Yellow Evening Primrose

Evening-primrose (Onagraceae family):

Oenothera biennis L.

EPPO code:

OEOBI

Other names:

Common evening-primrose, evening-primrose

Species information

Lifecycle:

Biennial or short-lived perennial.

Propagation:

Reproduces by seed.

Emergence:

According to Hall et al. (1987), seeds do not germinate if placed deeper than 5 mm in the soil. Seeds prefer warm soils, so peak germination likely occurs in late spring to early summer.

Habitat:

Yellow evening-primrose is found throughout Ontario, but most commonly on roadsides, in waste areas and pastures, and more recently in crop fields under no-till production.

Competitiveness:

No data exits on the competitiveness of yellow evening-primrose.

Identification clues

Seedling

Cotyledons:

Rhomboid, very small (100 mm), with a stalk the same length.

Young leaves:

Grows initially as a basal rosette. The rosette leaves are spoon-shaped with a prominent primary vein that is white and often tinged with pink or red. Sometimes with red blotches near the tip.

Mature leaves:

Stem leaves are alternate, narrow, long and have a pointed tip and prominent veins.

Mature plant

Stem:

The weed’s stem is erect and grows up to 2 m in height. It is branched at the base, hairy, and green with a reddish tinge or red spots.

Flowers:

The flowers of yellow evening-primrose have four large yellow petals with four narrow greens sepals underneath that originate from the leaf axil. They form a dense terminal spike.

Fruit and seeds:

Has long, cylindrical seed pods that are green, hairy and covered in red spots. The inside is divided into four chambers, each of which contains several irregular-shaped, reddish-brown to black, rough-surfaced seeds that are roughly 1.5 mm long.

Roots:

Taproot

Note of interest

Traditionally, the young leaves and taproot have been consumed as a cooked vegetable (Hall et al., 1987).