The Collaborative International Dictionary of English v.0.48:

Goat's beard \Goat's beard\, goatsbeard \goatsbeard\n. (Bot.),
   A weedy European annual with yellow flowers, of the genus
   Tragopogon; -- so named from the long silky beard of the
   seeds. One species is the salsify or oyster plant; it is
   naturalized in US.

   Syn: meadow salsify, shepherd's clock, Tragopogon
        pratensis.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

goatsbeard
    n 1: weedy European annual with yellow flowers; naturalized in
         United States [syn: meadow salsify, goatsbeard,
         shepherd's clock, Tragopogon pratensis]