a family of plants of order Polygonales chiefly of the north temperate zone; includes the buckwheats

The family Polygonaceae, also known as the knotweed family or smartweed family, are a group of dicots, comprising about 50 genera and 1120 species of monoecious and dioecious herbs, shrubs and small trees. Some well known members include buckwheat, sorrel (but not wood sorrel), rhubarb, and knotgrass. The family is named for the shape of the seed; that of rhubarb, for example, has a triangular cross-section.