Crown thinning is a pruning technique primarily used on hardwood trees.
The intent is to improve a tree’s structure and form while also making life uncomfortable for tree pests.
Crown thinning is the removal of a percentage of the smaller/tertiary branches, usually around the outer crown. This produces a uniform density of foliage around an evenly spaced branch structure.
This practice is usually confined to broad-leaved Tree Species.
Crown thinning does not change the overall size or shape of the tree. Branches should be removed systematically and evenly throughout the tree, the works should not exceed the stated percentage, usually up to 20% and not be more than 30% overall.
Usually crown thinning works are undertaken to allow more light to pass through the tree canopy, it also reduces wind resistance, reduces overall weight (but this does not necessarily reduce leverage on the structure.)
Thinning Crowns are rarely a once only operation particularly on species that are known to produce large amounts of epicormic growth, such as Lime Trees.
During a Crown Thin, all major deadwood should also be removed as standard.
Thinning a tree is usually a preferred practice compared to Crown reductions whenever possible.