While many trees will naturally form their adult shape as they grow, others need a little assistance to create a clear trunk and a well-spaced canopy of branches. It is wise to keep an eye on young trees and carry out formative pruning as required.
This technique is suitable for young trees, from one-year-old until their formative pruning is completed after about four to five years. Most trees sold in garden centres will already be at least partially trained.
One-year-old trees are called ‘maidens’ and are sold as feathered or un-feathered.
Feathered maidens: are sold with their sideshoots attached. On these plants, the side shoots have been kept on and will form the main branches. These trees may be more expensive than un-feathered maidens.
Un-feathered maidens: are sold without their sideshoots, as a single stem. They are often cheaper than feathered maidens, and almost as satisfactory.
When to carry out formative pruning of trees
Pruning of deciduous trees (those that lose their leaves in winter) is often best carried out in winter, as it is easier to see the branch structure.
Pruning of evergreen trees is often carried out in April, as they come into growth.
Exceptions to these rules include tender deciduous trees, best pruned in spring, once the risk of frost has passed, and also stone fruit trees (cherries, flowering cherries, apricots, peaches, plums and nectarines). These can be pruned in winter while young, but are later best pruned in summer. They can be at risk of catching the diseases silver leaf and bacterial canker if large branches, those thicker than your wrist, are pruned in autumn or winter.
How to carry out formative pruning of trees
Most ornamental trees are trained in a central-leader standard, with a clear trunk and a head, or canopy, of branches.
Forming a central-leader standard tree
Young trees can be trained to grow as standards with a 1-2m (3¼-6½ft) trunk.
Where trees grow with a clear central-leading branch that grows upwards ahead of the other branches, it is important not to cut this central leader, as this could spoil the final shape of the tree.
- Remove all side branches from the lower third of the main stem
- Shorten by half all the sideshoots on the middle third of the main stem
- Leave the sideshoots on the top third of the main stem unpruned, apart from the removal of dead, diseased or damaged growth
- Cut to outward facing buds, so that the resulting growth extends outwards rather than into the centre of the tree
- Remove completely the sideshoots that were shortened by half in year one (which should be now be in the lower third of the tree)
- Shorten by half the sideshoots on the middle third of the tree
- Remove any crossing or misplaced branches in the upper third of the tree
Follow the same steps as for year two.
Years four and five
- Clear the trunk of side branches to the height desired
- Continue to remove any crossing, dead, diseased or misplaced branches from the canopy
Then proceed as for a mature specimen, following the advice for the tree in question from a book such as: RHS Pruning & Training by Christopher Brickell and David Joyce, available to buy online from the RHS Book Shop.
Growing a central-leader standard as a branched-head standard to control its size
Some trees, oaks for example, develop as central-leader standards while they are young, but then lose their leader naturally after a number of years, and develop as branched-head standards.
It is possible to reduce the final height of trees that would otherwise grow as central-leader standards by removing the leader and pruning as a branched-head standard.
It is advisable to check in a book first as to whether this technique is suitable for the tree in question, as some trees can be spoiled in shape by premature removal of the leader.
Years one to three
Follow the steps above as for a central-leader standard.
- Remove the leading shoot, cutting to an uppermost strong sideshoot
- Leave three or four sideshoots in the top third of the tree unpruned to form the branches of the branched-head canopy. Only remove any badly placed branches or those that are crossing or rubbing
- Shorten the sideshoots on the middle third of the tree by two-thirds, leaving stubs that can form replacement branches if needed
- Remove all sideshoots from the lower third of the tree, to start creating a clear trunk
- Remove any strongly upward-growing branches that threaten to dominate the canopy
- Remove any crossing or rubbing branches
- Shorten the canopy branches and sideshoots a little to balance the shape. Cut to an outward facing bud to encourage open growth
- Clear the desired height of trunk of any growth. If new growth is stimulated from the trunk by this pruning, rub off the shoots as soon as they emerge
Where upright shoots threaten to compete with the leader of a central-leader standard tree, then a single leading shoot will have to be selected, and the others removed. Choose one that is upright and in line with rest of the tree.
Where the leader is broken by wind, snow or accidental damage, then cut it back to a strong side shoot that is growing fairly vertically. Attach a cane to this side shoot and tie the shoot in to the cane as it extends, training it upwards as a new leader.