Crown lifting is the removal of the lowest branches and/or preparing branches for future removal. Good practice dictates crown lifting should not normally include the removal of large branches growing directly from the trunk, as this can cause large wounds which can become extensively decayed leading to further long term problems.
Crown lifting on older, mature trees should be advised or restricted to secondary branches or shortening of primary branches rather than the whole removal wherever possible.
Crown lifting is an effective method of increasing light to areas closer to the tree or to enable access under the crown, but should be restricted to less than 15% of the live crown height and leave the crown at least two thirds of the total height of the tree.