If done improperly, trimming can damage the overall health of your tree. For example, many people make the mistake of making one clean cut to remove a branch. However, they don’t consider what’s known as the branch collar. Improper cuts will hinder the tree’s ability to grow over that wound. Additionally, if you’re pruning interior branches, you can cut off too much foliage. This can either hamper the tree’s ability to grow— as it needs leaves for photosynthesis— leave the interior open to sun or wind damage, or even compromise the complete structure of the tree.

However, the proper trimming will not hurt the tree. A good rule to follow is never to remove more than 20% of the green canopy. You can always trim more in a few years, but you can’t undo what you’ve trimmed.