Isatis indigotica Seeds | Woad Root
LATIN NAME: Isatis indigotica
COMMON NAME: Isatidis Radix, Ban Lan Gen, Indigo Woad
Plant Profile
Isatis indigotica is a biennial of the cabbage family, grown in China for two drugs from one plant: the root, ban lan gen, and the leaf, da qing ye. In its first year it makes a rosette of long, grey-green leaves; in the second it sends up a metre of stem carrying yellow flowers and pendulous winged pods.
The root is a straight taproot, thirty centimetres or more, pale yellow inside and out, and it is sliced and dried within days of lifting because it darkens and loses quality in storage. Cultivation is concentrated in Hebei, Jiangsu and Anhui. The root is lifted in late autumn, washed, and cut across the grain while still firm.
Science & Biotechnology
The dye chemistry is the interesting part. Leaves contain indican, an indoxyl glucoside, and isatan B; when the tissue is crushed, a glucosidase releases indoxyl, which oxidises in air to indigo blue and to its red isomer indirubin. Indirubin turned out to be a cyclin-dependent kinase inhibitor, and it has been studied in chronic myeloid leukaemia and in psoriasis, though the trials are small.
Antiviral work on ban lan gen has been largely in vitro against influenza, with a handful of small clinical studies in China that are difficult to assess for blinding and allocation. The root also contains polysaccharides and a range of phenolic acids. Indigo naturalis, the processed leaf product, has the better documented clinical record, in ulcerative colitis.
Uses & Benefits
Root slices are decocted for sore throat, fever and the first days of a cold, usually nine to fifteen grams, and the taste is flat and slightly sweet rather than bitter. In China the prepared granules are sold as a household remedy.
The leaf preparation is a stronger medicine. Indigo naturalis is given for psoriasis and colitis under supervision, and it can cause gastrointestinal upset and, rarely, liver enzyme changes. Long courses are not advisable without monitoring, and the herb is used with caution alongside anticoagulants. Children are given a milder preparation, and the decoction is not taken on an empty stomach.
Growing from Seed
Sow in late summer for a spring lift, or in early spring for an autumn one. The seed germinates readily without pretreatment at 15 to 20°C, and a cold frame is enough. Deep, stone-free loam gives the straight root the slices are cut from.
The rosette overwinters and bolts in the second spring; if the aim is root, lift before the stem runs, because flowering hollows the core. The species has escaped cultivation in western North America, where Isatis tinctoria is listed as a noxious weed, so seed heads should be cut before they shatter. A pH near neutral suits it, and the crop tolerates light frost once the rosette is established.
Our Take
A useful two-crop plant for the medicinal grower, easy from seed and quick to lift, provided the flowering stem is cut before it ruins the root.
Related Reading
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