Tree roots can cause anxiety for property owners due to potential damage to foundations, utility pipes, and paved walkways. Mitigating this risk requires selecting the right tree species and ensuring proper planting methods. Choosing trees with naturally contained or deep root structures allows homeowners to enjoy a mature landscape without structural hazards. This guidance identifies species and techniques that minimize root intrusion.
How Tree Roots Become Invasive
Tree roots grow primarily to seek oxygen, water, and nutrients. Roots are opportunistic, proliferating wherever the soil environment is favorable, typically within the top 12 to 36 inches where oxygen is readily available. Most of a tree’s root system consists of shallow, spreading lateral and fibrous roots, rather than a single, deep taproot, especially in urban or compacted soils.
Roots follow paths of least resistance where resources are concentrated. For example, cracked water or sewer lines leak moisture and nutrients, creating an ideal environment roots will exploit. Compacted soil or poor drainage also forces roots closer to the surface, increasing the likelihood of them lifting sidewalks or driveways as they expand. Shallow, frequent watering encourages surface root development, while deep, infrequent watering promotes roots to grow downward.
Non-Invasive Species for Small Spaces
Trees planted close to structures or in small yards should naturally possess smaller root masses or fibrous, non-aggressive root systems. These smaller ornamental trees do not develop the large, woody lateral roots capable of extensive structural damage. Their reduced canopy size corresponds to a proportionally smaller root system.
The Japanese Maple (Acer palmatum) is a favored choice due to its compact size and delicate, non-intrusive root structure, making it safe for foundation plantings. The Eastern Redbud (Cercis canadensis) and the Kousa Dogwood (Cornus kousa) are excellent options, known for their manageable root balls and attractive seasonal interest. Crape Myrtles (Lagerstroemia indica) are popular for their vibrant summer blooms and shallow, non-invasive roots, though their mature height requires careful placement. For cooler climates, the Amur Maple (Acer ginnala) offers a slow-growing, fibrous root system.
Large Shade Trees with Contained Root Systems
All large shade trees require significant space, but some species develop deeper root systems or less aggressive lateral spread, making them relatively contained. Trees that establish a strong taproot or a well-developed heart root system are preferred because these anchoring roots grow more vertically than horizontally. This characteristic helps the tree access deeper water sources and provides better wind stability without relying on widespread surface roots.
The Ginkgo (Ginkgo biloba) is prized for its deep-reaching roots and tolerance of urban conditions, making it one of the safest large trees for infrastructure. Certain Oaks, specifically the Willow Oak (Quercus phellos) and the Northern Red Oak (Quercus rubra), are better choices because they tend to develop deeper root systems. The Kentucky Coffee Tree (Gymnocladus dioicus) is another recommended species, known for its adaptability and a root system less prone to causing heaving or cracking of hardscapes.
Ensuring Safe Planting Distances
Proper planting distance is the most reliable method for preventing future root damage, even with non-invasive species. A general rule is to consider the tree’s mature height and spread, as the root system can extend one to three times the canopy diameter. For small ornamental trees that mature under 25 feet, a distance of at least 10 to 15 feet from foundations is advisable.
Larger shade trees exceeding 50 feet in height should be planted a minimum of 20 to 30 feet from any structure, sewer line, or sidewalk. Before planting, property owners should contact local utility services to mark the location of buried lines. If proximity cannot be avoided, installing a vertical root barrier can redirect root growth downward and away from the structure. This method is most effective when installed during the initial planting of a young tree. Promoting deep, healthy root growth through infrequent, thorough watering also discourages the formation of shallow, surface roots.