Tree pollarding has been common in Europe since medieval times and is practised today in urban areas worldwide, although very little now in the UK, primarily to maintain trees at a predetermined height that is smaller than they would normally grow.
In the UK today pollarding is generally not used in conjunction with modern practices. It should not be carried out unless a tree has previously been pollarded as large wounds created during the pollarding process can initiate fatal decay in mature trees.
Traditionally, trees were pollarded for one of two reasons: for fodder to feed livestock, or for wood. Fodder pollards produced “pollard hay”, which was used as livestock feed; they were pruned at intervals of two to six years so their leafy material would be most abundant. Wood pollards were pruned at longer intervals of eight to fifteen years, a pruning cycle that tended to produce upright poles favoured for fence rails and posts, as well as boat construction. An incidental effect of pollarding in woodland is the encouragement of underbrush growth due to increased levels of light reaching the woodland floor. This can increase species diversity.
The problem with pollarding is that trees with weaker wood are prone to producing multiple shoots that can become hazardous. Some of the weakly-attached branches can break off and fall to the ground. A similar problem can occur with trees with more hardy species such as beech, oak and sweet chestnut. Their branches become heavy when pollarding lapses for several decades, and these may break away in windy weather.
Pollarding is commonly requested by those not understanding its severe nature; often a crown reduction would be more suitable. Therefore, please always seek advice.