A hardy biennial (or short-lived perennial if flower heads are cut before seeding), it grows on a taproot, from 50 cm-1.2 m (20 in-4 ft.) tall. In the first year it produces a rosette of ovate leaves, from which branching stems with lanceolate leaves topped by racemes of yellow flowers grow in summer, followed by pendulous black seeds.
History and traditions
Woad was the source of the blue body paint of the ancient Britons, described by Pliny and other Roman writers. Although largely replaced by indigo, from the subtropical indigofera species, in the 1630s and then by synthetics at the end of the 19th century, a factory producing dye from woad existed in England until the 1930s.
Growth
Grow in humus-rich, moist but well-drained soil, in full sun. Propagated by seed sown in containers in spring, maintaining a temperature of 13-18°C (55-64°F) or in autumn for overwintering in a cold frame. Does not flourish in the same ground for more than a few years.
Parts used
Leaves dried, fermented and also powdered for use as a dye. Leaves and roots dried for Chinese herbal preparations.
Uses
Medicinal
Traditionally a wound-healing herb, as well as a dye, it has long been used In Chinese herbal medicine and recently discovered to have antiviral properties. General The leaves yield a very fast blue dye.
