Source : Webster's Revised Unabridged Dictionary (1913)

Stoneroot \Stone"root`\, n. (Bot.)
   A North American plant ({Collinsonia Canadensis}) having a
   very hard root; horse balm. See {Horse balm}, under {Horse}.

Source : WordNet®

stoneroot
     n : erect perennial strong-scented with serrate pointed leaves
         and a loose panicle of yellowish flowers; the eastern
         United States [syn: {horse balm}, {horseweed}, {stone-root},
          {richweed}, {stone root}, {Collinsonia canadensis}]