Oxalis tuberosa (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Oxalis tuberosa Molina

Family: Oxalidaceae

Oxalis crenata Jacquin, O. crassicaulis Zuccarini, O. arracacha G. Don.

• Oca (En, Sp, South America). Truffette acide (Fr).

Oca is only known from cultivation; it was domesticated in ancient times in the Central Andes of Peru and Bolivia. At present it is cultivated in the Andes from Venezuela to Chile and occasionally elsewhere, e.g. in Mexico, New Zealand, southern Europe. It is most important in Colombia and Peru.

The tubers form one of the principal carbohydrate foods for the Indians of the high Andes and are eaten boiled, roasted or candied. Oca is sometimes considered as the second most important root crop of the high Andes after Irish potato. For preservation, harvested tubers are dried. Dried tubers of bitter cultivars are called "chuña", those of sweet cultivars are called "cavi". Chuña is usually soaked and then used as an ingredient in stews, cavi is eaten often cooked with honey or cane sugar syrup. The chemical composition of oca tubers on dry weight basis is approximately: protein 3-8%, fat 0.5%, carbohydrates 83-89%, fibre 4-5%, ash 2-3%. The energy value per 100 g edible portion is about 1550 kJ. Some cultivars contain calcium oxalate crystals in the tubers.

Perennial, erect herb, often grown as an annual, pubescent, about 30 cm tall. Rhizome branched, the ends thickening into cylindrical tubers 5-7.5 cm long, 2-4 cm in diameter, white, yellow, red or purple. Leaves alternate, trifoliolate; petiole 7-10 cm long; leaflets obcordate, up to 25 mm × 22 mm, incised at apex. Inflorescence a 5-8-flowered umbel on peduncle 15-17 cm long; pedicel 7-20 mm long; flowers yellow, 5-merous, trimorphic, i.e. associated with 3 distinct tuber forms: long-styled with sweet tubers, mid-styled with white and short-styled with red tubers. Fruit a capsule with 1-3 seeds.

There are many cultivars. The best crop is grown at altitudes of 2700-4200 m. Propagation is by planting whole tubers or pieces with 1-3 eyes. Planting distance 50-90 cm between rows, 20-40 cm in the row. Tubers are harvestable 8 months after planting, yield is 4-5(-20) t/ha. Oca is a promising crop for the cooler parts of the tropical highlands of South-East Asia, suffering less from diseases and pests than Irish potato.

11, 20, 28, 31, 33, 40, 43, 44, 45.

L.E. Groen, J.S. Siemonsma & P.C.M. Jansen