A crown lift involves the removal of lowest branches with the aim of lifting the height of the base of the crown. This is carried out to increase the clearance between the ground and the base of the crown.
Main benefits of a crown lift:
Allow for access below the tree. 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 underneath the tree
Enhance the trees appearance by creating a level lower crown
Prevent interference with structures, property, fences, telephone lines etc
When crown lifting trees, the larger primary branches should be left as removing them could create large wounds with a chance of leading to decay.
British standard for tree works BS3998:2010 states that crown lifting should be restricted to no more than 15% of the crown height in order to leave the crown at least two thirds of the total height of the tree. It is possible to crown lift a tree too much, advice should be sought about each instance of such work to see if it is appropriate and beneficial.