Answer: Unlike humans, there's no way to repair a broken limb on a tree. Prune the broken limb back to its main source, the trunk if necessary. Use a sharp pruning saw and make a clean cut. Don't leave a "stub" with your cut, which allows entry for disease. Also, if cutting back to the trunk, don't cut absolutely flush with the trunk, but just outside a slightly raised area where the branch comes out, called a "collar." This specialized collar tissue is able to heal itself quickly, preventing disease and insect entry.
Do not apply any type of tar, paint, etc. to the pruning cut. Although once recommended, research now shows that this interferes with the tree's ability to heal itself.
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