General: Evening Primrose Family (Onagraceae). Oenothera biennis is a biennial, herbaceous forb. The family is so-named because the flowers are partially to fully closed during the day and open in the evening. The bright yellow to gold corolla is 2-5 cm wide, with four petals. The fragrant flowers usually last only one to two days. The erect stem, which sometimes branches near the top, can be covered with hairs. The plant grows from 3-25 dm tall. Basal leaves, which form a rosette, are from 10-30 cm long. The stem has alternate, lanceolate-shaped leaves, 2.5-15 cm long, that are shallowly toothed and wavey at the edges. The leaves are usually hairy. The plant flowers can from June through October.
Distribution: For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Weedy evening-primrose, German rampion, hog weed, King’s cure-all, fever-plant
Range and Habitat in Illinois
Regularity: Regularly occurring
Regularity: Regularly occurring
Common evening-primrose grows in dry open fields, along roadsides, railroad embankments, waste areas and in open woods.
Range and Habitat in Illinois
These plants do best in well-drained soils in full sun. They can be easily grown from seed. The seeds are ripe when the seed capsule begins to split open, usually in October. To insure even planting, mix the seeds with a small amount of sand prior to sowing. The seeds usually germinate within four weeks. Thereafter, the plants will generally self-sow. Please use care when cultivating this plant as it has become invasive in many parts of the world.
Flower-Visiting Insects & Birds of Common Evening Primrose in Illinois
(Bees collect pollen or suck nectar, while hummingbirds & moths suck nectar; observations are from Robertson, Moure & Hurd, and Grundel et al. as indicated below)
Trochilidae: Archilochus colubris sn fq (Rb)
Apidae (Apinae): Apis mellifera sn cp fq (Rb); Apidae (Bombini): Bombus pensylvanicus sn cp fq (Rb); Anthophoridae (Ceratinini): Ceratina calcarata (Gnd); Anthophoridae (Eucerini): Anthedonia compta sn cp fq olg (Rb), Melissodes bimaculata bimaculata cp (Rb), Svastra obliqua obliqua cp (Rb); Megachilidae (Megachilini): Megachile mendica cp (Rb)
Halictidae (Halictinae): Agapostemon virescens cp (Rb), Augochlorella aurata (Gnd), Halictus ligatus (Gnd), Lasioglossum oenotherae cp olg (MH), Lasioglossum pictum (Gnd), Lasioglossum pilosum fq (Gnd), Lasioglossum vierecki (Gnd); Halictidae (Nomiidae): Nomia nortoni nortoni cp (Rb)
Sphingidae: Hyles lineata sn (Rb)
Foodplant / parasite
Erysiphe howeana parasitises Oenothera biennis
Foodplant / feeds on
pycnidium of Phoma coelomycetous anamorph of Phoma onagracearum feeds on Oenothera biennis
Foodplant / spot causer
punctiform aggregated in spot centre, blackish-brown pycnidium of Septoria coelomycetous anamorph of Septoria oenotherae causes spots on live leaf of Oenothera biennis
Molecular Biology and Genetics
Barcode data: Oenothera biennis
Statistics of barcoding coverage: Oenothera biennis
Public Records: 3
Specimens with Barcodes: 15
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Cultivars, improved and selected materials (and area of origin)
These plants are readily available from commercial sources. Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Please contact your local agricultural extension specialist or county weed specialist to learn what works best in your area and how to use it safely. Always read label and safety instructions for each control method. Trade names and control measures appear in this document only to provide specific information. USDA, NRCS does not guarantee or warranty the products and control methods named, and other products may be equally effective.
This plant may become weedy or invasive in some regions or habitats and may displace desirable vegetation if not properly managed. Please consult with your local NRCS Field Office, Cooperative Extension Service office, or state natural resource or agricultural department regarding its status and use. Weed information is also available from the PLANTS.
Relevance to Humans and Ecosystems
Ethnobotanic: The Cherokee, Iroquois, Ojibwas, and Potawatomi were among several Native American tribes that used common evening-primrose for both food and for medicinal purposes. The roots were boiled and eaten like potatoes. The young leaves were cooked and served as greens. The shoots were eaten raw. A tea was made from the plant and used as a dietary aid or stimulant to treat laziness and “overfatness.” A hot poultice made from the pounded roots was applied externally to treat piles and boils. A poultice made from the entire plant was used to treat bruises. The roots were chewed and rubbed onto the muscles to improve strength. The plant was used to treat pain associated with menstruation as well as bowel pain. Handfuls of people still use the plant today, medicinally and for food.
Other: Common evening-primrose is commercially cultivated in over 15 countries for its oil which contains the essential fatty acids, linoleic acid and gamma linolenic acid (Kemper 1999). When the seedpods ripen, the tall stalks can be cut and used as interesting additions to dried arrangements.
Wildlife: Hummingbirds visit the flowers to obtain nectar and insects to eat. The seed capsules provide food for many other birds during the winter months. It is thought that the plants are pollinated by night-visiting hawk moths, which feed on their nectar. Japanese Beetles prefer the leaves of common evening-primrose to those of other garden plants.
Oenothera biennis (common evening-primrose, 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. Evening primrose oil is produced from the plant.
Growth and flowering
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.
It is also known as weedy evening-primrose, German rampion, hog weed, King's cure-all, and fever-plant.
The seeds of the plant are important food for birds.
The mature seeds contain approximately 7–10% gamma-linolenic acid (GLA), an essential fatty acid. Evening primrose oil (EPO), containing GLA, is often used to treat some medical conditions, and is considered a dietary supplement rather than a drug.
Evening primrose is considered to have beneficial health effects, largely due to its GLA content. Evening primrose is sometimes used to treat eczema. The Mayo clinic examined evidence for the safety and effectiveness of evening primrose for several conditions; it was considered that there was good evidence (grade B, vs "strong evidence", grade A) that it produced a moderate improvement in eczema. Grade C, unclear, evidence for benefit is listed for many conditions, including some reduction of blood pressure. Research has shown a lack of significant beneficial effects on heart function and health. Many conditions for which evening primrose is a traditional remedy or there is a theory suggesting efficacy are listed by the Mayo clinic, without comment.
The symptoms of eczema can be exacerbated due to scratching and drying out the skin. Supplementation with EPO may help rehydrate skin that has been scratched due to eczema.
There are conflicting opinions and evidence for the medicinal effects of GLA, the active constituent of EPO, which has been promoted to treat ailments including breast pain and eczema; such marketing was described by the British Medical Journal (BMJ) as ethically dubious—the substance was likely to be remembered as "a remedy for which there is no disease". The BMJ said in 2003 that it was of no use in atopic dermatitis. The American Cancer Society said in 2010 that there was very little evidence for its effectiveness as an anti-cancer agent, for which it is sometimes promoted, and "neither GLA nor other GLA-rich supplements (such as evening primrose oil) have been convincingly shown to be useful in preventing or treating any other health conditions."
EPO is considered likely to be safe in recommended doses. It may increase the risk of bleeding, a concern for patients with bleeding disorders or taking drugs that may increase bleeding. The Mayo clinic recommends caution in people with seizure disorders or mania, and by pregnant or breastfeeding women, and publishes a long list of possible side-effects.
Most studies evaluating the effectiveness of EPO used a dose of 1600 mg of standardized extract (4 capsules) by mouth twice daily for up to 12 weeks.
Primrose moth (Schinia florida) in flower
|Wikimedia Commons has media related to Oenothera biennis.|
|Wikispecies has information related to: Oenothera biennis|
- "The Plant List: A Working List of All Plant Species". Retrieved 7 December 2014.
- "BSBI List 2007" (xls). Botanical Society of Britain and Ireland. Retrieved 2014-10-17.
- Germplasm Resources Information Network: Oenothera biennis
- http://www.umm.edu/altmed/articles/evening-primrose-000242.htm (Retrieved 6/17/13)
- http://nccam.nih.gov/health/eveningprimrose (Retrieved 6/17/13)
- Borealforest: Oenothera biennis
- Plants of British Columbia: Oenothera biennis
- Jepson Flora: Oenothera biennis
- Ultraviolet Flowers: Oenothera biennis
- Blanchan, N. (1922). Wild Flowers Worth Knowing. Project Gutenberg Literary Archive Foundation.
- "Lady Bird Johnson Wildflower Center". Retrieved 7 December 2014.
- Mayo Clinic - Drugs and Supplements: Evening primrose (Oenothera spp.) - Evidence
- 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
- Richmond, C. (2003). "David Horrobin". BMJ 326 (7394): 885. doi:10.1136/bmj.326.7394.885.
- Smith, R. (2003). "The drugs don't work". BMJ 327 (7428): 0–h. doi:10.1136/bmj.327.7428.0-h.
- "Gamma Linolenic Acid". American Cancer Society. 13 May 2010. Retrieved August 2013.
- Mayo Clinic - Drugs and Supplements: Evening primrose (Oenothera spp.) - Safety
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