Oenothera biennis

Species Native to Missouri
Common Name: common evening primrose
Type: Herbaceous perennial
Family: Onagraceae
Native Range: Eastern North America
Zone: 4 to 9
Height: 3.00 to 5.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: June to September
Bloom Description: Yellow
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Suggested Use: Naturalize
Flower: Showy
Attracts: Birds, Butterflies
Tolerate: Drought

Culture

Easily grown in average, medium moisture, well-drained soils in full sun. Tolerates some part afternoon shade and some drought. Grows well in gravelly or sandy soils. May spread in the landscape by self-seeding in a somewhat weedy fashion.

Noteworthy Characteristics

Oenothera biennis, commonly known as evening primrose, is an upright biennial that is native throughout Canada and the U.S. except for Idaho, Wyoming, Utah, Colorado and Arizona. It is primarily found in eastern and central North America with only scattered locations in much of the West. In Missouri, it commonly grows throughout the State in fields, prairies, glades, thickets, waste ground, disturbed sites, and along roadsides and railroad right-of-ways (Steyermark). Plants were exported to Europe in the 1600s where they have now naturalized throughout the continent.

In the first year, this biennial typically produces a basal rosette of shallow-toothed, lanceolate, light green to olive green leaves (to 4-8” long and 2” wide) but no flowers. In the second year, a stiffly-upright, rough-hairy, purple-tinged flower stem (usually a single stem but sometimes multiple stems) with spirally arranged leaves rises from the center of the rosette to 3-5’ tall, topped by a showy summer to fall (June to September) bloom of bowl-shaped, four-petaled, lemon yellow flowers (each to 1-2” across). Flowers bloom in a multi-flowered terminal panicle and, if present, in panicles at the tips of major stems, with a single flower blooming at the base of upper leaf-like bracts. Flowers open at dusk and close again in the morning when hit by sun, hence the common name of evening primrose. Flowers are fertilized by night-flying moths which are attracted by the mild lemon flower fragrance and by bees in the early morning before closure. Each flower has 4 petals, 4 reflexed sepals, 8 stamens and a prominent style with a cross-shaped stigma. Fruits are capsules (narrow seed pods to 1 1/2” long) which split open when ripe to release numerous seeds (to 100 seeds per capsule). Plants die after setting seed, but will remain in the landscape through self-seeding.

Genus name is unclear but may have come from the Greek words oinos and theras meaning wine-seeker in probable reference to an ancient use of the roots of genus plants in scenting wine.

Specific epithet identifies the biennial growing cycle of this plant.

Seed oil (plant seeds contain gamma-linolenic acid) has been used in a number of different medicinal applications (particularly in Europe) since the 1600s as reflected in the sometimes used common names of King’s Cure-All and Fever-Plant. Evening primrose oil is now commercially cultivated in 15 countries. All parts of this plant including the roots were once used as food by American Indians.

Problems

No serious insect or disease problems. Leaf spot and powdery mildew may occur.

Garden Uses

Biennial for beds and borders. Wildflower gardens. Cottage gardens. Herb gardens.