The best time to prune a tree depends on the reason for pruning it. Removing dead branches can be done any time of year, but live shoots and limbs should only be cut when the tree is moving into a dormant phase.
Trim summer branches and blooms at the end of the growing season but before fall. Pruning during fall months invites disease, as freshly cut wounds heal more slowly on trees and plants. Winter or very early spring is the best time to prune most trees. Cool, crisp air helps trees heal more quickly, and trees that bloom in the spring produce more flowers after a winter pruning.