Crown thinning of a trees leaf bearing branches this technique often lets more sunlight through the trees branch work.
The Thinning process is aimed to reduce the density of the foliage, thus letting more light and air into and through the crown and reduces wind resistance.
In crown thinning, an even density of foliage should be retained
throughout a well-spaced and balanced branch structure which could, if required, provide an adequate framework for a possible future crown reduction. If the objective is to lessen the overall loading on a defective branch or stem, crown reduction and reshaping should be chosen in preference to crown thinning.
Crown thinning is not the most suitable method of reducing the overall loading on a defective branch or stem, since it does not reduce leverage and sometimes increases the probability of branch failure. It is rarely a once-only operation.
The percentage of the leaf-bearing twig structure to be removed in crown thinning should be kept to the minimum required to achieve the objective and in any case should not exceed 30%. Bs3998 2010