Surface tree roots are a common issue for homeowners, creating tripping hazards, making lawn mowing difficult, and competing with turfgrass for resources. The majority of a tree’s root system, which handles water and nutrient absorption, grows horizontally in the top four to fifteen inches of soil where oxygen is available. Soil conditions like compaction, poor drainage, and erosion force roots even closer to the surface in their search for air and moisture. Over time, as these shallow roots thicken, they push up through the turf, creating the visible problem.
Assessing the Risks of Root Severance
The temptation to cut exposed surface roots to restore a level lawn is strong, but doing so carries significant risks to the tree’s health and stability. Tree roots anchor the tree and absorb water and nutrients. Severing a large root compromises the tree’s ability to anchor itself, drastically increasing the risk of the tree toppling over during high winds or storms.
Structural roots, which provide stability, are typically the larger roots flaring out from the trunk. Most arborists advise against cutting any root that is two inches or larger in diameter, as removing these can destabilize the tree or cause severe health decline.
If root cutting is necessary, such as when a root is damaging a foundation or sidewalk, it should be treated as a last resort. Small feeder roots, which are thin and numerous, can be cut with minimal risk because the tree can replace them quickly. However, the wound created by any cut provides an entry point for diseases, fungi, and pests, which can lead to decay and long-term decline.
A general guideline is to avoid cutting roots closer to the trunk than three to five times the diameter of the trunk itself. For example, a tree with a 12-inch trunk diameter should not have major roots cut within 36 to 60 inches of the trunk. If a root larger than two inches must be removed, consulting a qualified arborist is recommended to assess the risk and ensure the cut is made cleanly and at the safest possible location.
Non-Destructive Methods for Concealment
A safer approach to managing exposed roots involves covering them and altering the landscape without causing harm to the tree. The primary non-destructive method is the careful application of organic mulch, which protects the roots from damage and conserves soil moisture. A two to four-inch layer of wood chips or shredded bark should be spread over the exposed root zone, extending out to the tree’s drip line if possible.
It is important to avoid “volcano mulching,” which involves piling mulch high against the trunk. Mulch should be pulled back several inches from the trunk, leaving the root flare—the base where the trunk widens—exposed. This prevents moisture buildup, rot, and insect infestation, while the donut-like application provides a protective layer.
The addition of topsoil directly over exposed roots is not recommended because it can suffocate the root system by limiting oxygen exchange. However, a minimal application of a light, porous soil mixture, such as a half-inch layer of compost or a sand-compost mix, may be used sparingly to smooth the surface. Any soil application deeper than two to three inches risks causing root rot or decline, as it drastically reduces the air available to the shallow roots.
Alternative Landscape Solutions and Root Barriers
When turfgrass consistently struggles due to heavy shade or intense competition from surface roots, an alternative landscape design offers a long-term solution. Replacing the lawn with shade-tolerant groundcovers eliminates the need for mowing over and potentially damaging the roots. Options like hostas, wild ginger, mondo grass, and creeping phlox are well-suited for planting in the dry shade beneath a tree canopy.
Planting should be done by hand-digging small pockets in the soil between the visible roots rather than using a tiller or spade that could damage the tree. Since these groundcovers are often shallow-rooted, they can establish themselves with minimal disturbance to the tree’s network. This approach transforms the area into a low-maintenance garden bed that protects the tree and improves the yard’s aesthetics.
Hardscaping materials, such as interlocking pavers or gravel paths, can also be incorporated but must be installed carefully to avoid compacting the soil. Porous, breathable materials are preferable to solid concrete, which restricts air and water flow. The hardscape should be built to accommodate the existing roots, often requiring a permeable base layer rather than a thick, suffocating one.
In scenarios where root growth needs to be actively managed to protect structures like foundations or walkways, physical root barriers can be installed. These barriers do not stop root growth entirely but redirect it, forcing roots to grow deeper or away from the protected area. The barrier should be positioned with a slight outward angle and installed to a depth of 24 to 48 inches to be effective.