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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 Europe since medieval times and is practised 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 two to six years so their leafy material would be most abundant. Wood pollards were pruned at longer intervals of eight to 15 years, a pruning cycle that tended to produce upright poles favored for fence rails and posts, as well as boat construction. One consequence of pollarding is 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, 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 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 recutting 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.
As with coppicing, only species with vigorous epicormic growth may be made into pollards. In these species (which include many broadleaved trees but few conifers), removal of the main apical stems releases the growth of many dormant buds under the bark on the lower part of the tree. Trees without this growth will, of course, die without their leaves and branches. Some smaller tree species do not readily form pollards, because cutting the main stem stimulates growth from the base, effectively forming a coppice stool instead. Examples of trees that do well as pollards include broadleaves such as beeches (Fagus), oaks (Quercus), maples (Acer), black locust or false acacia (Robinia pseudoacacia), hornbeams (Carpinus), lindens or limes (Tilia), planes (Platanus), horse chestnuts (Aesculus), mulberries (Morus), redbud (Cercis canadensis), tree of heaven (Ailanthus altissima) and willows (Salix), Corylus, Fraxinus excelsior, Castanea sativa, Ulmus spp, Populus spp, Betula spp, Ligustrum ovalifolium, Juniperus spp, Cornus spp, Malus spp, Prunus spp, Rhus spp, Ilex spp, Eucalyptus spp, Laurus nobilis, Cotoneaster spp, Cytisus spp, a few conifers, such as yews (Taxus), and even vines as Lonicera spp, Clematis, and Wisteria spp.
The technique is also used in Africa for moringa trees, to bring the nutritious leaves into easier reach for harvesting. Pollarding is also used in urban forestry in certain areas for reasons such as tree size management, safety and health concerns. It removes rotting or diseased branches for the overall health of the tree, living and dead branches that could harm property and people, as well as expanded foliage in spring for aesthetic, shade and pollution concerns. Trees may be "rejuvenated" by pollarding – for example Bradford pear (Pyrus calleryana "Bradford"), a beautiful flowering species when young, but brittle and top-heavy when older.
Oaks, when very old, can form new trunks from the growth of pollard branches - i.e. surviving branches which have split away from the main branch naturally.
"Poll" was originally a name for the top of the head, and "to poll" was a verb meaning "to crop the hair". This use was extended to similar treatment of the branches of trees and the horns of animals. A pollard simply meant someone or something that had been polled (similarly to the formation of "drunkard" and "sluggard"); for example, a hornless ox or polled livestock. Later, the noun pollard came to be used as its own verb: "pollarding". Pollarding has now largely replaced polling as the verb in the forestry sense. Pollard can also be used as an adjective: "pollard tree".
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