The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus Polygonum, and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers to the many swollen nodes the stems of some species have. It is derived from Greek; poly means many and goni means knee or joint. Polygonaceae contain some of the worst weeds, including species of Persicaria, Emex, Rumex, and Polygonum, such as Japanese knotweed.