Scientific Name: Oenothera biennis

Common Name: common evening primrose

Other Common Names: hoary eveningprimrose

Synonyms: Oenothera biennis ssp. Caeciarum, Oenothera biennis ssp. Centralis, Oenothera biennis var. pycnocarpa, Oenothera muricata, Oenothera pycnocarpa

Habit: Usually a biennial or a winter annual, but may rarely occur as a summer annual. Common eveningprimrose has narrow leaves with untoothed margins and produces many showy yellow flowers. This weed is primarily a weed of landscapes, nurseries, some agronomic crops, and occasionally turfgrass and lawns. Common eveningprimrose can be found in dry soils, meadows and open places. They are often planted in perennial gardens.

Leaves: Cotyledons are 6 to 11 mm long, and are usually egg-shaped with a short petiole. The stem at the base of the cotyledons has a reddish tint. Leaves initially develop as a basal rosette. Upper leaf surfaces of young leaves may have a few hairs near the base. Leaves are elliptic to lanceolate in outline, are relatively narrow, and have untoothed margins. Leaves have a distinctive white or pink midvein and may have wavy margins. Leaves along the erect flowering stem are alternate and become progressively smaller up the stem.

Identifying Characteristics: Eveningprimrose gets its name from its unusual behavior. The flowers open in the evening between 4:00 and 10:00 pm. It releases its sweet fragrance and attracts many night-flying moths after it opens. Oil produced by eveningprimrose seeds is now being used for experimental medicinal purposes.

Flower Seed Head: Flowers grow from June to September. Flowers are yellow, with 4 petals, and an X-shaped stigma in the center of the flower. They have reflexed sepals, arranged all around the leafy stalk. Flowers occur in the upper leaf axils and are without flower stems (sessile).

Seed Fruit: An erect, hairy capsule that is approximately 1/2 to 1 1/2 inches long. Many seed are arranged in rows within the capsule.

Where Found: Common Evening Primrose can be found throughout the US.

  • Life cycle: biennial

  • Milky sap: Not Present

  • Plant type: Herb

  • Thorns: Not Present

  • Plant family: Onagraceae

  • Leaf arrangement: rosette

  • Leaf shape: lance; oval

  • Ochrea: Not Present

  • Leaf margin: wavy

  • Stem hairs: has hairs

  • Flower color: yellow; white

  • Growth habit: upright and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: has hairs

  • Flower diameter: nickle; quarter; half dollar

  • Flower symmetry: radial symetery

  • Root structure: taproot

  • Leaf stalk: none