Oenothera biennis, commonly known as common evening primrose, is a biennial wildflower native to North America and now widespread in Europe and Asia. It is distinguished by its tall, erect stems and large, fragrant yellow flowers that open at dusk and close by morning, adapted to attract night-flying moths. The name biennis refers to its two-year life cycle, with a leafy rosette in the first year and flowering in the second. Unlike many wild species, its seeds are rich in oil valued for medicinal and cosmetic uses, giving this humble roadside plant both ecological and cultural significance.