The Collaborative International Dictionary of English v.0.48:

blueweed \blue"weed\ n.
   a coarse prickly European weed (Echium vulgare) with spikes
   of blue flowers; naturalized in the U. S.

   Syn: blue devil, blue thistle, viper's bugloss.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

blueweed
    n 1: a coarse prickly European weed with spikes of blue flowers;
         naturalized in United States [syn: blueweed, blue
         devil, blue thistle, viper's bugloss, Echium
         vulgare]