Common Evening Primrose

Order:

Family: Onagraceae

Genus: Oenothera

Species: O. biennis

Identifying Characteristics:

- This native biennial plant can be 8' tall, although it is often shorter.

- There is usually a central stem with alternate leaves, but sometimes there will be multiple stems in open areas, creating a bushy appearance. The stems are light green or red, and are covered with white hairs. The light or olive green leaves are up to 8" long and 2" wide, but usually smaller. They are lanceolate and resemble willow leaves. The margins of the leaves are smooth or slightly dentate, and are nearly hairless. Smaller secondary leaves often appear at the axils of major leaves on the central stem.

- A panicle of pale yellow flowers occurs at the apex of the plant (or at the ends of major stems, if the plant is bushy). Each flower is about 1" across when fully open, with 4 petals and prominent stamens, and a long green calyx. The flowers remain open from evening to early morning, but will remain open longer on cloudy days. They have a mild lemony scent, and bloom from mid-summer to fall on mature plants. Long narrow seedpods develop, which split open from the top to release many tiny, irregular brown seeds. They are small enough to be dispersed by the wind, and can remain viable in the soil after 70 years. The root system consists of a fleshy taproot.

Special Adaptations:

-The preference is full sun, average moisture, and a soil that is somewhat sandy, but other growing conditions are acceptable

-This plant forms a stubby rosette during the first year, but becomes tall during the second year, at which time it flowers, sets seed, and dies.

-Common Evening Primrose is easy to grow, but often becomes rather unsightly as the season progresses. Disease can cause small brown spots to form on the leaves, while drought causes the lower leaves to turn yellow and fall off the plant.

-It is a common plant that is particularly conspicuous during late summer or fall. Disturbed areas are favored in both natural and developed habitats, including mesic to dry black soil prairies, sand prairies, thickets, glades, lakeshore dunes, abandoned fields, roadsides and railroads, slopes of drainage ditches, vacant lots, etc.