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Crown Thinning

Crown thinning operations in tree surgery are used for 5 reasons:  Crown Thinning Diagram

1.   To reduce the density of the canopy to allow more light threw to the ground (plants, lawn) or building below.

2.   To reduce branch leaf density in order to reduce weight and loading on a branch with a defect.  Usually specified as works to an area or a branch.

3.   As part of cyclical crown reductions in order to promote greater lateral branching to enable more natural crown reductions in the future.

4.   To reduce the overall sail effect / drag of the entire canopy to reduce loading on an issue at the base of the tree.

5.   Increase movement of air threw the canopy to reduce standing air and humidity.  This can impact on harbouring pests within the canopy (often used with fruit  trees).

British Standard 3998:2010 Tree Work - Recommendations states that the overall amount of twig bearing foliage to be removed should be no greater than 30% and that branch removal should be limited to secondary branches unless a significant reason is found to remove a limb back to the stem.  A uniform branch density should be retained as uneven thinning or over-thinning a tree can increase the probability of branch failure.  The thinning operation should not be restricted to the inner canopy thus leaving branches with long clear stems and only foliage at the end (lions tailing).

As with all our tree surgery operations the position of the cuts made has to be acurate to reduce points of infection and reshooting growth.  

A crown thinning operation will not impact on the overall size of the tree.

Please be aware if selecting a crown thinning tree surgery operation for your tree that the tree will always try and optimise its crown and fill in open areas within the canopy.  The tree work will not offer an indefinate cure for light threw the canopy but if undertaken on a cyclical basis such as 4-8 years the canopy density can be controlled.

Certain species are less suitable for crown thinning, in particular during periods of intense sunlight (if we ever get any!).  Beech trees (Fagus spp.) naturally develop a thick canopy with little light penetration in order to surpress plant growth under the tree.  They also have thin bark which can become damaged by a sudden change in sunlight intensity, so it is always worth discussing the options with one of our Arboricultural advisers before deciding on the most suitable pruning regime to remedy your tree related problem.