Oxalis pes-caprae

Oxalis pes-caprae is a species of tristylous yellow-flowering plant in the wood sorrel family Oxalidaceae. Oxalis cernua is a less common synonym for this species. It is commonly known as African wood-sorrel, Bermuda buttercup, Bermuda sorrel, buttercup oxalis, Cape sorrel, English weed, goat's-foot, sourgrass, soursob or soursop; Afrikaans: suring; Arabic: hommayda (حميضة). 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.

Description

A herb which keeps growing from year to year. It has an underground stem which produces many bulbs. The leaves have 3 leaflets are are arranged in a ring near the base. The leaflets have 2 lobes. They are on long leaf stalks. The leaflets have a few stiff hairs underneath. The flower stalks arise from the base and are longer than the leaves. There can be 3-16 flowers in a cluster. The flowers are large and yellow. The petals are 2-2.5 cm long.

Edible Uses

The leaves are edible raw or cooked with a pleasant acid flavour, making a welcome addition to mixed salads — children are particularly fond of eating them on their own. Use in moderation. The flowers are also edible raw, with the same pleasant acid flavour and an attractive appearance in the salad bowl. The root can be eaten cooked.

Traditional Uses

CAUTION: The leaves contain oxalates and can affect calcium absorption. They probably damage kidneys. They should not be eaten in large amounts. They are best eaten with a readily available source of calcium such as cream or coconut milk. They are eaten raw in salads. They are also added to soups and stews. The flower stalks are eaten. The bulbs are eaten grilled.

Medicinal Uses

None known

Known Hazards

The leaves or roots 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. Oxalic acid is toxic in large quantities, a concern in regions such as southern Australia where Oxalis pes-caprae grows invasively in enormous quantities and in high densities. Various sources suggest that oxalis ingestion causes calcium oxalate kidney stones, but clinical experience and physiological considerations make it unlikely that any realistic intake of Oxalis would affect human liability to kidney stones. Accordingly, some Australian references to the hazards of oxalis to livestock tend to be dismissive of this risk. However, in spite of its comparatively benign nature, where it has become dominant in pastures, as sometimes happens outside South Africa, Oxalis pes-caprae certainly can cause dramatic stock losses. For example, when hungry stock, such as sheep released just after being shorn, are let out to graze in a lush growth of Oxalis pes-caprae, they may gorge on the plant, with fatal results, as has been found in South Australia at least. Such stock fatalities patently have little logical connection with the presence or absence of oxalate kidney stones. For one thing, the fatal effects on sheep are far too rapid to result from the growth of bulk kidney stones. The plant has been found to be nutritious, but too acidic to be good fodder, largely being left untouched by grazing stock. When stock do consume large quantities, the effects typically involve death in several weeks with symptoms suggesting chronic oxalate poisoning, including tetany, or sudden death with extensive renal damage. Such damage suggests the twofold effect of calcium immobilisation (the tetany) and the formation of Calcium Oxalate Monohydrate raphides in the kidney tissue. The histotoxic effects of the raphides in kidney have by now been investigated. Oxalis poisoning of stock is not a serious forage concern in South African pastures, unless exceptionally favoured by overgrazing.

Distribution

It grows in warm temperate and Mediterranean climate areas. It grows in dry areas. It is native to South Africa. It can grow in hot arid areas with a marked dry season. The dry season can be 6-11 months. It grows in coastal regions and between 50-500 m above sea level. It can tolerate shade. It can grow in arid places. Tasmania Herbarium.

Where It Grows

Afghanistan, Africa, Argentina, Asia, Australia, Bermuda, Brazil, Britain, Canary Islands, Chile, China, Cyprus, East Africa, Egypt, Ethiopia, Europe, France, Greece, India, Indonesia, Iran, Iraq, Israel, Italy, Kenya, Libya, Mediterranean, Middle East, Morocco, Namibia, New Zealand, North Africa, North America, Pakistan, Palestine, Portugal, Qatar, Saudi Arabia, SE Asia, Sicily, South Africa*, Southern Africa, South America, Spain, St Helena, Syria, Tanzania, Tasmania, Tunisia, Turkey, Türkiye, Uruguay, USA,

Cultivation

Easily grown in a sandy soil in a warm dry position. This species is not very cold-hardy in Britain, though it is naturalized in parts of south-western England. It tolerates temperatures down to about -5°c. Plants spread rapidly when in a suitable environment and can quite easily become a weed in virtually frost-free environments. Plants seldom produce seed in Europe but they spread by means of asexually produced bulbils.

Propagation

Seed is best sown as soon as ripe in a cold frame. Prick out seedlings into individual pots when large enough to handle and plant out in late spring or early summer. For division in spring, larger divisions can go directly into their permanent positions. Smaller divisions are better potted up and grown on in light shade in a cold frame until well established before planting out in late spring or early summer.

Other Uses

None known

Other Information

The leaves are eaten especially by children as a snack.

Notes

There are about 500 Oxalis species.

Nutrition

Synonyms

Also Known As

Acite, Agrio, Alelias, Auriduci, Cannacitula, Eksi yonca, Eksili, Eksilice, Elhounida essafra, Geelsuring, Kati Booti, Koca eksiyonca, Suring, Suuring, Vinagrillo

References (48)

• Ali-Shtayeh, M. S., et al, 2008, Traditional knowledge of wild edible plants used in Palestine (Northern West Bank): A comparative study. J Ethnobiol Ethnomed. 4: 13
• Biscotti, N. et al, 2018, The traditional food use of wild vegetables in Apulia (Italy) in the light of Italian ethnobotanical literature. Italian Botanist 5:1-24
• Blamey, M and Grey-Wilson, C., 2005, Wild flowers of the Mediterranean. A & C Black London. p 111
• Ciftcioglu, C. G., 2015, Sustainable wild-collection of medicinal and edible plants in Lefke region of North Cyprus. Agroforest Syst. Springer
• Cordero, S. E., Abello, L. A., & Galvez, F. L., 2017, Plantas silvestres comestibles y medicinales de Chile y otras partes del mundo. CORMA p 212

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