The Collaborative International Dictionary of English v.0.48:

bluestem \bluestem\ n.
   tall grass with smooth bluish leaf sheaths grown for hay in
   Western U.S.

   Syn: blue stem, Andropogon furcatus, Andropogon gerardii.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

bluestem
    n 1: tall grass with smooth bluish leaf sheaths grown for hay in
         the United States [syn: bluestem, blue stem,
         Andropogon furcatus, Andropogon gerardii]