Woad, Dyer's woad

Isatis tinctoria

Physical Characteristics

Isatis tinctoria is a BIENNIAL/PERENNIAL growing to 1 m (3ft 3in) by 0.5 m (1ft 8in). See above for USDA hardiness. It is hardy to UK zone 7 and is not frost tender. It is in flower from June to August, and the seeds ripen from August to September. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very alkaline soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

Distribution

C. and S. Europe. Naturalized in S. and C. England.

Habitats

Cultivated Beds; East Wall. In. South Wall. In. West Wall. In.

Edible Uses

Edible Parts: Leaves Edible Uses: Leaves - they require long soaking in order to remove a bitterness, and even then they are still bitter[177, 179]. There is no record of the seeds being edible, but they contain 12 - 34% protein and 12 - 38% fat on a zero moisture basis[218].

Medicinal Uses

Antibacterial Antiviral Astringent Cancer Woad has rather a mixed press for its medicinal virtues. One author says it is so astringent that it is not fit to be used internally - it is only used externally as a plaster applied to the region of the spleen and as an ointment for ulcers, inflammation and to staunch bleeding[4]. However, it is widely used internally in Chinese herbal medicine where high doses are often employed in order to maintain high levels of active ingredients[238]. The leaves are antibacterial, anticancer, antiviral, astringent and febrifuge[148, 176, 218, 238]. It controls a wide range of pathogenic organisms, including viruses[218, 238]. It is used internally in the treatment of a wide range of disorders, including meningitis, encephalitis, mumps, influenza, erysipelas, heat rash etc[238]. The leaves are harvested in the summer and can be used fresh or dried[238]. They are also macerated and the blue pigment extracted. This is also used medicinally, particularly in the treatment of high fevers and convulsions in children, coughing of blood and as a detoxifier in infections such as mumps[238]. The root is antibacterial and anticancer[176]. It is used in the treatment of fevers, pyogenic inflammation in influenza and meningitis, macula in acute infectious diseases, erysipelas, mumps and epidemic parotitis[176]. Its antibacterial action is effective against Bacillus subtilis, haemolytic streptococcus,, C. diphtheriae, E. coli, Bacillus typhi, B. paratyphi, Shigella dysenteriae, S. flexneri and Salmonella enteritidis[176]. Both the leaves and the roots are used in the treatment of pneumonia[218]. The root and the whole plant have anticancer properties whilst extracts of the plant have shown bactericidal properties[218].

Known Hazards

None known