Sow direct where it’s to grow in mid to late spring, once the risk of frost has passed and the soil has warmed up. Choose a sunny, well-drained site and rake the soil to a fine tilth. Sow seeds thinly in shallow drills about 3mm (¼in) deep and 30cm (12in) apart.
Lightly cover with soil and water gently. Keep the soil moist during germination, which usually takes 1–3 weeks. Once seedlings are large enough to handle, thin them to around 20–30cm (8-12in) apart to give each plant space to grow.
Avoid sowing too thickly as overcrowding encourages mildew and reduces airflow.
If you want earlier colour, you can start clary under glass in spring. Sow the seeds shallowly in seed trays filled with good seed and keep at 16-18°C (61-64°F). When the seedlings are large enough to handle, thin them out and pot on individually into small pots to grow on. Gradually harden them off before planting out at 25cm (10in) intervals in a sunny, well-prepared bed. When watering, it is best to give the plants a really thorough soak when the soil gets dry, rather than applying a little water every day.