Cut or pinch the stems, Do not prune during shooting season, Prune if you want to improve plant shape, Prune prior to new growth, Remove deadheads
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