The art of pruning
There are several reasons for pruning – to keep plants within bounds, to promote fewer but stronger stems, to remove diseased or damaged branches, to encourage flowers and to train plants to a desired shape. The right tools are essential: a pair of sharp secateurs, a pair of long-handled loppers, a narrow-bladed pruning saw and strong gloves if thorny branches are to be tackled.
First cut out any branches that are diseased or damaged, cutting right back to healthy or undamaged wood. If two branches are crossing, cut the most awkwardly placed one back to the main stem. Take out weak branches altogether, right down to the base.
Pruning to preserve the shape of a tree or shrub, or to promote growth, is done between the buds on the stems.
Generally, buds grow either opposite each other or alternately along the stem.
Where the buds are opposite, choose a suitable pair and make a straight cut just above them.
If the buds alternate, make the cut slightly angled, starting on the opposite side of the stem and slanting upwards so that the top of the cut is about ¼ in above the bud.
Remember that whichever way the bud you prune back is facing, that is the direction the next branch will grow.
If you prune back to two or more buds, growth will be in two or more directions. This is how you can determine the shape of the tree or shrub.
For example, if the plant is encroaching over a path, prune to a bud that will encourage it to grow away from the path while, if possible, not spoiling the overall shape of the plant.
To stimulate growth on a tree or shrub that is growing more vigorously on one side than the other, prune back hard on the weaker side.

WHEN TO PRUNE WHICH PLANT?
Shrubs such as Buddleia davidii flower on the current year’s growth, and are pruned in early spring for further growth and flowering later in the season.
Shrubs such as weigela and deutzia, that bloom on one-year-old wood and flower early in the year, are cut back as soon as the flowers have faded to ensure flowering the following season. In early spring, too, severely prune shrubs that are grown for their coloured winter stems.
In late spring, when flowering has finished, do any necessary trimming of shrubs that produce their flowers on short growths extending from the main branch. Cut back the current season’s growth to three buds – chaenomeles are prominent in this group.
Keep an eye on shrubs with variegated leaves.
Occasionally, they may produce a stem carrying plain green leaves, which must be cut right back. These shoots are more vigorous than those with variegated leaves, and will take over the plant if not pruned out.

CUTTING BACK CLIMBERS.
Pruning of climbing plants is governed by their flowering times. Some flower on the current year’s shoots from midsummer onwards, others flower between early spring and early summer on growth made the previous summer.
Cut back the late-flowering group into older wood, just above the dormant bud.
Clematis that flower late, such as C. x jackmanii, should be cut back to 8-9in above ground level in late winter or early spring. Lightly trim early flowering varieties, such as ‘Nellie Moser’, cutting off any dead shoots at the start of the season. Cut them hard back only when they have outgrown their allotted space.
This also applies to self-supporting climbers, which should be pruned back by several feet in late summer if they start to obstruct gutters and windows or to overwhelm a host plant.

See also: Pruning Roses