Sow 13mm (½in) deep in 7cm (3in) pots of a good, freedraining, moist seed compost, at 20-25°C (68-77°F). Place pots in a propagator or seal them inside a polythene bag until after germination which takes approx. 5-7 days.
Gradually acclimatise to outdoor conditions for a few days before planting out after all risk of frost has passed, 90cm (36in) apart. Can also be sown direct outdoors once the soil has warmed. Sow two seeds every 90cm (36in) and later thin to the strongest seedling.