Bruised and peeled bark
Bruised and peeled bark should be treated to promote rapid healing. Trim around the wound to sound tissue on each side (Figure 1). Use a sharp knife and do cut any deeper than necessary. The top and bottom should be rounded instead of forming a sharp point. This will facilitate movement of moisture and nutrients around the damage area. When done properly, healing will occur completely around the wound.

If the damaged area is less than 25 percent of the circumference of the trunk, the wound should gradually heal over and no permanent injury should result. If the damage involves more than 50 percent of the circumference, the tree may be seriously reduced in vigor. It may lose branches and become quite unsightly. However, the corrective procedures of pruning, irrigation, and fertilization should be practiced until the tree recovers or until it is evident that the tree should be removed.

Lawn mower and weed-trimmer damage
Injury and infection started by a lawn mower or weed trimmer can seriously threaten a tree's health. The most severe injury occurs when the tree bark is slipping (loose due to cambium growth), in early spring during leaf emergence, and in early fall during leaf drop. The site of injury is usually the root buttress, since it flares out from the trunk and gets in the path of the mower or weed-trimmer. Although large wounds are more serious, repeated small wounds can also add up to trouble. Injury can be prevented by the removal (by hand trimming) or prevention (use of a herbicide or mulch) of grass and weeds from growing at the base of the tree.

Wounds are serious enough by themselves, but the wounded tree must also protect itself from pathogens that invade the wound. These microorganisms often attack the injured bark and invade adjacent healthy tissue, greatly enlarging the affected area. Trees can be completely girdled from microbial attack following injury. Decay fungi also become active on the wound surface, and structural deterioration of the woody tissues beneath the wound will often occur.

Prepared by: Erv Evans, Consumer Horticulturist, NC State University

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