common evening primrose

Scientific name: Oenothera biennis. Verified common names: common evening primrose, evening primrose. Family: Onagraceae. Genus: Oenothera. It is a typical member of the evening-primrose family and shares the family’s four-part floral structure.

Oenothera biennis is an erect biennial that typically forms a basal rosette the first year and produces a tall flowering stalk in its second year. Plants often reach around one to two meters in height when flowering. Flowers are showy and usually open in the evening or at night: they typically have 4 broad petals, 4 sepals, and a tubular floral base (hypanthium). Petal color is commonly bright yellow when newly open and often fades to pink or orange with age. Stamens are generally 8 and the stigma is 4-lobed. The fruit is a cylindrical capsule that contains many small seeds. Leaves are alternate, lanceolate to oblong, typically toothed, and may be rough- to hairy-textured. Seasonal variation includes the basal rosette stage in year one and the tall, flowering and seeding stalk in year two; flowers open mostly in the evening and may wilt or change color by the following day.

Common evening primrose typically colonizes open, disturbed sites such as roadsides, fields, meadows, pastures, and open woodlands. It often prefers full sun to partial shade and tolerates a range of soils but is commonly found on well-drained, sandy or gravelly substrates. Moisture preference is generally moderate to dry; the species can persist in comparatively dry conditions. Geographic distribution includes much of the United States (observed in AL, AR, AZ, CA, CO and many other states) and it is widespread across temperate North America.

Flowers open at dusk and are well adapted to attract night-flying pollinators, especially long-tongued moths; they also provide nectar and pollen to various daytime insects when flowers remain open. The plant’s nectar-rich flowers make it an important nectar source in evening and nocturnal pollination networks. Seed capsules release many small seeds that can persist in the soil seed bank and support recolonization of disturbed ground.

Oenothera biennis is generally common and not considered threatened across its range; it often behaves as a weedy or colonizing species. Notable adaptations include nocturnal flower opening and a long floral tube suited to moth pollinators, and the flower color change from yellow to pink as blooms age.