The Collaborative International Dictionary of English v.0.48:

Hard grass \Hard" grass`\ (gr[.a]s`). (Bot.)
   A name given to several different grasses, especially to the
   Roltb["o]llia incurvata, and to the species of Aegilops,
   from one of which it is contended that wheat has been
   derived.
   [1913 Webster]