Bark grafting as a method of wound treatment in urban trees

The major hypotheses regarding tree responses to wounding are reviewed. Particular emphasis is placed on cellular activity, and callus formation, in relation to the isolation of damaged and diseased wood in living trees. Four models, that describe the development and subsequent restriction of decay in living trees, are identified and discussed. While the pool of knowledge regarding tree responses to wounding and damage is substantial, understanding of the processes involved is incomplete. Having considered existing scientific literature, a series of trials investigated an alternative approach to wound treatment. Conventional arboricultural practice dictates that limb removals should be just outside the branch collar to encourage maximum callus formation and speedy wound closure. Large trunk wounds should have the wound edges clear of ragged tears so that callus growth will eventually enclose the site. In some instances large wounds can be treated with bridge grafts. The trials undertaken investigated the possibility of using bark patch grafts to treat wound sites on living trees. Trial 1 involved six tree species; Acacia dealbata, Banksia integrifolia, Eucalyptus viminalis, Platanus acerifolia, Pinus radiata and Quercus robur. Trial 2 involved only two tree species; Corymbia maculata (syn. Eucalyptus maculata) and Populus deltoides X tricocarpa. At the completion of both trials it was apparent that bark patch grafts successfully reattach and that they may assist the rate of callus formation after wounding. The use of bark patch grafts, as tree wound treatments, is therefore acceptable as an arboricultural technique. A series of recommendations are offered as guidelines to practicing arborist