Common evening primrose
Oenothera biennis (L.)
other common names: night willow-herb, large rampion, tree-primrose, king's cure-all, scurvish, evening primrose
Oenothera: a name used by Theophrastus for a species of Epilobium, another genus in this family. It also is Greek for "wine scented," referring to the scent of the flowers or to the fact that the roots were once used for wine.
Biennis: meaning "biennial," for its characteristic of living two years
Evening primrose family: Onagraceae
Photograph by Thomas Rosburg, Wildflowers of the Tallgrass Prairie: The Upper Midwest, Second Edition