Bai Wei

Cynanchum atratum (Bai Wei, swallowwort) is a perennial herb in the Apocynaceae family (formerly Asclepiadaceae), growing 30 to 70 centimeters tall from a short rhizome bearing a dense fascicle of slender, pale yellowish-brown to dark brown radial roots that are the medicinal material. The erect, simple, finely pubescent stems bear opposite, ovate to broadly elliptic leaves 6 to 12 centimeters long, with entire margins, acute tips, and softly hairy surfaces. From late spring to summer, dense axillary cymes of small dark purple-black, almost blackish, star-shaped flowers about 1 centimeter across are produced; the corolla has five spreading lobes, and a characteristic dark corona sits at the center. The fruits are slender, spindle-shaped follicles 5 to 7 centimeters long, splitting along one side to release flat seeds tipped with silky white coma. Native to East Asia, including China, Korea, Japan, and the Russian Far East, growing in grasslands and open woodland. Roots are harvested in spring or autumn.