Helianthus tuberosus. Jerusalem artichoke. Sunchoke.
Composite Family - Compositae
American Indians drank the leaf and stem tea, or ate the flowers to treat rheumatism. Jerusalem artichoke contains high amounts of inulin. Inulin is an oligo-saccharide of fructose which putatively assists in controlling diabetes. For a reasonably fair treatment of inulin see this article http://www.naturalnews.com/022356_inulin_food_ingredients.html