Oxalis pes-caprae

Oxalis pes-caprae (African wood-sorrel, Bermuda buttercup, Bermuda sorrel, buttercup oxalis, Cape sorrel, English weed, goat's-foot, sourgrass, soursob or soursop, Ξινήθρα) is a species of tristylous yellow-flowering plant in the wood sorrel family Oxalidaceae. Oxalis cernua is a less common synonym for this species. Some of the most common names for the plant reference its sour taste owing to oxalic acid present in its tissues. Indigenous to South Africa, the plant has become a pest plant in different parts of the world that is difficult to eradicate because of how it propagates through underground bulbs.

The plant is palatable and in modest quantities is reasonably harmless to humans and livestock. Oxalis pes-caprae has been used in various ways as a source of oxalic acid, as food, and in folk medicine. The raw bulbs have been used to deal with tapeworm and possibly other worms. The plant has been used as a diuretic, possibly hazardously, in the light of observations in the following section. The lateral underground runners, which tend to be fleshy, have been eaten raw or boiled and served with milk. The golden petals can be used to produce a yellow dye.

The leaves or roots of Oxalis pes-caprae are used in some parts of the world as a food, although the high levels of calcium oxalate in the plant may bear some risks. Such risks can be reduced if the plant parts are boiled first.

Oxalis pes-caprae is an invasive species and noxious weed in many other parts of the world, including the United States, Europe, The Middle East and Australia.