Sowing
Sow in a tray half a centimetre deep. Germination is slow and uneven, ten to thirty days, and improves a great deal with three or four weeks of cold in the fridge before sowing. Transplant at four to six true leaves. It is perennial: the first year makes mostly foliage and root, and full flowering comes in the second. Sow in autumn or at the end of winter. Harden the plants off outdoors for a week before planting and give them 30 to 40 cm of room, because the clump widens over the years.