The Collaborative International Dictionary of English v.0.48:

Penstemon \Penstemon\ prop. n.
   A large genus of subshrubs or herbs having showy blue or
   purple or red or yellow or white flowers; found mostly in
   Western North America.

   Syn: genus Penstemon.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Penstemon
    n 1: large genus of subshrubs or herbs having showy blue or
         purple or red or yellow or white flowers; mostly western
         North America [syn: Penstemon, genus Penstemon]