Traditionally pollarding involves the removal of all branches from the trunk. It is not advisable to pollard mature trees that have not been pollarded before because the large wounds that such treatment produces may jeopardise the long term future of the tree. Pollarding can also refer to the regular (annual or biannual) pruning back of small branches to the same point which results in the formation of a 'pollard head'. Pollarded trees usually require regular cut back of re-growth.