Oenothera biennis

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Common evening primrose
Oenothera biennis, Vic-la-Gardiole 01.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Myrtales
Family: Onagraceae
Genus: Oenothera
Species: O. biennis
Binomial name
Oenothera biennis
  • Brunyera biennis Bubani
  • Oenothera chicaginensis de Vries ex Renner & Cleland
  • Oenothera chicagoensis Renner ex R.E.Cleland & Blakeslee
  • Oenothera grandiflora L'Hér.
  • Oenothera muricata L.
  • Oenothera pycnocarpa G.F. Atk. & Bartlett
  • Oenothera renneri H.Scholz
  • Oenothera rubricaulis Kleb.
  • Oenothera stenopetala E.P. Bicknell
  • Oenothera suaveolens Pers.
  • Onagra biennis (L.) Scop.
  • Onagra muricata (L.) Moench

Oenothera biennis (common evening-primrose,[2] evening star, or sun drop) is a species of Oenothera native to eastern and central North America, from Newfoundland west to Alberta, southeast to Florida, and southwest to Texas, and widely naturalized elsewhere in temperate and subtropical regions.[3] Evening primrose oil is produced from the plant.[4][5]

Growth and flowering[edit]

Open flower in the evening.
2 men and a pig
Closed flowers
Illustration Oenothera biennis

Oenothera biennis has a life span of two years (biennial) growing to 30–150 cm (12–59 in) tall. The leaves are lanceolate, 5–20 cm (2.0–7.9 in) long and 1–2.5 cm (0.39–0.98 in) broad, produced in a tight rosette the first year, and spirally on a stem the second year.

Blooming lasts from late spring to late summer. The flowers are hermaphrodite, produced on a tall spike and only last until the following noon. They open visibly fast every evening producing an interesting spectacle, hence the name "evening primrose."

The blooms are yellow, 2.5–5 cm (0.98–1.97 in) diameter, with four bilobed petals. The flower structure has an invisible to the naked eye bright nectar guide pattern. This pattern is apparent under ultraviolet light and visible to its pollinators, moths, butterflies, and bees.

The fruit is a capsule 2–4 cm (0.79–1.57 in) long and 4–6 mm (0.16–0.24 in) broad, containing numerous 1–2 mm (0.039–0.079 in) long seeds, released when the capsule splits into four sections at maturity.[6][7][8][9]

English names[edit]

It is also known as weedy evening-primrose, German rampion, hog weed, King's cure-all, and fever-plant.[10]


The seeds of the plant are important food for birds.[11]

Cultivation and uses[edit]

The mature seeds contain approximately 7–10% gamma-linolenic acid, an essential fatty acid.

Its leaves are edible and traditionally were used as a leaf vegetable.[12] The roots are also edible.[11]

Evening primrose is sometimes used to treat eczema. Natural Standard has given evening primrose oil a "B" score for the treatment of eczema; meaning there is good scientific evidence supporting its use.[13] The symptoms of eczema can be exacerbated due to scratching and drying out the skin. Evening primrose oil contains linoleic acid, which is the primary oil found in the stratum corneum.[14] Supplementation with EPO may help rehydrate skin that has been scratched due to eczema. Furthermore, gamma-linoleic acid is metabolized into anti-inflammatory compounds, which may contribute to its ability to provide symptomatic relief in eczema. Most studies evaluating the effectiveness of EPO used 4 capsules of standardized extract (~1600 mg of evening primrose oil TOTAL) dosed by mouth twice daily for up to 12 weeks.

Evening Primrose Oil has been shown to slightly reduce blood pressure, can increase clotting time (use with caution if you take warfarin or aspirin), and should not be used by epileptics as it lowers the seizure threshold. Safety has not been evaluated in pregnant or nursing women.


  1. ^ "The Plant List: A Working List of All Plant Species". Retrieved 7 December 2014. 
  2. ^ "BSBI List 2007" (xls). Botanical Society of Britain and Ireland. Retrieved 2014-10-17. 
  3. ^ Germplasm Resources Information Network: Oenothera biennis
  4. ^ http://www.umm.edu/altmed/articles/evening-primrose-000242.htm (Retrieved 6/17/13)
  5. ^ http://nccam.nih.gov/health/eveningprimrose (Retrieved 6/17/13)
  6. ^ Borealforest: Oenothera biennis
  7. ^ Plants of British Columbia: Oenothera biennis
  8. ^ Jepson Flora: Oenothera biennis
  9. ^ Ultraviolet Flowers: Oenothera biennis
  10. ^ Blanchan, N. (1922). Wild Flowers Worth Knowing. Project Gutenberg Literary Archive Foundation. 
  11. ^ a b "Lady Bird Johnson Wildflower Center". Retrieved 7 December 2014. 
  12. ^ Gaertner, Erika E. (1968). "Additions to the list of wild edible plants preservable by the deep freeze method". Economic Botany 22 (4): 369. doi:10.1007/BF02908133 
  13. ^ http://www.naturalstandard.com/databases/herbssupplements/primrose.asp
  14. ^ Angelo, Giana. "Essential Fatty Acids and Skin Health." Linus Pauling Institute: Micronutrient Information Center. Oregon State University, Feb. 2012. Web. 30 Nov. 2012.

External links[edit]