The following are sections extracted from chapter eight of The Fruit Tree Handbook by Ben Pike.
Why prune fruit trees?
One way to find out why fruit trees are pruned is to look at what happens when a tree is not pruned. The photograph below shows a plum tree that is only five years old; it has never been pruned and, despite its tender years, it already has a number of branches growing in an unruly fashion that will hit each other as soon as a strong wind blows. As the tree grows, it is likely to become a mass of tangled branches; it will still fruit, but little sunlight will find its way to much of the tree where it is needed to ripen the fruit. Long, unpruned branches will break in the wind or through the weight of a heavy crop, and disease is likely to enter when broken branches are not pruned back to leave a clean cut. Over time, fruit on an unpruned tree tends to become smaller and suffer from fungal diseases, which thrive in the moist environment that arises when there is little airflow through the tree.
There are many reasons for pruning:
- Forming a sound framework of branches that will provide a strong base for the tree during the rest of its life. This is known as formative pruning.
- Maintaining a balance between the vegetative growth and fruit production.
- Stimulating new growth of healthy young wood.
- Ensuring that the tree is stable and not prone to blow over or lose branches in strong winds.
- Increasing fruit production by allowing sunlight to reach the fruit and wood. Both the fruit and the wood need sunlight for ripening.
- Replacing exhausted growth with new branches.
- Removing dead, diseased and damaged wood. Fungal canker is a good example of a disease that can be controlled by pruning.
- Encouraging the tree to grow into a form that is desired, such as an espalier, spindlebush or standard.
Learning how to make pruning cuts in the correct fashion will ensure that your pruning has the desired effect, rather than opening the tree up to disease and potential structural weakness.
Small pruning cuts
Small cuts are those made with secateurs, usually to a particular bud whose growth you want to encourage. When cutting to a bud, the cut should be gently sloping, slightly above the bud.
Cutting to a bud will encourage that bud to grow on, so the direction that the bud is facing will determine the future direction that the branch takes. For this reason, pruning is usually to an outward-facing bud, encouraging growth towards the outside of the tree (see Diagram 19). However, it is not only the topmost bud that will shoot after pruning; the first two or three buds are likely to form strong shoots. A bud that is likely to form a shoot heading in the ‘wrong’ direction, usually inwards, towards the middle of the tree, can be rubbed out with your finger at the time of pruning.
Larger pruning cuts
Larger cuts are those that need to be made with loppers or a pruning saw. While it is all right for smaller branches to be cut to a bud in the middle of the branch, larger branches should be cut to a junction with another branch, as in Diagram 20, or to the trunk of the tree. The branch that you cut to is known as the replacement branch: this is usually a younger branch that will replace the growth that is being cut. Avoid leaving a stub when cutting larger branches: this stub will either put on new growth in an inappropriate way, or die back.
If you are cutting back to a replacement branch, this should be at least a third of the size of the branch that you are cutting, to ensure that the replacement branch is able to take up the vigour of the main branch. Alternatively, a large branch can be cut back to its origin from the trunk of the tree.
Where it is necessary to cut back to the trunk, trying to remove a branch with just one cut can lead to the weight of the branch tearing the bark on the trunk of the tree. Diagram 21 shows the correct technique for removing a large branch, by making several cuts. Firstly, an undercut should be made about 40cm (1’4″) away from the final cut. This cut should be around a third of the way into the branch. This is followed by a downward cut, slightly further away, which will remove the branch without any tearing of the bark. What remains is a small section of branch that can be supported while the final cut is made. This final cut should be just outside the branch collar. Like all pruning cuts, it should leave a clean surface without any tearing or roughness. Any imperfections can be cleaned up with a sharp pruning knife.
The use of wound paints to protect a cut from disease is now recommended only for the stone fruits – plums, cherries, peaches, nectarines and apricots. See page 140 for more information on wound paints.
We hope you have found this extract helpful. For information on pruning principles, the best time to prune fruit trees and to read the rest of The Fruit Tree Handbook you can find it here.