"Yam tubers can grow up to 1.5 m [4.9 ft] in length and weigh up to 70 kg [154 lb] and 3 to 6 inches high. The vegetable has a rough skin which is difficult to peel, but which softens after heating. The skins vary in color from dark brown to light pink. The majority of the vegetable is composed of a much softer substance known as the "meat". This substance ranges in color from white or yellow to purple or pink in mature yams."
"Yam is the common name for some species in the genus Dioscorea [family Dioscoreaceae]. These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania. There are many cultivars of yam."
"Although the sweet potato [Ipomoea batatas] has traditionally been referred to as a yam in parts of the United States and Canada, it is not part of the Dioscoreaceae family."
"Yams are a primary agricultural commodity in West Africa and New Guinea. They were first cultivated in Africa and Asia about 8000 BC. Due to their abundance and consequently, their importance to survival, the yam was highly regarded in Nigerian ceremonial culture and used as a vegetable offered during blessings."
"Yams are still important for survival in these regions. The tubers can be stored up to six months without refrigeration, which makes them a valuable resource for the yearly period of food scarcity at the beginning of the wet season."
"'Yam powder' is available in the West from grocers specializing in African products, and may be used in a similar manner to instant mashed potato powder, although preparation is a little more difficult because of the tendency to form lumps. The 'yam powder' is sprinkled onto a pan containing a small amount of boiling water, and stirred vigorously. The resulting mixture is served with a heated sauce, such as tomato and chili, poured onto it. To avoid lumps forming, the powder and the water are mixed before putting on the heat, then stirred continuously as the mixture is heating."
Text Credit: Wikipedia