Red clover is a herbaceous, short-lived perennial plant, variable in size, growing to 20–80 cm (8–31 in) tall. It has a deep taproot which makes it tolerant to drought and gives it a good soil structuring effect. The leaves are alternate, trifoliate (with three leaflets), each leaflet 15–30 mm (0.6–1.2 in) long and 8–15 mm (0.3–0.6 in) broad, green with a characteristic pale crescent in the outer half of the leaf; the petiole is 1–4 cm (0.4–1.6 in) long, with two basal stipules that are abruptly narrowed to a bristle-like point. The flowers are dark pink with a paler base, 12–15 mm (0.5–0.6 in) long, produced in a dense inflorescence, and are mostly visited by bumblebees.
The red clover is native to Europe, Western Asia, and northwest Africa, but it has been naturalized in other continents, like North and South America. Specifically, the red clover was brought to Argentina and Chile over 100 years ago, although it is not clear how exactly it was introduced. The red clover has become increasingly important as a source of economic stability in Chile, which has made the need for pollinators even more important. One important pollinator, which was also brought from Europe, is Bombus ruderatus, or the large garden bumblebee. This bumblebee has been one of the important pollinators of red clover in South America and other countries such as New Zealand.
In alternative medicine, red clover is promoted as a treatment for a variety of human maladies, including symptoms of menopause, coughs, disorders of the lymphatic system and a variety of cancers. Several systemic reviews and meta-analyses concluded that red clover extract reduces the frequency of menopause hot flashes. Most added that further research needed to confirm the results. There is no evidence in the human trial literature that red clover has been tested for effects on cough, lymphatic system or cancer prevention/treatment. Dietary amounts of red clover are safe, but dietary supplement extracts may cause rash-like reactions, muscle ache, headache, nausea, vaginal bleeding in women, and slow blood clotting.
Red clover contains coumestrol, a phytoestrogen. Due to its activity on oestrogen receptors, red clover is contraindicated in people with a history of breast cancer, endometriosis, ovarian cancer, uterine cancer, uterine fibroids or other oestrogen-sensitive conditions, although some authors have suggested the high isoflavone content counteracts this, and even provides benefits in these conditions.
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^Morales, Carolina L; Arbetman, Marina P; Cameron, Sydney A; Aizen, Marcelo A (2013-07-15). "Rapid ecological replacement of a native bumble bee by invasive species". Frontiers in Ecology and the Environment. 11 (10): 529–534. doi:10.1890/120321. ISSN1540-9295.
^Ghazanfarpour M, Sadeghi R, Roudsari RL, Khorsand I, Khadivzadeh T, Muoio B (2016). "Red clover for treatment of hot flashes and menopausal symptoms: A systematic review and meta-analysis". J Obstet Gynaecol. 36 (3): 301–11. doi:10.3109/01443615.2015.1049249. PMID26471215.
^Dean W. Roberts, Daniel R. Doerge, Mona I. Churchwell, Gonçalo Gamboa da Costa, M. Matilde Marques & William H. Tolleson (2004). "Inhibition of extrahepatic human cytochromes P450 1A1 and 1B1 by metabolism of isoflavones found in Trifolium pratense (red clover)". Journal of Agricultural and Food Chemistry. 52 (21): 6623–6632. doi:10.1021/jf049418x. PMID15479032.CS1 maint: Multiple names: authors list (link)
Vleugels, Tim; Roldan-Ruiz, Isabel; Cnops, Gerda (April 8, 2014). "Influence of flower and flowering characteristics on seed yield in diploid and tetraploid red clover". Plant Breeding. 134 (1): 56–61. doi:10.1111/pbr.12224.