This may be carried out to increase the clearance between the ground and the lower branches in order to:
- Allow for access below the tree, particularly vehicles. (In the UK, highways regulations state that the clearance over a highway must be 5.2 meters and 2.5 meters over a footway)
- To help improve light levels
- Aesthetically enhance the tree by creating a balanced lower crown
- Remove interference with structures or property such s fences, telephone lines etc
When crown lifting trees, large primary branches growing directly from the trunk should be left as removing them can create large wounds potentially leading to decay.
Similarly, crown lifting on older, mature trees should be restricted to secondary branches to minimise stress and reduce recovery time. It is possible to crown lift a tree too much, suitable advice should be sought about each particular instance of such work to deem if it is appropriate. The British standard for tree works BS3998:2010 recommends that crown lifting is restricted to no than than 15% of the live crown height in order to leave the crown at least two thirds of the total height of the tree.