The crepe myrtle (Lagerstroemia indica) is a popular ornamental tree known for its summer flowers and exfoliating bark. Homeowners often choose this species for its manageable size, frequently planting it near structures or walkways. Understanding the composition and growth habits of its root system is important for proper placement, ensuring the tree thrives without creating maintenance issues.
Understanding the Structure and Depth
The crepe myrtle root system is shallow and fibrous, differing significantly from trees that develop a deep taproot for stability. This structure consists of many fine, branching roots that spread out extensively just beneath the soil surface. This design means the tree relies on a broad network of surface roots, making it highly efficient at absorbing water and nutrients from the topsoil layer.
The majority of the root mass remains concentrated within the top 12 to 18 inches of soil. While this depth allows for easy water uptake, it also makes the tree susceptible to drought stress if the upper soil dries out completely. This structure provides adequate support for the tree’s size, with stability derived from the wide horizontal spread of its fine roots.
Horizontal Spread and Proximity Concerns
The horizontal spread of the crepe myrtle’s root system is often much wider than the visible canopy. Roots can extend outward to a distance of 1.5 to 3 times the diameter of the canopy, creating a wide, shallow disc of growth. This extensive lateral growth is generally not considered aggressive, as the roots are relatively weak and not prone to inserting themselves into solid foundations or utility pipes.
However, the shallow nature of the roots can lead to issues with nearby hardscapes when planted too closely. As the roots thicken over time, they can exert upward pressure that may lift or buckle surfaces like sidewalks, driveways, or patios. The roots also tend to grow right beneath the surface of the lawn, which can make mowing difficult and compete with turfgrass for water and nutrients.
Standard crepe myrtles should be planted at least 5 to 10 feet away from walkways and foundations. Smaller, dwarf cultivars can be placed closer, but a minimum distance of 4 to 6 feet is recommended for medium varieties. Proper planning ensures the tree has enough space to mature without its root expansion causing practical problems in the surrounding landscape.
Managing Root Suckers
Root suckers are a common maintenance issue arising directly from the crepe myrtle’s root system. Suckers are adventitious shoots that emerge from the roots or the root crown, often appearing as small sprouts that quickly develop into a thicket around the base of the tree. While this is a natural reproductive mechanism, it detracts from the tree’s appearance and consumes energy needed for the main canopy.
Suckering is frequently triggered by stress factors, such as severe pruning, injury to the trunk or roots, or poor growing conditions. For instance, a common mistake is “crape murder,” or aggressive topping, which stresses the tree and encourages the development of numerous suckers. To manage this growth, the suckers should be removed as soon as they appear, preferably with sharp loppers or shears.
Prune suckers with a clean cut as close to their point of origin on the root or trunk as possible, avoiding the temptation to tear them off. Leaving a small stub can lead to disease or stimulate the growth of multiple new shoots from the injury site. Consistent and clean removal starves the roots of the energy these shoots provide, which is the most effective long-term method for control.