Grow in moist, humus rich or boggy soil in full sun, or in drier soils grow in partial shade. Will not thrive in soils that dry out in summer. Divide and replant every 3-4 years to maintain vigour and flower quality, discarding any old, woody rhizomes. May be damaged by late spring frosts
Flowering stems may be cut back when flowers fade, or left standing for winter interest
Propagate by
division in winter or early spring; replant immediately or pot up to plant out in spring when re-established