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Learn what to do before you hack Japanese maples and crape myrtles

Japanese Maples and Crape Myrtles are two of the last trees to enter full dormancy and lose their leaves in late winter. Both can be safely pruned in late January or early February after you’ve finished your other pruning chores. We see a lot of poorly pruned Japanese maples and crape myrtles in our neighborhoods.
Japanese Maples and Crape Myrtles are two of the last trees to enter full dormancy and lose their leaves in late winter. Both can be safely pruned in late January or early February after you’ve finished your other pruning chores. We see a lot of poorly pruned Japanese maples and crape myrtles in our neighborhoods. Modesto Bee file

Japanese maples and crape myrtles (Lagerstroemia indica) are two of the last trees to enter full dormancy and lose their leaves in late winter. Both can be safely pruned in late January or early February after you’ve finished your other pruning chores. We see a lot of poorly pruned Japanese maples and crape myrtles in our neighborhoods. These can be some of the most beautiful trees in our landscapes if care is taken when pruning to preserve their naturally lovely shapes.

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Japanese maples can grow 25 to 50 feet tall and 30 feet wide, depending on species. Their grace and their spectacular fall leaf color make them popular for planting right beside the front door or next to the living room window. Then follows a constant struggle to control the size of a large tree planted in a small space.

The most common mistake made in pruning Japanese maples is to cut straight across a branch. That cut results in an unsightly tuft of leaves sprouting from the cut end. After a couple of years of this type of cut, the tree is bushy and misshapen. That’s when many frustrated gardeners start whacking off branches, exposing the tender inner wood to sunburn.

There aren’t many good guides available on how to prune Japanese maples, but most good pruning books will have clear illustrations on how to make lateral and thinning cuts that will help control for size and maintain the natural shape. Look for Ortho’s excellent “All About Pruning” which is available online. A well-pruned, well-trained young Japanese maple will need much less pruning when mature.

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Potted Japanese maples need root pruning every two to four years. This isn’t as hard as it might seem. Remove the tree from the pot and check the roots. Cut out the thickest, woodiest roots and any roots that are circling the rootball and then replace the soil in the pot with an acid-type potting soil mix such as an azalea planting mix. If the rootball is severely compacted, it might be time for a larger pot, Cover drainholes with fiberglass window screen to slow soil loss. Fill the bottom of the pot and set the rootball on the soil so that the top soil level will be 2 to 3 inches below the rim. The root flare should be visible above soil level. Keep the potted tree well watered for several months after root pruning and feed lightly once or twice annually with a low-number granular fertilizer. A rose food with extra sulfur to lower soil pH levels (3 percent to 5 percent) will provide adequate nutrients.

Crape myrtles bloom on the current year’s wood. Perhaps that’s why many gardeners prefer to cut back all the branches to the main trunk, leaving a stick with a knob at the end. The knob will produce short, rather weak flowering branches, but if you’ve ever seen a crape myrtle that has been allowed to grow to full size (20 feet wide by 20 feet high) and develop multiple branches loaded with huge clusters of flowers, you’ll want to learn how to prune to cut off all spent flowers, then thin out the branches to produce new wood for next year’s flowers while still controlling size for the available space. Again, making lateral and thinning cuts is the secret to proper pruning of both Japanese maples and crape myrtles.

Elinor Teague: etgrow@comcast.net

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