Clockwise from above: A ground cover of oxalis; Oxalis oxalidaceae or sour-sob; Oxalis in the vegie patch.
Oxalis is of the Oxalidaceae family which has over 850 different species worldwide, with about 30 species in Australia, seven of these native. A number of species are grown as ornamental plants. Oxalis is from the Greek oksos meaning sour, referring to the taste of the leaves and stems.
A common weed, oxalis is actually part of the sorrel family and is found in most parts of the world, being especially diverse in the tropical areas of Brazil, Mexico and South Africa.
Oxalis originates from the highlands of South America where it has been cultivated since Incan times. The Incas domesticated many of their prized crops from pernicious weed species creating vigorous, low-maintenance vegetables that were able to thrive in adverse conditions.
In Australia, The Most Common Varieties Are:
Oxalis pes-caprae: also known as thumb, sour-sob, yellow sour grass, buttercup oxalis, Bermuda buttercup and English weed. Particularly common in the southern area of Australia.
Oxalis corniculata: produces small yellow flowers soon followed by the emergence of upright seed capsules. It also has a variety with purple-coloured leaves.
Oxalis debilis: produces deep pink flowers typically during the months from July through to September.
Oxalis latifolia: produces deep pink flowers during the months May through to September.
A perennial growing to 15 cm, oxalis is easily mistaken for clover, so look carefully for what sets it apart: three heartshaped leaflets and small five-petaled pink, purple, white or yellow flowers with ten stamens. Clover, on the other hand, has leaves that are shaped like a tear. Typically oxalis reproduces itself through the seeds it produces or the bulbs it forms.
This persistent weed will grow in dry, open areas as well as moist, nutrient-rich soils, and in both sun and shade. Oxalis can form a dense groundcover often excluding native species, especially in shady sites.
Oxalis is commonly seen as the invasive weed that takes up water and garden space, instead of the delicate, edible plant that gives a carpet of colour. Lawns or soils that are thin, weak and deprived of nutrients are also desirable places for weeds like oxalis. This can make it a useful plant in marginal areas needing some greening up.
Once oxalis gets into your garden, it’s there. The more you dig at it to get it out, the more it spreads. So, like many edible weeds, if you can’t beat it, eat it.
Oxalis has been consumed by humans for centuries. All parts are edible, including the root bulb which can be succulent and sweet. Some say the leaves and stems taste much like rhubarb but not as tart, while others say oxalis leaves have a lemon flavour.
The leaves and stems of oxalis varieties can be used in salads, made into soup or pesto, or used as stuffing for fish and chicken. The leaves will wilt quickly, so they should be used shortly after picking.
The tubers, including the larger Oca variety, are as versatile as the humble spud. Eaten raw they have a crisp apple-like texture and tart flavour which makes them a wonderful addition to salads and coleslaws.
When cooked (be it roasted, chipped, mashed, boiled or baked), they are similar to new potatoes and their sharpness becomes a mild tanginess with a rich, waxy flavour and texture.
The larger fleshy, juicy tubers of Oca have long been cultivated for food in Colombia and elsewhere in the northern Andes of South America. Oca is now grown and sold in New Zealand as New Zealand Yam (although not a true yam), and varieties are available in yellow, orange, apricot, and pink, as well as the traditional red-orange. This variety is better suited to cooler climates as temperatures over 28ÅãC cause plants to wilt.
Among Indigenous American tribes, oxalis also had medicinal value. As Dr. James Duke notes in his Handbook of Edible Weeds (CRC Press 2000), ‘The Kiowa Indian tribe chewed wood sorrel to alleviate thirst on long trips, the Potawatomi Indians cooked it with sugar to make a dessert, the Algonquin Indians considered it an aphrodisiac, the Cherokee ate wood sorrel to alleviate mouth sores and a sore throat, and the Iroquois ate wood sorrel to help with cramps, fever and nausea.’
And if all else fails, learn to tolerate oxalis. With weeds, it’s all about how you look at them. Many gardeners have given up struggling to eradicate it and decided that oxalis makes a pretty groundcover and a nice addition to the vegie basket.