Sourgrass is a common name given to several species of Oxalis, including Oxalis pes-caprae, also known as Cape Sorrel or Bermuda Buttercup; Oxalis grandis, the large yellow wood sorrel; Oxalis montana, the common wood sorrel; and Rumex acetosella, sheep sorrel. These grow as weeds in many parts of the United States. Oxalis pes-caprae is considered a major nuisance in parts of California.
These plants have a pleasant lemony taste and are sometime used to season salads, and in herbal remedies. All of these plants contain oxalic acid, which is toxic in high levels and may cause or exacerbate kidney stones. Children like the sour taste of "sourgrass" and can be observed eating the flower stems. Children's affection for oxalis is recorded by ethnographers. See, for example, "Archival data on wild food plants used in Poland in 1948" by Łukasz Łuczaj, published in the Journal of Ethnobiology and Ethnomedicine 2008, 4:4.