Basic Crape Myrtle Care

Crape myrtles bloom on new growth, and new growth is dependent on moisture. Use soaker hoses, bubblers or drip irrigation emitters or take the lawn sprinkler off the end of your hose and soak their soil deeply.

Keep water off your crape myrtle’s foliage as much as you can. That will keep its weight from pulling the flower heads down, but it also will lessen the spread of diseases.

Crape myrtles produce their flowers on new growth, so apply high-nitrogen, lawn-type fertilizer (no “weed-and-feed” products) to promote that new growth. Follow label directions as to amount to apply; for most inorganic fertilizers you’ll want to use 1 pound of fertilizer per cumulative inch of trunk diameter or, for dwarf varieties, per 100 square feet of bed space. Follow each feeding with a thorough watering.

First application should be made as new growth begins in early April. The second feeding should come two months later in early June. A third and final feeding should be made in early August to promote a flush of late summer and early fall growth and bloom.

Crape myrtles are host to several insects and diseases. Learn to recognize them early on, and step to your plants’ rescue before the problems get out of hand.

Crape myrtle bark scale

These pests were first observed in the United States in Richardson, Texas, in 2004. For the first several years they were limited primarily to Dallas and Collin Counties, but they have since spread throughout the crape myrtle regions of the South.

Pertinent facts about crape myrtle bark scale…

• Adults are white, resembling large mealy bugs. Adhere to stems and trunks of crape myrtles.

• When pressed, live adults exude red body fluids.

• They overwinter in crevices of exfoliating bark.

• As they feed, adults exude sticky honeydew residue onto leaves and stems below.

• This particular scale does not seem to weaken the plants significantly, although it is very unsightly.

• Research is under way to determine the best possible control measures, but at this point, the best results have been had with a soil drench of Imidacloprid made in mid-May.

Important to watch for these friends…

• Concurrent with buildups of populations of crape myrtle scales, you are also likely to see increased populations of ladybugs, most notably a black type with two red dots on its wings, the twice-stabbed ladybug.

• This ladybug is a voracious eater. Its populations will build quickly enough that they can consume all of the scale insects, leaving only white chaff behind.

• Learn to recognize what the immature ladybugs look like so you don’t apply insecticides prematurely.

The black sooty mold most people notice…

• In severe scale infestations, an accumulation of sooty mold will grow on the honeydew substrate, giving the plants an unsightly black appearance. If you can reach the trunk and limbs, you might scrub them with a soft brush and soapy water. This will not only remove much of the mold, but it may also help remove some of the overwintering female scales and egg masses.

Crape myrtle aphids

There is one species of aphids that attacks crape myrtles, and it is active primarily in July and early August. The adults and nymphs are pale yellow-green with black spots on their abdomens. They generally feed on the undersides of the plants’ leaves by inserting their needle-like mouthparts into the soft plant tissues. As they feed they inject their saliva into the leaf tissues. That in turn causes yellow spots to develop.

As aphids are feeding they are also excreting honeydew. It coats all of the leaves, giving the plants a varnished appearance. Sooty mold grows in the honeydew, and affected leaves soon start to fall off. Spiders form webs to capture insects, and the entire plant becomes quite a mess.

Many general-purpose insecticides will control aphids fairly handily, but it will help if you apply them with the force of a hose-end sprayer. That will also help break open the webs and clean up the plants.

Powdery mildew

Since crape myrtles were first planted in the South, powdery mildew has been a common invader. It’s usually worst in late spring as it coats tender new growth with a powder-like dusting that grows in thin layers on leaves and flower buds.

Warm days and cool nights (60F-80F) favor the development of powdery mildew. Spores are carried by the wind and can germinate and start growing within three to five days. The first round of blooms in June will often be ruined if powdery mildew is left unchecked.

Neem oil extract and potassium bicarbonate have been shown to be effective when used correctly, and several inorganic fungicides also offer good control. Treatment will normally not be needed once temperatures climb into the 90s.

A great deal of the pruning that is done to crape myrtles is either unneeded or it’s done incorrectly. Know why you’re pruning your crape myrtles – be sure that your reasons are valid.

Basic pointers of pruning…

• Never use pruning as a means of controlling height or width of a crape myrtle. In other words, never “top” a crape myrtle. If you have a plant that is too large for the space where it’s planted, either move it or remove it entirely.

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• All crape myrtles are shrubs genetically. When we remove side shoots to train crape myrtles tree-form, they are likely to send out sprouts and revert to growing as shrubs. We must remove those sprouts completely flush with the trunk for a year or two. Eventually, the plant will quit producing them.

• There is no need to remove seed heads. It does not hasten additional blooming cycles during the growing season.

• There is no need to remove dry seed heads from the ends of the branches over the winter. The end 5 or 6 inches of the shoots will die back due to the cold, and as new growth begins in the spring, those ends and the seed heads attached to them will fall to the ground. Moreover, trying to prune them off during the winter tempts one to top the plants to get the job done more quickly.

Timing of pruning…

• You can prune crape myrtles to remove unwanted branches and trunks at any time of the year.

• Winter is the easiest time to train crape myrtles tree-form. You can see their growth habits then while they’re devoid of foliage.

Pruning tools to use…

• Bypass shears allow you to remove sprouts flush with trunks. They are better at making those clean cuts than anvil-type shears.

• Long-handled lopping shears allow you to cut larger branches and trunks with leverage.

• Pruning saws will occasionally be needed to remove trunks and branches larger than 3/4-inch in diameter.

Pruning techniques…

• Make each pruning cut flush with a remaining branch or with the main trunk.

• Never leave stubs. Stubs are where unsightly branch angles develop as new shoots emerge.

• Prune above buds that face away from the centers of the plants. That will encourage outward growth.

• Pruning sealant paint is not needed and not recommended with crape myrtles if you follow correct pruning practices.

Training a young crape myrtle into tree form…

All crape myrtles grow naturally as shrubs. We have to train them if we want them to grow in the forms of small trees.

• Allow the plant to develop with 8-10 trunks for the first 12-18 months.

• When the plant is 5-6 ft. tall, select the strongest, straightest 6-7 trunks. Remove the others clear to the ground.

• Once those trunks have become sturdy and able to stand on their own, usually by the end of their second growing season, remove all but the ones you want to be your permanent trunks. Always prune to an odd number, probably 3 or 5 trunks.

• As the plant grows taller, remove side branches. However, do so gradually, never coming up more than 40 percent of the total height of the plant. Leave the side branches that emerge at 45-48 inches. You can always remove them later – you don’t want to prune the plant too far up its trunks.

Special note regarding plants that have previously been topped…

• It is almost impossible to reshape and retrain a topped crape myrtle in a way that will conceal the scars of prior toppings.

• The quickest way to get a handsome plant back is to cut it completely to the ground and then retrain the new shoots that are produced according to the outline above. You can have a beautiful crape myrtle within just a couple of years.

If a crape myrtle variety freezes to the ground…

Several varieties that are commonly sold in the nursery industry have notably poor records of surviving early or extreme freezes. In our plantings in McKinney, that list always seems to include Natchez, Muskogee, Tuscarora, Sioux and Country Red, although others will also freeze partially or completely on occasion. When that happens, cut the frozen trunks completely to the ground and proceed as outlined above.

An exception to pruning as it pertains to dwarf types…

• Dwarf crape myrtles (those that stay at 4-5 ft. at maturity) can become rather lanky if left unpruned.

• You may want to treat them almost as you would a shrubby perennial such as Salvia greggii by pruning their tops back by half in mid-winter. That pruning will keep them bushy and compact, and it will also stimulate a fresh flush of regrowth for blooms the following summer.

Unless you are interested in hybridizing crape myrtles as you seek new colors or features, you will be starting new plants primarily from cuttings. That consists of taking a stem section from the mother plant and causing it to develop roots of its own so that it can be a freestanding plant of the same genetic make-up (variety).

Hardwood cuttings…

This was the chosen method of field propagation for decades in the early Texas nursery industry. Nursery employees would gather branches 2 to 6 feet long from the mother trees, bundle and label them and put them into cool storage over the winter dormant period. They would often pack them in dry sawdust or peat moss.

In late winter they would cut those branches into 6- to 8-inch cuttings and plant them directly into ground beds, planting each cutting so that only 1 or 2 inches would remain above the soil. They took extreme care to insert the cuttings right ends up, because they knew that if they stuck them in an inverted position they would never develop roots.

Hardwood cuttings rooted in this manner were subsequently lifted and transplanted into nursery rows where they would be dug, balled-and-burlapped for sale a year or two later.

As production in pots became the trend, cuttings were stuck directly into 1-gallon pots for rooting. However, growers found that softwood cuttings produced superior and more uniform plants more quickly.

Softwood cuttings…

This is the newer and current means of starting new crape myrtles.

These cuttings are really quite amazing. This form of propagation requires a greenhouse with a mist bench or fog system to maintain almost 100 percent humidity.

Cuttings of vigorous vegetative growth are taken in late May or early June. The shoots are tender and crisp and the cuttings taken are only 1 to 1-1/2 inches long. They’re about as succulent as a coleus or begonia cutting, which means they need to be stuck into the propagation bench as quickly as possible. If not, precautions must be taken to prevent wilting.

Roots develop very quickly on these softwood cuttings. They can often be lifted and potted into 4-inch pots within just a couple of weeks, then shifted into 1-gallon containers before fall.

Many growers choose to plant three cuttings per container so that they can get a salable plant more quickly. If you ever see a crape myrtle with two different colors on the same “plant,” there are good odds that there’s been a mix-up at this stage of the planting and that two varieties made it into the same 4-inch or 1-gallon pot.