Sow seeds on the surface of a good, free- draining, damp seed compost. Then lightly cover, 3mm (1/8in) deep, with vermiculite or compost. Place container in a propagator or seal inside a polythene bag at a temperature of 20-30?C (68-86?F) until after germination which usually takes 7-14 days. Direct sow outside from late April once the soil has warmed. Sow seeds thinly at a depth of 3mm (1/16in).
Transplant seedlings when large enough to handle, taking care not to damage the fragile roots, into trays or 7.5cm (3in) pots. Gradually acclimatise plants to cooler conditions for a few weeks before planting out, after all risk of frost, 30cm (12in) apart.