Sow seeds directly outdoors in a sunny site with good soil from mid to late May. Seeds can also be started indoors in a soilless mix 8 weeks before the last frost date. Maintain temperature at 70°F (21°C) for the 10-14 day germination period, growing at a slightly cooler temperature before hardening off and transplanting outdoors once danger of frost has passed.
Sow seeds 3mm (1/8in) deep and 2.5cm (1in) apart, then thin them out to 25-30cm (10-12in) apart in the garden.