Like light pruning, the repair of wounds and cavities, and the bracing of trees' weak spots, are good things for the home owner to practice on a small scale, or to study and supervise, if only because they will help him to recognize the larger needs of his major trees when he does call in professionals.

What a scalpel is to an m.d. a jackknife is to a tree owner: his tool for preliminary work on wounds of all degrees. Pocket arsenals can be bought which contain every weapon from a can opener to a farrier's awl, but for tree repair only two knife blades are needed. One should have a long, narrow "toad-stabber" point for probing and picking out. The other should be short and sturdy with a more rounded end and a fine-honed cutting edge, for tracing and carving.

Tracing is when you incise around a wound to cut back to undamaged bark, and bevel its edges down to the juicy cambium layer. From those juices will grow the callus that is a tree's scar tissue for healing its wounds. Basic to the repair of all tree wounds is remembering that a tree's sap circulation is longitudinal, not lateral, throughout all its members. To help any wound heal you must shape it at both ends into points, like the ends of an ellipse. This lets the cambium channels merge again after having been separated by the wound's width. Within these rejoining points callus will form evenly, without interruption, about a half inch each growing season.

No abrasion or slashing of the bark deep enough to damage the cambium layer should be ignored, especially in young trees. Bark lesions are just like bleeding cuts in your own skin. Great sores from little lesions grow, or can grow, and they are a pleasure for any tree lover to mend when he finds how simple it is.