The Collaborative International Dictionary of English v.0.48:

goldenrod \gold"en*rod`\, golden-rod
\gold"en-rod`\(g[=o]ld"'n*r[o^]d`), n. (Bot.)
   A tall herb (Solidago Virga-aurea), bearing small yellow
   flowers in a graceful elongated cluster. The name is common
   to all the species of the genus Solidago.
   [1913 Webster]

   Golden-rod tree (Bot.), a shrub (Bosea Yervamora), a
      native of the Canary Isles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

goldenrod
    n 1: any of numerous chiefly summer-blooming and fall-blooming
         North American plants especially of the genus Solidago