THE TREE DOCTOR AND THE NEGLECTED WOUNDS
Wounds due to the unskillful removal of large limbs, or to the breaking off of limbs by the wind, or to injury by rabbits or field-mice -- in short, to barking from any cause -- as when an auto in the hands of an incompetent driver attempts to climb a tree -- should be promptly disinfected and water-proofed.
Cavities in a tree are treated substantially as a dentist treats a tooth, and they originate from the same cause, neglect. Often they begin with improper pruning. But, whatever the cause, the first thing is to remove all the decayed or insect-infected wood. For tree dentistry all the tools needed are a gouge, a mallet, a chisel, and a knife. In cutting around the edge of a cavity, use nothing but very sharp tools, as dull ones will injure the cambium. The cambium is the thin layer of tissue which slips so easily in the spring when you loosen the bark to make a whistle. It is like thick sap and was formerly supposed to be sap. It is from this tissue that new wood originates on one side and new bark on the other. A comparatively slight injury will kill portions of the cambium, and once killed the dead area can never again give rise to bark or wood.
As soon as it has been cut away, in removing all the decayed portion of the wood, the cambium and edge of the bark should be given a coat of shellac. Then the remainder of the cavity should be sterilized by applying creosote with a brush. This is to prevent further infection. After the creosoting, the tree is protected from moisture by a heavy coat of coal-tar. The cavity is then filled with cement.
HOW THE TREE SURGEON REMOVES LIMBS
All this we might call "tree dentistry," but both the filling of cavities and the removal of limbs come under the head of "tree surgery." In the strictly surgical operations the same precautions have to be observed as in the dentistry: namely, to remove the limb so as not to tear the bark or injure the cambium, and to sterilize, shellac, and water-proof the scars. The surgical instruments are a saw -- for large limbs a good-sized saw, with teeth set so as to make a wide cut -- a mallet, a gouge, a chisel, and a knife. For limbs high up, one or more ladders may be used. A steady head and ability to climb are necessary for work in the top of a tree. Tennis-shoes, or other soft-soled shoes, should be used in climbing about in a tree, to prevent injury to the tree and also to the climber, who is thus less liable to take a tumble.
Of course anybody can saw off a limb; but here, as so often happens, a little knowledge is a dangerous thing, and a little more will often save a dear old friend of the family and the neighborhood. Three cuts, each in a different place, so Uncle Sam's experts tell us, are necessary in the removal of a limb of any considerable size, otherwise the limb will strip the bark as it falls. So you make a preliminary cut on the under-side, from six inches to a foot beyond the point where the final cut is to be made. This cut should be from a quarter to half way through the limb. A good time to stop cutting is when the saw becomes pinched in the cut. A second cut is then made on the upper side of the limb, an inch or more beyond the first, and continued until the limb falls. A third cut, to remove the stub, is then made close to the trunk. When nearly severed, the stub should be supported so as to avoid any possibility of stripping the bark on the trunk as it falls.
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