The aim of most pruning is to keep plants healthy and improve flowering, by removing older, less productive wood. Over time, if shrubs have not been regularly pruned, they can become overcrowded, and less productive.
Hard pruning usually stimulates strong new growth, but unfortunately will result in the loss of flowers for a year or two for some shrubs (particularly those, such as Philadelphus and Camellia, that flower on the previous season’s growth).
You can renovate shrubs in two ways: robust shrubs can be completely renovated in one year, but where the response is unknown, carry out a staged renovation instead.
This is the most drastic pruning, and is suitable for almost all deciduous shrubs, including:
Cut all stems 10-20cm (4-8in) from the ground or to branches low down, 20-45cm (8-18in) in the shrub. Follow up this hard pruning with a feed and mulch in spring. This growth may need subsequent thinning out to select the strongest, best placed shoots.
Pruning is spread over two or three years to gauge response or maintain the natural shape. This is suitable for any shrubs whose response you are uncertain of or are not growing vigorously, but especially:
Four steps to renovation:
- In the first year remove dead, damaged, diseased, crossing and rubbing shoots down to ground level, aiming to remove up to half the shrub. Cut back remaining older stems by half, to a vigorous side shoot or healthy outward-facing bud.
- In year two thin out new shoots if excessive, and cut back or shorten the remaining older branches.
- In the third year remove any remaining older stems. In subsequent years return to the normal pruning regime.
- Follow up heavy pruning with a feed and mulch in spring.