Pruning Fruit Trees
Pruning can be used to control growth, remove dead or diseased wood or stimulate the formation of flowers and buds of fruit trees. Young trees are primarily pruned to create a strong, balanced framework and attractive shape. However, the main objective for established trees is to obtain an abundant crop of fruit as opposed to a tree with a profusion of lush yet unproductive foliage.
The Risks of Under- and Over-Pruning
Under-pruned trees tend to produce large crops of small, worthless fruit, with much of the crop out of reach at the top of the tree. This can cause damage to the tree as the branches may break under weight of the fruit, and crop production may become biennial (that is, only bearing fruit every other year).
On the other hand, over-pruned trees tend to produce light crops of large, flavourless fruit that does not store well. Pruning is therefore carried out to achieve a good balance between leaf growth and fruiting spurs, with the leaf growth providing sufficient energy for the trees to crop satisfactorily.
Formative Pruning
Formative pruning of fruit trees such as apple (Malus domesticata), pear (Pyrus communis), quince (Cydonia oblonga) and medlar (Mespilis germanica) trees should be undertaken during the dormant period between November and March during the first four years of the tree's life. This will enable the tree to develop a strong framework capable of bearing the weight of the crops that will be borne in later years. This regime initially involves hard pruning; however, in later years pruning will be lighter and carried out in order to encourage fruiting.
Young pome (stone) fruit trees such as cherries (Prunus avium), plums (Prunus domestica), peach (Prunus persica) and apricots (Prunus armeniaca) should not be pruned during the dormant months; any work should be delayed until spring.
Year 1 - The Maiden Tree
Immediately after planting, trim maiden whips (trees with no side shoots) to about 75 cm (30 in) high. Cut just above a healthy bud, ensuring that there are at least two more healthy buds below it. This pruning will encourage the production of primary branches during the first growing season.
Feathered maidens (trees with several side branches) should be trimmed back to three or four strong shoots at 75 cm (30 in) from the ground. Side shoots should be shortened by two thirds of their length to an upward or outward facing bud and any shoots on the lowest third of the tree should be removed flush with the stem.
Year 2
Remove shoots from the lowest third of the tree and then prune between three and five of the best placed shoots by half to an upwards or outwards facing bud. These will become the tree's main structural branches. Remove any inwards facing shoots.
Year 3
Remove stems from the lowest third of the tree and then prune the leading shoots of branches selected to become the framework by half to a bud facing in the desired direction. Select four healthy, well-placed laterals to fill the framework and shorten these by a half. Prune any remaining laterals to four buds to form fruiting spurs.
Year 4
By this time, the tree should have begun to fruit, and so only limited formative pruning should be required. Shorten leaders by one third and prune any laterals not required to extend the framework to four buds.
When pruning, always take into account the vigour both of the individual shoot and of the whole tree. Vigorous growth should be pruned lightly by completely removing a small number of shoots and leaving the remainder unpruned. Weaker growth may be pruned more severely. However, it is always a good idea to make sure that the weakness is not being caused by disease.
Annual Pruning
When the tree has been planted for more than four years, it is considered to be established and should be annually pruned. Most fruit trees should be pruned during winter; however, established pome fruit trees such as cherry, plum and peach should only be pruned in the summer.
Fruit trees may be divided into two main categories: tip bearing and spur bearing. It is important to distinguish between the two varieties before pruning so that the correct technique may be used. Spur bearing trees bear most of their fruit on older wood, whilst tip bearers bear their fruit not on spurs but at the tips of slender shoots grown the previous summer.
Tip Bearers
Tip bearers such as acid cherries (Prunus cerasus) produce their fruit on one year old wood; when pruning, remove approximately one third of the older wood and trim any long new shoots (more than 22 cm/9 in) lightly. Any shorter maiden shoots should be left untouched as they will have fruit buds at their tips.
Spur Bearers
As spur bearers tend to produce their fruit on wood that is two years old or more, it is important that many of the older shoots are retained. Cut back the leading shoots on each branch; strong shoots should be cut back by a quarter, whilst weaker ones may be halved. Cut back strong side shoots to six buds and weak shoots to four.
Overcrowded spurs should be thinned out to improve fruit quality. The weakest shoots should be removed from each spur; remove approximately one-third to create an open spur. The total number of spurs on a branch can be reduced by removing any weak ones.