Lagerstroemia spp (Crepe Myrtle)
By Sara Malone, Sonoma County Master Gardener
Crape (sometimes spelled crepe) myrtles are shrubs and small trees indigenous to temperate and tropical regions from Asia to Australia. They are not myrtles at all – the myrtle in their name is a nod to the fact that their leaf shape resembles that of a true myrtle. The ‘crape’ part of their name is obvious once you see one in bloom: the flowers are brightly-colored and crinkly and look like they are made of crepe paper! If you have ever traveled in the American South you have seen these shrubs along freeways, in front yards, and used abundantly as hedges, screens, small trees and specimen plantings. They grow equally well here in Sonoma County, with our hot summers and mild winters. With age many can get quite large, although the most popular mature at around 15-25’. They are available in shades from palest pink or lilac to deep pinky-red or purple, and white.
Two attributes make crape myrtles a wonderful addition to the garden: the timing and length of their bloom. In this part of the world they bloom from July to October, peaking generally in August and September, which, as noted, is a time when most of our gardens could use a shot in the arm. They are also among the longest-blooming trees – it is not uncommon for a crape myrtle to bloom for over 100 days, and 60 days is the normal minimum. That would be enough for most people at least to consider a crape myrtle, but it has two other attributes just in case you’re not fully convinced: dramatic fall color and interesting bark. The leaves, which in summer are medium to deep green and sometimes bronze-tinged (depending on variety), turn attractive shades of yellow, peach, orange or red in autumn. They are deciduous, so leaves fall before winter sets in, but since they are small they do not produce much debris. The exfoliating bark is beautifully mottled and multi-colored, especially on certain cultivars. When the plants are pruned of their lower branches the bark really stands out, particularly in winter, and looks lovely in the rain. Finally, since we are all concerned about water usage here in Sonoma, I am happy to report that while it requires regular water when young (the first 1-2 years), the crape myrtle gets by on low water once established.
To decide where to site your crape myrtle, consider that it needs full sun and enough room to develop a nice, bushy, crown. A 5 gallon shrub will be a small tree within 10 years – a 15 gallon even more quickly. I like to grow them as multi-trunked trees, rather than standards (trees with one trunk), because that way I get more ‘oomph’ from the bark and I think that they look more graceful. The crape myrtle never develops an enormous trunk the way a shade tree does, and that enormous crown of flowers sitting atop one spindly stem always looks a little out of balance to me. Once you’ve surveyed the sunny spots in your yard, select one with good drainage. Crapes don’t like wet feet. Now that you’ve got the site picked out, it’s time to go shopping. You’re going to want to go soon, as you want to pick out a crape myrtle when it’s in flower – that way you are assured of the bloom color that you want. You should also pay attention to the shape of the plant, especially if you buy a 15 gallon size. The branching is quite individual and the plant you choose will depend on your own taste.
Crape myrtle culture is relatively easy if your pick your site properly. While the literature mentions scales and aphids as sometime pests, I have never seen evidence of either insect on my plants, and I have a large collection here in my garden in Petaluma. Crape myrtles are susceptible to powdery mildew, but, by selecting a resistant variety, you avoid this problem almost entirely. Give your plant enough water in the first year or so, and prune to maximize bloom and enhance shape. Since crape myrtles bloom on the current season’s wood, you want to prune them early in the growing season – I usually do mine in February or March. (You can prune them in late fall, as they are dormant in winter, however if there is an unseasonal hot spell in late winter, the plants may leaf out. This new growth is then subject to frost damage.) Prune judiciously for shape – excessive pruning can cause overproduction of branches and the plant winds up looking like a thicket, with all of that beautiful bark hidden. You do want to remove all of the ‘suckers’ (the leafy growth from the base of the plant) and any internal, crossing branches. Otherwise, you can just prune out a few of the lower branches to highlight the bark on the remaining trunks, and shorten any extremely long branches. Take care not to cut them down below the existing branch intersections. If you prune carefully the first few years your plant will need little pruning thereafter. The best rule of thumb for pruning crape myrtles is that if you err to one extreme, pruning less is almost always better than pruning too much. Selecting the right variety for your site will minimize your pruning responsibilities – varieties are available from approximately 18” all the way up to tree size.
Which varieties are best for our gardens? The most popular crape myrtles are crosses between lagerstroemia indica and l. fauriei or l. speciosa. You don’t have to remember that, as they are sold by their varietal names, such as ‘Tuscarora’ (hot pink flowers) or ‘Dynamite’ (deep reddish pink flowers with beautiful bronze foliage). There are a series of hybrids developed by the U.S. National Arboretum known as the ‘Indian Tribe Group’. These were developed to have superior resistance to powdery mildew (susceptibility to which is one of crape myrtle’s few drawbacks) and have names of Native American tribes, such as ‘Cherokee’ (deep pink/almost red flowers) and ‘Seminole’ (medium pink flowers). Start with the flower color that you desire and the size that suits your site and you will still have a multitude of choices. I always try to plant the varieties with the most attractive bark. Sometimes the biggest problem with selecting a crape myrtle is that there are so many lovely varieties to choose from!
