Dioscorea mexicana

Dioscorea mexicana, Mexican yam or cabeza de negro is a species of yam in the genus Dioscorea.

Dioscorea mexicana is a caudiciform dioscorea having either a partly to completely above-ground dome-shaped caudex with a thick, woody outer layer up to 3 feet(90 cm) in diameter and 8-10 inches(20 to 25 cm) in height. The caudex of D. mexicana is divided into regular polygonal plates that become protuberant with age, and separated by deep fissures. The vigorous annual vines which may reach 30 feet (9 m) long before dying back in winter, that grow up from the caudex, bear heart-shaped leaves.