Crown cleaning is the straightforward removal of anything in the crown that should not be there. This could be Squirrel Drays, birds nests or Ivy / creepers. "Created" items such as Drays and nests can have a negative impact on the health of a tree: they are often formed in natural crotches, and can help to contain water pockets which in time can cause disease in the tree.

The bigger problem is that of Ivy - Hedera Helix: A tree is an amazingly natural, well balanced structure, where the root plate formed is sufficient to hold the crown of the tree under most excesses of weather. The crown in this context is considered to be the "natural sail area" of the tree - i.e. the resistance to the forces of wind likely to be applied to it. When the sail area becomes unnaturally larger than the root plate is "designed" for, through the growth of Ivy into the crown, the root plate is no longer adequate for the sail area, and therefore the tree can become prone to uprooting in severe weather. (Generally, this is the only problem with Ivy, as it is not-parasitical - i.e. it does not feed on the tree itself, it just uses it as a climbing frame!)

For Crown cleaning, the tree would normally be climbed, removing Ivy along the way to gain access into the crown, and then all Ivy / Drays / nests removed. It is particularly important that this type of work is not done during nesting times, as it is an offence under the Countryside and Wildlife Act 1981, to disturb nesting birds, Bat roosts, Red Squirrels, etc, and there is nothing worse than coming face-to-face with an angry Grey Squirrel when up a tree!

Crown cleaning is normally done at the same time as Deadwooding.