Advice
Renovating old shrubs
Most pruning is aimed at keeping plants flowering well by removing older, less productive wood. In time, shrubs may become overcrowded, over large and produce little new growth or flowers. Hard pruning will result in the loss of flowers for a season or two for some shrubs, but usually stimulates strong new growth important for longevity. Not all shrubs respond well to renovation - in these cases it is best to attempt staged renovation or replace the shrub.
Timing
Renovate deciduous shrubs between autumn and spring. Renovate most evergreens, as they come into growth in spring. Response in some can be weak.
Complete renovation
This is the most drastic pruning, taking all stems close to the ground or to branches low down in the shrub. The result is vigorous new growth in many shrubs, such as Spiraea and Berberis. This growth may need subsequent thinning out to select the strongest, best placed shoots.
Staged renovation
Pruning is spread over two or three years to gauge response or maintain the natural shape. This works well with evergreens such as Camellia.
- 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 sideshoot 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.
Tips
- Take care not to cut back beyond the scion in grafted plants. Severe pruning may result in growth below the scion which will should be removed.
- Weak or sickly plants are best replaced. Improving the soil before replanting will get a healthy young plant off to a good start.
- It is worth trying to propagate older shrubs or plants of sentimental value before heavy pruning in case they do not recover. Choose young growth for propagation material.
- Follow up heavy pruning with a feed and mulch in spring.