Oxalis tuberosa Molina
oca
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.
N.; S.; St.: scattered localities throughout.
Colombia 1958
Waste places in the vicinity of gardens, especially round rubbish dumps.
FL Mar-Apr.
Oca is very commonly cultivated for its edible tubers in most parts of the country. Most plants in N.Z. belong to 1 of 2 forms. One has purple stems and petioles: the other has green. There may also be differences in colour of parts of the fl. but only the purple form has been observed with fls. Most wild occurrences are of a few isolated plants; these presumably originate from tubers because the sp. seldom fls and is not known to set seed in N.Z.
Oca is erroneously called yam in N.Z., but is very dissimilar to true yams, a name applied to various spp. of the monocotyledonous genus Dioscorea L. Because Dioscorea spp. (usually D. alata L.) have been imported into N.Z. increasingly in the last 2 decades to cater for immigrants from tropical Polynesia, the use of "yam" for Oxalis tuberosa is very confusing. O. tuberosa has been previously known in N.Z. as O. crenata.
