Pruning is generally not necessary for this group of plants. These plants have great natural growth habits, and can tend to look unnatural when pruned unnecessarily.
Only remove dead, diseased, damaged, congested, or crossing shoots in late winter or early spring. Shoots that are growing in unwanted directions can also be pruned out.
Prune back to just above a healthy bud. If the buds are positioned on alternating sides of the stem, prune to an outward facing bud as this will avoid future congestion within the plant. If the plant is producing flower buds wait until it has finished flowering.
When pruning small diameter stems, use sharp secatures; anvil-type ensure a clean cut. Stems with a diameter of more than 2 cm should be pruned using long-handled pruners (loppers) or a pruning saw. Dead wood is a lot tougher than live stems.