Commelina communis, commonly known as the Asiatic dayflower, is an herbaceous annual plant in the dayflower family. It gets its name because the blooms last for only one day. It is native throughout much of East Asia and northern parts of Southeast Asia. In China, the plant is known as yazhicao (simplified Chinese: ; traditional Chinese: ; pinyin: yzhco), roughly translating to 'duckfoot herb', while in Japan it is known as tsuyukusa ( tsuyukusa?), meaning 'dew herb'. It has also been introduced to parts of central and southeastern Europe and much of eastern North America, where it has spread to become a noxious weed. It is common in disturbed sites and in moist soil. The flowers emerge from summer through fall and are distinctive with two relatively large blue petals and one very reduced white petal. The Asiatic dayflower plant serves as the type species for its large genus.