CULTIVATION A tender annual, it has small, oval, bright-green leaves appearing in threes and creamy-yellow flowers from midsummer. It grows to a height of 30-60cm (12-24in) and prefers fertile, well-drained soil. Propagate it by sowing seeds in spring and midsummer, thinning the seedlings to 15 cm (6in) apart. Harvest the leaves and flowers whenever they are available and the seeds from late summer. A pretty garden, border, container and conservatory herb.