Tree roots breaking the soil surface are a frequent sight in lawns, creating bumps that make mowing difficult, presenting tripping hazards, and generally detracting from a smooth landscape aesthetic. This common issue is often a result of natural tree growth, soil erosion, or soil compaction that forces roots upward in search of oxygen. While the immediate impulse is to conceal these roots, any attempt to do so must prioritize the tree’s health over quick cosmetic fixes. The solutions for managing exposed roots range from thin, gentle coverings to full landscape redesigns, depending on the severity of the exposure.
Understanding the Risks of Root Coverage
Applying too much material over tree roots can cause significant harm, even leading to tree death. Tree roots need to exchange gases with the atmosphere, and most feeder roots reside in the top 12 to 15 inches of soil where oxygen is most available. Piling soil or mulch too deeply—even a few inches—suffocates these roots by blocking the necessary oxygen exchange, a condition known as root suffocation. This lack of air is a serious stressor that can cause the tree’s overall health to decline slowly over time.
Excessive coverage also creates an environment conducive to root rot and fungal diseases. The area where the trunk meets the roots, called the root flare, is particularly vulnerable. This part of the tree is not protected by the same bark tissue found on the trunk and is meant to be exposed to air. If the root flare is constantly wet from buried soil or mulch, the bark can decay, creating an entry point for pests and pathogens. Therefore, any covering method must ensure the root flare remains visible and dry.
Safe Landscaping Techniques for Minor Exposure
For roots that are only slightly or moderately exposed, a thin layer of organic material can provide protection without suffocating the tree. The safest method involves applying organic mulch, such as shredded wood or bark chips, in a thin layer. A depth of two to three inches is generally recommended to buffer the roots from foot traffic and lawn equipment while still allowing gas exchange. This mulch layer should be spread out to the tree’s drip line, which is the edge of the canopy, if possible, to mimic the natural forest floor environment.
It is essential to keep the mulch pulled back several inches from the trunk, creating a bare ring around the root flare. This “donut” application prevents moisture from accumulating directly against the trunk, which is vital for avoiding decay. If a very minor root is exposed, a topdressing of a finely textured compost or topsoil blend can be used, but this layer must be applied at a maximum depth of one to two inches. Roots will eventually grow through this thin layer, meaning the process may need to be repeated every few years.
Using Groundcover Plants
A different approach is incorporating shallow-rooted groundcover plants into the area, which can stabilize the soil and provide a softer visual transition. Suitable options are typically shade-tolerant species, like periwinkle, sweet woodruff, or creeping Jenny, that do not require deep soil preparation. When planting, use a hand trowel to create small pockets between the existing tree roots to avoid damaging them. The goal is to establish the groundcover without significantly raising the soil grade around the tree.
Design Alternatives for Heavily Exposed Roots
When roots are severely exposed, numerous, or large, attempting to cover them with even a thin layer of material is often impractical or unsafe. In these cases, the best solution is to eliminate the surrounding lawn entirely and redesign the space to accommodate the root zone. Removing the grass reduces competition for water and nutrients, which benefits the tree, and it also removes the need for mowing, eliminating the primary source of mechanical damage to the roots.
Creating a designated natural area beneath the tree allows the roots to become a feature rather than a problem. This space can be defined with a low, decorative border to visually separate it from the remaining lawn without altering the soil level. Permeable hardscaping offers a more formal alternative for high-traffic areas, such as using spaced flagstones or open-celled pavers that sit above the root crown. These materials allow water and air to reach the soil while stabilizing the ground for walking.
For a substantial change, a low, built-up deck or raised walkway can be constructed over the root zone, provided it is built on piers or posts that minimize soil disturbance. This solution effectively raises the walking surface without adding soil mass over the roots, which is the primary danger. The ultimate goal for severely exposed roots is to stop fighting the natural growth pattern and instead integrate the root system into a new, safe, and sustainable landscape design.