Crape myrtles (sometimes spelled crepe) are shrubs and small trees indigenous to temperate and tropical regions from Asia to Australia. As members of the Lythraceae family, they are not myrtles at all. The “myrtle” in their name is a nod to the similarity of their leaf shape to that of a true myrtle (Myrtus). The “crape” part of the name refers to their brightly-colored flowers, crinkly enough to look like they are made of crepe paper.
Several attributes make crape myrtles a wonderful addition to Sonoma County gardens. Besides adapting easily to our hot summers and mild winters, they offer weeks of bloom in mid-to-late summer and into autumn, usually July to October or earlier, in shades from palest pink or lilac to deep pinkish red, red, purple, and white. They are among the longest-blooming of all trees.
Once crape myrtle’s vibrant blossoms have faded, dramatic fall color and interesting bark become focal points. In summer, foliage is medium-to-deep green, sometimes bronze-tinged, before turning shades of yellow, peach, orange or red in autumn. Because leaves are small, they do not produce much debris after dropping and are easy to clean up for the compost pile. Bare branches reveal beautifully mottled exfoliating bark, multi-colored in shades of tan and gray on certain cultivars. The winter aspect is most pleasing when trees are pruned to show off multiple stems or trunks.
There are two important considerations when selecting a crape myrtle: structure and blossom color. Plants are available either as single- or multi-trunked specimens. Multi-stemmed trees are more shrub-like as they develop height. Single-trunked trees develop a round crown that may be difficult to prune, although pruning is optional, and their wide-spread flowering branches appear out-of-balance to some gardeners. Multi-trunked trees require more space near ground level.
Selecting a plant when it is in flower will assure you of purchasing the exact blossom color that your want. When planting a crape myrtle, keep in mind that flowering is most prolific in full sun. Give it a site where there is enough room to develop a full crown. In maturity, many become quite large, spreading 15-25 ft. as wide as they are tall. A 5- or 15-gallon shrub will become a small tree within 10 years, though never developing an enormous trunk the way many shade trees do.
While crape myrtle requires regular water when young during the first 1-2 years, it needs only low water once established. Good drainage is important to prevent soil from becoming water-logged, which will stymie growth and damage roots. They don’t like wet feet.
Although pruning is not essential to crape myrtle culture, it does maximize flowering and enhance shape. Because bloom occurs on the current season’s wood, pruning is best performed no later than February or March, allowing time for new growth. Branches may be cut back 12 to 18 in. Prune judiciously for shape; excessive pruning can cause overproduction of branches and unattractive density. Do remove all suckering shoots from around the base of the plant, internal dead or crossing branches, and any extremely long branches. By pruning carefully the first few years, your plant will need little pruning thereafter. Pruning less is almost always better than pruning too much.
Crape myrtles are generally trouble-free when sited properly, although they are susceptible to powdery mildew; however, by selecting a resistant variety, this problem rarely surfaces. There are a series of hybrids developed by the U.S. National Arboretum known as the Indian Tribe Group with names such as ‘Cherokee’ (deep pink/almost red flowers) and ‘Seminole’ (medium pink flowers).