While careful pruning enhances a tree or shrub, heavy cutting back usually spoils a plant’s shape, at least temporarily, but it might become necessary if a plant has outgrown its space. Before hard cutting back consider removing some shrubs or trees completely from a planting to allow room for the development of the remainder.
The best method of cutting back trees or shrubs is to reduce the number of branches. Completely remove, at source, half of the plant’s branches. Careful selection of the branches for removal will allow the plant to retain its shape. This thinning process may achieve enough size reduction. If not, shorten the remaining branches by one-third or half of their length.
Another method, for shrubs only, is to cut the plant right down to ground level. The cut stumps will sprout again and the shrub will regenerate itself. This rather drastic treatment should be carried out in April and may occasionally cause a shrub to die off.
To actually kill off tree stumps and prevent sprouting, paint the cut surfaces with Roundup. If the tree stem diameter is more than 10 centimetres, drill one hole for each 10 centimetres of diameter of the stump using a bit and brace and place some undiluted Roundup in the holes.