Trees and larger shrubs are vulnerable to damaging wounds to their bark and roots, caused by both man and nature. Some damage is normal to the tree or shrub's life, and if the wound is treated promptly and correctly, only scars will remain on the plant. If left untreated, wounds can be attacked by pest insects and disease spores possibly causing the ultimate death of the tree or shrub.
Symptoms and Causes of Wounds
Wounds can be caused in nature by storms, high winds, insects, and animals. Man does his share of harm with lawn mowers, automobiles, nails, fence staples, and grass trimmers. Every time you prune a tree or shrub you are creating a wound on that plant. A tree wound is any injury that damages living tissue. Living tissue includes external bark, phloem, cambium and sapwood in the sylem. The larger the injured area, the more vulnerable the plant becomes to insect or disease invasion.
Control of Wound Problems
Trees and shrubs have active defenses against wounds, an if conditions are good, can prevent most wounds from getting worse all by themselves. Usually the tree or shrub will produce a callus growth over the wound, closing it to insects and disease. More importantly, a healthy tree will wall off the area behind the wound with a barrier of resistant wood. You can can encourage this callus growth by protecting wounds from heat, light and drying out for four to eight weeks after the injury.
The normal approach to treating a wound is to paint it with a pruning paint sold at the local garden center or nursery. This treatment has come under some question in recent years, but the tree experts have yet to come to any agreement on the issue. Some say that feeding the tree or shrub and making sure it has sufficient water is the best way to treat a wound, and that the paint is not effective. It does no harm, but some experts believe it does no good either.
Some of the newer paints are made with a polyvinyl base which maintains a more elastic, durable, and crackfree protective coat. This material appears to be as effective as any in keeping a wound free of insects disease while keeping the plant's injured fibers from drying out. We recommend for any wound larger than 6 inches in diameter, you use this flexible paint to protect the injury from insects and disease.