[Wikipedia] Asia native, Description: Polygonum argyrocoleon, common names silver-sheath knotweed[2] and Persian knotweed, is an Asian species of plants in the buckwheat family. It is native to Siberia, western China, Central Asia, and the Middle East.[3] It has also become naturalized in parts of the United States, primarily the Southwest, and northwestern Mexico.[4][5] 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.[6][3] (contributed by Mary Ann Machi)