Sow on a windowsill in a propagator or in a greenhouse at approximately 18-21°C (65-70°F) into a good quality compost. Cover with 3mm (1⁄8") of finely sieved, moist compost. Germination 7-21 days. Transplant resulting seedlings into trays spacing them out 5cm (2") apart and grow on. Plant out after carefully acclimatising to outside conditions approximately 30cm (12") apart. Alternatively, sow directly outside in April/May into finely raked, moist soil 6mm (¼") deep where the plants are to flower.