''Polygonum'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of about 130 species of

flowering plants Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

in the buckwheat and knotweed family

Polygonaceae The Polygonaceae are a Family (biology), family of flowering plants known Common name, informally as the knotweed family or smartweed—buckwheat family in the United States. The Botanical name, name is Basionym, based on the genus ''Polygonum'', ...

. Common names include knotweed and knotgrass (though the common names may refer more broadly to plants from

). In the

Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman Conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English pe ...

glossary A glossary (from , ''glossa''; language, speech, wording), also known as a vocabulary or clavis, is an alphabetical list of Term (language), terms in a particular domain of knowledge with the definitions for those terms. Traditionally, a gloss ...

of herbs ''Alphita'' ( 1400–1425), it was known as ars-smerte. There have been various opinions about how broadly the genus should be defined. For example,

buckwheat Buckwheat (''Fagopyrum esculentum'') or common buckwheat is a flowering plant in the knotweed family Polygonaceae cultivated for its grain-like seeds and as a cover crop. Buckwheat originated around the 6th millennium BCE in the region of what ...

(''Fagopyrum esculentum'') has sometimes been included in the genus as ''Polygonum fagopyrum''. Former genera such as ''Polygonella'' have been subsumed into ''Polygonum''; other genera have been split off. The genus primarily grows in northern

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

regions. The species are very diverse, ranging from prostrate

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 ...

annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. Globally, 6% of all plant species and 15% of herbaceous plants (excluding trees and shrubs) are ...

s to erect 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 ...

s. ''Polygonum'' species are occasionally eaten by humans, and are used as food plants by the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e of some

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

species – see list. Most species are considered weeds in Europe and North America.

Description

When the genus is defined narrowly, ''Polygonum'' species are annual or

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

herbaceous plant 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 o ...

s, rarely

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

by, with much branched stems. The leaves are arranged alternately, usually less than long, with a length greater than the width. They have a membranous

ochrea An ochrea (Latin ''ocrea'', greave or protective legging), also spelled ocrea, is a plant structure formed of stipules fused into a sheath surrounding the stem, and is typically found in the Polygonaceae The Polygonaceae are a Family (biology ...

(a sheath around the stem nodes). The flowers are usually

bisexual Bisexuality is romantic attraction, sexual attraction, or sexual behavior toward both males and females. It may also be defined as the attraction to more than one gender, to people of both the same and different gender, or the attraction t ...

, rarely

unisexual Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

, and have five (occasionally four)

tepal A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...

s, the outer being slightly different from the inner ones. There are usually four to six

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s and three (rarely two)

style Style, or styles may refer to: Film and television * ''Style'' (2001 film), a Hindi film starring Sharman Joshi, Riya Sen, Sahil Khan and Shilpi Mudgal * ''Style'' (2002 film), a Tamil drama film * ''Style'' (2004 film), a Burmese film * '' ...

s. The fruit is three-sided.

Taxonomy

The genus ''Polygonum'' was first described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1754. The genus name is usually said to be from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

(''poly''-, 'many') and (''gonu'', 'knee' or 'joint'), in reference to the swollen jointed stem. p. 404 p. 148. However, long before Linnaeus, the name was used in Greek and Latin for a plant used medically. Discussing the plant he knew as ''polygonum'' in 1655, Matthias Martinius referred to Scribonius Largus (who wrote a list of prescriptions around 47 AD) and gave an alternative etymology, based on (''gonos'', 'offspring', 'seed'), the meaning of the name then being the Latin , i.e. 'fecund', 'with many offspring'. The ''Flora of North America'' says that a derivation meaning 'many seeds' is the "grammatically correct interpretation". Many members of the family

that are now placed in separate genera were at one time or other placed in ''Polygonum'', including species of '' Fagopyrum'', '' Fallopia'', '' Persicaria'' and '' Reynoutria'', and older sources frequently use much wider definitions of the genus.

Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies, particularly in the 21st century, have led to major changes. Clarifying the circumscription of genera split from ''Polygonum'' was described in 2015 as "still ongoing".

Classification and phylogeny

''Polygonum'' is placed in the tribe Polygoneae of the subfamily Polygonoideae. Within the tribe, it is most closely related to the genera ''

Duma A duma () is a Russian assembly with advisory or legislative functions. The term ''boyar duma'' is used to refer to advisory councils in Russia from the 10th to 17th centuries. Starting in the 18th century, city dumas were formed across Russia ...

'' and '' Atraphaxis'', forming the so-called "DAP clade".

Species

Between 65 and 300 species have been recognised at various times, depending on the circumscription of the genus. A number of species that had been included in ''Polygonum'' have been moved into several other genera, including ''

Bistorta ''Bistorta'' is a genus of flowering plants in the family Polygonaceae. about 40 species are accepted. It has been supported as a separate clade by Molecular phylogenetics, molecular phylogenetic analysis. ''Bistorta'' species are native through ...

'', '' Fagopyrum'', '' Fallopia'', '' Koenigia'', '' Persicaria'' and '' Reynoutria''. Other genera, such as ''Polygonella'', have been subsumed into ''Polygonum''. ,

Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...

Reclassified species

Many species formerly placed in ''Polygonum'' have been moved to other genera in the subfamily Polygonoideae. Some synonyms are listed below.

''Polygonum'' species that have been reclassified as ''Bistorta''

*''Polygonum amplexicaule'' → '' Bistorta amplexicaulis'' *''Polygonum bistorta'' – bistort → '' Bistorta officinalis'' *''Polygonum bistortoides'' Pursh – American bistort, western bistort, smokeweed or mountain meadow knotweed → '' Bistorta bistortoides'' *''Polygonum tenuicaule'' Bisset & S.Moore → '' Bistorta tenuicaulis'' *''Polygonum viviparum'' – alpine bistort → '' Bistorta vivipara''

''Polygonum'' species that have been reclassified as ''Fagopyrum''

*''Polygonum fagopyrum'' L. – buckwheat → '' Fagopyrum esculentum''

''Polygonum'' species that have been reclassified as ''Fallopia''

*''Polygonum aubertii'' L.Henry → '' Fallopia aubertii'' *''Polygonum baldschuanicum'' Regel – Russian vine → '' Fallopia baldschuanica'' *''Polygonum convolvulus'' L. – black bindweed, wild buckwheat → '' Fallopia convolvulus'' *''Polygonum dumetorum'' L. → '' Fallopia dumetorum'' *''Polygonum scandens'' L. → '' Fallopia scandens''

''Polygonum'' species that have been reclassified as ''Koenigia''

*''Polygonum alpinum'' → '' Koenigia alpina'' *''Polygonum campanulatum'' – lesser knotweed, bellflower smartweed → '' Koenigia campanulata'' *''Polygonum davisiae'' W.H. Brewer ex A. Gray and ''Polygonum newberryi'' Small → '' Koenigia davisiae'' *''Polygonum molle'' → '' Koenigia mollis'' *''Polygonum polystachyum'' Wall. ex Meisn. → ''Koenigia polystachya''

''Polygonum'' species that have been reclassified as ''Persicaria''

*''Polygonum alatum'' → ''Persicaria nepalensis'' *''Polygonum amphibium'' – amphibious bistort, longroot smartweed, water smartweed → ''Persicaria amphibia'' *''Polygonum capitatum'' – pinkhead smartweed → ''Persicaria capitata'' *''Polygonum chinense'' L. → ''Persicaria chinensis'' *''Polygonum coccineum'' Muhl. ex Willd. → ''Persicaria amphibia'' *''Polygonum filiforme'' Thunb. → ''Persicaria filiformis'' *''Polygonum hydropiper'' – water-pepper → ''Persicaria hydropiper'' *''Polygonum hydropiperoides'' Michx. – swamp smartweed → ''Persicaria hydropiperoides'' *''Polygonum lapathifolium'' – pale persicaria or nodding smartweed → ''Persicaria lapathifolia'' *''Polygonum longisetum'' → ''Persicaria longiseta'' *''Polygonum minus'' – small water-pepper → ''Persicaria minor'' *''Polygonum mite'' Schrank – tasteless water-pepper → ''Persicaria mitis'' (Schrank) Assenov *''Polygonum nepalense'' → ''Persicaria nepalensis'' *''Polygonum odoratum'' Lour. – Vietnamese coriander → ''Persicaria odorata'' *''Polygonum orientale'' → ''Persicaria orientalis'' *''Polygonum pensylvanicum'' – Pennsylvania smartweed or pink knotweed or pinkweed → ''Persicaria pensylvanica'' *''Polygonum perfoliata'' – Asiatic Tearthumb → ''Persicaria perfoliata'' *''Polygonum persicaria'' – redshank or persicaria or lady's thumb → ''Persicaria maculosa'' *''Polygonum praetermissum'' → ''Persicaria praetermissa'' *''Polygonum punctatum'' Elliott – dotted smartweed → ''Persicaria punctata'' *''Polygonum runcinatum'' → ''Persicaria runcinata'' *''Polygonum sagittatum'' – arrowleaf tearthumb, American tear-thumb or scratchgrass → ''Persicaria sagittata'' *''Polygonum tinctorium'' → ''Persicaria tinctoria'' *''Polygonum virginianum'' L. → ''Persicaria virginiana''

''Polygonum'' species that have been reclassified as ''Reynoutria''

*''Polygonum multiflorum'' Thunb. → ''Reynoutria multiflora'' *''Polygonum cuspidatum'' Siebold & Zucc. – Japanese knotweed → ''Reynoutria japonica'' *''Polygonum sachalinense'' F.Schmidt – giant knotweed → ''Reynoutria sachalinensis''

Unresolved species

*''Polygonum vaccinifolium'' Wall. is an unresolved species name. ''Persicaria vaccinifolia'' may be a synonym.

Uses

Several species can be eaten cooked, for example during famines. The species '' Polygonum cognatum'', known locally as "madimak", is regularly consumed in central parts of Turkey.

References in literature

In ''The Man Who Laughs'' Victor Hugo wrote of the Comprachicos (child-buyers) who created artificial dwarfs, formed "by anointing babies' spines with the grease of bats, moles and dormice" and using drugs such as "dwarf elder, knotgrass, and daisy juice". The idea of such use was also known to Shakespeare, as Beatrice K. Otto pointed out, quoting ''A Midsummer Night's Dream'':

References

External links

Natural History Museum, London: Nature-navigator websiteRoyal Horticultural Society: Plant Finder section website
{{Authority control Polygonum, Polygonaceae genera Taxa named by Carl Linnaeus