Lawn Mower Damage to Young Maple: Wound Care Steps

A 2-year-old maple with a 4–5 inch trunk suffered a 6-inch-high, 1-inch-wide gash from a lawn mower. The bark remains attached at top and bottom but was puckered out until pressed back. The owner asks how to help the tree heal.

Assessing the Injury

On a small tree, a 1-inch-wide wound represents a significant percentage of trunk circumference. Maples have thin bark, making them especially vulnerable to mower/string-trimmer damage. The good news: the bark is still attached, preserving the cambium (living tissue) underneath. If the cambium survived, the tree can compartmentalize the wound.

Immediate Actions

1. Trim loose bark cleanly. Use a sharp, sterilized knife to remove any bark that's detached or jagged. Cut back to firmly attached bark—create a clean, vertical elliptical shape if possible. This speeds callus formation.
2. Do NOT apply wound paint, tar, or sealant. Research shows these trap moisture, promote decay, and hinder the tree's natural compartmentalization process (CODIT model).
3. Protect from borers. Stressed maples attract flatheaded borers (Chrysobothris spp.) and clearwing borers. Apply a preventive bark spray labeled for borers (e.g., permethrin or bifenthrin) in late spring and mid-summer, following label rates. Focus on the lower trunk.
4. Mulch widely. Apply 2–3 inches of wood chips in a 3-foot radius (keep 6″ from trunk). This eliminates future mower contact and conserves moisture.
5. Water during dry spells. 10–15 gallons weekly for a tree this size, unless rainfall exceeds 1 inch.

What to Expect

Callus tissue will form from the wound edges and gradually roll inward. Complete closure may take 2–4 years on a maple this size. The wound wood will always be visible as a seam, but the tree remains structurally sound if decay doesn't advance.

Prevention: The Best Cure

Install a permanent mulch ring or trunk guard (expandable plastic mesh) to prevent repeat injury. Many young trees die from cumulative mower damage over years—this single wound is recoverable if protected going forward.