Plant in full sun or light shade, in moist but well-drained soil enriched with organic matter. Space them with good airflow to help prevent mildew, and water during prolonged dry spells, especially in their first season. Protect emerging foliage in spring from slugs, which can cause early damage.

Stake with brushwood or canes early in the season to support the upright stems. Apply a 5-7cm (2-3in) mulch of well-rotted compost in spring to retain moisture and suppress weeds. Deadhead regularly to extend the flowering period and reduce unwanted self-seeding. Cut back the faded flowering stems in late summer to neaten the plant and encourage possible late blooms. Divide congested clumps in spring or autumn to maintain vigour.