When to Trim Japanese Maples

Pruning Japanese maples annually helps them keep their form.

The elegant Japanese maple (Acer palmatum) has deeply lobed leaves in hues of chartreuse, purple and crimson, and a graceful branching structure. These trees look most striking when regularly pruned and maintained, but this task can intimidate new gardeners, notes Michelle LeStrange, University of California Master Gardener. With the right approach -- including time frame -- pruning these trees doesn't have to be scary.

Time Frame

Japanese maples can be pruned on a couple different time frames. The easiest time to shear these pants is during the dormant season, before the leaves emerge. This runs from late winter to early spring. You can also prune in the summer, but it's harder to see the wood beneath the leaves, making your task of determining where to cut tricky. Some trees can get away with infrequent pruning, but these do best with annual pruning to maintain the form and structure.

Reasons

When pruning these trees, you have three main objectives: tree size, tree form or shape and tree health. A good pruning job takes care of all three. Since tree health is of utmost importance, you should check the maple tree throughout the summer and fall for signs of insect pests or diseases that may require you to do more trimming. Whenever you notice diseased or dead wood, you should remove it. This goes a long way toward keeping Japanese maples healthy.

Process

First, remove dead or damaged wood. Check in the late winter and remove what you find then, then perform regular upkeep of this step. Once you've eliminated the problem wood, step back and examine the tree. Decide how much you want to trim back long branches, then head them back to a Y-intersection or swollen tissue node using pruning tools. Then shape the form: Remove branches from crowded areas to thin out the canopy. Prune offshoots that detract from your tree's appearance, or wood that compresses other branches.

Summer Pruning

Summer pruning has its place, and you may wish to do one spring pruning to get your tree looking good, then fine tune the job in summer. Japanese maples look best when pruned into layers, with no overlap between, notes Master Gardener Michelle LeStrange. Branches that grow up or down should be removed or pruned back far enough that they no longer lean up or down. Since the weight of leaves can make them bend, this step works in summer much better than early spring.

References

• Master Gardener Newspaper Articles Tulare/Kings County; Pruning Japanese Maple; Michelle LeStrange; 2010
• Gardening in Western Washington; Japanese Maples; Joan Helbacka; 2003