Sow in a propagator on a windowsill or in a greenhouse at approximately 15-18°C (60-65°F) onto a good quality, finely sieved, firmed, moist compost. Cover with 3mm (1⁄8") compost. Germination usually takes 15-20 days, throughout which time the compost should be kept moist. Transfer seedlings, spacing them 5cm (2") apart in trays and grow on. Acclimatise the plants to outside conditions before planting out 23cm (9") apart in a sunny position.