any of a number of plants that grow readily on cleared or burned-over land; esp., a species (Epilobium angustifolium) of willow herb, with purplish-red flowers
See fireweed in American Heritage Dictionary 4
noun
Any of various plants of the genus Epilobium, especially E. angustifolium, having long, terminal, spikelike clusters of pinkish-purple flowers. Also called willow herb.
Any of several weedy North American plants of the genus Erechtites, having small white or greenish flowers grouped in discoid heads.