"Red Sunset" maple (Acer rubrum "Red Sunset"), a North American native, pleases with its graceful, round form and its bright fall foliage. Growing in U.S. Department of Agriculture plant hardiness zones 3 to 9, this natural variety of Acer rubrum casts dense shade beneath its upright branches. "Red Sunset" is somewhat self-pruning, dropping unproductive secondary branches in high winds. Your pruning efforts should focus on removing the occasional dead or crowded branch.
Remove branches that cross or crowd each other. Crowding results in thin, weak branches, while touching branches rub away bark, exposing the tree to disease. If the branches are young or small, cut them with lopping sheers. If the branches are too big for your loppers, use a pruning saw.
Prune away suckers, straight, vertical branches that rise from horizontal branches. Suckers crowd the canopy and weaken their parent branch. Use lopping sheers. This is also a good time to remove stray branches that don't contribute to an overall pleasing shape, or those that threaten to touch the house or other structures. Maple tree branching should generally follow an upward- and outward-facing direction.
Cut out dead or diseased branches with a pruning saw. If it is a large branch -- 3 inches in diameter or larger -- do the job in three steps to avoid tearing the bark on the main trunk. First, cut a line (a kerf) 1 inch deep into the underside of the branch, about 2 inches from the trunk or parent branch. Move out about 4 inches and cut the branch all the way through. Finally, remove the stub by cutting through the branch, just a little lower than the kerf.