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 practiced today in urban areas worldwide, primarily to maintain trees at a predetermined height.
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. 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.
As in coppicing, the tradition of pollarding is to encourage the tree to produce new growth on a regular basis in order to maintain a supply of new wood for various purposes, particularly for fuel. In some areas dried leafy branches are stored as winter fodder for stock. Depending upon the use of the cut material, the length of time between cutting will vary from one year for tree hay or withies, to five years or more for larger timber. Sometimes only some of the regrown stems may be cut in a season – this is thought to reduce the chances of death of the tree when re-cutting long-neglected pollards.
Pollarding was preferred over coppicing in wood-pastures and other grazed areas, because animals would browse the regrowth from coppice stools. Historically, the right to pollard or "lop" was often granted to local people for fuel on common land or in royal forests; this was part of the right of Estover.
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. However, in woodland where pollarding was once common but has now ceased, the opposite effect occurs as the side and top shoots develop into trunk-sized branches. An example of this occurs in Epping Forest in London/Essex, UK, the majority of which was pollarded until the late 19th century. Here, light levels on the woodland floor are extremely low owing to the thick growth of the pollarded trees.
Pollards cut at only about a metre or so above the ground are called stubs (or stubbs). These were often used as markers in coppice or other woodland. Stubs cannot be used where the trees are browsed by animals, as the regrowing shoots are below the browse line.
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