A clear zone around the base of a tree is a fundamental practice for promoting tree health. Establishing this grass-free area protects the tree from physical harm while eliminating competition for resources in the soil. The primary goal is to create an environment where the tree can thrive without the detrimental effects of turfgrass proximity.
Why Grass Removal is Essential
Grass growing directly up to a tree’s trunk creates two major hazards for the tree’s long-term health. The first issue is intense resource competition. Turfgrass has a dense, fibrous root system that aggressively seeks water and nutrients in the shallow topsoil layer where young tree feeder roots are concentrated. This competition can stunt the tree’s growth, especially in newly planted or young specimens.
The second major problem stems from mechanical injury during routine lawn maintenance. Using mowers or string trimmers too close to the trunk can easily nick or girdle the bark. Damage to the bark compromises the tree’s vascular system, exposing the inner tissues to pests, diseases, and fungal infections.
Non-Chemical Methods for Eradication
Non-chemical methods are the safest way to remove turfgrass around trees, ensuring that no harmful substances reach the root zone. Manual removal involves carefully hand-digging the grass and its roots using a small spade or trowel. Do not dig deeper than two inches to avoid damaging the fine tree roots that are often close to the surface.
A passive, effective non-chemical technique is sheet mulching, also known as lasagna gardening. This method uses layers of organic material to smother the grass by blocking light and suppressing growth. The process begins by laying down dampened cardboard or several layers of newspaper over the mowed grass, ensuring the layers overlap to prevent light penetration. This barrier is then covered with organic material, such as wood chips or compost, which weighs down the barrier and breaks down the turf beneath.
The cardboard barrier eventually decomposes, adding carbon to the soil. This layer is then covered with organic material, such as wood chips or compost, which weighs down the barrier and breaks down the turf beneath. Sheet mulching is a slow process, taking a few months to fully kill the grass, but it significantly improves the soil health around the tree roots.
A third approach is solarization, which uses the sun’s energy to superheat the soil. This requires covering the area with clear plastic sheeting, typically two to six millimeters thick, during the hottest part of the year. The plastic creates a greenhouse effect, trapping heat and moisture, which encourages the existing grass and weed seeds to germinate before the extreme heat kills them.
The soil must be thoroughly moistened before laying the plastic, as wet soil conducts heat more effectively. For solarization to be successful, the sheet must be secured tightly against the ground for at least six weeks during peak summer temperatures. This method is less suitable for areas heavily shaded by the tree canopy, as insufficient heat will be generated to eliminate the grass.
Safely Using Herbicides
Using chemical weed killers requires extreme caution to prevent damage to the tree. If a chemical approach is chosen, it is safest to use a non-selective, contact herbicide containing an active ingredient like glyphosate, which generally kills only the plant tissue it touches and has little activity in the soil. Systemic herbicides or soil-residual materials that stay active for a long time should be avoided completely, as tree roots can absorb them, causing extensive damage.
One of the most significant dangers is spray drift, where fine herbicide droplets are carried by the wind onto the tree’s trunk or foliage. Herbicide contact with the bark or leaves can be irreversible. To mitigate drift, application should be done on a calm day, and a physical shield, such as a piece of cardboard or plastic sheeting, should be held between the sprayer and the trunk.
Direct application should target only the grass blades, as the herbicide is absorbed through the green tissue. Herbicide treatments offer no preventative effect, meaning new growth will still emerge, requiring follow-up maintenance. For grassy weeds specifically, some professionals suggest using a grass-specific herbicide like sethoxydim, which targets monocots like turfgrass without harming broadleaf plants.
Proper Mulching and Ongoing Maintenance
Once the grass has been successfully removed, the area should be covered with an organic mulch to maintain the clear zone and benefit the tree. Organic mulches, such as wood chips or shredded bark, are preferable because they decompose over time, enriching the soil and providing nutrients. Mulch also helps to conserve soil moisture, moderate soil temperature, and suppress the re-emergence of weeds and grass.
The mulch layer should be applied at a depth of two to four inches, as exceeding four inches can inhibit the oxygen exchange needed by the roots. The most important rule of proper mulching is placement: the material must be kept several inches away from the tree’s trunk. Piling mulch directly against the bark creates a moisture trap, promoting rot, decay, and attracting pests, a common mistake known as a “mulch volcano”.
Instead of a volcano shape, the mulch should be applied in a flat, “donut” or “bagel” shape, ensuring the root flare—the base where the trunk widens at the ground—remains slightly exposed. The ideal diameter of the mulch ring should extend at least four to six feet from the trunk, or ideally out to the tree’s drip line. A wide mulch ring reduces the area where tree roots must compete with turfgrass, allowing the tree to thrive.