South Dakota Native Plant Research
Onagraceae : Oenothera biennis

Onagraceae : Oenothera biennis


Download Seed: The reddish brown seeds of common evening primrose are 1.2-1.6 mm long. (59 KB)

Download Seedlings - year 1 SDSU common garden (786 KB)

Download Plants - year 2 SDSU common garden (1.2 MB)

Download Leaves (717 KB)

Download Flowers (240 KB)

Download Fruiting: Cylindrical capsules contain the seeds. (533 KB)

Family Name


Common Name

Common evening primrose

Native American Name

Lakota: Canhlo'gan hu'nla


Oenothera biennis is a biennial herb with greenish, erect branching stems 50-200 cm tall, often covered with hairs. The first year plants form rosettes of petiolate leaves, oblanceolate to spatulate, 6-30 cm long, 1-7 cm wide, with an entire to wavey margin and pointed tips. The second year the stems elongate and the cauline leaves are alternate, lanceolate to oblanceolate, 1-10 cm long and 4-20 mm wide with wavey to sparsely toothed margins and pointed tips. The lower stem leaves petiolate, becoming reduced in size and sessile toward the top. The inflorescence is a terminal spike, sometimes with branches, the flowers subtended by hair covered bracts 1-3 cm long. The flower buds are erect and open near sunset. The slender, greenish yellow floral tube is is 2-5 cm in length, with a scattering of hairs. The 4 linear-lanceolate sepals are 1-2.5 cm long with free lobes 1-4 mm long. The 4 yellow obovate petals are 1-2.5 cm long, notched, and become reddish before wilting. There are 8 yellow stamens surrounding a style with a cross-shaped stigma in the center. The fruit is an ascending, hairy, cylindrical capsule, 1.5-3.5 cm long and 3-6 mm in diameter. Common evening primrose blooms From July into October along streams and lakeshores, open woodlands and waste places scattered throughout South Dakota.

Additional Notes

Evening primrose is easy to grow, producing flowers in the second year. This plant readily reseeds itself, with some of the seeds germinating the same year and flowering the following summer. Although sometimes labeled a weed, it can be a nice addition to a native plant garden, with a long bloom time, benefiting moths at night and butterflies and native bees in the morning hours. Note: When grown in moist, rich soils, removed from competition, this plant can be very aggressive. In my garden it grew very large and was not very attractive. It was difficult to eradicate seedlings even after 2 years.

Horticulture Notes

Seed Collection: Collect seed in Aug.-Oct. when seed capsules begin to split open.

Germination: No pretreatment needed

Soils: Sandy or gravelly well drained.

Light: Full sun

Water: Medium dry to dry.

Onagraceae : Oenothera biennis