Pruning Crapemyrtles

The appeal of crapemyrtle

One of Virginia’s most popular yet mistreated landscape plants is the beautiful crapemyrtle (Lagerstroemia indica, L. fauriei, and L. indica with L. fauriei or L. speciosa hybrids ). Selected and prized for their long summer bloom period (often called the “plant of the 100 day bloom”), cultivars have a range of flower colors, with an interesting seed head following the flower. In addition, crapemrytles have lustrous green leaves that change to bright fall colors, subtle to stunning multi-colored bark, and unique winter architecture that makes this plant exceed most landscape choices for four-season interest and appeal.

Choose the right cultivar for your landscape

Crapemyrtles are low-maintenance and easy to grow if provided with sunny locations and soil with moderate moisture and fertility. Various nurseries, private breeders, and The United States National Arboretum have developed a wide variety of crapemyrtle cultivars (cultivated varieties) that can fit almost any landscape need. Cultivars now range in size from dwarfs that can be grown in containers and hanging baskets, or used as shrubby ground covers, to shrub (up to about 15 feet) and tree forms (to 25 to 30 feet).

Choosing the right crapemyrtle for your landscape requires evaluating where it will be planted, not just what color its flowers are. Will the plant be used in a perennial border or near a building foundation, or will it be a centerpiece specimen in a large grassy area or bed? The smaller the space available, the smaller the crapemyrtle (at maturity) should be, so be sure to choose a cultivar that will not require pruning to make it “fit” into the landscape (see cultivar listing at the end of this publication).

These crapemyrtles require yearly pruning because they are a cultivar that grows too large for this location.

Preventing “crape murder”

Crapemyrtles generally require a minimum amount of pruning when properly chosen and maintained. Though some pruning may be beneficial, there is a definite right way and a definite wrong way to prune these plants, with the wrong way often referred to as “crape murder.”

The wrong way to prune. A misconception that crapemyrtles need to be severely cut back in late winter or early spring in order to flower well in summer has led to the unhealthy practice of topping these plants. If necessary, crapemyrtles can be reduced in height without being topped.

Topping (buck horning or dehorning) involves cutting stems back at an arbitrarily chosen height rather than pruning back to a bud, side branch, or main stem. Topping trees and shrubs is harmful in many ways and regarded as an unacceptable practice by trained horticulturists and arborists. Research shows that stem decay significantly increases when topping cuts are made, and that more dead branches also occur within the canopy (Gilman, E.F. and G.W. Knox. 2005. Pruning type affects decay and structure of crapemyrtle. Journal of Arboriculture 31(1):48-52.).

Topping crapemyrtles results in numerous vigorous shoots originating from the top of the cut stems. This ruins the natural form of the plant, which is especially obvious in winter after leaf drop. These quick growing, succulent shoots are poorly attached. The large bloom that develops on the end of each shoot is top heavy, often causing the shoot to break off in strong winds. In addition, topping can greatly reduce the number of bloom days because only one main flower cluster is borne on the end shoots instead of many smaller flower clusters with staggered bloom times.

The same cultivar, naturalistically pruned (left) and topped (right). Note the “witches’ broom” appearance of the topped plant.

Another problem caused by topping is increased susceptibility of the succulent shoots to pest problems (especially aphids), resulting in otherwise unnecessary use of pesticides.

Plants wounded by topping often produce large numbers of basal suckers. Though re-suckering can sometimes be suppressed by applying naphthalene acetic acid (NAA) after pruning, picking the wrong cultivar relative to height and then having to repeatedly top or prune back the plant results in added expense. Avoid fertilizing crapemyrtles unless a soil test indicates a special need because excessive fertilization can encourage sucker growth and reduce flowering.

Crapemyrtles that have previously been topped can, to an extent, be “untopped.” Select two or three of the stronger shoots per “topping knuckle” (the knob that develops where the topping cut was made) and prune the others off. Then prune (head back) the selected shoots above outward facing buds to begin to develop a new branch pattern. The plant will never again have its true or natural crapemyrtle form, but it can be improved.

The right way to prune. Some of the prettiest crapemyrtles in Virginia are old, unpruned plants along roadsides. Individual flower clusters are often smaller but the number of flower clusters is generally far greater than on over-pruned plants, and the bloom season is extended.

Because crapemyrtles are summer-blooming trees, producing flowers from new wood or current season stems, the proper time to prune is late winter or early spring prior to new growth. Do not prune crapemyrtles in late summer or early fall because new shoots that grow may freeze if they fail to go fully dormant.

Pruning a crapemyrtle requires the same procedures used for any tree or shrub. Proper pruning techniques will ensure an abundance of blooms, as well as a healthy plant for many years to come.

When pruning crapemyrtles, practice naturalistic pruning that maintains the shape and form of each unique cultivar. Start early in the life of the plant by removing dead, diseased, broken, crossing, and rubbing branches to improve overall plant health and appearance. A well-trained crapemyrtle will not need yearly pruning so continue that practice only as needed to develop sound structure and enhance the plant’s health.

If only part of a branch needs to be removed make a heading cut above an outward facing bud or side branch. If an entire branch needs to be removed, make a thinning cut just outside the branch collar of the stem to which the branch is attached. Do not apply any materials (pruning paint, etc.) to the cut ends. Encouraging new stems to grow away from the center opens up the plant, increasing light penetration and air movement, and reduces potential wind damage and insect (aphids) or disease (powdery mildew) problems.

If suckers develop, rub them off while they’re young and succulent or prune them off with a thinning cut back to the main stem. Sometimes branch tips are cut back after flowering occurs to remove old flower clusters or prevent seedpods from forming. Though summer tip pruning may lead to a second flowering in cultivars that bloom before mid-July, its generally impractical, produces inconsistent results, and isn’t necessary to promote flowering the following year.

If larger and more profuse flowers are desired on dwarf crapemyrtles used in containers or as low plants in shrub borders, prune them back severely (to within six inches of the ground) each year. 

A plant that has been thinned of small twigs (above left). Making a heading cut (above right and below left). Making a thinning cut (below right).

Select Crapemyrtle Cultivars for Virginia

New cultivars of crapemyrtle have flooded the market in recent years, particularly in the dwarf and mid-size offerings. If you want to learn what would work for you based on size, growth habit, flower color and other attributes, please seek out information directly from the companies who specialize in crapemyrtle plant introductions. You will want to ensure the cultivar of interest is suitable for where you live based on growing zone details. You might also seek assistance from your local Virginia Cooperative Extension office or a local independent garden center.

Single vs. multiple-trunk tree forms

If you want a tree-form crapemyrtle, select a taller growing cultivar and be sure you have adequate space for its crown to mature without excessive pruning. Crapemyrtles to be used as small trees can be purchased or pruned either into single or multiple trunk forms. To develop a single trunk form, start with just one stem or rooted cutting. To develop a multi-trunk tree form, select three to five evenly spaced stems and remove all others at ground level. As the tree grows, gradually remove lower branches (crown raising) to no more than one-third to one-half way up the plant.

The Natchez cultivar trained as a single stem (left) and a multi-stem (right).

Continue to remove lower branches until the desired form or clearance under the tree is attained. Limbing up exposes more attractive bark for winter landscape interest. Also continue to remove small interior branches.

Resources on the Web

For an extensive listing of crapemyrtle cultivars consult Crapemyrtle in Florida -
www.edis.ifas.ufl.edu/pdffiles/MG/MG26600.pdf

To see pictures of many of the cultivars well adapted to Virginia go to The United States National Arboretum Crapemyrtle Introductions Photo Gallery on the Web at http://www.usna.usda.gov/PhotoGallery/CrapemyrtleGallery/

Reviewers: Greg Eaton, Extension Horticulture Specialist, Virginia Tech; Adam Downing, Extension Forestry Agent, Madison County; Lynette Swanson, Extension Horticulture Agent, Norfolk