Crown Lifting
Crown lifting describes the activity of pruning to achieve a desired vertical clearance above ground level or other surface. Sometimes this is necessary to facilitate site usage, for example over footpaths and roads.
Extensive crown lifting should, if possible, be phased over a number of years, with a view to providing some opportunity for physiological and biomechanical adaptation to the resulting wounding and branch removal.If crown lifting involves the removal of branches which form a substantial proportion of the lower crown of a mature or old tree, the resulting wounds on the stem(s) have the potential to become the seat of extensive decay, which could lead to mechanical failure.
Crown lifting should be avoided or at least minimised in mature or old trees if possible, since it can increase the probability of stem failure. It may be that such works are unavoidable, if this is the case work should ideally involve the removal of secondary branches or branch shortening rather than the removal of branches back to the stem. This of course relies on the fact that the desired clearance can be achieved, when deciding which option to take consideration should include such factors such as the size, growth potential, branching habit and the shade tolerance of the tree concerned.
Crown lifting should, preferably, not involve the removal of more than 15% of the 'live' crown height. The remaining crown, should make up at least 66% of the height of the tree.
It is important that when specifying or planning crown lifting , the points between which the clearance will be measured are clearly stated.
Bawden Tree Care would be delighted to provide more detailed and specific advice if required, please do not hesitate to contact us in this respect.