The Collaborative International Dictionary of English v.0.48:

crownbeard \crownbeard\ n.
   any plant of the genus Verbesina having clustered white or
   yellow flower heads.

   Syn: crown beard.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

crownbeard
    n 1: any plant of the genus Verbesina having clustered white or
         yellow flower heads [syn: crownbeard, crown-beard,
         crown beard]