Oxalis tuberosa Molina

Rhizomatous perennial herb; tubers numerous, elongated, to c. 12 × 4 cm, with reddish pink skin and yellow flesh; scales many, minute and in a long groove, otherwise tubers smooth and shining. Stems numerous, erect, to c. 75 cm tall, hairy, green or purple, succulent, moderately thick. Lvs 3-(4)-foliolate, cauline, white-pilose. Petiole 3-8 cm long, slender; stipules 5-8 mm long, adnate to petiole, membranous. Lamina of leaflets equal, sessile, 10-32 × 8-30 mm, broad-obovate, hairy, the hairs denser beneath; apex emarginate; calli 0. Fls few in cymes; peduncles to 11 cm long, ± hairy; pedicels to 10 cm long, densely hairy. Bracts 4-5 mm long, subulate; calli 0. Sepals 7-10 mm long, lanceolate, glabrous except at base and apex; calli 0. Petals c. 1.5 cm long, obovate, yellow with dark red veins, glabrous. Stamens at 2 levels; filaments dilated below, upper whorl hairy in lower 1/2. Styles of intermediate length between stamen whorls, hairy. Capsule not seen.

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.

The tubers are acid when fresh but are dried slightly then cooked and eaten. The bitter kinds are freeze dried and stored for later use. They can be used in soups and stews. The young leaves and shoots can be eaten. CAUTION Fresh tubers contain calcium oxalate.

Plants are grown from tubers or cut pieces of tubers which contain 1-3 eyes. Planting is normally done at the beginning of the rainy season and plants are weeded and soil mounded around them. A spacing of 20-40 cm x 20-36 cm is recommended.