Prune by heading back as much of the new-ish growth as desired in May. In small gardens, spent blooms can be individually removed if desired to extend the bloom period. Remove dead seed heads in the Fall (October), but save deeper pruning for Spring maintenance (1). Consider leaving some of the pruned dry seed heads in the garden for food, nesting material, and habitat for birds and other critters you want around (S). Older plants that look like they need refreshing can be cut back hard into older wood in November (as low as a 4″ stubs if desired (7)). Expect new growth to emerge within a few weeks (1). If damaged by frost in the winter, wait a few weeks before pruning damaged areas. You will want to be sure of the extent of the damage first, and the damaged parts can help protect healthy tissue if the cold spell lasts over a few nights (1). References