Fragrant and showy, Oenothera biennis (Common Evening Primrose) is an erect biennial featuring large, bowl-shaped, lemon-scented, yellow flowers, up to 2 in. across (5 cm), at the top of a stiff, purple-tinged flower stem. Blooming profusely from early summer to early fall, the flowers open in the evening and remain open through late morning. They rise on leafy, branched stems from a basal rosette of oblong, long medium green leaves.