Oenothera is a genus of about 145[3] species of herbaceous flowering plants native to the Americas.[4] It is the type genus of the family Onagraceae. Common names include evening primrose, suncups, and sundrops. They are not closely related to the true primroses (genus Primula).


The species vary in size from small alpine plants 10 centimeters tall, such as O. acaulis from Chile, to vigorous lowland species growing to 3 meters, such as O. stubbei from Mexico. The leaves form a basal rosette at ground level and spiral up to the flowering stems. The blades are dentate or deeply lobed (pinnatifid). The flowers of many species open in the evening, hence the name "evening primrose". They may open in under a minute. Most species have yellow flowers, but some have white, purple, pink, or red. Most native desert species are white. Oenothera caespitosa, a species of western North America, produces white flowers that turn pink with age.[5] One of the most distinctive features of the flower is the stigma, which has four branches in an X shape.[6]


Evening primrose flower, open, showing pollen attached to sticky viscin threads
Evening primrose

Oenothera flowers are pollinated by insects, such as moths and bees. Like many other members of the Onagraceae, however, the pollen grains are loosely held together by viscin threads, so only insects that are morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical scopa cannot hold it. Also, the flowers open at a time when most bee species are inactive, so the bees which visit Oenothera are generally vespertine temporal specialists: bees that forage in the evening. The seeds ripen from late summer to fall.

Oenothera are used as food plants by the larvae of some Lepidoptera species, including the large white-lined sphinx (Hyles lineata).[7] The flower moths Schinia felicitata and S. florida both feed exclusively on the genus, and the former is limited to O. deltoides.

In the wild, some species of evening primrose act as primary colonizers, quickly appearing in recently cleared areas. They germinate in disturbed soils, and can be found in habitat types such as dunes, roadsides, railway embankments, and waste areas. They are often casual and are eventually out competed by other species.

Based on observations of evening primroses (O. drummondii), a study discovered that within minutes of sensing the sound waves of nearby bee wings through flower petals, the concentration of the sugar in the plant's nectar was increased by an average of 20 percent. Experiments were also conducted on flowers with the petals removed. No change in nectar production was noted, indicating that it is indeed the flowers that have the job of the ears.[8]


The genus Oenothera may have originated in Mexico and Central America,[9][10] and spread farther north in North America and into South America. With the advent of international travel, species are now found in most temperate regions of the world. In Europe alone there are about 70 introduced species of Oenothera.[4] During the Pleistocene era a succession of ice ages swept down across North America, with intervening warm periods. This occurred four times, and the genus experienced four separate waves of colonization, each hybridizing with the survivors of previous waves.[10][11] This formed the present-day subsection Euoenothera. The group is genetically and morphologically diverse and the species are largely interfertile, so the species boundaries have been disputed amongst taxonomists.[9][12]


Painting of Hugo de Vries, making a painting of an evening primrose, which had apparently produced new forms by large mutations in his experiments, by Thérèse Schwartze, 1918

The pattern of repeated colonizations resulted in a unique genetic conformation in the Euoenothera whereby the chromosomes at meiosis can form circles rather than pairs. This is the result of several reciprocal translocations between chromosomes such that the pairing occurs only at the tips. This phenomenon apparently has non-Mendelian genetic consequences; with this mode of chromosome segregation and a system of balanced-lethal genes, genetic recombination is prevented and the plants display the hybrid vigor of heterosis.[13] This resulted in the evolution of many sympatric races in North America east of the Rocky Mountains. Analysis of the cytology of these races and of artificial hybrids between them increased understanding of the genetic and geographic evolution of the Euoenothera. This subject was a major area of genetic research during the first half of the 20th century.[14][15]

The appearance of sudden changes in Oenothera lamarckiana led the pioneering geneticist Hugo de Vries to propose what he called "mutation theory" in 1901 (Mutationstheorie in the German the original article was written in).[16] This asserted that speciation was driven by sudden large mutations able to produce new varieties in a single step. The understanding that the observed changes in hybrids of the plant were caused by chromosome duplications (polyploidy) rather than gene mutation did not come until much later.[17][18]


Evening primroses were originally assigned to the genus Onagra, which gave the family Onagraceae its name. Onagra '[food of] onager' was first used in botany in 1587, and in English in Philip Miller's 1754 Gardeners Dictionary: Abridged. The modern name Oenothera was published by Carolus Linnaeus in his Systema Naturae. Its etymology is uncertain, but it is believed to be derived from the Greek words οίνος θήρα (oinos thera) 'wine seeker'.[19]

The genus is divided into 18 sections and additionally into several subsections and series.[1]

Dietary uses and side effects

Certain Oenothera plants have edible parts. The roots of O. biennis are reportedly edible in young plants.[20]

The common evening primrose, O. biennis, is commonly sold as a dietary supplement in capsules containing the seed oil.[21] The main phytochemical in this evening primrose seed oil is gamma-linolenic acid.[21]

There is no high-quality scientific evidence that O. biennis or evening primrose oil has any effect on human diseases or promotion of health,[21][22] and specifically no evidence that it is effective to treat atopic dermatitis or cancer.[21][23] Research indicates that orally-administered evening primrose oil does not relieve symptoms of premenstrual syndrome,[24][25] and does not have an effect on shortening the length of pregnancy or labor.[26][27][28][29]

Consuming evening primrose oil may cause headache or stomach upset, may increase the risk of complications during pregnancy, and may increase the risk of bleeding in people given prescription drugs as anticoagulants, such as warfarin.[30]


A number of perennial members of the genus are commonly cultivated and used in landscaping in the southwestern United States. Popular species include tufted evening primrose (Oenothera caespitosa), Mexican evening primrose (Oenothera berlanderii), and Saltillo evening primrose (Oenothera stubbei).[31]

Annual evening primroses are also popular ornamental plants in gardens. Many are fairly drought-resistant.

The first plants to arrive in Europe reached Padua from Virginia in 1614 and were described by the English botanist John Goodyer in 1621. Some species are now also naturalized in parts of Europe and Asia, and can be grown as far north as 65°N in Finland. The UK National Council for the Conservation of Plants and Gardens, based at Wisley, maintains an Oenothera collection as part of its National Collections scheme.



  1. ^ a b "Genus: Oenothera L". Germplasm Resources Information Network. United States Department of Agriculture. 2004-03-22. Archived from the original on 2023-01-09. Retrieved 2023-01-09.
  2. ^ "GRIN Species Records of Oenothera". Taxonomy for Plants. USDA, ARS, National Genetic Resources Program. Retrieved July 11, 2010.
  3. ^ Singh, S.; et al. (2012). "An updated review on the Oenothera genus" (PDF). J. Chin. Integr. Med. 10 (7): 717–25. doi:10.3736/jcim20120701. PMID 22805077.
  4. ^ a b Mihulka, S.; Pyšek, P. (2001). "Invasion history of Oenothera congeners in Europe: a comparative study of spreading rates in the last 200 years" (PDF). Journal of Biogeography. 28 (5): 597–609. doi:10.1046/j.1365-2699.2001.00574.x. S2CID 55661900.
  5. ^ Gumbo Lily (Oenothera caespitosa). Native Wildflowers of the North Dakota Grasslands. USGS Northern Prairie Wildlife Research Center.
  6. ^ Peterson, R. T. and M. McKenny (1968). A Field Guide to Wildflowers of Northeastern and North-central North America. Boston: Houghton Mifflin. ISBN 978-0-395-91172-3.
  7. ^ "White-lined Sphinx Hyles lineata (Fabricius, 1775)". Butterflies and Moths of North America. Retrieved 2017-11-14.
  8. ^ Lay summary: Nield, David (January 19, 2019). "Plants May Not Have Ears, But They Can 'Hear' Way Better Than We Thought". Science Alert. Veits, Marine; Khait, Itzhak; Obolski, Uri; Zinger, Eyal; Boonman, Arjan; Goldshtein, Aya; Saban, Kfir; Seltzer, Rya; Ben‐Dor, Udi; Estlein, Paz; Kabat, Areej; Peretz, Dor; Ratzersdorfer, Ittai; Krylov, Slava; Chamovitz, Daniel; Sapir, Yuval; Yovel, Yossi; Hadany, Lilach (2019). "Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration". Ecology Letters. 22 (9). John Wiley & Sons Ltd.: 1483–1492. doi:10.1111/ele.13331. ISSN 1461-023X. PMC 6852653. PMID 31286633. French National Centre for Scientific Research (CNRS). Veits is cited by many reviews: Kumar, A.; Memo, M.; Mastinu, A. (2020). "Plant behaviour: an evolutionary response to the environment?". Plant Biology. 22 (6issn=1435–8603). John Wiley & Sons Ltd.: 961–970. doi:10.1111/plb.13149. PMID 32557960. S2CID 219902795. Virant-Doberlet, Meta; Kuhelj, Anka; Polajnar, Jernej; Šturm, Rok (2019). "Predator-Prey Interactions and Eavesdropping in Vibrational Communication Networks". Frontiers in Ecology and Evolution. 7. Frontiers Media SA. doi:10.3389/fevo.2019.00203. ISSN 2296-701X. S2CID 173992538. Khait, I.; Obolski, U.; Yovel, Y.; Hadany, L. (2019). "Sound perception in plants". Seminars in Cell & Developmental Biology. 92. Elsevier BV: 134–138. doi:10.1016/j.semcdb.2019.03.006. ISSN 1084-9521. PMID 30965110. S2CID 106407725. Biorxiv: Veits, Marine; Khait, Itzhak; Obolski, Uri; Zinger, Eyal; Boonman, Arjan; Goldshtein, Aya; Saban, Kfir; Ben-Dor, Udi; Estlein, Paz; Kabat, Areej; Peretz, Dor; Ratzersdorfer, Ittai; Krylov, Slava; Chamovitz, Daniel; Sapir, Yuval; Yovel, Yossi; Hadany, Lilach (2018). "Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration". bioRxiv. Cold Spring Harbor Laboratory (CSHL). doi:10.1101/507319. S2CID 92674047.
  9. ^ a b Raven, P. H.; et al. (1979). "An outline of the systematics of Oenothera subsect. Euoenothera (Onagraceae)". Systematic Botany. 4 (3): 242–252. doi:10.2307/2418422. JSTOR 2418422.
  10. ^ a b Dietrich, W.; et al. (1997). Systematics of Oenothera section Oenothera subsection Oenothera (Onagraceae). Laramie: The American Society of Plant Taxonomists. ISBN 978-0-912861-50-0.
  11. ^ Cleland, R. E. (1972). Oenothera - Cytogenetics and evolution. Boston: Academic Press. ISBN 978-0-12-176450-0.
  12. ^ Rostanski, K. (1985). "The classification of subsection Oenothera (section Oenothera, Oenothera L., Onagraceae)". Feddes Repertorium. 96 (1–2): 3–14. doi:10.1002/fedr.4910960103.
  13. ^ Rauwolf, U.; et al. (2008). "Molecular marker systems for Oenothera genetics". Genetics. 180 (3): 1289–1306. doi:10.1534/genetics.108.091249. PMC 2581935. PMID 18791241.
  14. ^ Cleland, R. E. (1972). Oenothera - Cytogenetics and Evolution. Boston: Academic Press. ISBN 978-0-12-176450-0.
  15. ^ Harte, C. (1994). Oenothera - Contributions of a Plant to Biology. Berlin: Springer-Verlag. ISBN 978-3-540-53114-2.
  16. ^ de Vries, Hugo. Die Mutationstheorie. Versuche und Beobachtungen über die Entstehung von Arten im Pflanzenreich (in German), Leipzig, Veit & Comp., 1901-03.
  17. ^ Endersby, Jim (2007). A Guinea Pig's History of Biology. Harvard University Press. pp. 148–162, 202–205. ISBN 978-0-674-02713-8.
  18. ^ Ramsey, Justin; Ramsey, Tara S. (August 2014). "Ecological studies of polyploidy in the 100 years following its discovery". Phil. Trans. R. Soc. Lond. B. 5 (369): 898–900. doi:10.1098/rstb.2013.0352. PMC 4071525. PMID 24958925.
  19. ^ Gledhill, D. (2008). The Names of Plants (4 ed.). Cambridge University Press. p. 278. ISBN 978-0-521-86645-3.
  20. ^ Oenothera biennis. Ohio Perennial and Biennial Weed Guide. The Ohio State University Extension.
  21. ^ a b c d "Evening primrose oil". National Center for Complementary and Integrative Health, US National Institutes of Health. 1 September 2016. Retrieved 24 June 2020.
  22. ^ Bamford JT, Ray S, Musekiwa A, van Gool C, Humphreys R, Ernst E, et al. (2013). "Oral evening primrose oil and borage oil for eczema". Cochrane Database of Systematic Reviews. 4 (4): CD004416. doi:10.1002/14651858.CD004416.pub2. PMC 8105655. PMID 23633319. CD004416.
  23. ^ "Gamma Linolenic Acid". American Cancer Society. 13 May 2010. Retrieved 13 August 2013.
  24. ^ "Evening primrose oil". National Center for Complementary and Integrative Health. 2015-02-14.
  25. ^ Douglas, Sue (November 2002). "Premenstrual syndrome. Evidence-based treatment in family practice". Canadian Family Physician. 48 (11): 1789–1797. PMC 2213956. PMID 12489244.
  26. ^ McFarlin, B. L.; Gibson, M. H.; O'Rear, J.; Harman, P. (1999). "A national survey of herbal preparation use by nurse-midwives for labor stimulation". J Nurse-Midwifery. 44 (3): 205–216. doi:10.1016/S0091-2182(99)00037-3. PMID 10380441.
  27. ^ Tenore, Josie L. (15 May 2003). "Methods for Cervical Ripening and Induction of Labor". American Family Physician. 67 (10): 2123–2128. PMID 12776961.
  28. ^ Adair, C. (September 2000). "Cervical Ripening And Labor Induction Nonpharmacologic Approaches to Cervical Priming and Labor Induction". Clinical Obstetrics & Gynecology. 43 (3): 447–454. doi:10.1097/00003081-200009000-00005. PMID 10949749.
  29. ^ Dove, Dorinda; Peter Johnson (May–June 1999). "Oral evening primrose oil: Its effect on length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women". Journal of Nurse-Midwifery. 44 (3): 320–324. doi:10.1016/S0091-2182(99)00055-5. PMID 10380450.
  30. ^ "Evening primrose". Drugs.com. 14 October 2019. Retrieved 24 June 2020.
  31. ^ Jones W. and C. Sacamano. Landscape Plants for Dry Regions. Fisher Books. 2000. ISBN 1-55561-190-7

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