Oxalis tuberosa

What to Eat

Edible parts: Flowers, Leaves, Root, Tubers, Vegetable

The tubers can be eaten raw or cooked and have an acid, lemon-like flavour when first harvested. Left out in the sun, they become sweet — in some varieties so sweet that they are said to resemble dried figs and are sold as fruits in local markets in South America. The cooked root is delicious whether in its sweet or acid form and can be boiled, baked, or prepared in similar ways to potatoes. Good-sized tubers reach 8cm or more in length. The slightly waxy skin makes them very easy to clean. Tubers contain approximately 70–80% moisture, 11–22% carbohydrate, 1% fat, 1% fibre, and 1% ash. The carbohydrate is rich in sugar and easy to digest. Acid types contain up to 500ppm oxalic acid, while sweet forms contain much less oxalic acid than is found in potatoes. Young leaves and flowers are also edible raw or cooked but are of poor quality. Use in moderation.

Known Hazards

Where to Find It

A temperate plant. It mostly grows in the Andes from Colombia to Chile at between 3,500 and 3,800 m altitude. The plant is frost hardy. They grow in the high altitude tropics. (2,800 - 4,560 m in the Andes). In Argentina it grows between 1,200-2,800 m above sea level. In the hot tropical lowlands, tubers perish quickly. A daylength of 9 hours is best for tuber formation. Vegetative top growth occurs under long day lengths. It suits hardiness zones 7-11.

Andes, Argentina, Australia, Bolivia*, Britain, Central America, Chile, Colombia, Ecuador, Europe, Mexico, New Zealand, North America, Pacific, Papua New Guinea, PNG, Peru, South America, Tasmania, USA, Venezuela,

How to Identify

A small annual herb up to 30 cm high with leaves of 3 leaflets. The stems are round and succulent. The leaves are spirally arranged. The flowers are orange-yellow. Three different kinds of flowers occur associated with three different kinds of tubers. The tubers have scales which cover long deep eyes. Tubers vary considerably in shape. The tubers are wrinkled and vary in colour between red, orange, yellow, or white. Some varieties have bitter tubers. They are about 5-8 cm long and 2-4 cm across. The plant rarely sets seed in the field but seed can be produced by self pollinating. When seed form, they occur in 5 celled locules with 1-3 tiny seeds in each.

Nutrition Score: 25/100

How to Grow

Prefers a light rich soil in a warm sunny position. Tolerates a pH range from 5.3 to 7.8. Plants succeed in areas with an average rainfall ranging from 570 - 2150mm per year. Oka is widely cultivated in the Andes for its edible tubers, there are many named varieties. This species has an excellent potential as a major root crop in temperate zones, it has the potential to yield as highly as potatoes but does not have the susceptibility to pests and diseases that are a bugbane for potato growers. Plants are slightly more hardy than the potato, tolerating light frosts but the top-growth being severely damaged or killed by temperatures much below freezing. The main drawback is that development of the tubers is initiated by the number of hours of daylight in a day. In Britain this means that tubers do not begin to form until after the 21st of September and, if there are early frosts in the autumn, yields will be low. There are possibly some forms in southern Chile that are not sensitive to daylength, these will be more suitable to higher latitudes such as Britain. It is said that the varieties with white tubers are bitter because they contain calcium oxylate crystals whilst those with tubers that are of other colours are sweet. However, we are growing one variety with white tubers and it most certainly is not bitter. Yields tend to average about 7 - 10 tonnes per hectare but experimentally yields of 40 tonnes per hectare have been achieved. Earthing up the growing stems as they start to form tubers can increase yields significantly.

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. Seed is not usually produced in Britain. Harvest tubers in late autumn after frosts have killed the top growth, store in a cool, dry, frost-free place, and plant out in April. For basal cuttings in spring, harvest shoots with plenty of underground stem when they are about 8–10cm above ground, pot into individual pots, and keep in light shade in a cold frame or greenhouse until rooting well before planting out in summer.

Medicinal Uses

None known

Other Uses

None known

Oxalis tuberosa is a perennial herbaceous plant that overwinters as underground stem tubers. These tubers are known as uqa in Quechua, oca in Spanish, yams in New Zealand and several other alternative names. The plant was brought into cultivation in the central and southern Andes for its tubers, which are used as a root vegetable. The plant is not known in the wild, but populations of wild Oxalis species that bear smaller tubers are known from four areas of the central Andean region. Oca was introduced to Europe in 1830 as a competitor to the potato, and to New Zealand as early as 1860. In New Zealand, oca has become a popular table vegetable and is called yams (although not a true yam). It is available in various colors, including yellow, orange, pink, apricot, and traditional red.

Production

Tubers mature in about 8 months. Average yields in the Andes are about 3.7 t / ha. After digging tubers are cured in the sun for several days.

Other Information

It is a commercially cultivated vegetable. "Stew without chunu is like life without love!" It has only recently been introduced to Papua New Guinea to try it out. It is an important food in high altitude areas in the Andes.

Notes

There are about 500 Oxalis species.

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