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Exposed roots are common as trees mature and often reflect soil conditions, watering or a species’ natural growth pattern. Arborists advise against cutting or repeatedly mowing over them; a 2- to 3-inch layer of organic mulch is one way to protect and cover roots without burying them.
A Country Living gardening report citing arborists and extension specialists advises homeowners not to cut exposed tree roots and to avoid piling deep layers of soil over them. The guidance matters because surface roots can create mowing and tripping hazards, but damaging them can harm a tree’s long-term health or stability.
Exposed roots are common in mature trees, and their presence does not by itself mean a tree is unhealthy. Barbara Fair, a certified arborist and North Carolina State University extension specialist, says roots grow where they can most easily reach oxygen, water and nutrients. Most tree roots grow within about three feet of the soil surface and spread laterally beyond the canopy’s drip line, according to the report.
Soil compaction, including compaction linked to construction, can make it harder for roots to grow downward. Frequent, shallow lawn irrigation may also encourage roots to remain near the surface, says Blake Watkins, a master arborist. Some species, including redwoods, camphors, Southern magnolias, maples, sycamores and willows, commonly develop shallow roots. Watkins says that pattern does not necessarily signal a tree problem.
For roots that need covering, the report recommends two to three inches of organic mulch, such as wood chips or pine straw, spread over the roots and toward the drip line. Keep mulch a few inches from the trunk so the root flare—the junction between trunk and roots—remains visible. A light soil top-dressing is another option, but Fair says to add no more than two inches and use sandy, loamy soil. Roots may continue growing, so soil may need to be added again over time.
Protecting Roots Without Harming Trees
The advice addresses a common conflict in yards: people may want a smooth lawn or a tidier appearance, while tree roots need access to air, water and nutrients. Cutting roots can affect a tree’s long-term health, and repeatedly running a mower over them can cause wounds that leave the tree more vulnerable to disease and pests, according to Mary Carol Sheffield, a certified arborist and University of Georgia extension agent.
Adding too much soil can also cause harm by reducing the air available to roots. The report says a homeowner should not bury roots under a deep layer of soil, and warns against expecting grass to thrive beneath large trees. Grass and tree roots compete for water and nutrients, Fair says, particularly in the case of warm-season grasses such as Bermuda and zoysia.
Where roots are lifting a sidewalk or creating another structural concern, the consequences may extend beyond appearance and lawn care. Watkins recommends consulting a certified arborist for advice on options that do not compromise the tree’s stability or health.
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Why Surface Roots Appear
The report describes surface roots as a result of both tree growth and local growing conditions. Roots form a laterally spreading root plate, including larger buttress roots that help support the tree. As a tree matures, roots may become visible, and runoff from the canopy can carry soil away from the area around them.
Watering practices can influence where roots grow. Watkins says regular watering during drought can encourage deeper rooting, while shallow, frequent irrigation may keep roots near the surface. For a mature tree, the report suggests slow watering for several hours about once a month during drought; homeowners with irrigation systems may ask about bubbler-style emitters that deliver a larger volume of water. These are general recommendations from the cited experts, not a guarantee that exposed roots will disappear.
Planting under a tree is possible, but digging can damage roots. Fair recommends choosing shade-tolerant groundcover or perennials, such as ferns, hostas or small hydrangeas, and avoiding large planting holes. Bare-root perennials may require less digging. Growing a dense lawn beneath a large tree is unlikely to work well because the plants compete for resources.
“It often says more about the soil and growing site than about the tree itself.”
— Blake Watkins, master arborist
When Roots Signal a Problem
The supplied report does not identify a single cause for any particular tree’s exposed roots, and the roots’ appearance alone cannot establish whether a tree is unhealthy. It also does not offer a universal remedy for roots that have lifted paving or created a safety hazard. The best response depends on the tree, its site and the extent of the damage; an arborist’s assessment may be needed for structural concerns.
The report gives general watering guidance but does not specify a schedule for every climate, soil type or tree species. It also cautions that light soil cover may need annual renewal as roots continue to grow. Homeowners should not assume that mulch or soil will resolve the underlying cause of exposed roots.
Practical Steps for Homeowners
Homeowners can first keep mowers and other equipment from repeatedly striking surface roots and avoid cutting them. For a less exposed appearance, they can apply a thin layer of organic mulch, keeping it away from the trunk, or consider carefully selected shade-tolerant plants. Any soil top-dressing should remain within the report’s limit of two inches.
During drought, slow watering may help support the tree, though results depend on local conditions. If roots are lifting a sidewalk or causing a substantial stability or safety concern, contact a certified arborist before altering them. The report does not describe a single next regulatory or industry milestone; the next step for an affected homeowner is assessment and a site-specific plan.
Key Questions
Should I cut exposed tree roots?
No. The arborists cited in the report advise against cutting roots because doing so can harm a tree’s long-term health. Repeated mower strikes can also injure roots and leave the tree more susceptible to disease and pests.
How much mulch can I put over exposed roots?
The report recommends two to three inches of organic mulch, such as wood chips or pine straw. Keep it a few inches away from the trunk so the root flare remains visible; avoid rocks as a covering.
Can I cover exposed roots with soil?
A light top-dressing may help, but Fair recommends using sandy, loamy soil and adding no more than two inches. A deeper layer can deprive roots of air and harm the tree. The report says this may need to be repeated as roots continue growing.
Will grass grow beneath a tree with surface roots?
It may be difficult to establish a healthy lawn under a large tree because grass and tree roots compete for water and nutrients. The report suggests considering shade-tolerant plants such as ferns or hostas, while taking care not to damage roots during planting.
Who should I contact if roots lift a sidewalk?
Contact a certified arborist. The report says an arborist may be able to suggest an approach that addresses the structural issue without compromising the tree’s health or stability.
Source: countryliving.com
