Maple trees are recognizable for their brilliantly-colored fall foliage, which naturally appears in shades of bright red or yellow. As a shade tree, maples perform well thanks to a spreading, deciduous canopy of green leaves. But as a landscaping tree, maple requires a little extra care and attention. Knowing when and how to properly prune maple trees is essential, as improper pruning will cause more harm than good.
Many gardeners limit pruning to fall and winter, when the tree is dormant and no longer creating new growth. Pruning does not have to be limited to dormant phases of the tree's life, however. Maple trees contain sap, which will "bleed" if the tree is pruned in early spring or late winter. To avoid this phenomenon, pruning may be put off until summer. The only time that's off-limits is early summer, when pruning may damage tender new bud growth.
Maple trees may be pruned for shaping purposes; this is the practice of thinning and trimming trees to make them look more attractive. For some trees, the practice of thinning branches is a necessity because canopy growth becomes too dense for tree health. When pruning branches in order to maintain a specific tree shape or thin out the canopy, cuts may be made any time but early spring.
Light pruning is an ongoing process for any tree. Cutting away damaged and diseased branches is an absolute necessity that occurs throughout the year, any time the gardener notices a problem. Heavier, shape pruning is usually restricted to fall or winter after the tree has gone dormant for the season. Any time you notice a branch that is unhealthy, that's the best time to cut it off. Leaving diseased and damaged branches on the tree may only encourage the problem to spread.
When pruning a maple, always make cuts at an angle rather than vertically. To thin out a branch canopy, the entire branch is cut away back to its first joint next to the trunk. Prune away branches that are growing laterally across other branches. Do not cut into the collar of the branch, the ridge which is found just at the base of the branch itself, lest you create damage to the tree.