HOW TO CUT OFF A LIMB "The best pruning tool is the thumb and finger." So it is, even for trees in their infantile stages. Pinching back tender shoots forms the tree's head to the owner's liking, and yearly attention keeps it under control. This is the ideal way. In practice, however, limbs must be cut off—sometimes very large ones. Pruning knives and shears and the long-armed, strong-jawed pruners will easily cut limbs to an inch or a little more in thickness. After this, a good saw is the right tool. Axes and hatchets are unfit for use in pruning, as they leave the cut surface uneven and tear the bark.
The limb should be sawed off smooth and clean on a level with the surrounding bark. There will be some projection, inevit ably, for the limb has a flaring base. But no projecting stub of the branch itself should be permitted to remain. Better far a larger wound made by sawing well down in the enlarged basal part. If any tearing of the bark has occurred, unevennesses should be trimmed with a sharp knife.
The healing of the wound must be a slow process, for the inner bark has to a layer of new tissue that gradually rolls in and closes over the solid wood at the centre. There is no union between the wood and the healing bark, for the former is practically dead. Being porous, it absorbs rain that follows down its tubular wood fibres. Germs of wood-destroying fungi,
afloat in the air from rotting trees and twigs in the neighbourhood, lodge in the exposed wound, germinate, and send their filamentous hyphx down into the stub and on toward the heart of the tree. Sugary, starchy cell contents moistened by the rain make the best possible soil for such fungi. Better leave the tree unpruned than to expose the inert heart wood by careless work.
A covering of any waterproof substance protects the helpless tree against invasion by its worst enemies. A cheap oil paint like linseed oil and white lead fills the surface pores and lasts a long time. It should be generously applied, so that no entrance is left for disease. It likewise checks the bleeding, or flow of sap, which dries the exposed stub and makes more room for rain to enter with its accumulation of dirt and disease spores. Meanwhile, the new bark rolls in, and when it meets over the wound the paint has served its purpose. The covered wood has been kept sound. It is often years before the process is complete, depending on the size of the wound and the rate of the tree's growth. In many cases the paint needs renewing.