Lagerstroemia: Caring for Crepe Myrtles from the Bottom Up
The trees were named by Carl Linnaeus in honor of Swedish merchant Magnus von Lagerström, whose Far East traders provided the first specimens of crepe myrtles in Europe. Although von Lagerström never traveled to China himself, his name is forever associated with this tree of Asian heritage. Say "la-ger-STREEM-ee-a." They were brought to France by botanist André Michaux where they were very unhappy! Then he introduced them to South Carolina, and well, the rest is history!
Before you choose a crepe myrtle, do some research on the website of the United States National Arboretum to discover the cultivar that is perfect for you. Consider not just the color of the flowers but maybe most importantly, the ultimate size of the tree. Do you plan to prune and/or groom it every year? Will you be viewing it out a window, as you drive up, or while gardening in the yard? Will it be a hedge, a shrub, or part of a clump? An alleé, perhaps (pictured left is the Crepe Myrtle Alleé at the Dallas Arboretum)? Or do you envision a single, elegant specimen tree? Consider carefully what you want the tree to look and act like in five years. Lagerstroemia grow quickly, and you don't want it to get too big for its allotted spot, which leads to awkward pruning complications.
You may feel as if you're being asked to select a rental car; compact, full-size, dwarf or luxury? Lagerstroemia can even trained as a single-stemmed standard or as bonsai. Here is a helpful table from the University of Georgia including different pruning solutions. There is even a groundcover size crepe myrtle, L. 'Rosey Carpet'.
Plant crepe myrtles where they'll get plenty of full sun. Lack of adequate sun is a leading cause of Lagerstroemia which don't flower as well as they can.
The soil should be well-draining, not swampy or water-logged, both of which can lead to reduced flowering and an unhealthy tree. Fertile soil is always helpful, although too much fertility can, with crepe myrtles, lead to foliage instead of flowers. Crepes are tolerant of sandy or clay soil.
If you don't get regular rainfall, it will be necessary to water your crepe myrtle for the first couple of seasons. Lagerstroemia are forgiving of dry, lean soils once established, which is one of the reasons they make such great street trees.
Plant your new crepe myrtle with the surface of the plant at or above the surface of the site. Gnarly, protruding roots can be an attractive feature, and are typical of the Lagerstroema look. Be careful not to damage your crepe's shallow roots when mowing the lawn or digging near it, although the trees do usually seem to survive. Image at right © John Hruzek.
When the small, multi-stemmed tree or shrub grows up from the roots, there may be several to many narrow stems or trunks. Pick the 3-6 strongest of these, and snap the other ones off below the surface or prune them back. You should have a small group of thin trunks with plenty of breathing room in the middle. Do not permit any trunks to grow sideways—laterally—or to touch any others. If you establish your crepe in such a way as to allow lots of circulation among the trunks and branches, you are less likely have trouble with fungus, mildew, bugs or aphids.
The trunks of the tree at right are outside our rented house in Texas. This is a classic case of what not to do. This Lagerstoemia has such tangled stems and strangled roots that it barely blooms, illustrating that even "crepe murder" is better than nothing.
The image at right is one I took on one of our walks around the neighborhood. The term "crepe murder" refers to the common practice of chopping Lagerstroemia off 3-4 feet above the soil, as you might do with a butterfly bush. While this is the right way to care for a butterfly bush, it is a particularly unattractive and gruesome way to murder a crepe—please don't do this with crepe myrtles. When hacked off in this way, it's true, they do flower more heavily the following year.
But this "murder" must be repeated every year or two, and it means your crepe will never acheive its full potential of having lovely, graceful, sinewy trunks. Don't constantly deprive your Lagerstroemia of a proper growing season.
|"Consider all your options when confronted with a large, old crape* [sic] myrtle in a space meant for a different shaped tree or shrub. To create clearance under the canopy, limb up old trees that have spread their lower limbs where they interfere with people or cars. Limb up above the roofline of a single story home to clear obstruction of a window or door. Eliminate one of the major trunks if it is leaning too close to a building." recommends the South Carolina Master Gardener Training Manual.|
*Lagerstroemia are known as "crepe myrtle" or "crape myrtle" or even "crapemyrtle," allegedly because their petals are like the crinkled tissue of crepe fabric or crepe paper. However, if you look at the website of the United States National Arboretum, which introduced 29 named cultivars, they are called "crapemyrtles," and in McKinney Texas, which has a crepe myrtle festival every year, they are crape myrtles.
I know from my horrendous French classes that a crêpe is a very thin pancake. Dictionary.com says that crape is confused with crepe. But now everybody says "crape myrtle," and as you know, once one web site says a thing, it must be true! Never-the-less, I will call them crepe myrtles. Or better still, call them "la-ger-STREEM-ee-a."
Before about 1960, hybridizers were working with only the initial genes available in L indica, which was only suitable for USDA zones 7 and above. They got a boost in the 1960s with the addition of genetic material from L. fauriei, collected in Japan and Korea. This new species of Lagerstroemia proved to have greater cold-hardiness and was markedly less susceptible to powdery mildew. Hybrids of the two are available in a wide variety of bark colorations (which is an attractive winter feature), maroon or bronze foliage, and bicolored blossoms, as well as a huge variety of sizes, from container-sized to large, towering trees.
An example is L. 'Rhapsody in Pink', at right, which has crimson new growth and flower buds, dark wine-to-green foliage, and soft pink flowers from late June until frost. (Photo © Terry.) 'Rhapsody in Pink' is only possible becasuse the original germplasm from L. indica, supplied by Michaux in 1790, was augmented in 1960 with genetic material from L. fauriei. Most modern crepe myrtle varieties posess genes from both L. indica and L. fauriei, shown by the designation indica x fauriei.
|Lagerstroemia leaves (which in some cultivars may fall in the winter) may be susceptible to powdery mildew, especially on pure L. indica cultivars. While this can be largely prevented by good maintenance and pruning, if you do experience damage from powdery mildew, you can try a commercial fungicide. They may also get Japanese beetles or aphids, which you may squirt off with a hose or treat with horticultural oil.|
|To me, this blossom at right (© jadajoy) is a lovely pure purple color, although some may see some blue in it. Lagerstroemia are available in many colors, but not true blue or yellow. The stamens of many cultivars boast bright yellow to contrast with the pink, as in the upper right photo of L. 'Pink Velour' © C_Ville Gardener.|
At left are the winter trunks of L. 'Natchez', showing their attractive variegated pattern resulting from exfoliation of the bark. USNA calls this "cinnamon brown," which is as good a word as any. The blooms are a snowy white, and 'Natchez' is reliably mildew-resistant. Photo © mgarr.
|Flowers: most crepes start flowering as early as late May or early June, and keep it up until frost. Many flowers have bright yellow stamens (see 'Pink Velour', top right) tucked among blooms of white, pink, lavender, scarlet and dark purple. So far, Lagerstroemia don't come in true blue or yellow, but they come in every shade of snowy white through pink, red and purple imaginable, and even some with more than one color, like 'Raspberry Swirl' at right. Picture © Aunt_A.|
With some cultivars of crepe myrtle, you may be able to produce a second and maybe even a third round of flowering if you trim the blossoms off once they have finished. If you can even reach the flowers, that is. If the flowers are too high to reach, the blossoms will ripen into attractive seeds. if they fall, these may produce offspring which may or may not look like the parent tree. I realize that's a lot of "mays" for one topic, but the behavior of hybrids from seeds is quite unpredictable, as you surely have noticed.
Some hybrids are marketed as "sterile" which should mean that their seeds are not fertile. You may wish to pot up the suckers which you prune from the shrub; those should be genetic clones of the parent plant. You may also propagate them by air-layering.
You may find your crepe myrtle showering you with blossoms, especially with a heavy rain. If you find this to be bothersome, do not plant them near where you park a car or have a pool! Some people enjoy this feature because their lawns change color. You also may discover aphids showering you with the "honeydew" they produce.
|One example of a Lagerstroemia which seems to have it all is USNA's introduction, 'Tuscarora', which has lush rose-colored flowers, silvery peeling bark and fabulous fall color. It is hardy from zones 7-9, resists mildew, has great silvery fall color and said to grow over 20 feet tall. Pictures of 'Tuscarora are © Kelley MacDonald.|
Leaving space around the branches and in the middle allows for air circulation to prevent mildew and insects.
If you prune, do so in late winter or early spring. Pruning too early in the fall may trigger the tree to try to produce new growth which will be damaged when cold tempertatures arrive, and pruning too late will not allow the flowers time to be produced.
Gardeners outside the South may wonder: can I grow a crepe myrtle in my garden? The good news is that since the introduction of indica x fauriei, there are now cultivars which are winter-hardy down to zone 6 and maybe even zone 5. Cold weather may kill the plant above the ground without killing the roots. You may never get a chance to prune your Lagerstroemia; the cold may do it for you! Experiment, and take mcicro-climates into your planning.
As I said above, crepe myrtles have very shallow root systems, so in colder areas, protect their tender roots with a thick layer of a iiving hardy ground cover. Mulch extra-heavily with compost, chopped leaves, straw or hay. Wrap tender bushes in burlap or bundle them in coats of straw or leaves. You can even surround Lagerstroemia with plastic bottles of water which will retain heat.
The best solution, if you can't reconcile yourself to one of the hardier Lagerstroemia cultivars, may be to choose one which is small enough to grow in a tub. If you are unable to insulate your tub sufficiently, perhaps you can truck it in and out of an unheated barn or garage. After getting established, crepe myrtles do tend to be drought-tolerant, but if you're pushing the zone envelope, you'll want to make sure it gets balanced fertilizer once a year and enough rainfall to keep it in tip-top shape.
photos not otherwise attributed are © Carrie Lamont.