Red Clover: History and Traditional Use
Red clover (Trifolium pratense) has lived two quite separate lives. For most of recorded history it was a farmer's plant: one of the first sown fodder crops in Europe, the green engine of the crop rotations that fed the eighteenth century, and the reason a great deal of the world's farmland could skip a fallow year. Its career as a medicine was quieter — a village "blood purifier," a cough syrup, a wash for troubled skin — until an outbreak of infertility in Australian sheep in the 1940s revealed that the plant carries hormone-like molecules, and those molecules turned red clover, in the 1990s, into a menopause supplement. This article follows both lives in order. Where something is tradition, it is named as tradition; where the trials came back negative, we say so.
Table of Contents
- A Meadow Legume: Origins, Botany and the Name
- From Flanders to the Four-Course Rotation: The Crop That Fed Europe
- Shamrocks, Four Leaves and State Flowers
- Blood Purifier, Cough Syrup and Skin Wash: Folk Medicine
- The Eclectics and King's American Dispensatory (1898)
- The Cancer-Tonic Chapter (1920s–1963)
- Clover Disease: Sheep, Isoflavones and the Birth of Phytoestrogen Science
- The Menopause Trials (1999–2021)
- Tradition, Evidence and Red Clover Today
- Key Research Papers
- Connections
- Featured Videos
A Meadow Legume: Origins, Botany and the Name
Red clover is a short-lived perennial of the pea family (Fabaceae), native to Europe, western Asia and north-west Africa and now naturalised on every temperate continent. Its Latin name is almost a field guide in itself. Trifolium means "three-leaf," for the trefoil leaflets that usually carry a pale crescent or chevron across each one; pratense comes from pratum, the Latin for meadow, so the whole binomial simply says "the three-leaved plant of the meadows." "Red" is generous: the globe-shaped heads are pink to purple, each a tight cluster of dozens of small pea-flowers, deep enough that long-tongued bumblebees are the chief pollinators.
Being a legume matters more than anything else in red clover's story. Like peas, beans and alfalfa, it houses Rhizobium bacteria in small nodules on its roots, and those bacteria pull nitrogen gas out of the air and turn it into a form plants can use. A field of clover therefore leaves the soil richer than it found it, a fact farmers exploited for centuries before the German agronomists Hermann Hellriegel and Hermann Wilfarth explained it in experiments published between 1886 and 1888: legumes grown in sterilised soil could not fix nitrogen unless inoculated with the right soil bacteria.
Two relatives are worth telling apart. White clover (Trifolium repens) is the low, creeping plant of lawns, with white heads and runners along the ground; it is the more common "shamrock" and a different herb altogether. Subterranean clover (Trifolium subterraneum), an annual that buries its own seed heads, is the Australian pasture plant at the centre of the sheep story told below. Red clover's cultivated forms are usually grouped under T. pratense var. sativum.
From Flanders to the Four-Course Rotation: The Crop That Fed Europe
Red clover's first great chapter was written by farmers rather than physicians. Medieval European agriculture rested on rotations that left a field fallow one year in two or three to recover its fertility. The alternative — sowing a legume that restores the soil while feeding livestock — was worked out in the intensively farmed Low Countries. The rotation that became famous as the "Norfolk four-course" (wheat, turnips, barley, then clover or ryegrass) is traced to the Waasland district of what is now northern Belgium in the early sixteenth century, roughly two centuries before it became standard in England.
The man usually credited with carrying clover across the Channel is Sir Richard Weston (1591–1652), a Surrey landowner and canal builder who spent part of the English Civil War in exile in Flanders. In 1644 he was in Ghent, Bruges and Antwerp studying Flemish farming, and around 1645 he wrote an account of it for his sons that described a rotation founded on clover, flax and turnips. The reformer Samuel Hartlib published an imperfect copy in 1650 as A Discours of Husbandrie used in Brabant and Flanders, and a corrected edition in 1652 with his own letters pressing Weston for more detail on the clover. Weston's promise was concrete: "being once sown, it will last five years; and then being ploughed, it will yield, three or four years together, rich crops of wheat, and after that a crop of oats." The Dictionary of National Biography credits him with introducing "the great clover, as it was then called" to English agriculture about 1645, and probably turnips as well — though as with most agricultural "firsts," he was popularising a practice rather than inventing it.
Over the following century clover-based rotations spread through the English countryside and were promoted in the eighteenth century by Charles Townshend, 2nd Viscount Townshend, whose enthusiasm for the Norfolk system earned him the nickname "Turnip" Townshend. The consequences were large: without a fallow year more land was under crop, clover hay and turnips carried cattle through the winter, more animals meant more manure, and more manure meant more grain. Historians count clover among the quiet engines of the British Agricultural Revolution. Red clover crossed the Atlantic with European settlers and became a staple hay and green-manure crop of North American farming, which is why it now grows wild along roadsides across the continent.
Shamrocks, Four Leaves and State Flowers
A plant this common in the fields was bound to gather folklore. The oldest strand is Irish. Which clover is "the" shamrock has been argued for centuries, and two botanists settled it as well as it can be settled by asking the public. In 1893 Nathaniel Colgan of Dublin invited people across Ireland to send him the plant they wore on St Patrick's Day and grew the specimens to flowering; in 1988 Charles Nelson repeated the exercise. Both found the same answer: about half of the samples were lesser clover (Trifolium dubium), a third white clover, and only a small remainder — six per cent in 1893, four per cent in 1988 — red clover. Red clover, in other words, is a shamrock to some, but not the shamrock.
The four-leaf clover, a rare variant on a normally three-leaved plant, is an old European luck charm; the tradition attaches to clovers in general, not to red clover specifically, and its origins are not documented well enough to date. The plant has, however, been formally adopted twice as an emblem. Vermont made red clover its state flower in 1894, and the statute is still on the books: "The State Flower shall be the red clover." Denmark's foreign ministry announced red clover as the national flower in 1936 for an international exhibition in Argentina; the choice never caught on with the public and was later superseded by the daisy.
Blood Purifier, Cough Syrup and Skin Wash: Folk Medicine
Compared with its agricultural record, red clover's medicinal history is thin before the modern era, and honesty requires saying so. It is not a plant of the great classical pharmacopoeias in the way that fennel or mint are; the ancient Greek and Roman herbals discuss trefoils in general terms that cannot be pinned to Trifolium pratense, and this article does not attribute to Dioscorides or Pliny what they may not have meant. The reliable documentary trail begins in the early-modern herbals of Europe and, above all, in the folk and professional medicine of the eighteenth and nineteenth centuries.
Within that tradition red clover had three settled uses. The first was as an alterative — the old term for a remedy taken over weeks to "cleanse the blood" and gradually restore health in chronic conditions. The idea, inherited from humoral medicine, was that stubborn skin eruptions, swollen glands and slow-healing sores reflected impurity in the blood, and that a plant drunk as tea over time would draw it out. Red clover tea, made from the dried flower heads, was one of the mildest and most popular of these. The second use followed from the first: taken internally and applied as a wash, poultice or ointment, red clover was a stock remedy for the eruptive skin conditions we would now call eczema and psoriasis, and for wounds and sores that would not close. The third was respiratory. A syrup or strong infusion of the flowers was given for coughs, bronchitis and, particularly in nineteenth-century America, whooping cough.
None of these uses was ever tested in the modern sense. What red clover did have was ubiquity, safety and a pleasant taste, which is enough to keep a household remedy in use for two hundred years. Modern chemistry has added one footnote: a 2019 study of traditional red clover preparations found that the way a tea or tincture is made changes which isoflavones end up in the cup, so the folk preparations and the modern tablets are not the same medicine even when they share a plant.
The Eclectics and King's American Dispensatory (1898)
Red clover's most detailed traditional record comes from the American Eclectic physicians, a nineteenth-century school of medical doctors who rejected bloodletting and mercury in favour of plant medicines and who ran their own colleges, journals and pharmacies, chiefly in Cincinnati. Their reference work, King's American Dispensatory, in the 1898 edition revised by Harvey Wickes Felter and John Uri Lloyd, gives red clover a full entry under Trifolium pratense.
The Dispensatory opens its assessment with the sentence that defined the herb for a generation of practitioners: "Red clover is an excellent alterative, and one of the few remedies which favorably influences pertussis" — pertussis being whooping cough. It lists an infusion of the flowers, a strong tincture of the freshly dried blossoms in dilute alcohol, and the concentrated "specific trifolium" given by the drop, and it describes a compound extract combining red clover with other alterative and eliminative botanicals for syphilis, scrofula (tuberculous swelling of the neck glands), chronic rheumatism, glandular disease and skin affections. It also records the Eclectics' belief that the plant "unquestionably retards the growth of carcinomata" and could be given to patients with cancerous conditions.
That last claim deserves to be read as what it is: an 1898 clinical impression, formed before biopsies, staging or controlled trials existed, in an era when many chronic ulcers and swellings called "cancer" were nothing of the kind. There has never been evidence that red clover treats cancer, and the Eclectics' confidence had consequences in the twentieth century, as the next section explains. But the entry is also a fair snapshot of what red clover meant to trained physicians in 1898: a gentle, long-course tonic for skin, glands and cough.
The Cancer-Tonic Chapter (1920s–1963)
The Eclectic idea of red clover as an anti-cancer alterative outlived the Eclectic movement. In the 1920s an American lay practitioner began marketing a herbal cancer treatment that became known as the Hoxsey therapy; its internal tonic combined red clover with liquorice, burdock root, stillingia, barberry, cascara, prickly ash bark, buckthorn bark and potassium iodide — recognisably a descendant of the nineteenth-century "Trifolium compound." Clinics offering it operated in several states through the 1930s, 40s and 50s.
The public record of what followed is brief and settled. In April 1956 the U.S. Food and Drug Administration issued an unusual public warning about the treatment, displayed in post offices across the country. On 21 September 1960 the FDA banned its sale and marketing in the United States, and the last American clinic closed in 1963. No controlled study has ever shown that the formula, or red clover on its own, treats cancer, and the agencies that have reviewed it since have reached the same conclusion. The episode is recorded here because it explains why a mild meadow herb still turns up in "cleansing" blends with an anti-cancer subtext, and why every responsible source says plainly that the subtext has no basis.
Clover Disease: Sheep, Isoflavones and the Birth of Phytoestrogen Science
The discovery that made red clover scientifically interesting was made by veterinarians, in sheep, and — a detail often blurred in retellings — on a different clover. In the 1940s farmers in the wheat-and-sheep belt of Western Australia, who had sown their pastures heavily with subterranean clover, began reporting ewes that would not conceive, difficult lambings, uterine prolapse and, in castrated males, abnormal development of the mammary tissue. In 1946 Harold Bennetts, with Eric Underwood and Frank Shier, published "A specific breeding problem of sheep on subterranean clover pastures in Western Australia," the paper that named the syndrome and tied it to the pasture; the same year Bennetts described the tissue changes in wethers grazed on young clover. "Clover disease," as it came to be called, cost the Australian industry millions of lambs over the following decades.
The chemistry followed quickly. In 1951 the Australian chemists R. B. Bradbury and D. E. White isolated two isoflavones from subterranean clover, formononetin and genistein, and showed that the plant's oestrogenic activity lay in this family of compounds. Isoflavones are plant polyphenols shaped enough like oestradiol to bind, weakly, to the body's oestrogen receptors — hence the word phytoestrogen, "plant oestrogen." Formononetin's odd name preserves an older piece of chemistry: it derives from Ononis, the spiny restharrow, whose root the Austrian chemist Heinrich Hlasiwetz had analysed in 1855, yielding the glycoside ononin of which formononetin is the sugar-free core. Red clover, it turned out, is one of the richest sources of formononetin and its methylated cousin biochanin A of any plant, along with smaller amounts of genistein and daidzein.
The puzzle was that formononetin itself is only feebly oestrogenic in the test tube. The answer came from the sheep's stomach. In 1965 Batterham, Hart, Lamberton and Braden reported in Nature that rumen microbes strip the methyl group from formononetin and reduce the product to equol — a far more potent oestrogen-like molecule, and the true cause of clover disease. Equol had a curious prior history: it was first isolated in 1932, by Guy Marrian and Geoffrey Haslewood in London, from the urine of pregnant mares, and was assumed to be an inert by-product until the sheep work explained where it came from. Human gut bacteria perform the same conversion in roughly a third of people, which is why modern trials speak of "equol producers" and "non-producers."
Clover disease is, in retrospect, the origin of the whole field of phytoestrogen research: the soy debates, the endocrine-disruptor literature and the menopause trials all trace back to those Western Australian paddocks. Breeders answered with low-formononetin cultivars, and a 2022 review in Frontiers in Endocrinology notes that oestrogenic pastures remain a live problem for sheep reproduction wherever old high-isoflavone stands persist.
The Menopause Trials (1999–2021)
If sheep infertility was the problem, someone was bound to ask whether the same molecules might be a solution elsewhere — specifically for the hot flushes that follow the fall in oestrogen at menopause. In the 1990s an Australian company developed a standardised red clover isoflavone extract, and the first randomised, placebo-controlled trials appeared in 1999 in the journal Climacteric: Knight, Howes and Eden tested 40 mg and 160 mg of isoflavones a day against placebo, and Baber and colleagues ran a crossover trial of 40 mg. Both were small and short, and neither found a statistically significant advantage over placebo for hot flushes, partly because of the large placebo response typical of menopause studies. A 2002 Dutch trial (van de Weijer and Barentsen, Maturitas) using 80 mg a day did report a significant reduction in flush frequency.
The decisive test was the Isoflavone Clover Extract (ICE) Study, a rigorous American trial funded by the National Institutes of Health and published in JAMA in 2003 by Jeffrey Tice and colleagues. It randomised 252 women with frequent hot flushes to one of two red clover isoflavone products or placebo for twelve weeks. Neither extract reduced hot flushes more than placebo; the authors concluded that the extracts had no clinically important effect.
The pooled analyses that followed tell the same story with more nuance. Coon, Pittler and Ernst's 2007 meta-analysis in Phytomedicine found a small reduction in hot flush frequency of doubtful clinical relevance. The Cochrane review of phytoestrogens for vasomotor symptoms, first published in 2007 and updated in 2013 by Lethaby and colleagues, concluded that there was no conclusive evidence that phytoestrogen supplements, red clover extracts among them, reduce hot flushes or night sweats, while noting that some genistein-rich products deserved further study. A 2015 systematic review by Ghazanfarpour and colleagues reached a modestly more positive verdict for red clover in the short term, and a 2021 meta-analysis of randomised trials by Kanadys and colleagues in Nutrients reported a statistically significant reduction in daily hot flushes with red clover extract compared with placebo — while cautioning that the trials were small, short and heterogeneous. Two decades of study have narrowed the answer to "at most a small effect, in some women, for a few months."
Tradition, Evidence and Red Clover Today
Red clover today is three things at once. To farmers it is what it always was: a nitrogen-fixing hay, silage and green-manure crop grown on millions of hectares, its value undiminished by anything in this article. To herbalists it remains the gentle alterative of the Eclectics, sold as dried blossom for tea, as tincture and in "cleansing" blends for skin and glands — uses that rest on tradition alone, since none has been examined in a controlled trial. And to the supplement industry it is a menopause product: standardised isoflavone extracts, typically 40–80 mg a day, whose evidence base is the mixed record above. In the United States the extract has a quality monograph in the United States Pharmacopeia–National Formulary, which sets standards for identity and content, not claims of effect.
The U.S. National Center for Complementary and Integrative Health, in its current summary, describes the trial results for hot flushes as inconsistent, with some studies at high risk of bias; notes that red clover may modestly improve cholesterol levels in postmenopausal women but that more research is needed; finds the handful of bone-density studies too few and too inconsistent to draw conclusions; and reports that clinical use for up to about two years appears well tolerated, while advising against use in pregnancy and breastfeeding. The standing cautions — oestrogen-sensitive cancers, hormone treatments such as tamoxifen, anticoagulants — are discussed on the isoflavones and safety page.
What is striking is how little the two lives of red clover have to do with each other. The folk tradition never knew about isoflavones and used the plant for coughs and skin; the modern trials tested isoflavones for a symptom no traditional herbalist treated with clover. The threads meet only in the sheep paddock, where a fodder crop planted for its nitrogen turned out to be a pharmacology lesson. The fair summary of its medicine, after four centuries, is a modest one: a safe and pleasant tea with a long tradition behind it, and a standardised extract that may take the edge off hot flushes for some women, for a while.
Key Research Papers
The list covers a modern review of the genus, the veterinary and chemical papers that founded phytoestrogen research, and the landmark menopause trials and meta-analyses. Historical primary texts (Weston's Discours of Husbandrie, King's American Dispensatory) are named in the article, not cited here.
- Kolodziejczyk-Czepas J (2016). Trifolium species — the latest findings on chemical profile, ethnomedicinal use and pharmacological properties. The Journal of Pharmacy and Pharmacology. — PubMed PMID: 27230819
- Marrian GF, Haslewood GA (1932). Equol, a new inactive phenol isolated from the ketohydroxyoestrin fraction of mares' urine. The Biochemical Journal. — PubMed PMID: 16744928
- Bennetts HW, Underwood EJ, Shier FL (1946). A specific breeding problem of sheep on subterranean clover pastures in Western Australia. The British Veterinary Journal. — PubMed PMID: 20275973
- Bradbury RB, White DE (1951). The chemistry of subterranean clover. Part I. Isolation of formononetin and genistein. Journal of the Chemical Society (Resumed). — doi:10.1039/jr9510003447
- Batterham TJ, Hart NK, Lamberton JA, Braden AWH (1965). Metabolism of Oestrogenic Isoflavones in Sheep. Nature. — doi:10.1038/206509a0
- Knight DC, Howes JB, Eden JA (1999). The effect of Promensil, an isoflavone extract, on menopausal symptoms. Climacteric. — PubMed PMID: 11910671
- Tice JA, Ettinger B, Ensrud K, Wallace R, Blackwell T, Cummings SR (2003). Phytoestrogen supplements for the treatment of hot flashes: the Isoflavone Clover Extract (ICE) Study: a randomized controlled trial. JAMA. — PubMed PMID: 12851275
- Coon JT, Pittler MH, Ernst E (2007). Trifolium pratense isoflavones in the treatment of menopausal hot flushes: a systematic review and meta-analysis. Phytomedicine. — PubMed PMID: 17239573
- Lethaby A, Marjoribanks J, Kronenberg F, Roberts H, Eden J, Brown J (2013). Phytoestrogens for menopausal vasomotor symptoms. The Cochrane Database of Systematic Reviews. — PubMed PMID: 24323914
- Kanadys W, Barańska A, Błaszczuk A, Polz-Dacewicz M, Drop B, Kanecki K, et al. (2021). Evaluation of Clinical Meaningfulness of Red Clover (Trifolium pratense L.) Extract to Relieve Hot Flushes and Menopausal Symptoms in Peri- and Post-Menopausal Women: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. — PubMed PMID: 33920485
PubMed Topic Searches
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