If you have taken care with planting your trees and with their routine maintenance during the early years, between seven and ten years according to the tree species and site, you will have reached the stage at which the trees will need to be pruned. There are a number of reasons to prune the trees.Pruning for quality timber | Pruning for pasture management
The overall objective of the formative pruning of broadleaved trees is to achieve a single, straight stem at least 5 metres in height and free from branches leaving it virtually defect free and able to attract a high market price. Poplar should be pruned higher, to a minumum of 6 metres and a maximum of 9 metres. The objective with conifers is similar but the defect-free stem is usually expected to be only 3.5 metres to 4 metres in length.
A balance must be struck between removing side branches with their green leaf and the subsequent growth of the tree. Broadleaved trees can be pruned up to between one-third and one-half of their total height. Conifers can be pruned up to one-half or even up to two-thirds of their total height when they are older. This will, of course, reduce the rate of growth of the trees but will result, in the longer term, in a greater volume of quality timber.
You may already have been pruning as described in the establishment phase management to ensure a single stem on each tree by removing the weaker or shorter shoot if a fork forms. You should continue this practice if forks develop as the trees grow.
Trees grown at wide spacing tend to develop heavy side branches. This varies greatly with species and provenance; the initial choice of trees which will have light branching is an obvious benefit in this respect.
Click here for examples of what material to remove from trees in formative pruning.
Formative pruning is designed to produce a single, straight stem. It should be carried out when the branches and forks are light enough to be removed with secateurs or a pruning knife. Formative pruning is generally carried out while the trees are still young. Some examples of formative pruning are shown in the diagram below. The red branches in the upper set of pictures have been removed to produce the single, straighter main stems in the lower set of pictures. Click here for when to prune.
The following table shows the best time to prune some broadleaved species based on Forestry Commission research looking at wood staining and dieback. The table also shows the best timing for pruning conifers in general. In most cases, it is best to prune in summer. However, this may have a bigger impact on the trees than winter pruning because of loss of sugars in bleeding sap and in leaves removed. Winter pruning may fit better with other farming pressures and it is better to prune in winter than not to prune at all. Wild cherry is the exception to this and should always be pruned in summer to avoid infection from silver leaf disease. Click here for how to prune trees.
Pruning method:A pruning cut can be a point of infection for various diseases and this risk must be minimised. A good clean cut is essential. This will also avoid the risk of damaging the bark on the main stem below the pruned branch. Most tree species produce an obvious branch bark ridge in the junction between the main stem and the branch. This ridge should not be damaged by the cut, if it is, infection can spread rapidly. The correct pruning cut should be made as close to the stem as possible without breaking the branch bark ridge. See diagram (a) which shows a single cut for a branch which is light enough to be pruned with a knife or with secateurs.
|The branch should not be cut flush with the main stem of the tree (diagram (b)) but at the angle shown in diagram (a). A flush cut can damage the branch bark ridge and creates a larger wound which can more easily become infected.|
| If the branch is
heavy, it will probably require to be cut with a pruning saw and it may fall,
tearing the bark on the main stem when it is weakened by cutting. In this case
most of the weight of the branch can be removed by making two preliminary cuts
as shown in diagram (c). This requires more work, emphasising that it is better
to prune when the branches are light than to leave pruning until the branches
are heavy and a saw is required.
Click here for information on which tools to use for pruning.
Diagrams adapted from the Forestry Commission Handbook 9, Growing Broadleaves for Timber. © Crown copyright material is reproduced by permission of the Controller of HMSO and Queen's Printer for Scotland.
For light branches (up to ½" (1 cm) in diameter) a pruning knife or a pair of hand secateurs will be adequate. For slightly heavier branches (up to 1½" or 2" (4 - 5 cm) in diameter), a pair of double-handled loppers may be required. Double-handed loppers can be used for light branches and can, over many hours of pruning, prove to be less tiring than using one-handed secateurs.
For heavy branches (greater than 1½" or 2" (4 -5 cm) in diameter), a pruning saw will be required.
When the stem to be pruned is above head height and up to 5 to 6 metres off the ground, a telescopic pruning saw will be required (see photo). Any pruning above 5 to 6 metres off the ground will require a tractor-mounted lift platform or "cherry picker"
Pruning tools should always be kept sharp to ensure a clean cut.
Whatever tools are used for pruning, a strong pair of work gloves will help to minimise the risk of blistering. When branches to be pruned are above head height, a hard hat must be worn.
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If trees are pruned regularly to half of their total height when the branches are still light enough to be cut cleanly with secateurs, it is unlikely that a separate pruning exercise will be required to reduce the tree canopy for the main purpose of allowing more light through to recover pasture production.
If the trees have been regularly pruned to encourage good timber quality and pasture production is falling to unacceptable levels, it will be necessary to thin the trees by selective felling. Selective felling involves the cutting down of the trees which would otherwise produce the poorest timber. Trees with the poorest growth form, such as bent main stems, heavy branches, pruning damage and those with the potential to produce the shortest logs should be removed first. If the trees have reached the stage at which selective felling becomes an issue, it will be advisable to call in an expert to provide professional advice from, for example, members of the Institute of Chartered Foresters.
If the branches of the trees have been allowed to become long and heavy, and, as a consequence pasture production has been lost due to shading, pruning may be necessary to recover pasture production. Under these circumstances care should be taken, as described in the section on pruning methods, to avoid damage to the bark of the main stem of the tree through bark tearing below the heavy branches as they fall to the ground during pruning.