Pruning Requires Knowledge Of Function Of Tree Parts

Press, Volume CX, Issue 32351, 17 July 1970, Page 6

Pruning Requires Knowledge Of Function Of Tree Parts

Pruning has been a recognised principle for successful fruit culture for many years. It may have arisen originally as a means of regulating the size of the trees and to restrict the production of inferior fruit, or obviate boughs touching or bearing down on the ground. Subsequently, experimentation proved beyond doubt that thinning of branches resulted in better quality fruit.

I From the old methods use ■ the present systems have been (evolved and doubtlessly trials 'will yet present us with considerably different concepts in the future. Climatic, soil and economic factors play an important part in the evolution of suitable systems. For instance the high-headed trees used among other systems in cooler regions of the world would not be successful in areas of considerable heat as the long exposed trunks would be burnt. There are many apt definitions of pruning which, from a purely economic point of view, could be said to be the removal of portions of a tree for the purpose of increasing the potential of the remaining limbs. The definition implies a knowledge of the parts and functions of the tree and without this knowledge it is not possible to prune correctly. There is some difference between pruning ornamental trees and shrubs, and fruit

trees. Often the primary objective with the former is to attain desirable shape although inducement to flowering sometimes also plays a major role. With fruiting subjects, after the initial shaping has been obtained, it becomes incidental to the main task of providing a bountiful fruit crop. Observations of old unpruned fruit trees will have revealed the tendency for fruit to be borne predomi’nantly near the extremities of the branches. Fruit is generally small, often prolific. The branch system is dense crisscrossing and with much bare or dead wood. The centre is dark and difficult to reach. Sunlight and air circulation is very restricted to all by the outer regions of the subject. Buds, leaves, spurs, even large branches will not mature properly if the foliage is too dense. Sunlight is essential for energy production, which enables the carbon dioxide of the air to be converted into food. In addition oxygen is required for respiration. Development is curtailed and greatly reduced if air and light are restricted. The fruiting subject is (there for the crops it is expected to produce. As has al(ready been noted unpruned (trees become partially barren. Therefore some form of (regulation is improvised to (ensure a continuity of such—• ’the art of pruning.

There are many pests and diseases which manifest themselves on fruiting stock and it becomes necessary to implement some form of spray schedule over the growing season to minimise and control outbreaks. This cannot be effectively achieved on a cloud scraping jungle of branches. Pruning is thus designed to achieve certain specific objectives which are briefly summarised as follows: (1) A shaping and thinning process by which branches are so spaced that all parts of the tree receive ample light and air. (2) Improving size and quality of the fruit by regu-

lating the* fruiting wood and ensuring that there is replacement wood available, the aim being a well balanced distributing of fruit on the tree. (3) providing a strong framework to support a development of healthy productive shoots at the same time maintaining a balance between growth and dropping. (4) Pruning is also designed to assist in obtaining adequate spray cover to all parts of the plant to enable all other cultural operations and harvesting to be carried out without impediments. The accompanying diagram shows some of the points of pruning.