''Trifolium repens'', the white clover, is a herbaceous

perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...

in the bean family

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

(otherwise known as Leguminosae). It is native to

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, including the British Isles, and

central Asia Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...

and is one of the most widely cultivated types of

clover 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 diversit ...

. It has been widely introduced worldwide as a

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...

crop, and is now also common in most grassy areas (

lawn A lawn () is an area of soil-covered land planted with Poaceae, grasses and other durable plants such as clover lawn, clover which are maintained at a short height with a lawn mower (or sometimes grazing animals) and used for aesthetic an ...

s and

garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...

s) of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. The species includes varieties often classed as small, intermediate and large, according to height, which reflects petiole 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.

Name

The genus name, ''

Trifolium 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 ...

'', derives from the Latin ', "three", and ', "leaf", so called from the characteristic form of the leaf, which almost always has three leaflets ( trifoliolate); hence the popular name "

trefoil A trefoil () is a graphic form composed of the outline of three overlapping rings, used in architecture, Pagan and Christian symbolism, among other areas. The term is also applied to other symbols with a threefold shape. A similar shape with f ...

". The species name, ', is Latin for "creeping".

Description

It is a

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of ...

. It is low growing, with flowering heads 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 wide, and are at the end of peduncles or inflorescence stalks.Richard H. Uva, Joseph C. Neal and Joseph M. Ditomaso, ''Weeds of The Northeast'', (Ithaca, NY: Cornell University Press, 1997), Pp. 236–237. The flowers are mostly visited by

bumblebee A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only Extant taxon, extant group in the tribe Bombini, though a few extinct r ...

s and often by

honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to mainland Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the ...

s. The leaves are trifoliolate, smooth, elliptic to egg-shaped and long-petioled and usually with light or dark markings. The stems function as

stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

s, so white clover often forms mats, with the stems creeping as much as a year, and rooting at the nodes. The leaves form the symbol known as shamrock. Almost always, a white clover will be trifoliolate. However, one can, but only sometimes, possess four or more leaflets.

Varieties and subspecies

*''Trifolium repens'' subsp. ''macrorrhizum'' (Boiss.) Ponert *''Trifolium repens'' var. ''nevadense'' (Boiss.) C.Vicioso *''Trifolium repens'' var. ''ochranthum'' K.Maly *''Trifolium repens'' var. ''orbelicum'' (Velen.) Fritsch *''Trifolium repens'' var. ''orphanideum'' (Boiss.) Boiss. *''Trifolium repens'' var. ''pipolina'' *''Trifolium repens'' subsp. ''prostratum'' Nyman

Distribution

It is native in Europe and Central Asia, ubiquitous throughout the British Isles, introduced in

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and elsewhere, and globally cultivated as a forage crop. White clover has been used as a

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

for global research into

ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

and urban evolution. As part of the Global Urban Evolution Project (GLUE) scientists from 26 countries examined the production of

cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...

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.

Ancestry

''Trifolium repens'' is an allotetraploid (2n = 4x = 32) of two diploid ancestors and exhibits disomic inheritance. In order to increase genetic diversity for breeding, research is focused on finding these ancestors. Proposed ancestors of ''T. repens'' include '' T. nigrescens'', '' T. occidentale'', '' T. pallescens'', and '' T. uniflorum''. 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.

Cultivation and uses

Forage

White clover has been described as the most important forage legume of the temperate zones. Symbiotic nitrogen fixation (up to of N, although usually much less, e.g. about ) 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''). 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. Such species mixtures also tend to avoid issues that could otherwise be associated with cyanogenic glycosides ( linamarin and lotaustralin) intake on pure or nearly pure stands of some white clover varieties. 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. The ''O''-methylated isoflavones formononetin and

biochanin A Biochanin A is an O-methylated isoflavone, ''O''-methylated isoflavone. It is a natural organic compound in the class of phytochemicals known as flavonoids. Biochanin A can be found in red clover in soy, in alfalfa sprouts, in peanuts, in chickpea ...

play a role in arbuscular mycorrhiza formation on white clover roots, and foliar disease can stimulate production of estrogenic coumestans in white clover.Adams, Norman R. "Detection of the effects of phytoestrogens on sheep and cattle." Journal of Animal Science 73, no. 5 (1995): 1509–1515. However, while there have been a few reports of phytoestrogenic effects of white clover on grazing ruminants, these have been far less common than such reports regarding some varieties of subterranean clover (''

Trifolium subterraneum ''Trifolium subterraneum'', the subterranean clover (often shortened to sub clover), subterranean trefoil, is a species of clover native to Europe, Southwest Asia, Northwest Africa and Macaronesia. The plant's name comes from its underground s ...

'') and red clover (''

Trifolium pratense ''Trifolium pratense'' (from Latin prātum, meaning meadow), red clover, is a herbaceous species of flowering plant in the bean family, Fabaceae. It is native to the Old World, but planted and naturalised in many other regions. Description ...

''). Among forage plants, some white clover varieties tend to be favored by rather close grazing, because of their

iferous habit, which can contribute to competitive advantage.

Companion planting, green manure, and cover crops

White clover grows well as a companion plant among

grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...

crops,

pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Types of pasture Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, c ...

grasses, and

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

rows. It is often added to

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 close mowing and

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

, and it can grow on many different

types Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

and pHs of soil (although it prefers

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

soils). As a leguminous and hardy plant, it is considered to be a beneficial component of natural or organic

management and lawn care due to its ability to fix nitrogen and out-compete

weed A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...

s. Natural nitrogen fixing reduces leaching from the soil and by maintaining

soil health Soil health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong ...

can reduce the incidence of some lawn diseases that are enhanced by the availability of synthetic fertilizer.''The Organic Lawn Care Manual'', Tukey, Storey Publishing. p 183. For these reasons, it is often used as a

green manure In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. Typically, the green manure's Biomass (ecology), biomass is incorporated with a plow or disk, as is often done with (brown) man ...

and cover crop.

Culinary uses

Besides making an excellent forage crop for

livestock Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The t ...

, its leaves and flowers are a valuable survival food: they are high in

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s, and are widespread and abundant. The fresh plants have been used for centuries as additives to

salads A salad is a Dish (food), dish consisting of mixed ingredients, frequently vegetables. They are typically served chilled or at room temperature, though some can be served warm. Condiments called ''salad dressings'', which exist in a variety of ...

and other meals consisting of leafy vegetables. They are not easy for humans to digest raw, but, this is however easily fixed by boiling the harvested plants for 5–10 minutes.Lee Allen Peterson, ''Edible Wild Plants'', (New York City: Houghton Mifflin Company, 1977), P. 56. Native Americans ate some species raw. Dried white clover flowers may also be smoked as a herbal alternative to tobacco.

Medicinal uses

In India, ''T. repens'' is considered a folk medicine against intestinal helminthic worms, and an experimental in-vivo study validated that the aerial shoots of ''T. repens'' bear significant anticestodal (anti-tapeworm) properties.Yadav, A. K. 2004. Anticestodal activity of ''Trifolium repens'' extract. Pharmaceutical Biology 42: 656–658.

References

Bibliography

External links

United States Department of Agriculture ''Trifolium repens'' fact sheet

Mother Earth News, Masanobu Fukuoka 'One-Straw Revolution'

Cyanogenesis in White Clover – video and commentary

Root nodules of White Clover – video and commentary
{{Authority control repens Flora of Africa Flora of Europe Flora of Asia Medicinal plants of Europe Medicinal plants of Africa Garden plants of Europe Forages Nitrogen-fixing crops Groundcovers Plants described in 1753 Plants used in traditional Native American medicine National symbols of the Republic of Ireland Melliferous flowers Taxa named by Carl Linnaeus