Sow thinly, indoors, February-April, in trays of moist compost, covering with a fine layer. Firm gently. Cover with glass or polythene and shade with paper. Maintain temperature at 15-20°C (60-68°F) and keep moist. Remove glass and paper when seedlings appear after 14-21 days. When large enough, transplant singly into 9cm (3½”) pots. Stand outside for a few days towards the end of May (avoid frosts). Transplant, 30cm (12”) apart, to flowering position in June. Choose a sunny spot with well-drained soil. Remove dead heads to prolong the flowering season. Flowers: July to October.