Lagerstroemia indica, commonly known as the Crepe Myrtle, is a ubiquitous ornamental shrub or small tree celebrated across the warmer regions of the United States for its striking, long-lasting summer blooms. Native to temperate and tropical Asia, its popularity stems from its vibrant colors, attractive peeling bark, and resilience in various conditions. The direct answer to whether it is invasive is complex: the Crepe Myrtle is generally not classified as an ecologically invasive species in the continental United States. However, its natural growth characteristics can make it a high-maintenance plant that exhibits aggressive spreading behavior in a residential landscape.
Ecological Status: Defining True Invasiveness
The term “invasive species” has a specific, scientific definition that goes beyond merely growing aggressively in a garden setting. An ecologically invasive species is non-native to the ecosystem under consideration, and its introduction causes or is likely to cause environmental or economic harm. This harm typically results from the plant spreading rapidly and outcompeting native flora, leading to reduced biodiversity and degraded habitats.
The Crepe Myrtle’s status in the U.S. is largely classified as “naturalized,” meaning it can reproduce and maintain its population without human intervention but does not typically displace established native ecosystems. Its spread into wild areas is generally limited, especially in cooler climates. However, in some tropical and subtropical regions, Lagerstroemia indica has been listed as a true invasive species due to its capacity to dominate disturbed sites.
While the Crepe Myrtle is a non-native species, it lacks the reproductive rate and ability to form dense monocultures that characterize the most destructive invasive plants in most of the continental U.S. This classification does not negate the maintenance challenges the plant presents to gardeners who perceive its rapid, uncontrolled growth as a form of invasiveness.
Understanding Crepe Myrtle’s Aggressive Growth Habits
The frustration gardeners feel often stems from three distinct growth characteristics that mimic invasive behavior on a smaller, localized scale. One of the most common complaints is the prolific production of suckers, which are shoots that emerge from the roots or the base of the plant. These suckers are often triggered by stress, such as aggressive pruning—an action sometimes called “crape murder”—or damage to the root system during nearby digging.
If left uncut, the suckers quickly grow into unwanted, multi-stemmed thickets, diverting energy and nutrients from the main trunk and canopy.
The Crepe Myrtle is also a heavy producer of viable seeds, which contributes to the problem of “volunteer seedlings.” The showy flowers result in countless seed pods that mature in late summer and early fall, easily escaping cultivation to sprout in lawns, flower beds, and cracks in pavement.
The root structure contributes to its aggressive reputation, developing a dense, fibrous root system. While not usually destructive to foundations or pipes, this shallow network can intensely compete with nearby turfgrass or smaller landscape plantings for water and nutrients. Even after a main trunk is removed, the remaining root system can store enough energy to continue sending up persistent suckers for several years.
Practical Strategies for Managing Spread and Suckers
Controlling the Crepe Myrtle’s aggressive growth requires a consistent, two-pronged approach targeting both the root-based suckers and the seed-based spread. For managing suckers, physical removal should be done by cleanly cutting the shoots off as close as possible to the root collar or point of origin, rather than merely shearing them. Prompt and thorough removal starves the root system over time, preventing the suckers from photosynthesizing and replenishing the stored energy that fuels regrowth.
If physical removal is insufficient, a systemic herbicide containing glyphosate or triclopyr can be used, applied directly to the foliage of young suckers. Systemic treatments are absorbed by the leaves and travel down to kill the root tissue, though repeated applications may be necessary due to the energy reserves in the roots. Alternatively, plant growth regulators, such as those labeled “Sucker Stopper,” can be applied to the cut base of the sucker to prevent regrowth for one season.
To prevent volunteer seedlings, the most effective cultural practice is deadheading, which involves removing the spent flowers before their seed pods have a chance to mature. This should be done in late summer or early fall before the capsules fully develop and disperse their seeds.
To minimize issues with the dense surface roots, it is advisable to plant Crepe Myrtles away from lawns or delicate garden beds where root competition is a concern.