Any of a number of plants of the buckwheat family having a sour taste because of the presence of oxalic acid in their juicy leaves and stems. The radical leaves of sorrel (Rumex acetosella) grow in a cluster. Shaped like an arrow at the base, the somewhat oval leaves measure about 10 cm (4 in.) in length. The flower stalks may attain a height of about 0.6 m (2 ft) or more. Anciently, the Israelites mixed sorrel with the fodder for their cattle and asses.​—Isa 30:24.