XIII The Mending of the Apple-Tree
Many accidents overtake the apple-tree. The hired man skins the tree with the harrow; fire runs through the dry grass; hard winters shatter the vitality, and parts of the tree die; borers enter; rabbits and mice gnaw the bark in winter; loads of fruit and burdens of ice crush the tree; wind storms play mischief; bad pruning leaves long stubs, and rot develops; cankers produce dead ragged wounds; fire-blight destroys the tissue; a poorly formed tree with bad crotches splits easily; grafts fail to take, and long dead ends are left; the tree is injured by pickers; vandals wreak their havoc. All these accidents must be met and the damages repaired. The surgeon must be summoned.
We must first understand how a wound heals on a tree. Note any wound,—knot-hole on the trunk, place where wood has been removed. The exposed wound itself does not heal; it is covered and inclosed by tissue built out from the edges or periphery of the wound. This tissue is like a roll. It is the callus. Eventually the tissue meets in the center, and the lid is thereby put on the place, and it is sealed. The exposed wood has died, if it is the cross-section of a branch or a deep wound, and it remains under the callus a dead body. If the wood has not started to decay in the meantime, the place is safe, but too often invasion has begun before the process is complete, the rot disease finally extends to the heart of the tree, causing it to become hollow. If the center of the wound falls in, the callus cannot cover it, and an open sore remains. In these cavities birds may sometimes build.
Therefore there are two points for the surgeon to consider in respect to the wound itself—whether it is so placed on the tree that the callus forms readily; whether the wound is kept healthy during exposure.
All ragged tissue being removed, deep-wound surfaces should be kept aseptic. For ordinary cases, white-lead paint with plenty of linseed oil is a good protective from the germs of decay. On old wood, no longer active, creosote is good, perhaps followed by coal-tar. Usually, however, paint is quite sufficient. Small exposures usually receive no dressing. When the fresh surface wood is exposed by removal of bark, it is necessary to keep the tissue from drying out, and antiseptics are usually not applied. Bandaging with cloth is the usual practice, after the wound is cleaned and trimmed.
The repairs fall into two classes,—those that require merely removal of injured parts and treatment of the wounds, and those that demand the ingrafting of new wood.
We have learned, in the discussion of pruning, that long projecting ends of severed branches do not heal. The branches to be removed should be cut back close to the larger branch or to the juncture with another. In repairing injured trees, all projecting parts that do not have life in themselves must be removed. All wounds should be left smooth, without splinters or hanging bark. Decaying wood is to be removed, and the area cleaned out and disinfected.
The nature-lover may find much to interest him in the observation of knot-holes as he comes and goes. Every knot-hole has a history; this history usually can be traced by one whose eye is keen and who becomes practiced in connecting cause with final result. One prides oneself on the ability to work out the obscure cases. An old neglected apple orchard thereby affords much entertainment.
If a very large branch breaks off, the remaining part is cut back to fresh hard wood; antiseptic is applied; the other part of the tree may be shortened-in to aid in restoring the proportion or balance.
Deep cavities caused by rot are cleaned out, disinfected with bordeaux mixture, gas-tar, or other material, and the place filled completely with cement.
In some cases, new wood is added in the form of cions of last year’s twigs. Such cions may be set around the edge of a stub, thrust between the bark and the wood, to start new branches where an important one was broken off. The cions are cut wedge-shape (much as those in Fig. 18) and a bandage is tied around the stub to hold them in place; the exposed parts are covered with grafting-wax. The operation is performed in spring.
Sometimes cions are used to bridge a girdle. Usually a girdle heals itself if the injury does not extend into the wood, and if it is bound up to prevent drying out; but when the injury is deep and the exposed wood has become dry and hard, the cions may be used. The cions are somewhat longer than the width of the girdle. The edges of the girdle are trimmed to fresh tight bark; cions are cut wedge-shape at either end; the ends are inserted underneath the bark at bottom and top of the wound; edges of the wound are securely bandaged; entire work is covered with wax. The cions are many, so close that they nearly touch. The buds on the cions are not allowed to produce branches. This process is known as bridge-grafting.
With some experience, the cultivator soon learns to make many deft applications of ingrafting. Sometimes a piece of bark may be used as a patch. In the bracing of crotches in young trees, the two trunks may be joined by uniting a small branch from either one, twisting them together to form a bridge like a bolt; they can be made to grow together, forming a solid union. Bolting the parts with iron rods, or holding them together by means of chains, is the usual and commonly the better method. The iron is not to go around a limb, however, for girdling results; the rods or chains should be secured by bolts bored through the wood and pulling against large heads or washers.
The usual repairs are easily made. When trees are badly injured, and particularly when the tree is low in vitality, it may not be worth while to engage in surgery. It may be better to plant a new tree. Saving very old trees by the mending processes is not likely to be satisfactory. The grower should transfer his affection to a young tree. If the tree has had good care throughout its life, it probably will not need much surgery in old age. The grower will be willing, when the time comes, to take a photograph for memory’s sake and to let the tree come to a timely and artistic end.