The Crepe Myrtle (Lagerstroemia indica) is a popular landscape feature, prized for its vibrant seasonal flowers and the smooth, multi-toned bark it reveals in winter. This adaptable tree often serves as a focal point in yards, but planting beneath its canopy requires thoughtful selection. The tree’s specific needs and the environment it creates present challenges for understory plants. Successfully underplanting a Crepe Myrtle involves understanding its root structure and choosing species that can thrive in conditions of varying light and limited resources.
Understanding the Crepe Myrtle Root Zone
The Crepe Myrtle develops a dense, fibrous root system that tends to be shallow, spreading out aggressively near the soil surface to capture water and nutrients. These roots compete directly with any understory plants for moisture, creating a naturally dry and competitive environment, especially as the tree matures. Disturbing these shallow roots with deep digging can potentially harm the tree, making careful planting essential for the Crepe Myrtle’s long-term health.
The light conditions beneath the tree change dramatically with the seasons. In winter and early spring, the deciduous Crepe Myrtle is bare, allowing full sun to reach the ground. However, once the leaves emerge and the canopy fills out, the area transitions to dappled shade or partial sun during the summer growing season. Companion plants must be tolerant of this seasonal shift, handling both high light levels early in the year and the later shade.
Low-Maintenance Plant Selections
The most successful underplanting selections are species known for their tolerance to dry shade, root competition, and low maintenance requirements. Plants that quickly form a dense groundcover are particularly effective, as they help suppress weeds without requiring deep soil disturbance during installation. These groundcovers and low perennials should not exceed 18 inches in height to maintain a balanced look beneath the tree’s canopy.
Groundcovers
Liriope muscari (Lilyturf) and Ophiopogon japonicus (Mondo Grass) are excellent choices due to their resilience and grass-like foliage. Liriope muscari is a clumping variety, with cultivars like ‘Big Blue’ reaching 12 to 15 inches tall. Liriope spicata is a rapidly spreading, creeping option ideal for mass planting and erosion control.
Mondo Grass is slower-growing and shorter, with the dwarf variety reaching only 3 to 6 inches high, offering a finer texture. Both Liriope and Mondo Grass are evergreen and highly tolerant of dry conditions once established.
Another reliable groundcover is Ajuga reptans, or Bugleweed, which forms a dense, low mat just a few inches high. Its varieties like ‘Chocolate Chip’ offer dark, attractive foliage that contrasts well with the tree’s bark and tolerate partial shade. While it prefers slightly moist soil during establishment, its ability to spread by runners makes it highly competitive against weeds.
For a perennial option, low-growing Hosta varieties, such as the blue-leaved ‘Halcyon’ or yellow-centered ‘Gold Standard,’ can tolerate the dry shade beneath the canopy. These varieties benefit from the early-season sun for initial growth before the canopy casts more shade in summer.
Safe Planting and Establishment Practices
Protecting the Crepe Myrtle’s shallow root system is the main consideration when installing new plants beneath it. Planting should be done using small starter plants or plugs rather than large container specimens, as these require smaller holes and less root disturbance. Digging must be minimal and performed carefully, often with a hand trowel, to avoid severing or damaging the tree’s surface roots. It is recommended to plant new additions at least 12 inches away from the tree’s main trunks.
The planting hole should only be slightly wider than the plant’s root ball, and the existing soil should be used for backfilling without significant amendment. Adding too much rich topsoil can create a “bathtub effect,” leading to poor drainage, or encourage the Crepe Myrtle roots to grow only in the amended zone. After planting, apply a 2 to 3-inch layer of organic mulch, such as shredded bark or pine straw, to conserve moisture and regulate soil temperature. Keep the mulch several inches away from the Crepe Myrtle’s trunks to prevent moisture retention and rot. New plants require consistent, deep watering for the first few weeks to establish their root systems, after which the watering frequency can be significantly reduced.