The Crape Myrtle (Lagerstroemia indica) is a celebrated ornamental tree known for its extended summer flowering season and attractive peeling bark. Understanding its physiological requirements is important for successful cultivation and site selection. Proper care begins beneath the soil surface, where the tree’s root system establishes its foundational support. This guide details the depth and spread of the Crape Myrtle’s underground structure, offering insights for planting and management.
Fundamental Root Structure
Crape Myrtles develop a fibrous and widespread root system, contrasting sharply with species that form a deep central taproot. The majority of the fine feeder roots, responsible for water and nutrient uptake, are concentrated within the upper 12 to 18 inches of the soil profile. This shallow distribution allows the tree to quickly absorb precipitation but also makes it susceptible to drought conditions during prolonged dry spells.
The horizontal spread of these roots is extensive, often extending well past the canopy drip line, especially in looser soil types. This high concentration of roots near the surface helps anchor the tree while maximizing its ability to absorb oxygen. This shallow structure also makes the species relatively easy to transplant compared to deep-rooted trees.
Managing Lateral Spread and Proximity Issues
Although the Crape Myrtle’s root system is wide-spreading, it is considered non-aggressive. The roots are numerous and fibrous but lack the significant girth that causes substantial damage, unlike the woody roots of larger shade trees like oaks or maples. However, planting too close to hardscapes can still lead to minor surface issues as the tree matures.
To mitigate potential problems, plant Crape Myrtles (depending on the cultivar’s mature size) at least 5 to 10 feet away from house foundations, sidewalks, or paved driveways. Surface roots seeking oxygen and moisture can exert minor pressure, potentially leading to slight lifting or cracking of thin concrete over decades. Underground utility lines should also maintain this minimum distance to avoid root entanglement, although root damage to the pipes themselves is uncommon.
A related consideration is the emergence of root suckers. These are small, undesirable shoots that sprout directly from the shallow root system. Suckers can appear several feet away from the main trunk, especially if the root system has been injured or if the tree is experiencing stress. Root suckers are primarily a maintenance issue, and they must be physically removed by cutting them off below the soil surface to maintain the tree’s ornamental appearance.
Techniques for Planting and Relocation
The shallow, fibrous nature of the root system dictates specific planting techniques to ensure long-term health. When preparing the planting site, dig a hole two to three times wider than the root ball but no deeper than the root ball itself. This wide, shallow approach encourages the rapid lateral spread of new roots into the native soil.
A frequent mistake is planting the tree too deeply, which can lead to root suffocation and eventual girdling. The root flare—where the trunk widens as it meets the roots—must be fully exposed and visible slightly above the finished grade of the soil. Mounding the soil slightly toward the center helps direct water while ensuring the trunk base remains dry and oxygenated, preventing crown rot.
Since the majority of the root mass is concentrated near the surface, Crape Myrtles are excellent candidates for successful relocation, especially when dormant. The best time for transplanting is late winter or early spring before new growth begins, allowing the tree to establish new roots before summer heat. When digging, maintain a generous root ball, typically 10 to 12 inches in diameter for every inch of trunk diameter, to minimize disturbance to the fine feeder roots.