naturally by the tree. As trees grow taller, we remove those lower branches so that we can walk under them. The collars on those branches contain the tissue which heals the wound caused by pruning. If the collar is left, it will grow new bark to cover the wound. If the collar is removed by cutting too close to the trunk, this healing process takes much longer and the wound may never be completely covered. If a stub of the branch is left on the tree the wound cannot be healed either because the collar tissue cannot grow over the stub.

Research has also shown that tree wound dressings or paints are detrimental to healing of pruning wounds.  They slow the healing process and actually make the tree more susceptible to attack by insects and diseases.

You can prevent bark tearing when removing large branches by using a three cut process. The first cut is an under cut made an inch or so deep about 6 inches from where the branch is connected. Then the second cut is a top cut about 2 inches further out. The weight of the branch often makes it break before it is completely cut through in this second cut. The first undercut prevents tearing of the bark below the branch, which leaves a large wound.  Then the third cut is made close to the base of the branch, but leaving the collar intact.

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