Helianthus tuberosus
Jerusalem artichokes are not related to either the globe artichoke or the chinese artichoke, nor do they have anything to do with Jerusalem. Rather, they are relatives of the sunflower and native to North America. There are many theories behind the name. Some people think it was given by the pilgrims who saw it as the food of the “New Jerusalem,” others believe that it is a permutation of the Italian word for sunflower (Girasole) or of a Holland farmer who popularized the plant in Europe (Terheusen). Currently, particularly in the United States, they are thought of mainly as a weed. They are, however, a nutritious addition to the diet, easy to cultivate and useful in a variety of dishes.
The jerusalem artichoke plant is a tall sunflower with broad leaves and several yellow flowers at the top. It produces a tuber that is about 1 inch in diameter and several inches long, knobby, and covered with a thin, rough skin. These tubers are the main part used in human consumption. It can be eaten raw or boiled, baked, or roasted.
The artichokes were adopted in Europe quickly after their discover in the sixteenth century, but lost favor later due to a combination of the difficulty involved in their preparation (the knobs make them difficult to peel thoroughly) and the fact that they can cause indigestion. This last is the result of the sugar inulin, which is the main sugar in the artichoke, and is difficult to digest. However the inulin in the tubers is broken down after storage in the ground or in refrigeration.
In addition, jerusalem artichokes can be used to produce fructose, alcohol, and as forage for livestock. In the case of fructose, the yield is significantly lower than that of corn, which is currently the dominant fructose crop. Alcohol production can yield fuel grade ethanol or butanol, but at a cost much higher than that of gasoline. As a livestock forage it doesn't measure up to more traditional plants such as alfalfa, which has a much higher protein content than the artichoke.
Cosgrove, D.R. et al. “Jerusalem Artichoke.” Alternative Field Crops Manual. Madison, WI: University of Wisconsin, 1991. 8 Jan 2009 http://www.hort.purdue.edu/NEWCROP/AFCM/jerusart.html.
Davidson, Alan. The Oxford Companion to Food. 2nd ed. Oxford University Press, USA, 1999.