Crown lifting, also referred to as crown raising, involves the removal of the very lowest branches. The practice should be carried out with care, especially when dealing with older, mature trees, as the pruning of lower branches that are directly attached to the trunk can result in substantial wounds, that can then easily become decayed, maybe even leading to short or even long term problems. For this reason, only secondary branches or the shortening of primary branches should be pruned back to avoid removal where possible. When making the decision to crown raise, there should be a fixed point in mind of the result. For example, to give a certain clearance below the tree.
(please refer to diagram below. The light green area to be raised)