Isatis indigotica Fort. is a biennial herb in the cruciferous family, and is used in medicine for its roots and leaves. The root is called Panax quinquefolium and the leaves are called Dazhongye. The root contains indigotin, indigo red, mustelin, β-sitosterol, palmitic acid, etc.. The leaves contain indigotoxin B, indigotoxin and indirubin. The roots and leaves are bitter in flavor and cold in nature. It has the function of clearing heat and detoxification and cooling blood. It is used for treating influenza, mumps, epidemic encephalitis B, acute infectious hepatitis and sore throat. The fresh leaves are also the raw material of Qingdai dye, which is in great demand. Mainly produced in Hebei Anguo, Jiangsu Nantong, in addition, Shandong, Anhui, Zhejiang and Jiangxi provinces are widely cultivated. Currently, planting bases certified by national GAP have been established in Fuyang City, Anhui Province and Yutian County, Hebei Province.

Figure 2-39 Morphology of woad plant

1. Upper part of plant 2. Lower part of plant and root 3. Flower 4. Petals 5. Stamens shown after removing petals

China has also introduced European woad (Isatis tinctoria L.) which, although having the same efficacy, has not yet been popularized in China.

In addition, the efficacy of similar plants of the same genus are small-fruited woad (I. minima Bunge) produced in China's Xinjiang, Central Asia, Iran and Pakistan, etc.; long round-fruited woad (I. oblongata DC.) produced in China's Liaoning, Nei Menggu, Gansu, Xinjiang, Russia, Siberia, Mongolia, also has a distribution.

Blue root is highly adaptable to climate and soil environmental conditions are not strict. It is cold hardy, but likes warmth and is afraid of waterlogging. It is a deep-rooted crop, suitable for cultivation in deep, loose, fertile sandy loam soil. Poorly drained low-lying land, easy to rot the roots, should not be selected.

Banlangen both collect roots and leaves, the whole body can be utilized, high economic benefits, cultivation technology is also relatively simple, easy to large-scale popularization of planting.