The collar is an important part of a tree's anatomy, and is especially important for those pruning trees to understand it's purpose. The collar is the folded bark tissue around the base of a branch. The image below is a great example of a collar found on an apple tree. Sometimes they are not so distinct.
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|Collar on an Apple Tree|
The collar's purpose is to aid in the healing of a cut branch. The next image shows various stages of a collar closing over a wound.
|Collars in Varied Stages of Healing|
In the previous post we discussed the importance of removing "stubs". While this is important, it is even more important to leave the collar intact, even if it requires leaving a small portion of the branch sticking out from the trunk as shown in the following image.
|Good Pruning Cut Example|
Notice that the ridge remains undisturbed. Also notice the angle at which the cut was made. Cutting a branch perpendicular to the direction of the branch minimizes the surface area of the cut. If the branch was cut vertical to the ground it would open up more area han necessary and cause the healing process to take longer.
If a pruning cut is too large, or the collar is damaged in the pruning process It will delay the healing process and may put your tree at risk of rotting before it is able to heal. Once this process has entered your tree it will continue into the trunk of your tree weakening it, increasing the risk of premature death and/or a loss of structural integrity.
|Improper Pruning Can Introduce Rot|