man-of-the-earth

from The Century Dictionary.

• noun The wild potato-vine, Ipomœa pandurata, so called from the great size sometimes attained by the root.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A long-rooted morning glory (Ipomoea leptophylla) of Western U. S.
• noun A tropical American prostrate or climbing herbaceous perennial (Ipomoea panurata or Ipomoea fastigiata) having an enormous starchy root; sometimes held to be source of the sweet potato.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun tropical American prostrate or climbing herbaceous perennial having an enormous starchy root; sometimes held to be source of the sweet potato
• noun a morning glory with long roots of western United States