You have released a lot of crapemyrtles over the years. Which one is
the best for my own garden and color preference?
When selecting a crapemyrtle, think about the flower color and ultimate
size first. With so many cultivars to select from, it isn’t difficult
to find the flower color you want in the size and shape that will fit your
planting site. Consider the impact of the autumn leaf color and the
color of the beautiful exfoliating bark that is so prominent in the winter
landscape.
The Crapemyrtle
Quick Guide Chart can serve as a quick guide to help you choose the
right variety for you. When you get to the chart, you can click on
the variety names to see images featuring flowers, fall foliage, and bark
How should I prune my crapemyrtle?
If you select the right crapemyrtle for the size of the space where it will grow, you will only have to do minor pruning. Remove small twiggy branches inside the plant to promote good air circulation. You can gradually remove lower branches or suckers that grow from the base of the trunk if you want the plant to be a small tree. If you are dealing with an older plant that has been neglected, a heavier hand may be needed. Remove any dead branches and cut the living branches back slightly to promote more vigorous growth that results in better flowering.
Crapemyrtles are often injured in bitterly cold winters near the northern edge of their range and they are naturally one of the last of the deciduous ornamentals to begin growth in spring. It’s difficult to tell the extent of cold damage until growth begins, so wait until late spring or early summer to prune. Never prune crapemyrtles in the fall or winter, since it compromises their cold hardiness.
Crapemyrtles bloom on the current season’s growth, so they can be pruned
in the spring and will still flower normally throughout the summer.
Larger, heavier flower clusters and rank growth often result when the branches
are cut back severely, and these flowers are often so heavy that they bend
toward the ground. For this reason, we do not recommend the practice
of pollarding or cutting the branches back to stubs every year.
How hardy are crapemyrtles?
Lagerstroemia indica and hybrids within this species are hardy
to USDA Hardiness Zones 7 to 9 but are often killed to the ground in severe
winters in Zone 7. Lagerstroemia fauriei is reliably hardy
as far north as USDA Hardiness Zone 6. The USNA hybrids that have
Lagerstroemia fauriei as a parent are hardier than Lagerstroemia indica cultivars,
and develop into large specimens even in the colder parts of Zone 7.
Varieties that have only Lagerstroemia indica parentage, such as
the USNA hybrids ‘Catawba’, ‘Conestoga’, ‘Potomac’, ‘Powhatan’, ‘Cherokee’,
and ‘Seminole’, are periodically cut back to the ground by severe winters.
Even if a severe winter kills most of the top growth on your crapemyrtle,
it is capable of growing back in a short time. Since they bloom on
the new growth, the injured plants are able to produce flowers as well.
In the coldest portions of their range, crapemyrtles probably won’t be
able to develop a main trunk and the beautiful exfoliating bark that they
are known for.
If you want to grow crapemyrtle in northern areas, various microclimates and cultural practices can enhance hardiness. Avoid excessive watering, pruning, or fertilizing in the fall which forces new growth that will not have time to harden off and is likely to be killed by winter cold. Avoid planting against south-facing walls which hold and radiate heat and may cause premature breaking of dormancy during brief winter warm spells. Established crapemyrtles fare much better than younger ones when it comes to withstanding the vagaries of winter weather because of their increased trunk size and decreased tendency to grow rampantly late in the season. Crapemyrtles are heat loving shrubs, and may not bloom well in cool climates.
Our most recent introductions, which are miniature plants that grow
no more than three feet in height, are small enough to allow you to take
some measures to protect them from winter cold. After leaf drop,
you can mulch them heavily with leaves, straw, or another loose material
to protect them from extremes in temperature. In areas where snow
cover is deep and protects the ground from freezing deeply, the miniature
crapemyrtles are worth a try, even though they are far north of the hardiness
range stated here. Remember that they need plenty of summer heat
to bloom well.
How should I care for my crapemyrtle?
Crapemyrtles revel in the full summer sun and heat, so find a place
that meets these requirements and you will be rewarded beyond your wildest
dreams. They grow best in any reasonably good soil with a pH of 5.0-6.5.
They are adapted to poor soil and don’t need much fertilizer–a light application
of 5-10-5 fertilizer in spring when growth begins is beneficial for older
plants or those growing on extremely poor soil. Crapemyrtles can
be planted at any time of the year, but in USDA zones 7 and 8, planting
is best done in late spring or summer when the plants are actively growing.
Recently transplanted plants should be given a thorough soaking at the
time of planting and during dry periods for the first two seasons.
Don’t irrigate plants in the autumn to help the growth harden off before
winter comes. After the plants are well established in the landscape,
avoid excess watering and fertilization to prevent rank vegetative growth
at the expense of flowering. Crapemyrtles are tough plants–don’t
kill them with kindness!
My crapemyrtle is reluctant to bloom. What am I doing wrong?
Crapemyrtles flower most heavily in full, uninterrupted sunlight.
Even an hour of shade during the day will compromise flowering. Frequent
irrigation, lack of heat, and overfertilization promote vegetative growth
at the expense of flowering. In extreme drought conditions or cool,
rainy summers, flowering may be delayed until the early autumn.
There is a white powdery film on the flower buds and leaves of my crapemyrtle and the flowers don’t open normally. What’s the problem, and how can I get rid of it?
It sounds like you have a problem with powdery mildew. Powdery mildew is a fungus disease that is most damaging in dry weather, typically near the end of summer when crapemyrtles are blooming. High humidity, lack of rain, and poor air circulation make powdery mildew worse. Both leaves and flower buds may be affected, but the flower buds often are more severely damaged.
All of the Arboretum’s crapemyrtle introductions have some degree of
tolerance for powdery mildew and are rarely damaged enough to warrant fungicide
application. Other cultivars may require preventative treatment with
any fungicide labeled for powdery mildew beginning when the foliage is
fully expanded and continuing at weekly intervals until the flowers open.
If you’d like a soft alternative to harsh fungicides, you may want to try
using horticultural oil on your crapemyrtles since it has been shown to
be quite effective in controlling powdery mildew.
The leaves of my crapemyrtle are covered with yellowish green insects. Many leaves have developed yellow spots and there is black stuff on the leaves. What should I do?
You are talking about the crapemyrtle aphid, Tinocallis kahawaluokalani. It can quickly reproduce in spring and summer when crapemyrtles are growing rapidly, and colonies of aphids may nearly cover the underside of the leaves. The aphids may have wings, but they are often wingless. Crapemyrtle aphids suck the sap out of the leaves and young stems and excrete droplets of a sugary substance called honeydew. Sooty mold often grows on the honeydew and may give the entire plant a dark cast.
In most landscape situations, ladybird beetles, tiny gnat-like wasps,
and other aphid predators control the crapemyrtle aphid. These beneficial
insects are easily killed by many pesticides while the aphids may survive
spraying, so easing off the use of pesticides is often enough to bring
the predator and pest relationship back into balance. Aphids can
also be blasted off the foliage with a strong stream of water from your
garden hose. Cut back on watering and fertilization since rampant,
succulent growth is attractive to aphids. If none of these measures
bring the aphid problem under control, spray your crapemyrtle thoroughly
with insecticidal soap.
The margins of the leaves of my crapemyrtle are chewed in an irregular pattern. Should I be concerned with this?
This damage is most likely caused by a metallic dark green flea beetle,
Altica
sp., that is common in nurseries and landscapes. It does little damage,
and really isn’t important enough to warrant any control measures.
Japanese beetles are really chewing up the flowers on my crapemyrtles. How can I get rid of them?
Remove the beetles by tapping infested branches over a bucket of soapy water. The beetles drop to the ground when disturbed, and a gentle tap is enough to induce them to drop into the water. Japanese beetles are generally found near the flower clusters at the tips of branches, so focus your effort on the ends of branches that are just coming into bloom.
Hand removal is most effective if you start early, just as the adult beetles emerge in early summer, and make their removal a daily task. Japanese beetles release two pheromones–one is an aggregation pheromone that signals other Japanese beetles to come to a suitable host plant to feed and the other is a sex pheromone that females use to attract males. If you remove the beetles daily, especially just when they are emerging, you will limit the amount of pheromone left on your crapemyrtles and often this measure is enough to avoid any real damage to the blossoms.
Traps containing pheromones are largely ineffective since they attract many more Japanese beetles than they trap. Treatment of turf with milky spore to control the grubs is a help, but large areas of turf must be treated–an entire neighborhood must participate if a noticeable reduction in numbers is expected, and effective control does not take place until about four years after the initial treatment.
Avoid spraying Japanese beetles with harsh pesticides, since many pesticides
kill aphid predators. A rebound aphid problem is often the result
when pesticides are used to control Japanese beetles and aphid predators
are inadvertently killed.
I live in the Deep South and my crapemyrtle seems to loose nearly all its leaves in midsummer. I have noticed that brown spots appear on the leaves before the leaves are shed. What can I do about this problem?
Your crapemyrtles are probably being attacked by a fungus, Cercospora lythracearum, that causes a leaf spot disease. In warm, wet weather, the disease can spread and lead to premature leaf drop. In severe cases, only the youngest leaves remain at the ends of branches. Flowering and vigor are often diminished because so many leaves are lost.
The following U.S. National Arboretum introductions are reported to have some resistance to this disease:
Apalachee
Caddo
Catawba
Sioux
Tonto
Tuscarora
Tuskegee
Yuma
If you want to try to prevent the disease on a susceptible crapemyrtle,
you’ll need to spray a fungicide labeled for leaf spots such as one containing
the active ingredient thiophanate-methyl. Begin applying the fungicide
when you first notice the spots on the leaves and continue applying the
fungicide at weekly intervals through early summer. There is no need
to spray if the weather is very dry and cool since the disease needs warmth
and prolonged wetness to spread.
Where can I see the crapemyrtles that have been introduced by the U.S. National Arboretum?
Many of our introductions have become the mainstay of crapemyrtles that
you might see in parks, corporate landscapes, home gardens, and even roadside
plantings. If you want to compare the varieties, visit the U.S. National
Arboretum’s Gotelli Collection of Dwarf and Slow Growing Conifers and the
areas around the National Arboretum’s Administration Building and Visitor
Center. Here you can find mature specimens of nearly all of our crapemyrtle
introductions. All are clearly labeled so you can easily compare
them. You can also check out our Crapemyrtle Photo Gallery.
Back to the Arboretum Home Page
Last Updated October 14, 2004 5:56 PM
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