- Woad is a hardy biennial or short-lived perennial and a member of the Brassica family.
- It has a stout taproot, erect stems and oblong-lanceolate gray-green leaves.
- Numerous small yellow flowers are borne in branched panicles in summer, followed by pendent, fiddle-shaped, black seed.
- The flowers are hermaphrodite (have both male and female organs) and are pollinated by insects.
- Needs well-drained, neutral to alkaline soil in semi-shade or full sun.
- Plants self-seed freely when they are grown in a suitable position, but they tend not to thrive if grown in the same position for more than two years.
Medicinal Uses. It is said that:
- The leaves, roots and pigment.
- The leaves are harvested in summer and can be used fresh or dried.
- They are also macerated and the blue pigment extracted.
- The roots are harvested during autumn and dried for later use.
- Woad is a commonly used herb in traditional Chinese medicine.
- The root is antibacterial, anti-viral and anti-parasitic and extracts from the root are known as Ban Lang Gen.
- The dried root (processed into granules and dissolved in hot water or tea) is called Banlangen Keli and is popular throughout China, where it is used to remove toxic heat, soothe sore throat and to treat influenza, measles, mumps, syphilis and scarlet fever.
- It is also used for pharyngitis, laryngitis, erysipelas, carbuncle, to prevent hepatitis A, epidemic meningitis and inflammation.
- Certain compounds in the roots have anti-cancer activity and root extracts have been used to treat patients with solid tumors and leukemia - a traditional usage that led to the purification of the component compound indirubin.
- Several published trials from China found oral administration of 150-200 mg of purified indirubin per day led to remission in 60 percent of patients with chronic myelocytic leukemia.
- A typical adult dosage of Isatis dried root is 1-2 g daily, in divided doses.
- Extracts from the leaf are known as Da Qing Ye.
- Isatis leaves contain alkaloids and agents with anti-inflammatory, anti-allergic, antibacterial, anti-cancer, anti-viral, astringent and febrifuge properties.
- Leaf extracts are used to clear heat and toxins from the blood and has been used in traditional medicine for the control of pathogenic organisms, including viruses and the treatment of infections, specifically encephalitis, meningitis, upper respiratory infection and gastroenteritis.
- The dye chemical extracted from Woad is indigo - it is the same dye extracted from "true indigo", Indigofera tinctoria, but in a lower concentration.