A one or two year old tree will have a central leader, or trunk, and several side laterals, called feathers. The lowest laterals should be removed when the tree is planted and the remainder cut to 10-15cm long, up to a height of approximately 1.5m. This can be done for you on the nursery if required.
After the first year the laterals on the lower half of the trunk should be removed. This should be done in early spring using sharp tools and cutting flush with the trunk. Check for, and remove, double leaders and basal shoots or suckers; and trim the head of the tree if necessary to maintain its shape.
The next year remove laterals on the trunk until you have the height of clear stem you require. Lightly prune the head, if required, to maintain shape.
Some trees are top worked. Any side shoots growing on the main stem below the graft and any suckers growing at the base of the tree should always be removed. The head of the tree should occasionally be thinned in winter to remove dead, crossing and weak branches.
Most trees of this age have had the feathers removed up to a height of 1.5m - 1.8m and are called standards. The crown of the tree has formed and only maintenance pruning is required.
These techniques are useful when growing trees for their ornamental bark or foliage. It is also used for certain varieties to keep the tree to a fixed height.
Coppicing is the process of winter pruning growth back to, or near, ground level. It can be successfully employed with the coloured stemmed willows, robinia, catalpa and paulownias. These trees can also be pollarded, along with tilias, platanus and eucalyptus varieties. Pollarding is similar to coppicing where the trees are cut back to a short trunk; it is practiced widely on the continent to control the final size of trees.