Yam

Yam, common name for any of several members of a genus of perennial herbs. Members of the genus are monocots and are native to tropical regions throughout the world. Yams are cultivated for their edible tubers, which grow up to 2.4 m(8 ft) long and weigh up to 45 kg (100 lb). The inconspicuous white or greenish-yellow flowers, arranged in spikes or racemes, have a six-parted calyx (outer flower whorl), a six-lobed corolla (inner floral whorl), six stamens, and a solitary pistil. The fruit of the yam consists of a membranaceous, three-winged capsule.

The water yam is a Southeast Asia species that is commonly cultivated. The Chinese yam, or Chinese potato, also known as cinnamon vine, is cultivated in the northern United States as an ornamental climbing vine; its thick tubers reach a length of about 1 m (about 3 ft). The air potato is native to South Asia; it bears white flowers and aerial tubers that attain a weight of several kilograms. The wild yam, native to the eastern United States, has rootstocks that are not enlarged. Yams are rarely cultivated in the United States; the few species grown are limited to Florida and several neighboring states. The name yam is commonly but incorrectly applied to varieties of the genus containing the sweet potatoes (see Sweet Potato).

Scientific classification: Yams make up the genus Dioscorea of the family Dioscoreaceae. The water yam is classified as Dioscorea alata; the Chinese yam, or Chinese potato, as Dioscorea batatas; the air potato as Dioscorea bulbifera; and the wild yam as Dioscorea villosa.