Crapemyrtle (Lagerstroemia indica) cultivars have long been acknowledged as a major contributor of summer color in the south. Crapemyrtle in full bloom rivals the flower show of any other landscape plant. Cultivars range in size from only 3 to 4 feet to tree forms, 20 feet or more. Some cultivars have brilliant fall foliage colors and the new ‘Whit’ cultivars have dramatic wine, wine-red or purple new growth, adding significant color before the blooms.
But, crapemyrtle are typically considered cold hardy only in zones 7 and higher (further south). With a gradual cool down in fall, tops survive 0 to -5 degrees F. When winter arrives early and abruptly, tops may be damaged at temperatures in the 20s. When severe temperatures damage tops, all is not lost because the roots remain undamaged and when soil warms in spring, the plants make a rapid recovery. Of the 10 ‘Whit’ cultivars, Rhapsody in Pink® requires the least amount of heat to trigger flowering in summer, whereas Dynamite® may be two to three weeks behind.
Crapemyrtle have a desirable attribute shared by few other woody plants – they flower on new growth. In addition, cultivars such as Red Rocket®, Pink Velour®, Burgundy Cotton®, Rhapsody in Pink®, Double Feature® and Double Dynamite® have spectacular red – wine or purple new foliage. As a result, even in northern areas such as zones 6 and 5, there is an early summer foliage show followed by mid- to late-summer flower show. As plant breeding has evolved, Lacebark now has three cultivars that are sterile (no deadheading required) and once flowering begins the show continues until stopped by cold temperatures. Cultivars Raspberry Sundae® and Tightwad® are sterile, but flowering is interrupted since production of a new panicle is required to bloom a second time. But, with the totally unique, Rhapsody in Pink®, Double Feature® and Double Dynamite®, flowers are produced continuously on the same panicle and without interruption providing a longer flower show. And, without energy going to produce seeds, a stronger/healthier plant.
In northern areas, treat crapemyrtle as a hardy perennial and follow these steps:
1. Locate crapemyrtle in full sun. Ahot location gives best results.
2. Plant crapemyrtle in the heat of summer when soil is warmest and root establishment is rapid. Do not plant late in the season after the soil has cooled. Getting the plant well established is key to survival.
3. After a few hard freezes in the fall, remove all stems a few inches above the soil line; place a disc of ground cover fabric 5 feet or more in diameter over the area and mulch. In more severe climates, heavier mulch is needed to insulate roots. Mulch well before soil freezes to keep the root-crown area warmer.
4. In spring, as soon as all chance of frost is past, remove mulch and fabric and allow soil to warm. Do not mulch during the growing season as bare soil heats faster than soil under mulch.
5. After a few seasons, instead of three to five stems, 10 or more may emerge. In this case, more is not better. Select the strongest five to eight stems and remove the others. This provides larger flower clusters and a greater flower show.
6. Crapemyrtle like it hot, so a location with reflected heat and light is desirable for this plant.
7. Almost any soil will do, but keep in mind flowering is on new growth, so more growth typically equals more flowers.
8. In most of Zone 6, flowering typically begins late July but not until early August farther north.
9. Fertilize crapemyrtle moderate to heavy once in spring, but not in fall.
10. Water during dry periods, but crapemyrtle are tough and will survive even when neglected.
Currently successful plantings of these new crapemyrtle ‘Whit’ cultivars are located in such diverse locations as Kansas City, Kansas, Ft. Atkinson, Wisconsin, Chicago, Philadelphia, Detroit and Newport, Rhode Island. Many climate and cultural factors are involved in tolerance of crapemyrtle to cold, therefore precise performance predictions cannot be assured. However, testimonials from nurserymen, landscapers and gardeners as well as personal observations prompted me to share this information. As one nurseryman in northern Maryland said, “Two large Dynamite® in front of our office survived the roughest winter we have had in years, no dieback at all, while other cultivars were severely damaged or killed to the ground. You need to promote this plant more.” Another common comment: “What beautiful plants – and then they flower.”