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Botanical name: Isatis indigotica
Common name: Isatis leaf, Woad leaf
Literal name translation: big green leaf
Family: Apiaceae, parsley family
Part used in Chinese medicine: leaf
Major Chinese medicine actions:
Clears heat, resolves toxicity, clears qi and blood level heat
Woad is the common name of the plant Isatis tinctoria and is sometimes listed as Isatis indigotica though this is considered by many to be a newer and invalid name for the same plant. One of its common names is dyer’s woad due to the blue dye produced from the plant.
According to Bensky, Clavey and Stoger, the identification of this herb is complex as there are many plants in China called Da Qing Ye. According to the Chinese Pharmacopoiea, the standard plant is considered to be Isatis indigotica, but in southern China the leaf of Baphicacanthus cusia is often used. In the Chinese Herbal Medicine Materia Medica by Bensky et.al., due to the lack of clear, precise identification, the herb is referred to as Isatidis/Baphicacanthis Radix.
In modern China, research on the herb has shown a correlation of the plants medicinal effects with its antibacterial, antiviral, antipyretic, and anti-inflammatory activity. The species Isatis tinctoria is thought to have the strongest of these actions, therefore is the plant cultivated most commonly for medicinal use, however this practice is considered questionable.
Growing and Propagation
The 30 species of Isatis are native to central and southern Europe and western and central Asia. In their native habitat, they grow in rocky, dry places and waste ground, hardy in a wide range of climate, in USDA zones 4 to 8. It is a short-lived perennial or biennial that grows 2-4 feet high with flowers that bloom in early summer. The plant grows easily in any soil but prefers moderately fertile, moist, well-drained soil, in full sun. Propagation is by seed sown in spring, or in the fall in containers in a cold frame. Plants can also be divided in the spring.
Harvesting and Preparation
For medicinal use, the good quality Da Qing Ye consists of thick whole leaves that are blue-green in color.