Edging around a tree establishes a clean separation between the lawn and the area directly beneath the canopy. This practice is primarily aesthetic, but it also serves important functions for tree health and lawn maintenance. A defined edge separates competing turfgrass from the tree’s root zone, allowing the tree better access to water and nutrients. Furthermore, it makes mowing simpler, preventing accidental damage to the tree trunk from lawn equipment.
Planning the Edging Perimeter
The size of the edged area should be determined by the tree’s maturity and its long-term health needs. For a young or newly planted tree, the ring should extend at least three feet from the trunk in all directions to reduce competition from the surrounding grass. Grass is a voracious consumer of water and nutrients, which can significantly slow the growth of a young tree.
For a mature tree, the perimeter should ideally extend to the drip line, the imaginary circle on the ground directly beneath the outermost tips of the branches. The majority of a tree’s feeder roots are concentrated within this area. A wider ring provides a greater benefit, as roots often extend well beyond the drip line. Use a rope, garden hose, or string anchored near the trunk to mark a clean, consistent circle or organic shape before cutting begins.
Step-by-Step Edging Technique
Begin the process by following your marked line using a half-moon edger or a sharp spade. The goal is to establish a clean, vertical cut into the soil, defining the boundary of the new tree ring. Watch for fine, fibrous tree roots, and avoid cutting major structural roots near the trunk.
After the initial vertical cut, create a small trench or bevel by slicing into the turf at an angle, facing toward the tree. This angled cut (V-shape) should slope inward and downward toward the tree ring. The trench should be four to six inches deep to prevent grass runners from crossing the barrier. Remove the severed sod and grass from the newly defined ring.
Finishing with Mulch
Once the edge is cut, the ring should be filled with an organic material, preferably wood chips. Applying mulch serves multiple purposes, including conserving soil moisture by reducing evaporation and regulating the soil temperature. Decomposition of organic mulch also enriches the soil, adding beneficial nutrients over time.
Spread the mulch evenly across the newly edged area to a depth of two to four inches. This depth is sufficient for weed suppression and moisture retention. A thicker layer is better for sandy soils, while a thinner application is advisable for poorly drained or clay-heavy soils.
Protecting the Tree Trunk and Roots
Proper mulching technique protects the tree’s health and prevents long-term damage. The most common mistake is piling the material directly against the trunk in a “mulch volcano.” This practice encourages rot, insect infestation, and the growth of girdling roots by trapping excessive moisture against the bark.
The mulch must be kept several inches away from the trunk flare, the part of the tree where the trunk widens at the base. The root flare must remain exposed to the air for proper gas exchange and to prevent decay. Maintaining a doughnut shape with the center open ensures the tree’s base stays dry and healthy.