Trifolium apertum

Clovers, also called trefoils, are plants of the genus ''Trifolium'' (), 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 tall. The leaves are trifoliate (rarely, they have more or fewer than three leaflets; the more (or fewer) 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. 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

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. 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. Fields of clover, used as forage and newly-invented silage, became an important part of the rural landscape; 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.

Imports of guano and the development of the Haber-Bosch process in the 20th century substantially displaced clover as a crop, with negative effects on pollinators, 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 is energy-intensive, prices are closely tied to energy prices. The 21st century has also seen interest in clover as a countermeasure to fight the global pollinator decline.

Cultivation

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.

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.

Clovers are most efficiently pollinated by bumblebees, which have declined as a result of agricultural intensification.Bumbles make beeline for gardens, study suggests
Retrieved 27 November 2010. 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.

'' 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, has potential for interbreeding with ''T. pratense'' to produce perennial crop plants.

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.

Uses

Bears, game animals, ruminants and birds forage for and eat clover, and it is edible by humans, although red clover in particular contains phytoestrogens that may carry risks during pregnancy. The plant is a traditional Native American food, which is eaten both raw and after drying and smoking the roots. The seeds from the blossoms are used to make bread. It is also possible to make tea from the blossoms.

Symbolism

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.

Clovers occasionally have four leaflets, instead of the usual three. These four-leaf clovers, like other rarities, are considered lucky. 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. The previous record holder, Shigeo Obara, had discovered an 18-leaf clover in 2002, a 21-leaf clover in 2008 and a 56-leaf clover in 2009, 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.

* A common saying in surgery egarding the appearance of wound after hemorrhoidectomyis "If it looks like clover, the trouble is over; if it looks like dahlia, it’s surely a failure."

*A cloverleaf interchange is named for the resemblance to the leaflets of a (four-leaf) clover when viewed from the air.

File:4-leaf clover.JPG, Four-leaf white clover ('' Trifolium repens'')
File:Five-leaf Clover, Megan McCarty128.jpg, Five-leaf red clover ('' Trifolium pratense'')

Phylogeny

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. 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.'' 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.''

Species

291 species of ''Trifolium'' are accepted:

* '' Trifolium absconditum''
* '' Trifolium acaule'' Steud. ex A.Rich.
* '' Trifolium affine'' C.Presl
* '' Trifolium acutiflorum''
* '' Trifolium × adulterinum''
* '' Trifolium affine''
* '' Trifolium africanum'' Ser.
* '' Trifolium aintabense'' Boiss. & Hausskn.
* '' Trifolium albopurpureum'' Torr. & A. Gray – rancheria clover
* '' Trifolium alexandrinum'' L. – Egyptian clover, berseem clover
* '' Trifolium alpestre'' L. – owl-head clover
* '' Trifolium alpinum'' L. – alpine clover
* '' Trifolium alsadami''
* '' Trifolium amabile'' Kunth
* '' Trifolium ambiguum'' M. Bieb.
* '' Trifolium amoenum'' Greene – showy Indian clover
* '' Trifolium amphianthum''
* '' Trifolium andersonii'' A. Gray – Anderson's clover or fiveleaf clover
* '' Trifolium andinum'' Nutt. – Intermountain clover
* '' Trifolium andricum'' Lassen
* '' Trifolium angulatum'' Waldst. & Kit.
* '' Trifolium angustifolium'' L.
* '' Trifolium ankaratrense''
* '' Trifolium apertum'' Bobrov
* '' Trifolium appendiculatum''
* '' Trifolium argutum'' Banks & Sol.
* '' Trifolium arvense'' L. – hare's-foot clover
* '' Trifolium attenuatum'' Greene
* '' Trifolium aureum'' Pollich – large hop trefoil
* '' Trifolium baccarinii'' Chiov.
* '' Trifolium badium'' Schreb.
* '' Trifolium barbigerum'' Torr. – bearded clover
* '' Trifolium barbulatum''
* '' Trifolium barnebyi'' (Isely) Dorn & Lichvar
* '' Trifolium batmanicum'' Katzn.
* '' Trifolium beckwithii'' W.H.Brewer ''ex'' S.Watson – Beckwith's clover
* '' Trifolium bejariense'' Moric.
* '' Trifolium × bertrandii''
* '' Trifolium berytheum'' Boiss. & C.I.Blanche
* '' Trifolium biebersteinii''
* '' Trifolium bifidum'' A.Gray – notchleaf clover
* '' Trifolium bilineatum'' Fresen.
* '' Trifolium billardierei'' Spreng.
* '' Trifolium bithynicum''
* '' Trifolium bivonae'' Guss.
* '' Trifolium blancheanum'' Boiss.
* '' Trifolium bobrovii''
* '' Trifolium bocconei'' Savi
* '' Trifolium boissieri'' Guss.
* '' Trifolium bolanderi'' A.Gray
* '' Trifolium bordsilovskyi''
* '' Trifolium brandegeei'' S.Watson
* '' Trifolium breweri'' S. Watson – forest clover
* '' Trifolium brutium'' Ten.
* '' Trifolium buckwestiorum'' Isely – Santa Cruz clover
* '' Trifolium bullatum'' Boiss. & Hausskn.
* '' Trifolium burchellianum'' Ser.
* '' Trifolium calcaricum'' J.L.Collins & Wieboldt
* '' Trifolium calocephalum'' Fresen.
* '' Trifolium campestre'' Schreb. – hop trefoil
* '' Trifolium canescens'' Willd.
* '' Trifolium carolinianum'' Michx.
* '' Trifolium caudatum'' Boiss.
* '' Trifolium cernuum'' Brot.
* '' Trifolium cheranganiense'' J.B.Gillett
* '' Trifolium cherleri'' L.
* '' Trifolium chilaloense'' Thulin
* '' Trifolium chilense'' Hook. & Arn.
* '' Trifolium chlorotrichum'' Boiss. & Balansa
* '' Trifolium ciliolatum'' Benth. – foothill clover
* '' Trifolium circumdatum'' Kunze
* '' Trifolium clusii'' Godr.
* '' Trifolium clypeatum'' L.
* '' Trifolium congestum'' Guss.
* '' Trifolium constantinopolitanum'' Ser.
* '' Trifolium cryptopodium'' Steud. ''ex'' A. Rich.
* '' Trifolium cyathiferum'' Lindl. – cup clover
* '' Trifolium dalmaticum'' Vis.
* '' Trifolium dasyphyllum'' Torr. & A.Gray
* '' Trifolium dasyurum'' C.Presl
* '' Trifolium davisii'' E.Hossain
* '' Trifolium decorum'' Chiov.
* '' Trifolium dedeckerae''
* '' Trifolium depauperatum'' Desv. – cowbag clover, balloon sack clover, or poverty clover
* '' Trifolium dichotomum'' Hook. & Arn.
* '' Trifolium dichroanthoides'' Rech.f.
* '' Trifolium dichroanthum'' Boiss.
* '' Trifolium diffusum'' Ehrh.
* '' Trifolium dolopium'' Heldr. & Hochst. ''ex'' Gibelli & Belli
* '' Trifolium douglasii'' House
* '' Trifolium dubium'' Sibth. – lesser hop trefoil
* '' Trifolium echinatum'' M.Bieb.
* '' Trifolium egrissicum''
* '' Trifolium elgonense'' J.B.Gillett
* '' Trifolium elizabethiae''
* '' Trifolium eriocephalum'' Nutt. – woollyhead clover
* '' Trifolium eriosphaerum'' Boiss.
* '' Trifolium erubescens'' Fenzl
* '' Trifolium euxinum'' Zohary
* '' Trifolium eximium'' Stephan ''ex'' Ser.
* '' Trifolium farayense''
* '' Trifolium fergan-karaeri''
* '' Trifolium fontanum''
* '' Trifolium fragiferum'' L. – strawberry clover
* '' Trifolium friscanum'' (S.L.Welsh) S.L.Welsh
* '' Trifolium fucatum'' Lindl. – bull clover or sour clover
* '' Trifolium gemellum'' Pourr. ''ex'' Willd.
* '' Trifolium gillettianum'' Jacq.-Fél.
* '' Trifolium glanduliferum'' Boiss.
* '' Trifolium globosum'' L.
* '' Trifolium glomeratum'' L. – clustered clover or bush clover
* '' Trifolium gordeievii'' (Kom.) Z.Wei
* '' Trifolium gracilentum'' Torr. & A.Gray – pinpoint clover
* '' Trifolium grandiflorum'' Schreb.
* '' Trifolium gymnocarpon'' Nutt. – hollyleaf clover
* '' Trifolium hatschbachii''
* '' Trifolium haussknechtii'' Boiss.
* '' Trifolium haydenii'' Porter
* '' Trifolium heldreichianum'' (Gibelli & Belli) Hausskn.
* '' Trifolium hickeyi''
* '' Trifolium hirtum'' All. – rose clover
* '' Trifolium howellii'' S.Watson – canyon clover or Howell's clover
* '' Trifolium humile''
* '' Trifolium hybridum'' L. – Alsike clover
* '' Trifolium hydrophilum''
* '' Trifolium incarnatum'' L. – crimson clover
* '' Trifolium infamia-ponertii''
* '' Trifolium israeliticum'' Zohary & Katzn.
* '' Trifolium isthmocarpum'' Brot.
* '' Trifolium jokerstii'' Vincent & Rand.Morgan
* '' Trifolium juliani'' Batt.
* '' Trifolium kentuckiense'' Chapel & Vincent
* '' Trifolium kingii'' S.Watson
* '' Trifolium lanceolatum'' (J.B.Gillett) J.B.Gillett
* '' Trifolium lappaceum'' L.
* '' Trifolium latifolium'' (Hook.) Greene
* '' Trifolium latinum'' Sebast.
* '' Trifolium leibergii'' A.Nelson & J.F.Macbr. – Leiberg's clover
* '' Trifolium lemmonii'' S.Watson – Lemmon's clover
* '' Trifolium leucanthum'' M.Bieb.
* '' Trifolium ligusticum'' Balb. ''ex'' Loisel.
* '' Trifolium longidentatum'' Nábelek
* '' Trifolium longipes'' Nutt. – longstalk clover
* '' Trifolium lucanicum'' Gasp.
* '' Trifolium lugardii'' Bullock
* '' Trifolium lupinaster'' L.
* '' Trifolium macilentum'' Greene
* '' Trifolium macraei'' Hook. & Arn. – Chilean clover, double-head clover, or MacRae's clover
* '' Trifolium macrocephalum'' (Pursh) Poir. – largehead clover
* '' Trifolium masaiense'' J.B.Gillett
* '' Trifolium mattirolianum'' Chiov.
* '' Trifolium mazanderanicum'' Rech.f.
* '' Trifolium medium'' L. – zigzag clover
* '' Trifolium meduseum'' C.I.Blanche ''ex'' Boiss.
* '' Trifolium meironense'' Zohary & Lerner
* '' Trifolium mesogitanum''
* '' Trifolium michaelis''
* '' Trifolium michelianum'' Savi
* '' Trifolium micranthum'' Viv.
* '' Trifolium microcephalum'' Pursh – smallhead clover
* '' Trifolium microdon'' Hook. & Arn. – thimble clover
* '' Trifolium miegeanum'' Maire
* '' Trifolium minutissimum''
* '' Trifolium modestum''
* '' Trifolium monanthum'' A.Gray – mountain carpet clover
* '' Trifolium montanum'' L.
* '' Trifolium multinerve'' A. Rich.
* '' Trifolium multistriatum'' W.D.J.Koch
* '' Trifolium mutabile'' Port.
* '' Trifolium nanum'' Torr.
* '' Trifolium nerimaniae'' M.Keskin
* '' Trifolium × neyrautii''
* '' Trifolium nigrescens'' Viv.
* '' Trifolium noricum'' Wulfen
* '' Trifolium obscurum'' Savi
* '' Trifolium obtusiflorum'' Hook. – clammy clover
* '' Trifolium occidentale'' Coombe
* '' Trifolium ochroleucon'' Huds. - sulphur clover
* '' Trifolium oliganthum'' Steud. – fewflower clover
* '' Trifolium olivaceum''
* '' Trifolium orbelicum''
* '' Trifolium ornithopodioides'' L.
* '' Trifolium owyheense'' Gilkey
* '' Trifolium pachycalyx'' Zohary
* '' Trifolium palaestinum'' Boiss.
* '' Trifolium pallescens'' Schreb.
* '' Trifolium pallidum'' Waldst. & Kit.
* '' Trifolium palmeri''
* '' Trifolium pamphylicum''
* '' Trifolium pannonicum'' Jacq. – Hungarian clover
* '' Trifolium parnassi'' Boiss. & Spruner
* '' Trifolium parryi'' A.Gray
* '' Trifolium patens'' Schreb.
* '' Trifolium patulum'' Tausch
* '' Trifolium pauciflorum'' d'Urv.
* '' Trifolium × permixtum''
* '' Trifolium peruvianum'' Vogel
* '' Trifolium philistaeum'' Zohary
* '' Trifolium phitosianum'' N.Böhling, Greuter & Raus
* '' Trifolium phleoides'' Pourr. ''ex'' Willd.
* '' Trifolium physanthum'' Hook. & Arn.
* '' Trifolium physodes'' Steven ''ex'' M. Bieb.
* '' Trifolium pichisermollii'' J.B.Gillett
* '' Trifolium pignantii'' Fauché. & Chaub.
* '' Trifolium pilczii'' Adamović
* '' Trifolium pilulare'' Boiss.
* '' Trifolium piorkowskii'' Rand.Morgan & A.L.Barber
* '' Trifolium plebeium'' Boiss.
* '' Trifolium plumosum'' Douglas ex Hook.
* '' Trifolium polymorphum'' Poir.
* '' Trifolium polyodon'' Greene
* '' Trifolium polyphyllum'' C.A.Mey.
* '' Trifolium polystachyum'' Fresen.
* '' Trifolium praetermissum'' Greuter, Pleger & Raus.
* '' Trifolium pratense'' L. – red clover
* '' Trifolium productum''
* '' Trifolium prophetarum'' M. Hossain
* '' Trifolium pseudomedium''
* '' Trifolium pseudostriatum'' Baker f.
* '' Trifolium pulchellum''
* '' Trifolium purpureum'' Loisel.
* '' Trifolium purseglovei'' J. B. Gillett
* '' Trifolium quartinianum'' A. Rich.
* '' Trifolium radicosum'' Boiss. & Hohen.
* '' Trifolium rechingeri''
* '' Trifolium reflexum'' L. – buffalo clover
* '' Trifolium repens'' L. – shamrock (white clover)
* '' Trifolium resupinatum'' L. – Persian clover, shaftal
* '' Trifolium retusum'' L.
* '' Trifolium × retyezaticum''
* '' Trifolium rhizomatosum''
* '' Trifolium rhombeum''
* '' Trifolium riograndense'' Burkart
* '' Trifolium rollinsii''
* '' Trifolium roussaeanum'' Boiss.
* '' Trifolium rubens'' L.
* '' Trifolium rueppellianum'' Fresen.
* '' Trifolium salmoneum'' Mouterde
* '' Trifolium sannineum''
* '' Trifolium sarosiense''
* '' Trifolium saxatile'' All.
* '' Trifolium scabrum'' L.
* '' Trifolium schimperi'' (Hochst.) A.Rich.
* '' Trifolium schneideri''
* '' Trifolium × schwarzii''
* '' Trifolium scutatum'' Boiss.
* '' Trifolium sebastiani'' Savi
* '' Trifolium semipilosum'' Fresen.
* '' Trifolium setiferum'' Boiss.
* '' Trifolium simense'' Fresen.
* '' Trifolium sintenisii'' Freyn
* '' Trifolium siskiyouense'' J.M.Gillett
* '' Trifolium somalense'' Taub. ex Harms
* '' Trifolium sonorense''
* '' Trifolium spadiceum'' L.
* '' Trifolium spananthum'' Thulin
* '' Trifolium spumosum'' L.
* '' Trifolium squamosum'' (or ''maritimum'') L. – sea clover
* '' Trifolium squarrosum'' L.
* '' Trifolium stellatum'' L.
* '' Trifolium steudneri'' Schweinf.
* '' Trifolium stipulaceum'' Thunb.
* '' Trifolium stoloniferum'' Muhl. ''ex'' A. Eaton – running buffalo clover
* '' Trifolium stolzii'' Harms
* '' Trifolium striatum'' L. – knotted clover
* '' Trifolium strictum'' L.
* '' Trifolium subterraneum'' L. – subterranean clover
* '' Trifolium suffocatum'' L.
* '' Trifolium sylvaticum'' Gérard
* '' Trifolium tembense'' Fresen.
* '' Trifolium tenuifolium''
* '' Trifolium thalii'' Vill.
* '' Trifolium thompsonii'' C.V.Morton – Thompson's clover
* '' Trifolium tomentosum'' L.
* '' Trifolium × traplii''
* '' Trifolium triaristatum'' Bertero ''ex'' Colla
* '' Trifolium trichocalyx'' A.Heller – Monterey clover
* '' Trifolium trichocephalum'' M. Bieb.
* '' Trifolium trichopterum'' Pančić
* '' Trifolium tumens'' Steven ''ex'' M.Bieb.
* '' Trifolium ukingense'' Harms
* '' Trifolium uniflorum'' L.
* '' Trifolium usambarense'' Taub.
* '' Trifolium variegatum'' Nutt. – whitetip clover
* '' Trifolium vavilovii'' Eig
* '' Trifolium velebiticum'' Degen
* '' Trifolium velenovskyi'' Vandas
* '' Trifolium vernum'' Phil.
* '' Trifolium vesiculosum'' Savi
* '' Trifolium vestitum'' D.Heller & Zohary
* '' Trifolium virginicum'' Small
* '' Trifolium wentzelianum'' Harms
* '' Trifolium wettsteinii'' Dörfl. & Hayek
* '' Trifolium wigginsii'' J. M. Gillett
* '' Trifolium willdenovii'' Spreng. − tomcat clover
* '' Trifolium wormskioldii'' Lehm. – cow clover
* '' Trifolium xanthinum''

See also

* Clover honey
* Clover lawn
* Cloverleaf quasar
* Green manure

References

External links

*

Quattrofolium


Edible parts and visual identification of wild clover.

Nitrogen fixation

{{Authority control

Forages
Garden plants
Groundcovers
Nitrogen-fixing crops

Taxa named by Carl Linnaeus