Japanese maples benefit from annual pruning to shape the tree and to remove dead and unhealthy wood. The best time to perform maintenance on a Japanes maple is in the late summer or the early spring. Summer pruning allows gardeners to see the foliage patterns before making the cuts, which is aesthetically easier. Spring pruning is less challenging since the tree is bare of leaves but prompts more new growth.
Check the branches of your Japanese maple, looking for dead, diseased or damaged wood. Deadwood feels brittle and doesn't move in the wind. Damaged or diseased wood looks scarred, wounded discolored or otherwise distinct. Removing this wood prevents disease from spreading.
Trim diseased or dead branches back to a healthy "Y" intersection or cut them back to the intersection with the trunk. In between each cut, spritz your lopping shears with disinfectant spray so you don't infect healthy wood. Throw the diseased wood into a garbage bin.
Trim off any branches that grow downward or crisscross other wood. Not only does this look ugly, it can harm other wood and create openings for disease.
Remove low-lying branches that impede movement under the tree. Fine Gardening advises removing a few of these per year and warns against making cuts above one another or opposite one another on the trunk, since this may lead to rotting.
Thin out the canopy of your Japanese maple. Cut long branches back by one-quarter. Work in this manner to open up the tree canopy to improve air circulation, but do not remove more than one-fifth of the tree canopy per year.