Polygonaceae is a family of flowering plants known informally as the "knotweed family" or "smartweed family". 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 that the stems of some species have. It is derived from Greek; poly means many and goni means knee or joint.
Polygonaceae comprises about 1200 species.  These are distributed into about 50 genera. The largest genera are Eriogonum (240 species), Rumex (200 species), Coccoloba (120 species), Persicaria (100 species) and Calligonum (80 species).   The family is present worldwide, but is most diverse in the North Temperate Zone.
Several species are cultivated as ornamentals  A few species of Triplaris provide lumber.  The fruit of the sea grape (Coccoloba uvifera) is eaten, and in Florida, jelly is made from it and sold commercially.  The seeds of two species of Fagopyrum provide grain. The petioles of rhubarb ( Rheum rhabarbarum) are a food item. The leaves of the common sorrel (Rumex acetosa) are eaten in salads or as a potherb. 
Polygonaceae contains some of the worst weeds. These include species of Persicaria, Emex, Rumex, and Polygonum. 
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