A monocot related to lilies and grasses, yams are vigorous herbaceous, perennially growing vines from a tuber. Some 870 species of yams are known, a few of which are widely grown for their edible tuber but others of which are toxic (such as D. communis).

Yam plants can grow up to 15 metres (49 feet) in length and 7.6 to 15.2 centimetres (3 to 6 inches) high. The tuber may grow into the soil up to 1.5 m (5 ft) deep.  The plant disperses by seed. 

The edible tuber has a rough skin that is difficult to peel but readily softened by cooking. The skins vary in color from dark brown to light pink. The majority, or meat, of the vegetable is composed of a much softer substance ranging in color from white or yellow to purple or pink in mature yams.