Pollarding is a method of pruning that keeps trees and shrubs smaller than they would naturally grow. It is normally started once a tree or shrub reaches a certain height, and annual pollarding will restrict the plant to that height.
Pollarding is a pruning technique used for many reasons, including:
Preventing trees and shrubs outgrowing their allotted space
Pollarding can reduce the shade cast by a tree
May be necessary on street trees to prevent electric wires and streetlights being obstructed
The best time for pollarding many trees and shrubs is in late winter or early spring. However, bear in mind least favourable time for pollarding is the autumn, as decay fungi may enter the pruning cuts
How to pollard Young trees
Once young trees or shrubs have reached the desired height, you can begin to pollard them. This involves choosing a framework:
On a shrub, this might be one stem cut to a metre high
 a mass of stems will grow from the top
With a tree, it is more typical to leave a trunk supporting three or five branches
 these branches are cut back to a
desirable length and the twiggy growth appears at these ends Initially, the new branches are held weakly in place as they grow rapidly from underneath the bark, rather than from within the tree. As the wood lays down annual growth rings, the union strengthens, often forming a thickened base where the shoot meets the trunk. Over a number of years, a swollen 'pollard head' forms where new shoots grow each year.
Maintaining a pollard
Once a tree or shrub is pollarded, continue the annual cycle of cutting.
Branches should be pruned just above the previous  pollarding cuts
In some cases, such as where some leaf cover is required, leave some branches intact or cut back to a side branch
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