Home Is Where Your Trees Are

Repairing Tree Wounds. Part 1

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. Right after tracing and shaping any wound, shellac its edges to protect the newly exposed cambium. Then take your time carving and scraping smoothly off the wound's surface all shredded, dry, or discolored fibers down to solid sapwood, and apply a neat dab of tree paint. Do the same wherever a branch has been recently torn off its parent member, before decay can set in. (See Fig. 6.)

Branch torn off

A form of damage that often puzzles new tree owners is when bark, usually on lower trunks or limbs and especially in young maples, splits open and separates from the wood for no apparent reason. This is caused by frost action, after a midwinter or "false spring" thaw. It can injure trees severely. The thing not to do is peel off the loose bark, thus exposing bare wood, until callus growth at the edges of the wound is well begun, in late spring or summer. Then chip away the flaked bark, shape the lesions (with pointed ends) and paint them up, taking care not to paint the new callus. When you pruned your first tree you cut off some dead branches and stubs whose decay had progressed into the branch bases, penetrating beyond the cambium to form an incipient cavity. (See Fig, 7.)

One of these lesions, at a handy height, is a good place to try your hand at cavity repair. Besides your knife you will need for this work a 3/4-inch gouge (curved) chisel and a wooden or hard-rubber mallet. The object of your work will be, after pruning the stub (Fig, 7), to trace and shape the wound with your knife, to cut away all dead tissues in and around the lesion so that callus can roll in and make a healthy seal. (See Fig. 8.) Use your chisel, tapped by the mallet or the heel of your hand, to chip and shave away all discolored material down to living wood. Slope and smooth the excavation as you go and don't worry if, on this first attempt, you go deeper than you wish you had. Shape, smoothness, and perfect drainage are the important results. Careful painting and the healing process will in time take care of your slips.

Decay progresses in wood at about the same rate as growth, going chiefly in and down instead of out and up. When its invasion at a stub lesion has gone past the sap-wood into heartwood, you will not only have to gouge out the decay's top and back limits but also follow its inroads downward to their bottom, which may be surprisingly deep. That is where little stub lesions deceive us. In trying to heal shut at their original openings, they conceal their true depth and thus escape or postpone attention. To find out how deep the decay has gone, enlarge the original opening enough to let you probe downward with your knife or chisel. If you still can't find hard bottom, take test borings from the outside with a quarter-inch auger, slanting the bit upward so that the hole will drain when you do get a bottom one. What you do next will depend on several things, but your main objects will stay the same: to clean out all the punky wood possible, paint all the exposed good wood that you can reach, and establish free drainage of the cavity.