One example of an evening primrose.
any of a genus (Oenothera) of plants of the evening-primrose family, with yellow, pink, or white flowers, many of which open in the evening
designating a family (Onagraceae, order Myrtales) of dicotyledonous plants found chiefly in temperate America, including the fuchsia, sundrops, and willow herbs
Any of various plants of the family Onagraceae and especially the genus Oenothera of the Americas, having four-petaled usually yellow flowers that open in the evening and whose seeds yield an oil used in herbal medicine.
(plural evening primroses)