Exposed tree roots are a common landscape issue, often creating tripping hazards, interfering with lawn care, or simply looking unsightly. While the impulse may be to bury them and restore a flat surface, any solution must prioritize the tree’s health above all else. Trees rely on the top layer of soil for the majority of their oxygen and nutrient absorption, meaning improper covering can slowly suffocate or destabilize them. Successfully managing exposed roots requires techniques that disguise the roots without compromising the tree’s ability to breathe and grow.
The Danger of Covering the Root Flare
The most significant risk in covering tree roots comes from burying the root flare, the area where the trunk widens just before entering the soil. This transitional zone is biologically distinct from the root system, as the bark tissue above ground is designed to be dry and exposed to air. When soil or mulch is piled directly against the trunk, it creates a condition known as “volcano mulching,” trapping moisture against the bark.
This constant dampness encourages fungal growth, bark decay, and the development of adventitious roots from the trunk tissue. These new roots grow in circles around the base, eventually becoming girdling roots that tighten and constrict the trunk’s vascular system. The constriction chokes the flow of water and nutrients between the canopy and the rest of the root system.
The root system’s ability to take in oxygen is also severely compromised when the base is covered with more than one to two inches of new material. Tree roots require gas exchange with the atmosphere, and piling deep soil or mulch cuts off this supply. Covering the root flare will lead to a gradual reduction in vigor and a shortened lifespan for the tree.
Safe Landscaping with Groundcovers and Mulch
Covering exposed roots involves using shallow-rooted groundcovers or a light layer of organic mulch. This method transforms the area into a dedicated garden bed, eliminating the need for foot traffic or mowing near the tree base. When choosing plants, select species that are highly tolerant of dry shade and require minimal soil depth for establishment.
Suitable options include Bugleweed (Ajuga reptans), Sweet Woodruff (Galium odoratum), or Japanese Spurge (Pachysandra terminalis). These plants thrive in the competitive environment of a tree’s root zone, and their shallow root systems will not compete aggressively with the tree roots for resources. When planting, avoid digging large holes or slicing into any root thicker than a pencil.
Instead of traditional digging, use small plant plugs and tuck them into existing soil pockets between the tree roots. You may add a very thin layer—no more than one inch—of compost or topsoil to help the plugs establish, but this must never touch the root flare. A layer of finely shredded bark mulch, applied two to four inches deep, will protect the roots and conserve soil moisture. The mulch must be pulled back at least six inches from the trunk to maintain the necessary air circulation around the root flare.
Integrating Exposed Roots with Hardscape Elements
For high-traffic areas, structural solutions like a raised boardwalk or stepping stones can mitigate the tripping hazard without damaging the root system. Any hardscape element must be designed to be freestanding, ensuring no load-bearing weight rests on the tree’s roots or trunk. This requires minimizing excavation and using support systems that bridge over the root zone.
Building a wooden boardwalk or low deck is an option, provided the support posts are placed in areas requiring minimal digging, outside the immediate root zone of the tree. The structure must be built with an air gap above the soil, usually six to twelve inches, to maintain gas and water exchange below the deck surface. Flexible joints and an adequate opening around the trunk must also be incorporated to accommodate the tree’s continued growth over many years.
If a path is needed, stepping stones or permeable pavers can be used, but they must be placed directly on the soil with minimal preparation. The stones should be carefully settled into pockets of soil between the major roots to avoid forcing them down and damaging the root tissue. Deep excavation for a traditional paver base or the use of solid concrete is prohibited, as these materials compact the soil and block the air and water exchange that shallow tree roots rely on for survival.