common evening primrose
Family
OnagraceaeScientific Name
Oenothera biennis
Other Common Names:
hoary eveningprimrose
Synonyms (former Scientific Names):
Oenothera biennis ssp. Centralis
Oenothera biennis var. pycnocarpa
Oenothera muricata
Oenothera pycnocarpa
Oenothera biennis ssp. Caeciarum
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.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
Varies:
nickle,
quarter,
half dollar
Dominant Flower Color
Varies:
white,
yellow
Flower Symmetry
radial symmetery
Leaf Hairs
has hairs
Leaf Shape
Varies:
lance,
oval
Leaf Arrangement
rosette
Leaf Margin
wavy
Leaf Structure
simple
Leaf Stalk
none
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
biennial
Ochrea
not present
Plant Type
Herb