Prune if you want to improve plant shape, Prune ocassionally, Prune when plant is dormant, Remove damaged leaves, Remove dead or diseased plant parts
A hard prune may be necessary if the plant becomes woody, Cut leaves after fall, Cut or pinch the stems, Pinch or prune as they grow to promote branching and bushiness, Prune for shortening long shoots, Prune in early summer, Remove deadheads