Crape myrtles (Lagerstroemia indica) are celebrated for their vibrant summer flowers and attractive, peeling bark, but they naturally grow as multi-stemmed shrubs. Transforming this plant into a defined tree structure requires targeted, structural pruning over general trimming. The goal is to establish a strong, clear trunk or trunks topped by a graceful, vase-shaped canopy that showcases the smooth bark. This process demands patience and an understanding of the plant’s growth habit to avoid damaging its long-term health and aesthetic appeal.
Timing and Preparation for Structural Pruning
The most appropriate time for this structural transformation is during the plant’s dormant season, from late winter to very early spring. Pruning should be completed before new leaf buds begin to swell and open, generally between mid-February and mid-March. Pruning outside this window risks removing new flower buds (since crape myrtles bloom on new growth) or encouraging tender new growth that can be damaged by a late frost.
Gathering the correct tools is necessary for making clean, precise cuts that heal quickly. You will need sharp bypass hand pruners for branches under a half-inch thick, loppers for branches up to about 1.5 inches in diameter, and a pruning saw for anything larger. Before starting, sanitize all cutting tools with diluted bleach or rubbing alcohol to prevent the transmission of plant diseases. Removing weeds or debris from the base of the plant allows for clear visibility of the root collar and lower stems, which is necessary for proper trunk selection.
Selecting Trunks and Clearing the Lower Growth
The first step is deciding whether to cultivate a single-trunk or a multi-trunk tree form. The multi-trunk style is most common and often preferred to highlight the species’ natural growth. For a multi-trunk tree, select an odd number of the strongest, most vigorous stems (typically three or five) that are well-spaced and growing slightly outward. Remove all other stems completely at ground level. For a single-trunk tree, select one straight, dominant leader and remove all competing shoots at the base.
Once the permanent trunks are selected, clear the lower growth, known as “limbing up,” to expose the trunk and its attractive bark. Remove all lateral branches (side limbs) from the bottom one-third to one-half of the selected trunks. This creates the clear trunk space necessary to define a tree form. Continuously monitor for and remove suckers (new shoots that emerge from the roots or base of the trunks), cutting them flush to their origin to prevent the plant from reverting to a shrub-like appearance.
Shaping the Canopy and Future Maintenance
With the permanent trunk structure established, attention shifts to shaping the canopy to promote healthy growth and abundant flowering. The goal is to thin the canopy by selectively removing branches that are growing inward, rubbing against each other, or crossing through the center of the crown. This thinning opens the canopy, improving air circulation and allowing sunlight to penetrate the interior, reducing the risk of fungal issues like powdery mildew.
Any remaining branches thinner than a pencil should be removed, as they are unlikely to support the weight of a full flower cluster. If height reduction is necessary, it should be minimal and achieved by cutting back the tallest branches to a strong, outward-facing side branch, aiming for a graceful, vase-like shape. Once the tree form is established, subsequent annual pruning should be light, focusing on maintaining the structure and thinning for air flow. Throughout the growing season, deadheading spent flower heads can encourage a fresh flush of blooms, and any emerging suckers should be promptly removed to maintain the clear trunk.
Avoiding Common Pruning Errors
The most common pruning mistake made on crape myrtles is a practice known as “Crape Murder.” This involves the indiscriminate topping of large, mature branches, often cutting them back to thick, unsightly stubs. The practice is often done mistakenly to control height or encourage larger flowers, but it damages the plant’s natural structure.
Topping creates a flush of weak, whip-like shoots (epicormic growth) from the cut ends, which are poorly attached and prone to breaking. It also ruins the plant’s graceful, natural form. Proper structural pruning, in contrast, focuses on making selective thinning cuts back to a main trunk or a healthy side branch, enhancing the tree’s architecture rather than mutilating it.