A guide to arboricultural terms
CROWN THINNING
Designed to lighten the crown to allow more light to penetrate and to leave an even, well balanced branch structure. It involves the removal of weak, thin and crossing branches and as many secondary branches as necessary to achieve the desired level of thinning. The maximum amount taken out is 25-30%.
CROWN REDUCTION
This method reshapes the crown of a tree to make it smaller. All branches are cut back to a suitable fork or bud. This method is not suited to all trees and should not exceed 30% of the foliage bearing structure. The natural shape of the crown is retained and minimises hazards of dysfunctional problems in tree circulation.
CLEAN OUT
This is the removal of all dead, dying and diseased limbs; in addition branches that are crossing one another are removed and climbing plants like ivy that can strangle a tree are “ringed” at the base or completely removed..
CROWN LIFTING
Involves the removal of lower branches to provide a desired amount of clearance above ground level. This can be achieved either by the complete removal of a branch or only parts of which extend below the desired height.
POLLARDING
This is also known as lopping or topping and involving the removal of whole branches to leave only the main trunk. In species such as willows and polars such significant pruning is acceptable with new branches developing from the pollard heads. Often thinning is required within 2 years to avoid numerous competing new branches forming end-loaded heads, Secondary pruning of the new wood can help form a new canopy to the tree several years after the initial pollard.