Spirea and barberry bushes belong to the same class of flowering shrubs--both produce their flower buds one season, then bear flowers on those buds the next spring. Accordingly, gardeners should wait to prune spirea or barberry bushes after they flower, since doing so before would reduce the number of blooms. The basic pruning process is the same for both bushes and focuses on removing undesirable and unhealthy wood, plus maintaining the plant's size and shape.
Look over the branches of your spirea or barberry bushes to find damaged or dead branches. Damaged branches may be diseased, bearing wounds, oozing sap or showing discoloration, while dead branches feel brittle to the touch.
Clip off dead or damaged branches using your pruning shears, cutting it back to the base without cutting into the bush's trunk. Remove all dead and damaged wood in this manner and discard it in the garbage bin so you don't spread disease to other plants.
Step back and assess the shape of your spirea or barberry bush, noting wayward and low-growing branches. Determine how much you want to trim long branches to keep the plant at a specific size.
Cut off wayward and low growing branches. Also remove branches that crisscross other branches, since these can damage the wood.
Trim back long branches, making your cuts at a 45-degree angle. Work one branch at a time to preserve the natural shape of each rather than shearing the shrub.