Once
established most evergreen shrubs need little or no regular
pruning. However, pruning may improve health and vigour and
is generally carried out in mid to late spring, with flowering
shrubs pruned after flowering. In some cases renovation will
be required to rejuvenate overgrown shrubs.
After pruning, plants will benefit from feeding with a general purpose fertiliser; most flowering shrubs will benefit from a rose fertiliser.
Small shrubs
Low growing sub-shrubs such as lavender (Lavandula), and heathers (Calluna, Erica) can prove to be short lived and need replacing after 10 years; annual pruning will prevent the plants from becoming too woody, will improve flowering and extend their life. Trim in mid-spring in cold areas. Slow growing shrubs require no regular pruning except the removal of unhealthy shoots in mid-spring.
Medium sized shrubs
Weak, crossing and rubbing shoots or growth which spoils the shape of the shrub are best removed in mid-spring. Prune winter and spring flowering shrubs such as Choisya, Berberis darwinii and Viburnum tinus after flowering. Summer flowering evergreens such as Escallonia are pruned after flowering, removing old flowered stems. A proportion of the older wood can be removed in spring.
Large evergreens
Shrubs such as rhododendron required little regular pruning except the removal of dead, diseased and damaged shoots.
Winter damage
In mid-spring or after all danger of frost has passed, prune out damaged wood, back to a healthy sideshoot or bud. If new growth is too vigorous thin out.
Renovation
A number of evergreens tolerate severe pruning, which is best carried out as they come into active growth in spring. Follow this treatment with an application of a general purpose fertiliser, and a mulch. Avoid drought stress in the season following renovation.
Aucuba, Buxus, Choisya, Euonymus, Ilex x altaclerensis, Ilex aquifolium, Prunus laurocerasus, Prunus lusitanica, Taxus, and Viburnum tinus all tolerate severe pruning. Many evergreens are best renovated over several years, removing one-third to half of shoots to ground level, and reducing all other shoots by one-third in the first year. Over the next couple of years remove half of the older shoots to ground level.