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Clover

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"Trifolium" redirects here. For the trematode parasite, see Cladocystis trifolium. For other uses, see Clover (disambiguation).

Clover
Trifolium repens (white clover)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Clade: Inverted repeat-lacking clade
Tribe: Trifolieae
Genus: Trifolium
L.
Subgenera and sections[1]

subg. Chronosemium
subg. Trifolium

sect. Glycyrrhizum
sect. Involucrarium
sect. Lupinaster
sect. Paramesus
sect. Trichocephalum
sect. Trifoliastrum
sect. Trifolium
sect. Vesicastrum
Synonyms[2]
  • Amarenus C.Presl (1831)
  • Amoria C.Presl (1831)
  • Bobrovia A.P.Khokhr. (1998), nom. illeg.
  • Calycomorphum C.Presl (1831)
  • Chrysaspis Desv. (1827)
  • Dactiphyllon Raf. (1818)
  • Dactiphyllum Raf. (1819)
  • Falcatula Brot. (1816 publ. 1817)
  • Galearia C.Presl (1831), nom. rej.
  • Lagopus Hill (1756)
  • Lagopus Bernh. (1800), nom. illeg.
  • Lojaconoa Bobrov (1967)
  • Loxospermum Hochst. (1846)
  • Lupinaster Fabr. (1759)
  • Micrantheum C.Presl (1831), nom. illeg.
  • Microphyton Fourr. (1868)
  • Mistyllus C.Presl (1831)
  • Ochreata (Lojac.) Bobrov (1967)
  • Paramesus C.Presl (1831)
  • Pentaphyllon Pers. (1807)
  • Triphylloides Moench (1794)
  • Ursia Vassilcz. (1979)
  • Ursifolium Doweld (2003)
  • Xerosphaera Soják (1985 publ. 1986)

Clovers, also called trefoils, are plants of the genus Trifolium (from Latin tres 'three' and folium 'leaf'), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with the highest diversity in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes on mountains in the tropics.

They are small annual, biennial, or short-lived perennial herbaceous plants, typically growing up to 30 cm (12 in) tall. The leaves are trifoliate (rarely, they have four or more leaflets; the more leaflets the leaf has, the rarer it is; see four-leaf clover), with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the calyx.[3] Other closely related genera often called clovers include Melilotus (sweet clover) and Medicago (alfalfa or Calvary clover).

As legumes, clovers fix nitrogen using symbiotic bacteria in their root nodules, and are used as an alternative or supplement to synthetic nitrogen fertilizers. They are also valuable food source for grazing livestock and bees. The domestication of clover caused substantial increases in agricultural productivity.

Cultivation history

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A clover with a drop of dew in the middle
A clover with a dewdrop in the middle
Colorful flowers of clovers beside Zarivar Lake in Iran
Lesser hop trefoil
Owl-head clover
White clover

Clover was first domesticated in Spain in around the year 1000. During European urbanization, crop rotations involving clover became essential for replacing the fixed nitrogen exported to cities as food.[4] Increased soil nitrogen levels from the spreading use of clover were one of the main reasons why European agricultural production in 1880 was about 275% of the production in 1750.[5] Fields of clover, used as forage and newly-invented silage, became an important part of the rural landscape;[4] adding clover made livestock feed more nutritious. Honey production also rose drastically, and clover remained the main nectar source for bees until the mid-twentieth century. Clover was carried around the world as a crop by European colonists, and some clover species became invasive in some areas.[5]

Imports of guano[5] and the development of the Haber-Bosch process in the 20th century substantially displaced clover as a crop, with negative effects on pollinators,[4] but in the 1990s and 2010s, the cost of industrially-fixed nitrogen rose substantially, approximately doubling, and reviving interest in forage mixes that include clover. As the fixation process in energy-intensive, prices are closely tied to energy prices. The 21st century also took interest in clover as a countermeasure to fight the global pollinator decline.[5]

Cultivation

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Several species of clover are extensively cultivated as fodder plants. The most widely cultivated clovers are white clover, Trifolium repens, and red clover, Trifolium pratense. Clover, either sown alone or in mixture with ryegrass, has for a long time formed a staple crop for silaging, for several reasons: it grows freely, shooting up again after repeated mowings; it produces an abundant crop; it is palatable to and nutritious for livestock; it fixes nitrogen using symbiotic bacteria in its root nodules, reducing the need for synthetic fertilizers; it grows in a great range of soils and climates; and it is appropriate for either pasturage or green composting.[3]

In many areas, particularly on acidic soil, clover is short-lived because of a combination of insect pests, diseases and nutrient balance; this is known as "clover sickness". When crop rotations are managed so that clover does not recur at intervals shorter than eight years, it grows with much of its pristine vigor.[3]

Clovers are most efficiently pollinated by bumblebees, which have declined as a result of agricultural intensification.[6] Honeybees can also pollinate clover, and beekeepers are often in heavy demand from farmers with clover pastures. Farmers reap the benefits of increased reseeding that occurs with increased bee activity, which means that future clover yields remain abundant. Beekeepers benefit from the clover bloom, as clover is one of the main nectar sources for honeybees.[7]

Trifolium repens, white or Dutch clover, is a perennial abundant in meadows and good pastures. The flowers are white or pinkish, becoming brown and deflexed as the corolla fades. Trifolium hybridum, alsike or Swedish clover, is a perennial which was introduced early in the 19th century and has now become naturalized in Britain. The flowers are white or rosy, and resemble those of Trifolium repens. Trifolium medium, meadow or zigzag clover, a perennial with straggling flexuous stems and rose-purple flowers,[3] has potential for interbreeding with T. pratense to produce perennial crop plants.[8]

Other species are: Trifolium arvense, hare's-foot trefoil; found in fields and dry pastures, a soft hairy plant with minute white or pale pink flowers and feathery sepals; Trifolium fragiferum, strawberry clover, with globose, rose-purple heads and swollen calyxes; Trifolium campestre, hop trefoil, on dry pastures and roadsides, the heads of pale yellow flowers suggesting miniature hops; and the somewhat similar Trifolium dubium, common in pastures and roadsides, with smaller heads and small yellow flowers turning dark brown.[3]

Uses

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Clover is foraged for by wildlife such as bears, game animals, and birds. Clover is edible by humans,[9] although red clover should be avoided by pregnant women.[10][medical citation needed] The plant is a traditional Native American food,[11] which is eaten both raw and after drying and smoking the roots. The seeds from the blossoms are used to make bread.[12] It is also possible to make tea from the blossoms.[12]

Symbolism

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Shamrock, the traditional Irish symbol, which according to legend was coined by Saint Patrick for the Holy Trinity, is commonly associated with clover, although alternatively sometimes with the various species within the genus Oxalis, which are also trifoliate.[13]

Clovers occasionally have four leaflets, instead of the usual three. These four-leaf clovers, like other rarities, are considered lucky.[3] Clovers can also have five, six, or more leaflets, but these are rarer still. The clover's outer leaf structure varies in physical orientation.

The record for most leaflets is 63, set on August 2, 2023, by Yoshiharu Watanabe in Japan.[14] The previous record holder, Shigeo Obara, had discovered an 18-leaf clover in 2002,[15] a 21-leaf clover in 2008[16] and a 56-leaf clover in 2009,[17] also in Japan.

  • A common idiom is "to be (or to live) in clover", meaning to live a carefree life of ease, comfort, or prosperity.[18]
  • A common saying in surgery [regarding the appearance of wound after hemorrhoidectomy] is "If it looks like clover, the trouble is over; if it looks like dahlia, it’s surely a failure."

Phylogeny

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The first extensive classification of Trifolium had been done by Michael Zohary and David Heller, and it was subsequently released in 1984. They divided the genus into eight sections: Lotoidea, Paramesus, Mistyllus, Vesicamridula, Chronosemium, Trifolium, Trichoecephalum, and Involucrarium, with Lotoidea placed most basally.[20] Within this classification system, Trifolium repens falls within section Lotoidea, the largest and least heterogeneous section. Lotoidea contains species from America, Africa, and Eurasia, considered a clade because of their inflorescence shape, floral structure, and legume that protrudes from the calyx. However, these traits are not unique to the section, and are shared with many other species in other sections. Zohary and Heller argued that the presence of these traits in other sections proved the basal position of Lotoidea, because they were ancestral. Aside from considering this section basal, they did not propose relationships between other sections. Since then, molecular data has both questioned and confirmed the proposed phylogeny from Zohary and Heller. A genus-wide molecular study has since proposed a new classification system, made up of two subgenera, Chronosemium and Trifolium.[21] This recent reclassification further divides subgenus Trifolium into eight sections. The molecular data supports the monophyletic nature of three sections proposed by Zohary and Heller (Tripholium, Paramesus, and Trichoecepalum), but not of Lotoidea (members of this section have since been reclassified into five other sections). Other molecular studies, although smaller, support the need to reorganize Lotoidea.[22][23]

Species

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291 species of Trifolium are accepted:[2]

See also

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References

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  1. ^ "Species Nomenclature in GRIN". Archived from the original on 2008-10-14. Retrieved 2010-08-04.
  2. ^ a b Trifolium Tourn. ex L. Plants of the World Online. Retrieved 22 September 2023.
  3. ^ a b c d e f  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Clover". Encyclopædia Britannica. Vol. 6 (11th ed.). Cambridge University Press. p. 561.
  4. ^ a b c Kjærgaard, Thorkild (January 2003). "A Plant that Changed the World: The rise and fall of clover 1000-2000". Landscape Research. 28 (1): 41–49. doi:10.1080/01426390306531. {{cite journal}}: |access-date= requires |url= (help)
  5. ^ a b c d Harris, Ciaran; Ratnieks, Francis L. W. (June 2022). "Clover in agriculture: combined benefits for bees, environment, and farmer". Journal of Insect Conservation. 26 (3): 339–357. doi:10.1007/s10841-021-00358-z. {{cite journal}}: |access-date= requires |url= (help)
  6. ^ Bumbles make beeline for gardens, study suggests Archived 2018-05-18 at the Wayback Machine Retrieved 27 November 2010.
  7. ^ Oertel, Everett (1967). Beekeeping in the United States. U.S. Department of Agriculture. p. 16. Archived from the original on 2023-01-16. Retrieved 2022-03-11.
  8. ^ Isobe, S.; Sawai, A.; Yamaguchi, H.; Gau, M.; Uchiyama, K. (2002). "Breeding potential of the backcross progenies of a hybrid between Trifolium medium × T. pratense to T. pratense". Canadian Journal of Plant Science. 82 (2): 395–399. doi:10.4141/P01-034.
  9. ^ Field guide to edible wild plants. [Harrisburg, Pa.] Stackpole Books. 1974. ISBN 978-0-8117-0616-2.
  10. ^ "3 Edible Weeds". 19 February 2016.
  11. ^ DAWSON, ARTHUR (2023-04-26). "Indigenous tribes utilized clover and the plant inspired a local city's name". Santa Rosa Press Democrat. Retrieved 2024-04-30.
  12. ^ a b Angier, Bradford (1974). Field Guide to Edible Wild Plants. Harrisburg, PA: Stackpole Books. p. 60. ISBN 0-8117-0616-8. OCLC 799792.
  13. ^ "Shamrock (Oxalis)". Fine Gardening. Archived from the original on March 1, 2017. Retrieved February 28, 2017.
  14. ^ "Most leaves on a clover". Guinness World Records. Archived from the original on August 8, 2024. Retrieved August 8, 2024.
  15. ^ "Clover - Most Leaves". Guinness World Records. Archived from the original on March 25, 2008. Retrieved 22 December 2016.
  16. ^ "21-leaf Clover Sets Record". Neatorama. June 11, 2008. Archived from the original on July 22, 2009. Retrieved August 8, 2024.
  17. ^ "Most Leaves on a Clover". Guinness World Records. Archived from the original on 2015-03-19. Retrieved 2011-04-23.
  18. ^ "Cambridge Dictionary". Cambridge Dictionary. June 26, 2021. Archived from the original on 2015-10-04. Retrieved June 26, 2021.
  19. ^ Pollard, Michael (1986). Travel by Road and Rail. Independence, Ohio: Schoolhouse Press. p. 31. ISBN 9780808610403.
  20. ^ Zohary, Michael (1984). The genus Trifolium. Heller, D. Jerusalem: Israel Academy of Sciences and Humanities. ISBN 978-9652080561. OCLC 11057949.
  21. ^ Ellison, Nick W.; Liston, Aaron; Steiner, Jeffrey J.; Williams, Warren M.; Taylor, Norman L. (2006). "Molecular phylogenetics of the clover genus (Trifolium—Leguminosae)". Molecular Phylogenetics and Evolution. 39 (3): 688–705. Bibcode:2006MolPE..39..688E. doi:10.1016/j.ympev.2006.01.004. PMID 16483799.
  22. ^ Vižintin, Liliana; Javornik, Branka; Bohanec, Borut (2006). "Genetic characterization of selected Trifolium species as revealed by nuclear DNA content and ITS rDNA region analysis". Plant Science. 170 (4): 859–866. Bibcode:2006PlnSc.170..859V. doi:10.1016/j.plantsci.2005.12.007.
  23. ^ Watson, L. E.; Sayed-Ahmed, H.; Badr, A. (2000-09-01). "Molecular phylogeny of Old WorldTrifolium (Fabaceae), based on plastid and nuclear markers". Plant Systematics and Evolution. 224 (3–4): 153–171. Bibcode:2000PSyEv.224..153W. doi:10.1007/BF00986340. ISSN 0378-2697. S2CID 45350663.
  24. ^ "Detox and Cleansing". 2014-12-24. Archived from the original on March 6, 2016. Retrieved March 12, 2016.
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