Oenothera cespitosa

About

Oenothera cespitosa, known commonly as tufted evening-primrose or fragrant evening-primrose, is a perennial plant of the genus Oenothera native to western North America from the western edge of the Great Plains and all parts of the Intermountain West in a wide range of dry habitats. Its flowers are open at night and fade by the next day. The species is cultivated in gardens, particularly in its native range.

Summary from Wikipedia