Flax-leaved Horseweed, South American Conyza, South American Horseweed: Conyza bonariensis (Synonym: Conyza floribunda) - Introduced from South America.
Canadian Fleabane, Canadian Horseweed, Horseweed: Conyza canadensis (Synonyms: Conyza canadensis var. canadensis, Conyza canadensis var. glabrata, Conyza canadensis var. sumatrensis, Erigeron canadensis) - Native.