The reasons for pruning are:
(i) To secure a desired form or height of the plant;
(2) To remove injured, diseased, or dead branches;
(3) To renovate or rejuvenate old plants;
(4) To maintain a balance between root growth and top growth (as shown in the operations of transplanting);
(5) To encourage the production of an abundance of flowers;
(6) To encourage the production of a few large flowers;
Pruning, however, is only a phase in the care of plants and must be accompanied by constant good cultivation, feeding, and management of plants. It is only through the process of intelligent pruning that shrubs especially can be maintained in a definite and natural condition of growth and also kept at a correct height to avoid in many instances the out-growing or over-powering of the design for which they were selected to become a part. Many incorrect ideas have become prevalent concerning the process of pruning, and the application of these incorrect methods often causes a slowing up or incorrect development not only in the growing habits of the shrubs but in the quality and the quantity of the flowers produced.
Pruning should be done only with a definite ideal and after arranging an intelligent program. No set rules can be offered. Climatic conditions may cause rules correct in one locality to prove valueless in another, and plants of the same species often vary in their habit of growth at different ages, and must be pruned accordingly. Pruning should be entrusted only to a careful workman. It is too common practice in pruning to have shrubs and trees with all the tips lightly snipped off with regularity; or to have trees with the main and lateral branches ruthlessly lopped off. The natural habit of the plant should be known and this form preserved when removing any wood. This fact should always be kept in mind except in the case of shrubs or trees which are to be trained in artificial shapes.
Pruning always arrests but does not permanently change the natural habits and growth of a plant. It often causes the plant to assume temporarily another form than it would naturally assume. Pruned plants constantly struggle to return to their natural habit, and when pruning has been undertaken for a specific purpose it should be continued throughout the life of the plant so long as that purpose is desirable.
Root pruning tends to reduce wood production and hence to increase fruit and flower production. Top pruning favours wood production and thus more top is produced by the seemingly contrary process of cutting it off. In the case of transplanted stock tops are cut back to compensate for the roots that are lost in moving. Removal of excess top growth insures to the remaining parts of the plant more nourishment, with subsequent better development, and it also decreases the area of leaf surface and the consequent evaporation of stored-up moisture before the roots begin functioning in the new location.
Pruning shears, pruning knives, and hand saws are the best tools to use. Pole saws and hooks should be avoided as they leave ragged wounds, and pole pruners should be used only for small twigs. Never use double edge saws as they are more apt, in the hands of a careless workman, to injure the tree. A ladder will be required for the larger trees and a block and ropes for removing limbs that are near wires or that might injure property.
For dressing wounds gas tar and liquid asphaltum have proven the most satisfactory. They hinder healing the least of the common dressings and are the most durable, adhesive, and antiseptic. Coal tar and pine tar seem to be injurious and white lead apparently has no injurious or antiseptic effect. Dressings give only physical protection and cannot hasten healing, which takes place through the activity of the plant itself.