Pollarding is a pruning system in which the upper branches of a tree are removed, promoting a dense head of foliage and branches. It has been common in Great Britain and Europe since medieval times and is practised today in urban areas worldwide, primarily to maintain trees at a predetermined height.
Pollarding encourages lateral branches by cutting off a tree stem six feet (2m ) or so above ground level. If pollarding is done repeatedly over the years, a somewhat expanded (or swollen) tree trunk will result, and multiple new side and top shoots will grow on it.
Pollarding is useful in pasture land as it encourages growth higher up the tree, effectively discouraging growth from ground level, thus increasing the area of land for livestock to feed on. And by pollarding above head height, valuable timber or poles are protected from by browsing animals such as rabbits or deer.
One consequence of pollarding is that pollarded trees tend to live longer than unpollarded specimens because they are maintained in a partially juvenile state, and they do not have the weight and windage of the top part of the tree. Older pollards often become hollow, and so can be difficult to age accurately. Pollards tend to grow slowly, with narrower growth rings in the years immediately after cutting.
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 2-6 years so that their leafy material would be most abundant. Wood pollards were pruned at longer intervals of 8-15 years, a pruning cycle that tended to produces upright poles favored for fence rails and posts as well as boat construction.