Trifolium pratense (red clover) is a herbaceous species of flowering plant in the bean family Fabaceae, native to Europe, Western Asia and northwest Africa, but planted and naturalised in many other regions.
It is a herbaceous, short-lived perennial plant, variable in size, growing to 20–80 cm tall. The leaves are alternate, trifoliate (with three leaflets), each leaflet 15–30 mm long and 8–15 mm broad, green with a characteristic pale crescent in the outer half of the leaf; the petiole is 1–4 cm 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 long, produced in a dense inflorescence, and are mostly visited by bumblebees.
The red clover is found natively in 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 now 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 like New Zealand.
It is widely grown as a fodder crop, valued for its nitrogen fixation, which increases soil fertility. For these reasons, it is used as a green manure crop. Several cultivar groups have been selected for agricultural use, mostly derived from T. pratense var. sativum. It has become naturalised in many temperate areas, including the Americas and Australasia as an escape from cultivation.
In alternative medicine, red clover is promoted as a treatment for a variety of human maladies, including coughs, disorders of the lymphatic system and a variety of cancers. However, according to the American Cancer Society, "available clinical evidence does not show that red clover is effective in treating or preventing cancer, menopausal symptoms, or any other medical conditions".
Dietary amounts of red clover are safe, but medicinal quantities 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.
Red clover is subject to bacterial as well as fungal diseases, including the red clover rust, Uromyces trifolii-repentis var. fallens. Other problems include parasitic nematodes (roundworms) and viruses.
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