n.1. Any of various plants of the genus Epilobium, especially E. angustifolium (syn. Chamerion angustifolium), having long, terminal, spikelike clusters of pinkish-purple flowers. Also called willow herb.
2. Any of several weedy North American plants of the genus Erechtites in the composite family, having small white or greenish flowers grouped in discoid heads.
[So called because the plants are pioneer species in areas where fire has destroyed other vegetation.]