Cyanodai is a perennial herb of Jurassicaceae, polygonum, Polygonum, Cruciferae, biennial herb of woad, the leaves of grass extracted from the dry pigment by soaking with lime water.

It is blue in color, and the powder is as delicate as dai, which can be used as a dye for painting, and also for medicinal purposes, so it is called qingdai. Autumn harvest of the above plant stems and leaves, add water to soak, until the leaf rot, leaf peeling, remove the leaves, add the right amount of milk of lime, mix thoroughly until the liquid from the green to crimson, fish out the liquid surface foam, sun-dried and become.

Powdered or lumpy. Hand research for a very fine dark blue powder, light and loose, like dust, color can be sticky hands sticky paper; powder sex is big, a shake is flying. It floats in water and seldom sinks; it shows purple-red flame when burned by fire. It has special grassy odor and sour taste. Or irregular porous lumps, particles, rubbed by hand into fine powder.

The planting method of Qingdai

Selection of land: Qingdai it is a very strong use of the environment in most parts of our country can be planted, and the sub-China has been widely planted, such as Jiangsu, Zhejiang, Liaoning, Hebei, Xinjiang and so on is the main origin of the Qingdai. Then in the choice of the planting place of Qingdai, and we try to choose the sunny, well-drained, loose soil, soil fertility sufficient sandy loam planting.

Scientific sowing: qingdai seeds should be selected high-quality, no pests and diseases of the seeds. Before sowing, we need to soak the seeds in warm water at a temperature of about thirty degrees, stirring constantly during the soaking process, soak for three or four hours and then fish out, drain the water, put it into the fine soil and mix it well, then you can sow the seeds. Qingdai can generally be planted in two seasons, respectively, spring and summer sowing, sowing is usually used in the way of strip sowing or sowing.