any of several hardy perennial herbs of the Polygonaceae, or buckwheat, family that are widely distributed in temperate regions. Sheep sorrel (Rumex acetosella) is a weed that is native to Europe and has become widespread in North America. It is an attractive but troublesome invader that occurs in lawns and gardens as well as meadows and grassy slopes. It sprouts from spreading rootstocks and has acid-tasting, slender triangular leaves and tiny yellow or reddish flowers. Sheep sorrel's pungent, sour leaves are used as a vegetable, as a flavouring in omelets and sauces, and as the chief ingredient of creamed sorrel soup. The young leaves are used in salads. Two related species are garden sorrel (R. acetosa) and French sorrel (R. scutatus); both are hardy perennials distributed throughout Europe and Asia. Garden sorrel, like sheep sorrel, has become naturalized in North America. The name wood sorrel is given to plants belonging to the genus Oxalis (family Oxalidaceae), which also have sour-tasting leaves.