The Collaborative International Dictionary of English v.0.48:

firebush \firebush\ n.
   1. An evergreen South American shrub *Streptosolen
      jamesonii) having showy trumpet-shaped orange flowers;
      grown as an ornamental or houseplant.

   Syn: marmalade bush, Streptosolen jamesonii.
        [WordNet 1.5]

   2. A densely branched Eurasian plant (Bassia scoparia)
      whose foliage turns purple-red in autumn; also called
      burning bush.

   Syn: summer cypress, burning bush, belvedere, Bassia
        scoparia, Kochia scoparia.
        [WordNet 1.5]