Evening Primrose
Evening primrose (Oenothera biennis) is often considered an annoying weed at best and an invasive at worst. It occupies the ditches along the roads, first as a rosette and then as a towering beast, reaching up to 8 feet with an explosion of flowers erupting from the top. Evening Primrose favors disturbed areas and has an incredible capacity to cover extended patches of bare ground aggressively. This is partly because of its unique seed survival—there is documentation of evening primrose seed being viable for one hundred years or more.1
Unsurprisingly, this species thrives in disturbed ground and has found itself alongside anthropogenic disturbed habitats. Abandoned fields, abandoned gravel pits, croplands, and roadsides are all perfect places for the evening primrose seed to bloom into life. This biennial takes two years to complete its life cycle, quickly overtakes a landscape, and offers a buffer between early succession and perennial plants.
Indigenous people of eastern and central North America used evening primrose for various purposes, including food, medicine, and incense.2 The roots and leaves of evening primrose are edible and have been eaten across the globe.3 Evening primrose seeds in particular were used as food, incense, and medicine.4 The seeds contain an oil with various medicinal and nutritional uses.5 Today, the oil is most recognized as the product of evening primrose, but the roots can be large and provide sizeable amounts of calories in poor-nutrient soils. The roots were often boiled and eaten like potatoes, as the Cherokee did. While the occasional weeding might pull up a thick and stringy-looking root, timing the harvesting of the primrose root is crucial to harvest the largest root possible. To harvest massive, peppery roots like these, harvest in the fall of the first season. The energy stored in the root during the first year is later used in the second year, leaving little for the person harvesting.
Oenothera may have spread from Central to North America between the successive ice ages of the Pleistocene epoch. This genus's prolific genetic diversity may be partly due to hybridization between survivors of different colonizing events. Common evening primrose is now endemic to much of North America, ranging from Mexico to Florida, north to central Ontario and Quebec, Canada, and west to North Dakota and Oklahoma. It can also be found along the Pacific coastline of North America.
From its origins in North America, O. biennis has been moved by man and established on all other continents, excluding Antarctica. Its first documented introduction to Europe was in 1870 in England, where it was imported for its medicinal qualities. However, it also had a short stint as a root vegetable, alongside other native crops with limited popularity in Europe, such as the sunchoke. I mean, this shouldn’t be a surprise. With massive roots like these, why weren’t the ever improved? Well, people tried.
Evening primrose plants produce flowers with the parts that make pollen (the male bits) and the parts that receive it.6 These flowers, often yellow and opening at dusk (hence the name EVENING primrose), and have a clever system that ensures they usually pollinate themselves. Before the flower fully opens, the pollen is released while still inside the bud. In many evening primroses, the part of the female organ that catches pollen is located right among the pollen-producing parts, so when the pollen is shed, it falls directly onto the receptive surface3. This arrangement strongly encourages the plant to use its own pollen to make seeds, sometimes up to 150,000 from a single plant.7
While insects like moths and bees visit the flowers and can move pollen around, the plant's design means self-pollination is the most common way it reproduces using seeds. This process, where a plant fertilizes itself, allows the evening primrose to maintain its genetic makeup over generations. This is a good thing, right?
Think of genes as instructions stored on structures called chromosomes inside a plant's cells. When plants reproduce sexually through seeds, they usually combine sets of chromosomes from two "parents" (or from the same plant if it self-pollinates). This process typically shuffles and mixes the genes on these chromosomes, so the offspring gets a unique combination of instructions, like getting a mix of traits from your parents and grandparents.
Evening primrose does things very differently. When the evening primrose is making its reproductive cells (like egg and pollen cells), its chromosomes don't pair up in the usual way. Instead, they link together end-to-end, forming a large ring structure.8 This ring formation is important because it prevents the normal shuffling and exchange of genetic material between chromosomes that happens in most other plants during sexual reproduction
The plant also has what are called "balanced lethal genes". These genes act like a filtering system. They prevent certain combinations of chromosomes from being viable in the pollen, egg cells, or even the developing seeds. The combined result of this unique system (the chromosome rings and the lethal genes) is quite remarkable: When an evening primrose plant self-pollinates, the genetic makeup of the resulting seed is identical to the parent plant.
Essentially, the plant has found a way to use seeds for reproduction and dispersal, while still ensuring the offspring has the exact same genetic instructions as the parent. This allows it to "maintain its genetic constitution constant down the generations." It can preserve a successful combination of genes, sometimes called "hybrid vigor," while still scattering seeds widely. However, this unique system comes with a trade-off. Because it prevents the typical shuffling and mixing of genes, the appearance of new gene combinations is "severely limited". This means the evening primrose could only adapt slowly in a changing environment, or in the case of trying to breed it for improved traits. In short, this plant is about as tricky as it can get to breed. This is why few varieties of evening primrose are available to grow despite its costly and in-demand oils and its beautiful flowers.
While we touched on how the plant was used, we have little documentation of its meaningful application in indigenous diets. However, given its ability to take over landscapes, there’s little doubt that this plant would have played a significant role, at least seasonally, in the diets of many indigenous groups. What likely happened, given the slash-and-burn “swidden” technique that evolved from the milpas of Central America, is that these plants took over abandoned farmlands and, similar to groundnuts, were seeded lightly to take over the croplands. These would be stopping grounds during hunting and harvested heavily by hunters (or at least, this is how many groundnuts were harvested). Again, we have no written record of their consumption or management other than that they simply were consumed. In other words, similar crops played similar roles while existing in a similar part of ecological succession, which can give us some insight into probable ways indigenous groups managed and consumed this plant.
Many indigenous peoples in North America used Oenothera spp. Generally (and common evening primrose, particularly), for food and medicinal purposes.9 As stated, the Cherokee cooked and ate common evening primrose leaves as greens and boiled the roots like potatoes. Seeds also had several uses. Members of the Gosiute used them for food, and the Lakota are reported to have burned them as incense. The Iroquois, Cherokee, Ojibwa, and Potawatomi peoples used O. biennis to varying degrees in medicine. This is reinforced by the dated book Culpeper’s Complete Herbal, which states the primroses were a commonly used remedy, and the leaves could be made into a salve to heal wounds.10
Modern research continues to focus on highlighting the benefits of evening primrose oil, but the benefits are far more modest than historic documents suggest. Gamma-Linolenic Acid, or GLA, is a key component in the seeds (and their oils), and is considered to drive many of the health benefits associated with evening primrose oil. It’s regarded as an “essential intermediate” in human metabolism, yet “not found in the normal diet”, and is essential in forming hormones.11
It’s because it influences hormones that it’s often used as a menstrual aid and supports individuals through menopause, although more research still needs to be done. Further, according to research, common evening-primrose extracts inhibit Escherichia coli and Staphylococcus spp.12
For this reason, as well as the root production and their essential role as native pollinator support, these unique flowers deserve a spot in your landscape alongside your crops. The small rosettes fit well beneath your tomatoes, creating large roots to harvest in the fall. The beautiful flowers bloom and fill with nutritious seeds that sit on the stems until late winter, providing a forager with a quick snack while out in the cold. While you may want to press your own oil, because of the unique traits of the seeds, pressing the oil at home is likely out of reach for most folks, and the benefits in the seed oil can be found by consuming the seed directly.
The future of this plant is murky—there are likely improved varieties out there; we need to find them. Fortunately, with its unique genetics, where there is one of these improved varieties, there will be many. Another alternative, which I wouldn’t particularly recommend, is utilizing atomic gardening, which effectively exposes plants to radiation to force genetic mutations. We’ll talk about atomic gardening at another point, but it’s worth mentioning, especially given the unique nature of evening primrose.
The real solution is to get out there, start digging up the roots, and see what’s waiting in your backyard.
If you’ve enjoyed this piece, which is equal to a 9-page chapter of (so far) a 1424-page book with 1042 sources, you can support our work in several ways. The first is by sharing this article with folks you think would find it interesting. Second, you can listen to the audio version of this article in episode #258 of the Poor Proles Almanac wherever you get your podcasts. If you’d like to financially support the project and get exclusive access to our limited paywalled content, you can become a paid subscriber on Substack or Patreon, which will both give you access to the paywalled content and, in the case of Patreon, early access to the audio episodes as well.
Darlington HT, Steinbauer GP (1961) The eighty-year period for Dr. Beal’s seed viability experiment. Am J Bot 48:321–325
Shahnaz Sultana1,2, Mohammed Ali1*, Showkat Rasool Mir, Chemical Constituents From the Roots of Oenothera biennis L. Phytochemistry Research Laboratory, Faculty of Pharmacy, Jamia Hamdard, New Delhi, 110 062, India
Hamel PB, Chiltoskey MU (1975) Cherokee Plants and Their Uses–A 400 Year History. Sylva, NC: Heard Publishing
Perry MJ (1975) Food Use of “Wild” Plants by Cherokee Indians. M.S. thesis. Knoxville, TN: University of Tennessee
Horrobin, D. F. 1990. Gamma linolenic acid. Reviews in Contemporary Pharmacotherapy 1(1):1-45.
Steckel, Lawrence E., et al. "Common evening-primrose (Oenothera biennis L.)." Weed Technology, vol. 33, 2019, pp. 757–760, doi:10.1017/wet.2019.53.
Hall, Ivan V., Erich Steiner, Paul Threadgill, and Richard W. Jones. "THE BIOLOGY OF CANADIAN WEEDS. 84. Oenothera biennis L." Can. J. Plant Sci., vol. 68, 1988, pp. 163-173
Lapinskas, P. "Evening Primrose - Origins and Cultivation." Leatherhead Food Research Association, 9 November 1982
Borchers AT, Keen CL, Stern JS, GershwinME (2000) Inflammation and Native American medicine: the role of botanicals. Am J Clin Nutr 72:339–347
Culpeper N (1653) Culpeper’s Complete Herbal. Primroses. Wakefield, UK: William Nicholson and Sons, Printers. 349 p
Grosman, Sylwia & Winiarz, Aleksandra & Wąsala, Katarzyna & Wokurka, Wojciech & Turek, Michał & Szlendak, Paula & Toś, Katarzyna & Wojtala, Kacper & Węgrzyniak, Agata & Drobek, Dominik. (2023). Supplementation of evening primrose oil (EPO) - benefits and limitations. Results of the latest studies. Journal of Education, Health and Sport. 34. 84-93. 10.12775/JEHS.2023.34.01.007.
Hayes LE (1947) Survey of higher plants for antibacterial substances. Bot Gaz 108:408–414