# Evening primrose (Oenothera biennis) *Tree primrose; *Oenothera biennis* of Linnaeus, Grieve’s *Cenothera*, with *Oenothera lamarckiana*; in pharmacy *Oenotherae oleum*, the oil of the seed* **Known today as.** *Oenothera biennis*, a North American biennial, carried first to Italy and since naturalised on river banks and sandy places across western Europe. The first year makes a flat rosette of leaves; the second, hairy stems three or four feet high with a long succession of large, fragrant, yellow flowers that “usually open between six and seven o’clock in the evening, hence the name of Evening Primrose.” Grieve’s medicine was the bark and leaves; the modern one is the fatty oil pressed or extracted from the seed. Kind: Plant > **Caution.** The European agency reports stomach upsets, nausea, soft stools, a rise in temperature, rashes, and headache, and does not recommend the oil for children under twelve, for want of data; overdose causes mild diarrhoea and abdominal pain. The Cochrane review notes a case report warning of possible inflammation, thrombosis, and immunosuppression with use over more than a year, and a study suggesting the oil “may increase bleeding for people on Coumadin” (warfarin). ## What was it used for? An astringent and sedative in the older practice. The drug, Grieve says, “though not in very general use,” had been employed with success in functional disorders of the stomach and bowels, asthma, and whooping cough, and in dyspepsia, “torpor of the liver,” and certain female complaints such as pelvic fullness. The roots were eaten in some countries in spring, and the French used them to garnish salads. The seed oil, the modern medicine, has been thought beneficial, the Cochrane reviewers note, for its gamma-linolenic acid. ## What does modern science say? Here the regulator and the trials point different ways. The European Medicines Agency’s herbal committee accepts the oil, taken by mouth, as a traditional herbal medicine “for the symptomatic relief of itching in acute and chronic dry skin conditions exclusively based upon long-standing use” (monograph of 2018). A Cochrane review of 2013, pooling the trials of the oil in eczema, nineteen of them on evening primrose, concluded that oral evening primrose and borage oil “are not effective treatments for eczema,” improvement being similar to placebo. The regulator’s listing is the newer, but it rests on use, not on trials. The oil is 65 to 85 per cent linoleic acid and 7 to 14 per cent gamma-linolenic acid. A 2021 meta-analysis found no effect of the oil on ripening the cervix before labour. ## Pharmacognosy and toxicology - **linoleic acid**: 65 to 85 per cent of the oil - **gamma-linolenic acid**: 7 to 14 per cent **Mechanism.** Not established in the sources read for this entry. **Standing.** European Union herbal monograph (2018): traditional use of the oil by mouth, “exclusively based upon long-standing use,” for itching in dry skin conditions. A Cochrane review (2013) found it no better than placebo for eczema. ## What lore surrounds it? In the language of flowers, Thiselton-Dyer writes, the evening primrose, from the hour its blossoms open, indicates silent love, refraining from unclosing “her cup of paly gold until her lowly sisters are rocked into a balmy slumber.” Its flowers are fertilised mostly by insects that fly at twilight, Grieve says, though later in the season the plants “keep ‘open house’ practically all day”; in America a troublesome weed, in English gardens one of the showiest hardy plants. ## What did the older authorities say? **Theophrastus, as Grieve reports him.** The genus name, from Greek *oinos*, wine, and *thera*, a hunt, was “an old Greek name given by Theophrastus to some plant, probably an Epilobium, the roots of which were eaten to provoke a relish for wine, as olives are now; others say it dispelled the effects of wine.” ## Sources - Grieve, M. *A Modern Herbal*, “Primrose, Evening.” As published on botanical.com. - Thiselton-Dyer, T. F. (1889). *The Folk-lore of Plants*, ch. 14, “Plant Language”. Project Gutenberg, 10118. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Oenotherae oleum (Evening primrose oil)*. EMA/HMPC/753041/2017, 5 June 2018. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Oenotherae oleum*. EMA/HMPC/753042/2017, 5 June 2018. - Bamford JT, et al. (2013). Oral evening primrose oil and borage oil for eczema. *The Cochrane database of systematic reviews*. PMID 23633319. - Moradi M, et al. (2021). The effect of evening primrose oil on labor induction and cervical ripening: A systematic review and meta-analysis. *Phytotherapy research : PTR*. PMID 33913585. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Oenotherae oleum (Evening primrose oil)*. EMA/HMPC/753041/2017, 5 June 2018. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Oenotherae oleum*. EMA/HMPC/753042/2017, 5 June 2018. - Bamford JT, et al. (2013). Oral evening primrose oil and borage oil for eczema. *The Cochrane database of systematic reviews*. PMID 23633319. --- *Evening primrose.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-16. The Thinking Press. https://thethinkingpress.org/materia-medica/evening-primrose Historical description, not medical advice.