Mechanical Injuries are a Threat to Tree Health
When a tree is bumped, scraped, or chewed by a lawn mower or weed eater, the resulting wound can seriously threaten the life of that tree. Not only is the wound itself damaging, but pathogens can enter the wound, causing further distress. Microorganisms often attack injured bark and invade the adjacent healthy tissues, greatly enlarging the affected area.
It is not unusual for a tree to be completely girdled from microbial attack following mechanical damage from mower or weed eater wounds. Decay fungi on the surface of the wound can cause structural deterioration of the woody tissues beneath the wound. The resulting internal decay can cause the wounded tree to break off at the stem or root collar.
These injuries occur when operators attempt to trim grass around tree trunks with a mower or weed eater. The root buttress is the most common site of injury, though wounds may be found anywhere from the roots to several feet above the ground. To prevent such injuries, turf around trees can be removed and replaced with mulch. Mulching conserves moisture for the tree roots, and competition from the surrounding turf is reduced. Hand trimming the grass immediately around the tree trunk can also prevent injuries.
The most severe injuries from lawn mowers occur during periods when the tree bark “slips” in early spring during leaf emergence and in early fall during leaf drop. During these periods, even minor injuries will produce large wounds.
Though the problem of lawnmower and weed eater injury has been well researched and scientists have been aware of the problem for years; lawnmowers and weed eaters (and their operators!) remain a constant threat to tree health.
Protect your trees from damage by mulching around them. For information on proper mulching search the internet using the keywords proper mulching, trees, and North Carolina. Both NC State Universtiy and the NC Urban Forest Council have excellent informational publications.