Oca

Oxalis tuberosa is an annual plant that overwinters as underground stem tubers. These tubers are known as oca , oka or New Zealand Yam. 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.

Edibility

The stem tubers of oca form in the ground in the autumn. These are commonly boiled before eating although they may also be eaten raw. The leaves and young shoots can be eaten as a green vegetable. Introduced to Europe in 1830 as a competitor to the potato and to New Zealand as early as 1860, it has become popular in that country under the name New Zealand yam and is now a common table vegetable. It is also widely known in the Polynesian islands of the South Pacific under the name yam.

The flavour is slightly tangy, and texture ranges from crunchy (like a carrot) when undercooked, to starchy or mealy when fully cooked. Though the original Andean varieties are widely variable in colour from purple to yellow, the usual New Zealand variety is a fleshy pink.

Most New Zealanders know the oca simply as the yam; the Dioscorea vegetables known elsewhere as yams are generally very uncommon there.

Yams are commonly confused with Sweet potatoes, although they are not even distantly related. In New Zealand Sweet potatoes are commonly referred to by their Māori name of kūmara.

Oca can be boiled, baked or fried. In the Andes it is used in stews and soups, served like potatoes or can be served as a sweet. Oca is eaten raw in Mexico with salt, lemon and hot pepper.

Cultivation

Oca is one of the important staple crops of the Andean highlands, second only to the potato due to its easy propagation, and tolerance for poor soil, high altitude and harsh climates.

Ocas need a long growing season, and are day length dependent, forming tubers when the day length shortens in the autumn. In areas with harsh winter climates, early frosts may cut back the foliage before the tubers have a chance to form. In tropical areas where the days are unchanging in length, oca will not set a crop successfully.

Ocas are fairly high in oxalates, concentrated in the skin, and traditional Andean preparation methods were geared towards reducing the oxalate level of the harvested vegetable. This is done by exposure to sunlight which increases the glucose content and sweet taste of the oca. Recent oca cultivars have a lower oxalate content, and have also been selected for more flexibility in day lengths.

Alternative names

Papa lisa (in Bolivia)

Translation

The word "Oca" occurs as such in the following languages: English, Dutch, Swedish.

Translation(s) in other languages: Aymara: Apilla, Czech: Oka (plodina), German: Knolliger Sauerklee, Spanish: Oxalis tuberosa, French: Oca du Pérou, Italian: Oxalis tuberosa, Lithuanian: Gumbinis kiškiakopūstis, Quechua: Uqa, Russian: Кислица клубненосная, Ukrainian: Ока (рослина).