August 21 2016 0Comment

Tree Surgery Best Practice

Tree pruning, removing dead branches and unsightly growth is a basic requirement to keep a tree in a safe and healthy condition, maintain a pleasing form and acceptable size, promote growth and uplift the quality of flowers, fruit and timber.  Incorrect pruning is often the cause of disease, trees becoming hazardous and losing an otherwise attractive form.

When engaging the services of a tree surgeon it is important to understand the basic terms commonly used to describe tree work in order to ask for the correct operation or understand what is being recommended. For example, a ‘crown thin’ will not reduce the height of the tree? Nor will a ‘crown lift to 6m’.

By and large there are three pruning options which are outlined below. These are very general summaries, please feel free to contact us for a more detailed explanation.

Crown Thin

Crown thinning is the process of removing smaller branches generally located on the outer edges of the crown. The desired result should be to create a consistent volume of growth around an evenly spaced branch architecture. This method is usually applied to broad-leaved tree species. Crown thinning should not alter the actual size or form of the tree. Foliage should be removed methodically throughout the tree, and should not exceed more than 30% overall. Crown thinning is usually requested to allow more light or wind to move through the tree and reduce the trees’ weight (it’s important to remember that this does not always reduce leverage on the trees’structure) and is generally an ongoing operation especially on species that are known to create a large amount of epicormic growth (a shoot growing from an epicormic bud, which lies underneath the bark of a trunk, stem, or branch.

Crown Lift or Crown Raising

Crown lifting is the process of removing the lowest branches of a tree. Best practice should not normally involve the removal of large branches growing directly from the trunk, as this can create large wounds which can decay leading to future problems or more immediate bio-mechanical instability. Crown lifting on more mature trees should be omitted or minimised to secondary branches or reductions of primary branches rather than complete removal where possible. Crown lifting is an effective way to let light pass through a tree at ground level or remove obstructions of an access area. Reductions should be limited to less than 15% of the live crown height and leave the crown at least two thirds of the total height of the tree. Crown lifting should be stated with reference to a specific point, e.g. ‘crown lift to allow 4.5m clearance above ground level’.

Crown Reduction

Crown reduction is the process of reducing the height and (foliage bearing parts) of the spread of the trees’ crown. Crown reductions are often undertaken to reduce stress on singular branches or the entire tree, adapt the tree to its surrounding environment or to limit the effects of shade and light loss. The desired result should be to retain the main architecture of the crown, and a significant part of the leaf bearing structure, and leave a similar, albeit smaller silhouette. Best practice crown reduction cuts should not exceed 100mm in diameter unless required. Reductions should be stated as specific measurements, if possible, and reflect the end result, but may also refer to lengths of parts to be removed for clarity, e.g. ‘reduce crown height by 2.0m and radial spread by 1.0m, all round, to finished crown dimensions of 20m in height by 15m in spread. Not all species are suitable for this process and crown reduction should not be confused with ‘topping’, which is a harmful practice.