The best time for tree trimming is typically in late winter or early spring, before the tree's buds break and new growth begins. This is when the tree is dormant, making it less stressful for the tree to undergo pruning. Trimming during the dormant season also allows the tree to heal and recover more quickly.
Another good time for tree trimming is in the mid-to-late summer, after the tree has completed its annual growth cycle. This can help maintain the tree's shape and encourage healthy growth for the next season.