Common evening primrose, evening star, yellow evening primrose
All across the western states, except Arizona, Colorado and Wyoming, though many populations have been naturalized; plant is more common in the eastern US
Grassland, roadsides; disturbed ground, generally at low elevations
Narrow, lanceolate, up to 7 inches long, lightly toothed edges
Like most members of this genus, the large, papery flowers of oenothera biennis open in early evening and persist only until late morning of the following day. They measure about 3 inches across, and all parts are yellow; the four petals (each formed of two lobes), the stamens and the four-pronged pistil. Stems have a covering of fine hairs and are often rich purple in color. The plant grows quite large, resembling a small shrub, with dense branches and many leaves; it has a two-year life cycle, sprouting basal leaves for the first year, then longer stalks with flowers during the second year.