Ironweed

ironweed, (genus Vernonia), genus of about 500 species of perennial plants of the aster family (Asteraceae). Small herbaceous species are distributed throughout the world, while shrubs and trees are native primarily to tropical regions. Some authorities have suggested that the genus be limited to only the North American species. A handful of autumn-blooming species are cultivated as border plants for their attractive white, purple, or pink flower clusters.