Ya Zhi Cao

Ya Zhi Cao is the dried aerial parts of Commelina communis L. (Commelinaceae), the common dayflower, an annual herb of moist disturbed ground throughout China, Korea, Japan, and now widely naturalized in temperate regions. Stems are decumbent and rooting at lower nodes, 20 to 60 cm long, bearing alternate lanceolate to ovate-lanceolate sheathing leaves. The distinctive flowers, enclosed in folded spathe-like bracts, open for a single morning and have two showy upper bright blue petals and one inconspicuous lower white petal, the source of a natural blue dye historically used in Japanese woodblock printing. In traditional Chinese medicine the herb is sweet, slightly bitter, and cold, entering the Lung, Stomach, and Small Intestine channels; it clears heat, resolves toxicity, and promotes urination, and is used for febrile illness with thirst, sore throat, edema with painful urination, carbuncles, and snakebite.