Trifolium macrorrhizumBoiss., syn of subsp.macrorrhizum
Trifolium nevadenseBoiss., syn of var.nevadense
Trifolium orbelicumVelen., syn of var.orbelicum
Trifolium orphanideumBoiss., syn of var.orphanideum
Trifolium biasolettiiSteud. & Hochst., syn of subsp.prostratum
Trifolium occidentaleCoombe, syn of subsp.prostratum
Trifolium repens, thewhite clover, is a herbaceousperennial plant in the bean familyFabaceae (otherwise known as Leguminosae). It is native toEurope, including the British Isles,[2] andcentral Asia and is one of the most widelycultivated types ofclover. It has been widely introduced worldwide as aforage crop, and is now also common in most grassy areas (lawns andgardens) ofNorth America,Australia andNew Zealand.[3][4][5][6][7][8][9] The species includes varieties often classed as small, intermediate and large, according to height, which reflectspetiole length. The term 'white clover' is applied to the species in general, 'Dutch clover' is often applied to intermediate varieties (but sometimes to smaller varieties), and 'ladino clover' is applied to large varieties.[10][11][12][13]
The genus name,Trifolium, derives from the Latintres, "three", andfolium, "leaf", so called from the characteristic form of the leaf, which almost always has threeleaflets (trifoliolate); hence the popular name "trefoil". The species name,repens, is Latin for "creeping".
It is aherbaceous,perennial plant. It is low growing, with floweringheads of whitish florets, often with a tinge of pink or cream that may come on with the aging of the plant. The heads are generally 1.5–2 centimetres (1⁄2–3⁄4 in) wide, and are at the end of7 centimetres (2+3⁄4 in)peduncles or inflorescence stalks.[14] The flowers are mostly visited bybumblebees[15] and often byhoney bees. The leaves aretrifoliolate, smooth, elliptic to egg-shaped andlong-petioled and usually with light or dark markings. The stems function asstolons, so white clover often forms mats, with the stems creeping as much as 18 cm (7 in) a year, and rooting at the nodes.[14] The leaves form the symbol known asshamrock. Almost always, a white clover will be trifoliolate. However, one can, but only sometimes, possessfour or more leaflets.[citation needed]
White clover has been used as amodel organism for global research intoecology andurban evolution. As part of theGlobal Urban Evolution Project (GLUE) scientists from 26 countries examined the production ofcyanide by over 110,000 clover plants from 160 cities. Cyanide can be useful to clover plants as a deterrent to herbivores.Analyzing urban-rural differences, scientists found that cyanide production tended to increase with distance from the center of cities, suggesting that clover populations were adapting to factors commonly found in urban centers worldwide. Possible factors could include temperature (freezing is related to cyanide content), herbivory pressures, and drought stress. As clover habitats, the downtowns of cities may more closely resemble other far-flung cities than nearby rural areas.[17][18][19]
Trifolium repens is an allotetraploid (2n = 4x = 32) of two diploid ancestors and exhibits disomic inheritance.[20] In order to increase genetic diversity for breeding, research is focused on finding these ancestors. Proposed ancestors ofT. repens includeT. nigrescens,T. occidentale,T. pallescens, andT. uniflorum.[20][21][22][23] Additionally, it is possible that one of the diploid ancestors has yet to be analyzed, either because it has not been discovered or is extinct.[24]
White clover has been described as the most important forage legume of thetemperate zones.[25] Symbiotic nitrogen fixation (up to 545 kilograms per hectare per year (486 lb/acre/a) of N,[26] although usually much less, e.g. about 110 to 170 kilograms per hectare per year (98 to 152 lb/acre/a)[27]) in root nodules of white clover obviates synthetic nitrogen fertilizer use for maintaining productivity on much temperate zone pasture land. White clover is commonly grown in mixtures with forage grasses, e.g. perennial ryegrass (Lolium perenne).[28][29][30] Such mixtures can not only optimize livestock production, but can also reduce the bloat risk to livestock that can be associated with excessive white clover in pastures.[31] Such species mixtures also tend to avoid issues that could otherwise be associated with cyanogenic glycosides (linamarin andlotaustralin) intake on pure or nearly pure stands of some white clover varieties.[32] However, problems do not inevitably arise with grazing on monocultures of white clover, and superior ruminant production is sometimes achieved on white clover monocultures managed to optimize sward height.[33]
TheO-methylated isoflavonesformononetin andbiochanin A play a role in arbuscular mycorrhiza formation on white clover roots,[34] and foliar disease can stimulate production of estrogenic coumestans in white clover.[35] However, while there have been a few reports of phytoestrogenic effects of white clover on grazing ruminants,[35] these have been far less common than such reports regarding some varieties of subterranean clover (Trifolium subterraneum) and red clover (Trifolium pratense). Among forage plants, some white clover varieties tend to be favored by rather close grazing, because of theirstoloniferous habit,[36][37] which can contribute to competitive advantage.
White clover grows well as acompanion plant amonglawns,grain crops,pasture grasses, andvegetable rows.[14] It is often added tolawn seed mixes, as it is able to grow and provide green cover in poorer soils where turfgrasses do not perform well. White clover can tolerate closemowing andgrazing, and it can grow on many differenttypes andpHs of soil (although it prefersclay soils).[14] As aleguminous andhardy plant, it is considered to be a beneficial component of natural or organicpasture management and lawn care due to its ability tofix nitrogen and out-competeweeds. Natural nitrogen fixing reduces leaching from the soil and by maintainingsoil health can reduce the incidence of some lawn diseases that are enhanced by the availability of synthetic fertilizer.[38] For these reasons, it is often used as agreen manure andcover crop.
Besides making an excellent forage crop forlivestock,[39] its leaves and flowers are a valuable survival food: they are high inproteins, and are widespread and abundant. The fresh plants have been used for centuries as additives tosalads and other meals consisting of leafy vegetables.[citation needed] They are not easy for humans to digest raw, but, this is however easily fixed by boiling the harvested plants for 5–10 minutes.[40] Native Americans ate some species raw.[41] Dried white clover flowers may also be smoked as a herbal alternative to tobacco.[42]
In India,T. repens is considered a folk medicine against intestinal helminthic worms, and an experimental in-vivo study validated that the aerial shoots ofT. repens bear significantanticestodal (anti-tapeworm) properties.[43]
^Duchen, P. & S. G. Beck. 2012. Estudio taxonómico de las Leguminosas del Parque Nacional Area Natural de Manejo Integrado (PN-ANMI) Cotapata, La Paz-Bolivia. Revista de la Sociedad Boliviana de Botánica 6(1): 13–51.
^Correa A., M.D., C. Galdames & M. Stapf. 2004. Catálogo de las Plantas Vasculares de Panamá 1–599. Smithsonian Tropical Research Institute, Panamá
^Marticorena, C. & M. Quezada. 1985. Catálogo de la Flora Vascular de Chile.Gayana. Botánica 42: 1–157.
^Porsild, A. E. & W. Cody. 1980. Checklist of the Vascular Plants of the Northwest Territories Canada i–viii, 1–607. National Museum of Natural Sciences, Ottawa
^Barnes, R. F., C. J. Nelson, M. Collins, and K. J. Moore (eds.). 2003. Forages: an introduction to grassland agriculture. Vol. 1. 6th ed. Blackwell Publishing. 556 pp.
^Hand, Melanie L.; Ponting, Rebecca C.; Drayton, Michelle C.; Lawless, Kahlil A.; Cogan, Noel O. I.; Brummer, E. Charles; Sawbridge, Timothy I.; Spangenberg, German C.; Smith, Kevin F. (2008-10-01). "Identification of homologous, homoeologous and paralogous sequence variants in an outbreeding allopolyploid species based on comparison with progenitor taxa".Molecular Genetics and Genomics.280 (4):293–304.doi:10.1007/s00438-008-0365-y.ISSN1617-4615.PMID18642031.S2CID24487483.
^Elgersma, Anjo; Hassink, Jan (1997), "Effects of white clover (Trifolium repens L.) on plant and soil nitrogen and soil organic matter in mixtures with perennial ryegrass (Lolium perenne L.)",Plant and Soil,197 (2):177–186,Bibcode:1997PlSoi.197..177E,doi:10.1023/A:1004237527970,S2CID32120149
^Andrae, John. 2004. White clover establishment and management guide. B 1251. Univ. of Georgia Extension.
^Ulyatt, M. J., D. J. Thomson, D. E. Beever, R. T. Evans, and M. J. Haines. "The digestion of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) by grazing cattle." British Journal of Nutrition 60, no. 01 (1988): 137-149.
^Evans, D. R., and T. A. Williams. "The effect of cutting and grazing managements on dry matter yield of white clover varieties (Trifolium repens) when grown with S23 perennial ryegrass." Grass and Forage Science 42, no. 2 (1987): 153-159.
^Moseley, G., and J. R. Jones. "The physical digestion of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) in the foregut of sheep." British Journal of Nutrition 52, no. 02 (1984): 381-390.
^Wolfe, E. C., and Alec Lazenby. "Bloat incidence and liveweight gain in beef cattle on pastures containing different proportions of white clover (Trifolium repens)." Animal Production Science 12, no. 55 (1972): 119-125.
^Crush, J. R., and J. R. Caradus. "Cyanogenesis potential and iodine concentration in white clover (Trifolium repens L.) cultivars." New Zealand Journal of Agricultural Research 38, no. 3 (1995): 309-316.
^Orr, R. J.; Parsons, A. J.; Penning, P. D.; Treacher., T. T. (1990), "Sward composition, animal performance and the potential production of grass/white clover swards continuously stocked with sheep.",Grass and Forage Science,45 (3):325–336,Bibcode:1990GForS..45..325O,doi:10.1111/j.1365-2494.1990.tb01957.x
^Siqueira, J. O., G. R. Safir, and M. G. Nair. "Stimulation of vesicular‐arbuscular mycorrhizal formation and growth of white clover by flavonoid compounds." New Phytologist 118, no. 1 (1991): 87-93.
^abAdams, Norman R. "Detection of the effects of phytoestrogens on sheep and cattle." Journal of Animal Science 73, no. 5 (1995): 1509-1515.
^Lane, L. A., J. F. Ayres and J. V. Lovett. "The pastoral significance, adaptive characteristics, and grazing value of white clover (Trifolium repens L.) in dryland environments in Australia: a review." Animal Production Science 40, no. 7 (2000): 1033-1046.
^Caradus, J. R. "Genetic diversity within white clover (Trifolium repens L.)." In Proceedings Agronomy Society of NZ, vol. 24, p. 2. 1994.
^The Organic Lawn Care Manual, Tukey, Storey Publishing. p 183.
^Coladonato, Milo (1993)."Trifolium repens". U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved2015-07-26.
^Lee Allen Peterson,Edible Wild Plants, (New York City: Houghton Mifflin Company, 1977), P. 56.
^Reiner, Ralph E. (1969).Introducing the Flowering Beauty of Glacier National Park and the Majestic High Rockies. Glacier Park, Inc. p. 10.
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