Isatis tinctoria, Dyer's woad - Indigo Dye, Occasionally known as Asp of Jerusalem & grown in Europe since the Stone Age, Originally known as 'glastum' where it was originally grown & used in the wool trade (Glastonbury translates 'place where the woad grows'). Leaves produce a natural indigo dye from the dark blue-green, spinach-like leaves, (1st yrs plants produce the best dye). An attractive plant with blue-green leaves & yellow flowers in late spring, Biennial to 1.2m, also known for its Chinese medicinal properties, It is warm enough to sow woad seeds in the UK when daffodils are in flower, Seed Count Approx - 40 avg SOWING - Seed is sown thinly spaced in either March or Nov, in shallow drills or seed trays, just covering the seed, Then transplanted a foot apart when large enough to handle.. harvested from July until September from spring planting. For dark colours, use plenty of nitrogen