Fertilize crape myrtles in spring for more blooms in summer

By for CAES News

Southern gardeners love crape myrtles, but unfortunately most don’t know how to properly care for them.

University of Georgia Cooperative Extension agents regularly answer questions regarding proper care and maintenance of the popular flowering tree. The keys to success with crape myrtles include adequate sunlight, proper soil pH, good drainage, proper pruning, adequate fertilization, proper mulching and insect control.

They love the sun

Crape myrtles need full sun -- eight hours or more of direct sun daily -- in order to thrive and bloom Crape myrtles will not be their best will less than eight hours of direct sun light. Gardeners should check the sun patterns in their yards before planting crape myrtles.

Crape myrtles thrive in slightly acidic soils with a pH of about 6 to 6.5. If the pH level is off, the plant will not use fertilizer properly and the gardener will be left with substandard crape myrtles. You should take a soil sample to your local Extension office for testing if you don’t know your soil’s pH.

Prune in late winter, fertilize in early spring

Late winter is the time to prune crape myrtles but gardeners don’t need to prune all of their crape myrtles every year. Some trees may not need to be pruned.

Gardeners should prune the trees so that they maintain a natural shape and to thin out branches and allow light into the canopy. You should not cut off the top of your crape myrtle trees. This pruning method is so drastic it is often referred to as “crape murder.”

To maximize spring growth and summer bloom, gardeners should fertilize their crape myrtles in early spring just prior to new growth.

Fertilizers like 8-8-8, 10-10-10, 12-4-8 or 16-4-8 will work fine and are ideal for crape myrtles but you shouldn’t go over board.

Over fertilizing the trees will cause causes excess growth and reduce the number of blooms on each tree. You soil test results will include a recommendation for the proper fertilizer. You can apply the tree’s fertilizer directly over its mulch.

Mulch to fight weeds, trap moisture

Gardeners should mulch their crape myrtles after planting to conserve moisture, reduce weeds and insulate roots against extreme temperatures. There should be a layer of about 3 to 5 inches surrounding the tree. Gardeners should plan to mulch an area larger than the planting hole.

Insect damage is a frequent problem on crape myrtles, and aphids cause much of that damage.

Left unchecked, aphids will release bodily fluids onto the foliage, and the resulting honeydew can lead to sooty mold, a black discoloration that can occur in the summer and fall.

Sooty mold usually causes little damage, but it can reduce the plant’s vigor. You can plant crape myrtle cultivars that are resistant to aphids or treat other cultivars with insecticides to reduce sooty mold. As always, follow label directions on all pesticides.

By following the practices outlined here, your crape myrtles should perform their best this growing season and in years to come.

William Tyson is the University of Georgia Cooperative Extension coordinator for Effingham County.
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