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

perennial plant A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

in the bean family

Fabaceae The Fabaceae or Leguminosae,International Code of Nomenc ...

(otherwise known as Leguminosae). It is native to

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, including the British Isles,Clapham, A.R., Tutin, T.G. and Warburg., E.F. 1968. ''Excursion Flora of the British Isles''. Cambridge University Press. and

central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...

and is one of the most widely cultivated types of

clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus ...

. 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 use ...

crop, and is now also common in most grassy areas ( lawns 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 and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

. 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 Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The gen ...

'', derives from the Latin ', "three", and ', "leaf", so called from the characteristic form of the leaf, which almost always has three leaflets (

trifoliolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular ...

); hence the popular name " trefoil". The species name, ', is Latin for "creeping".

Description

It is a herbaceous,

. It is low growing, with

heads A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals m ...

of whitish flowers, 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 bees. The leaves are

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

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

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'' 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 southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

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

model organism A model organism (often shortened to model) 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 workin ...

for global research into

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...

and

urban evolution Urban evolution refers to the heritable genetic changes of populations in response to urban development and anthropogenic activities in urban areas. Urban evolution can be caused by mutation, genetic drift, gene flow, or evolution by natural selecti ...

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

cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...

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 a tetraploid (4n=32) with two diploid ancestors. In order to increase genetic diversity for breeding, research is focused on finding these ancestors. Proposed ancestors of ''Trifolium repens'' include '' Trifolium nigrescens,

Trifolium occidentale ''Trifolium occidentale'', the western clover, is a clover plant belonging to the genus ''Trifolium'' in the legume family, Fabaceae. Its flowers are white, similar to white clover (''Trifolium repens''), with which it has long been confused. Th ...

, Trifolium pallescens,'' and ''

Trifolium uniflorum Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The gen ...

.'' 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 In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

. 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. Formononetin and biochanin A 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''). 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 lawns,

grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached 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 legum ...

crops,

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

grasses, and

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

rows. It is often added to lawn 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 A mower is a person or machine that cuts (mows) grass or other plants that grow on the ground. Usually mowing is distinguished from reaping, which uses similar implements, but is the traditional term for harvesting grain crops, e.g. with reape ...

and

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and ot ...

, and it can grow on many different types 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. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...

soils). As a leguminous and

hardy Hardy may refer to: People * Hardy (surname) * Hardy (given name) * Hardy (singer), American singer-songwriter Places Antarctica * Mount Hardy, Enderby Land * Hardy Cove, Greenwich Island * Hardy Rocks, Biscoe Islands Australia * Hardy, Sout ...

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 weeds. Natural nitrogen fixing reduces leaching from the soil and by maintaining soil health 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 produced to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal ...

and cover crop.

Culinary uses

Besides making an excellent forage crop for

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...

, 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 residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

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

Etymology

''Trifolium'' means 'trefoil' (three-lobed leaves); this is Pliny’s name for trifoliate plants.Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 328, 386 ''Repens'' means 'creeping' or 'stoloniferous'.

References

Tangpu, V., Temjenmongla & Yadav, A. K. 2004. Anticestodal activity of Trifolium repens extract. Pharmaceutical Biology 42: 656–658.

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
{{Taxonbar, from=Q148675 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