Basic Principles for Pruning Shrubs
Whilst some shrubs such as compact evergreens need little pruning to remain attractive, deciduous shrubs can be encouraged to grow vigorously and in a good, balanced shape by regular pruning attention. Some shrubs may need regular pruning in order for them to keep producing their full ornamental effects, such as buddleja (flowers), firethorn (berries), hazel (foliage) and dogwood (stems).
Pruning Regimes
The pruning regime for different deciduous shrubs may be divided into four groups:
- Shrubs that need minimal pruning.
- Spring pruning: shrubs that flower late in the year on new growth.
- Summer pruning: shrubs that flower early in the year, usually on the previous year's wood.
- Shrubs that are spread by suckers.
1. Minimal Pruning
These shrubs do not produce regular vigorous growths from their bases, and includes species such as Chinese witch hazel (Hamamelis mollis), buttercup witch hazel (Corylopsis pauciflora) and hop tree (Ptelea trifoliate).
Prune these shrubs straight after flowering by cutting any damaged, diseased or dead wood back to healthy growth and by pruning weak, unproductive or crossing shoots back to main stems. This will enable you to create a shrub with an open network of branches, which not only look attractive, but will reduce the risk of disease by maintaining a healthy air flow around the plant.
2. Spring Pruning
Shrubs that flower on new growths made during the current season and which usually flower in the second half of the summer or in the autumn, should be cut back in early spring to give them plenty of time to grow new shoots before flowering. These include examples such as butterfly bush (Buddleja davidii), Chinese plumbago (Ceratostigma willmottianum) and Tamarisk (Tamarix ramosissima).
Using long handled pruning loppers, cut back some of the main stems to the base of the plant. Then, with your secateurs, cut out any dead or damaged stems back to healthy looking growth. Remove any twiggy growth, either back to a main stem, or right back to the ground level. Prune other stems back to within 3 buds of older growth to help stimulate new flowering shoots.
All shrubs should be fed and mulched immediately after pruning.
3. Summer Pruning
Shrubs that flower in the first half of the year usually carry their blooms on the previous year's wood. This means that they should be pruned as soon as flowering is finished to allow the plant plenty of time before the winter to produce new flowering growth. Examples of shrubs that should be pruned in the summer include lilac (Syringa), mock orange (Philadelphus coronarius) and star magnolia (Magnolia stellata).
After flowering, prune away slightly less than a quarter of the oldest wood to within 5-8 cm (2-3 in) of the ground; this will ensure that the shrub maintains an open, well-balanced shape. Cut back any damaged, diseased or dead wood back to healthy growth and prune out any crossing stems. Weak and twiggy growth should be removed at the base of the plant, just above ground level. Finally, cut back flowered shoots back to a healthy bud or pair of buds.
4. Suckering Shrubs
The shrubs often carry flowers that bloom on the previous years wood, but produce the majority of their new growth from ground level. Examples include the early flowering shrub with sinuous green stems, Jew's mallow (Kerria japonica).
After flowering, cut back any dead, diseased or damaged wood and half of the flowered shoots to within 5-8 cm (2-3 in) of the ground. Prune the remainder of the stems to half their length, cutting back to healthy new shoots.