Pruning a tree should always be approached conservatively. After all, you can’t put any of it back. You can only hope that any pruning cuts you make don’t turn out to be detrimental to the tree.
There are many reasons to prune, but it’s important to not get carried away and over prune.
All of these are good reasons, but can also be quite harmful if done excessively or incorrectly.
When I’m asked about what to prune on a tree, it isn’t uncommon for someone to point at a large limb thinking the problem (and future problems) can be mitigated with the removal of as much of the limb as possible at once. And though it’s rare, sometimes that is the only way. Especially after a recent storm or damage of some sort.
However, there is always a compromise to some degree with pruning. Maybe, with the exception of deadwood removal. But as with any live growth pruning there will be at least a slight compromise. Think of it like this: a tree needs food energy to seal a wound. But the act of creating the wound (pruning the limb) eliminates some of the access to the food energy needed heal or seal the wound. Now, think of many wounds created and many energy resources eliminated. It’s a catch-22. The more pruning done, the more difficult for the tree to recover. There are other reasons to avoid over pruning as well:
My personal thought on tree pruning is: when you’re unsure what or how much to prune, then your answer should be none – and call an arborist. Though, when having a complete tree removal performed, a homeowner has a little more options of who to hire. But anytime you’re having pruning done and will need to maintain the health and safety of a tree, a certified arborist is always your best bet.