Like coppicing, Pollarding is a traditional way to encourage straighter pole like lengths of timber to grow for wood. Also used for fodder for livestock favouring Wych Elm and European Ash.
These days Pollarding is more often seen on mature trees in urban areas, where larger trees are located closely to properties. Once pollarded, these trees are easily maintained between re-pollarding that occurs generally within 3-5 years (species and growth rate depending)
Trees that are found to be in decline in the earlier stages, can be pollarded back to live wood. This encourages regrowth from the pollard heads to create a new crown (canopy). Helping to maintain the tree through its decline can give many years more enjoyment.
The process is carried out by removing the top of the tree, generally including all tertiary/secondary branches, leaving an even balanced main stem structure. Once the tree is pollarded, it should be repeated at the pollard heads on a cyclical regime. This is usually between 3-5 years depending on species and growth rate.
Please note not all species of trees are tolerant to pollarding and can adversely affect the health of the tree.