Polygonum argyrocoleon, common name silver-sheath knotweed, is an Asian species of plants in the buckwheat family. It is native to Siberia, western China, Central Asia, and the Middle East. It has also become naturalized in parts of the United States, primarily the Southwest, and northwestern Mexico.Polygonum argyrocoleon is an annual herb up to 80 cm (31 in) tall. It has very small leaves rarely more than 5 cm (2.0 in) long.