Pruning Shrubs – The Successful Pruning Guide
Shrubs are grown for the beauty of theiror foliage, or for the quality of their fruit, their brightly coloured winter stems or branches, their characteristic shape or outline, or a combination of these. The aim of regular pruning is to make the most of these attributes; the timing depends on the shrub’s flowering habits.
Not all shrubs need regular annual pruning — many, especially when grown as single specimens, require only occasional light trimming to maintain their shape. The necessity for regular pruning can also be reduced by care and forethought at the time of planting, by ascertaining the eventual size and shape of the shrub, and by allowing ample room for growth. Overcrowded shrubs require drastic pruning each year to prevent them becoming weakened and misshapen as they compete for the available root space, light, food and water.
The health and vigour of a shrub is maintained by correct pruning. It is important when pruning shrubs, to remove all dead or damaged wood immediately it is noticed. The longer dead wood is allowed to remain on a shrub, the greater is the risk of diseaseentering it, multiplying and eventually spreading to healthy tissue. In severe cases, extensive damage and even death of the whole shrub may occur. Branches that cross or rub against one another are also a potential source of damage, and should be cut away before diseases can enter through the wounds.
Thin, weak growths are of little use, especially if they are produced in the centre of a bush, where they are starved of light and air. Well-ripened branches stand up better to severe weather and to disease. Consequently, the purpose of pruning shrubs is also to keep the centre of a shrub fairly open so as to allow light and air to circulate freely round the branches.
Make pruning cuts cleanly, leaving no ragged edges, torn bark, or bruising and crushing of the stems, since this results in the tissues dying. The pruning will heal more rapidly if the cut is made nearly horizontally across a branch. As the buds are the only points from which further growth can develop along a stem, make pruning cuts as close as possible to a bud without damaging it, starting the cut on the side opposite to the bud and finishing immediately above it so that the cut face slopes downwards away from the bud. This ensures that water runs off the cut without rotting the bud.
Cut unwanted or damaged shoots flush with the main stem from which they arise — on no account leave a short length of branch, or snag, as this will almost certainly die back or produce unsightly clusters of short stems. Trim off the edges of any large pruning cuts using a sharp knife. Painting the cut surface with a bituminous wound-sealing paint may also prevent subsequent disease infection, but this is less important than with pruned or lopped trees.
Coloured leaved and variegated shrub varieties, such as Spiraea X bumalda ‘Goldflame’, sometimes produce shoots which lack the characteristic colour — golden-leaved varieties in particular tend to produce a few all-green shoots from time to time. These must be removed as soon as they appear, since they are frequently more vigorous than the coloured shoots and will ruin the effect of the plant. Cut out the rogue branch completely.