What is "pollarding"

Pollard \Pol"lard\, v. t. [imp. & p. p. Pollarded; p. pr. & vb. n. Pollarding.] To lop the tops of, as trees; to poll; as, to pollard willows.
--Evelyn.

vb. (present participle of pollard English)

Pollarding is a pruning system in which the upper branches of a tree are removed, promoting a dense head of foliage and branches. Pollarding in Ancient Rome was mentioned by Propertius during the 1st Century BC. 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. This is not a practice to use if one wants an attractive, natural tree as the natural growth is stunted. Many times this is done in southern states of the USA to crepe myrtles, and is called "crepe murder" by some. 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 favored for fence rails and posts, as well as boat construction. Supple young willow or hazel branches are harvested as material for weaving baskets, fences, and garden constructions such as bowers. 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, so can be difficult to age accurately. Pollards tend to grow slowly, with narrower growth rings in the years immediately after cutting.