Dioscorea sylvatica

Dioscorea sylvatica, commonly the forest elephant’s foot or wild yam and in Afrikaans the skilpadknol (tortoise bulb) or hottentotsbrood (Khoi bread), is a caudex succulent and slender climber. It grows one or two stems from the top of its caudex or tuber. The stems become up to 15 m high when supported by nearby vegetation.

The large, flattened tuber is from 30 cm to 1 m in diameter and about 12 cm thick. It is dark brown and corky, showing reticulate markings upon the surface, resembling tortoise shell that resulted in the first Afrikaans name given above. The tubers may be buried as deeply as 25 cm or exposed on the ground when growing in shallow soil. 

As throughout the Dioscorea genus, male and female flowers grow on different plants.

The simple, alternate leaves are long-stalked and heart-shaped, ending in a distinct tip that may be acute, only sometimes blunt. The leathery blades are bright green on top and pale green below, the margins entire. The leaf midribs and one or two pairs of incurving lateral veins are sunken on the upper surfaces, prominent below. Leaf dimensions are about 5 cm to 8 cm long and 6 cm wide.

The species distribution is widespread in the east of South Africa, from the east of the Western Cape coast, the Eastern Cape, the eastern Free State and KwaZulu-Natal to Mpumalanga, Gauteng and Limpopo, as well as in some neighbouring countries.

The habitat is inland and coastal forests, bushveld, thicket, grassland, suurveld and on mountains. In spite of its wide geographical distribution the habitat population is considered vulnerable early in the twenty first century, due to extensive medicinal and traditional medicine use, especially historically.

There are stories of 6000 tonnes of these wild yams being collected and processed in a Johannesburg factory. Cortisone is obtained from this and other Dioscorea plants, while several ailments have been treated by traditional healers using this plant, maybe today still. The plant also featured in cattle diseases.

Several yam species have been domesticated agriculturally in Africa as food. Whether D. sylvatica was ever used as a famine food is debatable, supported by the name hottentotsbrood.

The plant is still popular among gardeners (Smith, et al, 2017; Pooley, 1998; Bond and Goldblatt, 1984; iNaturalist; https://biblio.iita.org; https://www.pointshistory.org; http://redlist.sanbi.org).