Oenothera biennis aka Common Evening Primrose

Oenothera biennis is known as common evening primrose. It belongs to the Onagraceae family. Its native range runs from Canada to central Mexico. It has also become established across much of Europe. Wild plants grow in fields, prairies, and disturbed ground. Roadsides and railway banks also provide homes for it. Most plants live for two years, then die after seeding. New seedlings can keep a patch growing for years.

The first year brings a low rosette of leaves. Upright flower stems rise in the second year. Garden plants often reach 3–5 feet [0.9–1.5 metres] tall. NC State also reports heights of 7 feet [2.1 metres]. Spread varies from about 1.6–3 feet [0.5–0.9 metres] across. The green leaves have a long, narrow shape. Their edges have shallow teeth and may look wavy. RHS describes red veins and a slightly sticky surface. The flower stems bear hairs and may show red tones.

Yellow blooms appear from June to September. Each cup-shaped flower has four petals and a cross-shaped stigma. Flowers grow in clusters at the tops of stems. They open at dusk and stay open through morning. Daytime heat then brings them to a close. Their light lemon scent draws moths that fly at night. Bees visit before the blooms close in the morning. Narrow brown capsules follow the flowers in fall. Each capsule splits to shed as many as 100 seeds. Birds, including goldfinches, eat the seeds.

Grow this plant in full sun and well-drained soil. It also tolerates some shade, including shade in the afternoon. Poor to moderately fertile soil suits it. Sandy and gravelly soils work well. Plants prefer moderate moisture but withstand drought. Sources list USDA zones 4–9 and RHS hardiness H7. Sow seed in early summer to raise new plants. RHS advises cutting stems back once flowering ends. It suits borders, cottage gardens, and wildflower or herb gardens. Its flowers also draw butterflies and support wildlife.

Self-seeding can make this plant weedy and untidy. Seeds may remain viable in soil for 70 years. Serious pest and disease problems are uncommon. Leaf spot and powdery mildew can still occur. Primrose moth larvae eat the flower buds. PFAF lists cooked roots, flowers, leaves, and young seedpods as edible. Reports disagree about eating young shoots. Seed oil has food, cosmetic, and medicinal uses. The flowers also provide yellow dye. PFAF warns of seizure risks and interactions with some medicines. Its cautions include anticoagulants and phenothiazines. High doses may cause diarrhoea; other effects include nausea and headaches.