Evening primrose (Oenothera biennis) opens its four-petaled blossoms after sunset or on dark cloudy or rainy days. It is worth the time to visit an evening primrose plant at dusk and watch as the cream to bright yellow petals unfold like a slow-motion film. The show starts in June and continues through October.
Evening primrose belongs to the Onagraceae (evening primrose family), whose members also include fireweed and fuchsia. Its many common names allude either to its resemblance to other plants or to its historical reputation as an herbal panacea: scabish, king’s cure-all, night willow herb, and German rampion. A biennial with a sturdy taproot, evening primrose grows to about 8 feet tall and flowers in its second season. You might find this North American native in your backyard or in fields, along roadsides, or in waste areas throughout much of eastern North America, where it is naturalized. It is a weed in Europe, where it has escaped from cultivation.
All parts of evening primrose are edible. Native Americans in Utah and Nevada ate the seeds. The young leaves can be used raw in salads or as a potherb. They are usually cooked in several changes of water to get rid of their bitterness. English settlers in America took the seeds back to the British Isles as early as 1614, and in the decades following, evening primrose was grown in both English and German gardens for its nut-flavored roots, which were boiled like parsnips. The plant returned to North America in the mid-nineteenth century as a vegetable called German rampion for its similarity to rampion (Campanula rapunculus), a bellflower with edible roots and basal leaves. The seeds have also been used as a substitute for poppy seeds, which they resemble.
Native Americans also used evening primrose for a variety of medicinal purposes. The Ojibwa poulticed the whole plant on bruises. The Cherokee drank a tea made from the root to take off weight. The Forest Potawatomi considered the seeds a valuable medicine, but records documenting its use have been lost. European settlers began using the plant as medicine in the eighteenth century. The Shakers used the leaves or roots externally to promote healing of wounds and a tea of the leaf and root to settle an upset stomach.
One of the best-known uses of evening primrose oil among today’s consumers of herbal medicine is in mitigating discomfort associated with premenstrual syndrome (PMS). A number of double-blind, placebo-controlled studies have shown that evening primrose oil significantly reduced irritability, breast pain and tenderness, and mood changes associated with PMS; however, one study concluded that the relief of PMS symptoms by evening primrose oil was statistically insignificant compared with that of the placebo.
In recent years, evening primrose has garnered attention as an important dietary supplement and a good source of essential fatty acids: substances, like vitamins, minerals, and essential amino acids, that the body cannot manufacture yet needs to maintain health. They normally are obtained through the diet. Common essential-fatty-acid sources include vegetable oils and leafy green vegetables. A deficiency in essential fatty acids may produce scaly skin lesions, hair loss, poor wound healing, diminished immune response to infections, and fatty degeneration of the liver. It can also adversely affect the circulatory, nervous, digestive, endocrine, respiratory, genitourinary, and reproductive systems.
Essential fatty acids include cis-linoleic acid, which is commonly found in safflower, corn, cottonseed, soybean, and evening primrose oils; alpha-linolenic acid, which is similar to fish oils in composition and is found in canola and soybean oils, flaxseed, and leafy green vegetables; and a product of the metabolism of cis-linoleic acid, gamma-linolenic acid (GLA), which is found in human breast milk and evening primrose oil but is otherwise rare in the food supply. (Evening primrose oil consists of 50 to 70 percent cis-linoleic acid along with 7 to 10 percent cis-GLA and other compounds.)
GLA is an intermediate compound between cis-linoleic acid and prostaglandins (oxygenated unsaturated cyclic fatty acids that regulate various functions in the body). The natural conversion of cis-linoleic acid into prostaglandin E(1) is hampered in certain individuals who are elderly, malnourished, or alcoholic, or suffering from cancer or radiation damage. For these individuals, GLA supplied from evening primrose oil can be an important dietary supplement in increasing prostaglandin production.
In England, use of GLA supplied from evening primrose oil is approved in the treatment of atopic eczema (eczema due to allergy). (Clinical studies at eight research centers have shown that evening primrose oil produces 20 to 25 percent greater improvement in atopic eczema than that of conventional treatments such as steroids.) In Canada, evening primrose oil is an approved dietary supplement for treating essential-fatty-acid deficiencies. Under the provisions of the Dietary Supplement Health and Education Act of 1994, evening primrose oil is considered a dietary supplement in the United States. More than 120 studies in university hospitals in fifteen countries have been conducted on evening primrose oil, and recent research suggests that evening primrose oil may be useful for treating a wide range of conditions associated with imbalances and abnormalities of essential fatty acids, including atopic eczema, asthma, migraine, inflammations, PMS, metabolic disorders, diabetes, arthritis, and alcoholism.
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• Foster, S. Herbal Renaissance. Layton, Utah: Gibbs Smith, 1993.
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• Leung, A. Y., and S. Foster. Encyclopedia of Common Natural Ingredients Used in Foods, Drugs and Cosmetics. New York: Wiley, 1995.
• Olin, B. R., ed. “Evening Primrose”. Lawrence Review of Natural Products November 1993.
• Khoo, S. K., et al. Med. J. Australia 1990, 152:189.
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