Woad

About 30 species of annuals, biennials, and perennials belong to this genus, which occurs through Europe to C Asia. Isatis tinctoria (woad), a species found mainly on chalky soils, is best known as a dye plant, containing a pigment similar to that of indigo (Indigofera spp.), but is important as a medicinal herb. It was a major crop in many parts of Europe during the Middle Ages, notably in S France whence the expression "Land of Cockaigne" arose, after the earthenware cups (coques) in which the dye paste was sold. Both Julius Caesar and Pliny described how the Britons painted their bodies with woad, the blue dye produced by fermenting the foliage. The process of fermentation gave off such a foul smell that it was banned by Queen Elizabeth I within 8km (5 miles) of any of her palaces. Woad remained a popular dye for fabrics until the 1630s, when it was superseded by indigo from the tropics. According to Mrs. Grieve (A Modern Herbal, 1931). I tinctoria " is so astringent that it is not fit to be given internally as a medicine, and has only been used medicinally as a plaster, applied to the region of the spleen, and as an ointment for ulcers, inflammation, and to staunch bleeding". It was first mentioned in traditional Chinese medicine in the 1590s and is often prescribed in large doses are recommended to maintain high levels of active ingredients. Scientific research suggests pronounced anti-viral effects. The Chinese drug qing dai (from the leaf pigment of I. tinctoria) is also prepared from Indigofera suffruticosa and Persicaria tinctoria (syn. Polygonum tinctorium).

Biennial or short-lived perennial with a stout taproot and basal rosette of oblong-lanceolate, gray-green leaves, 4-10cm (1½-4in) long. Numerous small, yellow, 4-petaled flowers are borne in branched panicles in summer, followed by pendent, fiddle-shaped, black seeds.

Common Name:	Woad
Botanical Name:	Isatis tinctoria
Genus:	Isatis
Family:	Brassicaceae
Cultivation:	Rich, well-drained, neutral to alkaline soil in sun.
Propagation:	By seed sown in autumn or spring. Often self-seeds readily, but does not thrive in the same soil for more than two years.
Harvest:	Leaves are picked in summer for use fresh or dried in decoctions, or macerated for extraction of blue pigment, which is then dried as a powder. Roots are lifted in autumn and dried for use in decoctions.
Native Location:	C and S Europe, W Asia
Height:	50cm-1.2m (20in-4ft)
Width:	45cm (18in)
Hardiness:	Z3-8
Parts Used:	Leaves (da qing ye), roots (ban lang gen), pigment (qing dai).
Properties:	A bitter, chilling herb that lowers fever and reduces inflammation. It controls a wide range of pathogenic organisms, including viruses, and reputedly has anti-cancer effects.
Medicinal Uses:	Internally for meningitis, encephalitis, mumps, influenza, erysipelas, heat rash, sore throat, abscesses, and swellings (Leaves, roots); convulsions and high fevers in children, coughing of blood, and as a detoxifier in infections such as mumps, erysipelas, and yeast (pigment).
Bibliography:	Encyclopedia of Herbs by Deni Brown. Copyright © 1995, 2001 Dorling Kindersley Limited. pp 244-245