Elevated roots refer to the visible portions of a tree’s root system that grow above the soil surface, often radiating outward from the trunk. While this phenomenon is a natural occurrence, particularly in mature trees, it frequently becomes a concern for property owners due to the potential disruption it causes to lawns and walkways. Understanding why these structures develop above ground is the first step toward addressing the challenges they present in a cultivated landscape. This growth pattern is influenced by a combination of genetics, soil conditions, and past planting practices.
Why Roots Lift Above Ground
One of the most frequent reasons tree roots become elevated is incorrect planting depth during establishment. When a tree is placed too high in the landscape, the primary roots, known as the root flare, are never adequately covered by soil. These roots then continue to grow horizontally just beneath the surface, eventually expanding and pushing themselves fully above the grade line as the trunk increases in diameter. This initial shallow placement dictates the subsequent surface-level growth pattern for the tree’s entire life.
Environmental factors like poor soil structure also heavily influence root elevation. Tree roots require oxygen for respiration, and when soil is dense, heavy with clay, or severely compacted from construction or foot traffic, oxygen content decreases dramatically. Instead of expending energy trying to penetrate this resistant medium, the tree adapts by growing its fine feeder roots laterally and close to the surface where gas exchange is more favorable. This preference for oxygen-rich topsoil results in a dense mat of roots near the ground level.
Certain species possess a genetic predisposition to develop a shallow root system, regardless of optimal soil conditions. Trees such as Norway maples, willows, and birches naturally produce roots that spread widely and remain near the surface as a characteristic of their biology. This innate tendency allows them to efficiently capture rainfall and nutrients before they can percolate into deeper soil layers.
Another factor contributing to the appearance of elevated roots is the gradual loss of topsoil over time. Erosion, caused by wind or water runoff, can slowly wear away the layers of soil that once covered the root flare and main structural roots. While the roots themselves have not lifted, the surrounding grade has lowered, exposing the otherwise healthy underground structures.
Finally, roots that grow in tight circles, often a result of being pot-bound in a nursery container, can push themselves upward as they expand. These circling or girdling roots lack the space to grow outward effectively, causing the root mass to constrict the trunk base and displace itself vertically. This constriction also restricts the movement of water and nutrients within the tree.
The Risks of Exposed Roots
The exposure of the tree’s root system creates several challenges, beginning with increased vulnerability to physical damage. Surface roots are easily injured by routine lawn maintenance activities, such as being struck by a lawnmower blade or nicked by a string trimmer. These mechanical wounds compromise the protective bark layer and create direct entry points for wood-decay fungi, bacteria, and insect pests.
Roots growing above the soil are also susceptible to rapid dehydration and temperature extremes. The thin bark offers little protection from the sun, causing them to dry out much faster than roots insulated by soil. This moisture loss impairs the tree’s ability to efficiently absorb water and dissolved nutrients, placing the tree under stress, especially during periods of drought.
For the surrounding landscape, elevated roots introduce significant physical hazards. Roots that cross walkways or protrude into turf areas create uneven surfaces that pose a tripping risk for pedestrians. They also become obstacles that make it difficult to perform routine maintenance, often leading to damage to equipment like mower decks and aeration tools.
Additionally, the visual presence of a large, tangled root system can detract from a manicured landscape aesthetic. While the natural appearance of a mature tree is valued, the upheaval of turf or hardscaping by surface roots can disrupt the intended design. The resulting damage to concrete or asphalt further compounds the maintenance and replacement costs for property owners.
Managing and Protecting Elevated Roots
Addressing elevated roots requires careful consideration, as aggressive intervention can harm the tree’s long-term health and stability. The preferred method for protecting exposed roots is to apply a thin layer of organic mulch over the root zone, extending out to the tree’s drip line. This layer should be no more than 1 to 2 inches deep, helping to insulate the roots and retain moisture without suffocating the underlying soil. Avoid deep covering, often called “volcano mulching,” which piles material high against the trunk. Thick layers of mulch restrict gas exchange, leading to root suffocation and decay, and excessive moisture against the trunk encourages rot.
A practical approach involves adjusting landscape maintenance to accommodate the root system rather than attempting to eliminate it. This includes raising the cutting height of lawnmowers or, ideally, ceasing to mow the area directly surrounding the tree altogether. Eliminating turf grass in the root zone and replacing it with a shade garden bed removes the incentive to use damaging equipment near the trunk.
Incorporating the roots into the landscape design can turn a problem into a feature. Creating a dedicated area around the tree for low-growing, shade-tolerant ground cover, such as ivy or hostas, protects the roots while providing a finished look. Another option is to build a low, non-structural retaining wall a short distance from the trunk to visually frame the root zone. This wall must not be placed directly against the trunk or contain significant soil fill.
Root pruning should be approached with caution and is discouraged for established trees. Removing large structural roots can significantly reduce the tree’s stability and capacity to absorb water and nutrients. If removal is necessary, it should only be performed by a certified arborist who can assess the risk and target only minor, non-structural roots located well outside the tree’s root flare.
For areas where surface roots are minor, replacing turf with specialized ground covers that tolerate shallow, dry soil conditions provides a low-maintenance solution. These plants, unlike turf, do not require frequent cutting, significantly reducing the mechanical damage risk to the exposed root structures.