Branches are essential to the life of a tree but sometimes they may need to be removed for reasons of safety or for aesthetics. If the tree is to be grown for timber, then the owner may want to remove all the branches up to about 6 metres above ground level as this will create knot-free timber for the future that will be of greatly increased value.
When a live branch is removed from a tree, a wound is created its stem. Trees cannot repair damaged tissue but the wounds are walled off, or compartmentalised. Good pruning technique involves retaining the branch-bark ridge (see illustration below) that will maximise the tree’s ability to achieve this compartmentalisation. Bad technique can lead to fungal infections, decay and attacks by some insects.
Best practice guidelines:
- Do not use flush cuts, instead follow the red line on the left of the illustration above. Cutting too close to the main trunk causes an excessively large wound and removes the natural tissues (the branch-bark ridge), affecting the mechanism that promotes healing.
- Do not leave branch stubs. These may decay but meanwhile the diameter of the trunk will have to increase sufficiently to cover the stub, which can take several years.
- Always cut as closely as possible to the outer edge of the branch-bark ridge, but do not cut into or behind the ridge or into the branch collar.
- Pruning dead branches also requires care to reduce the risk of injury to the tree, and to promote fast healing. Do not cut into the living callus collar that forms around the base of a dead branch (see branch on right of illustration above).
Technique for large branches:
- Do not risk tearing the bark and wood fibres below the cut when removing larger branches. Remove most of the branch weight by using an under cut (1), followed by a top cut (2) to remove most of the branch, and then remove the stub (3) – see illustration above.
- (1) When under cutting do not cut too deep or the weight of the branch will pinch on the blade and even jam it completely.
- (2) The top cut should be slightly further out along the branch from the under cut.
Some other important pointers:
- Do not use wound dressings to cover pruning cuts, as was once recommended. They are ineffective and may even hinder the healing process.
- Clean your pruning tools before moving onto the next tree. You may inadvertently spread fungal and bacterial infections between trees.
- Finally, some health and safety tips: if you are pruning above your head wear a helmet and eye goggles, and be careful when handling sharp pruning tools.
The illustrations here were first prepared for a leaflet I produced on High Pruning; one of a series of practical guides that I illustrated and co-authored for the charity Woodland Heritage.