sundrops

Any of various plants of the genera Oenothera and Calylophus having four-petaled yellow flowers that bloom during the day.

A hardy biennial or perennial plant, Œnothera fruticosa, of eastern North America, a shrubby herb from 1 to 3 feet high, often cultivated for its profuse bright-yellow flowers. Differently from the related evening primrose, its flowers open by day. See cut under Œnothera.

Any one of the several species of Kneiffia, esp. K. fruticosa (syn. Œnothera fruticosa), of the Evening-primrose family, having flowers that open by daylight.

Evening primrose.

A day-flowering biennial or perennial of the genus Oenothera.