Pruning Deciduous Trees
The major reason for pruning a deciduous tree is to create a well balanced and attractive framework of branches. As described in Training and Pruning Young Trees, the central stem should be straight and the branches properly spaced. Once a deciduous tree is well established, there is often little need for further pruning.
When to Prune
Any pruning work carried out on deciduous trees should take place in the dormant season (late autumn or winter). As their sap pressure is high during late winter and early spring, you should avoid making any cuts during this period, as they will tend to 'bleed'. This loss of sap can weaken a young tree. Some trees such as horse chestnuts (Aesculus), birches (Betula), cherries (Prunus) and maples (Acer) have a tendency to bleed extensively and so should be pruned in mid-summer after new growth has matured.
Removing Congested Branches
However, occasional work may be necessary to remove congested branches from the centre of the tree, as these will restrict the amount of light and air that reach the central branches. Cut back inward-growing shoots and any branches that have become too dominant and unsightly. This work should be carried out in autumn or early winter to prevent sap from bleeding from the cuts.
Removing Competing Leaders
You may also need to undertake some judicial pruning if the tree develops two or more competing leaders. The narrow angle between these two branches can act as a focus for structural forces and may cause the tree to split open during high winds. Prune away the weaker, competing shoot by making a clean cut at its base. Make sure that you do not damage the remaining leader.
After pruning, a tree may grow epicormic (or water) shoots around the wound. Either rub them out with your fingers, or cut them back and rub them away as they re-grow.
Pruning to Reduce Size
If a tree outgrows its situation, avoid the temptation to simply trim around the whole tree to reduce its size. This approach (often known as 'haircut' pruning) will lead to the production of clusters of shoots on knobbly branches, which not only look unsightly, but will also diminish the production of flowers and fruit.
It is much more effective to carry out a more gradual programme of reduction by firstly removing any damaged or dead wood and any branches that cross or rub against each other or that spoil the framework. The following two years, thin out the sideshoots that result from the initial pruning to create a well-balanced framework. Remove any suckers or water shoots as soon as they appear. This technique may also be used to renovate a neglected tree.
After pruning, feed the tree by mulching with well-rotted manure. After renovating a tree, you should also apply fertilizer to the ground underneath the canopy in spring for two to three years.