Management - Thinning and pruning

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Trees are planted at a high stocking to enable selection and ensure competition for light, moisture, and nutrients to suppress branch development and encourage the trees to grow straight. As trees grow larger they begin to compete more strongly with one another. Thinning aims to reduce this competition by removing the less vigorous and poorly formed trees and allows the better trees to grow larger over a shorter period of time. Many growers are reluctant to let any of their trees go to waste but without thinning, the stand would eventually become stagnant, unproductive and susceptible to disease and insect attack.

Pruning in autumn and winter is recommended as trees pruned during spring or summer are placed under greater stress. There are two types of pruning: form pruning and clearwood pruning. The aim of form pruning is to correct the form of a young tree by removing faults such as forks and large branches. Have a close look at the trees in your plantation. If you cannot spot at least two straight, vigorous trees out of every five in a row, form pruning is recommended. Form pruning is best carried out from when trees are about 2 m tall. The aim of clearwood pruning is to minimise the diameter of the knotty core within the trunk and produce knot free wood which will have greater strength, a cleaner appearance and may be sold at a premium.

Pruning too early or too heavily slows tree growth unnecessarily while pruning too late delays the production of knot free wood (clearwood) and allows large branches to develop which are difficult to remove. It is best to remove branches before they exceed 2.5 cm in diameter and it is important that branches are pruned when they are still alive and green. As a general rule no more than 50% of the crown should be removed at anyone time. If too much foliage is removed, new shoots may develop from the main stem, negating the effect of the pruning carried out.

Timing is the key when carrying out thinning and pruning. If correctly done it can shorten the rotation length and improve the monetary value of the plantation.

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