''Polygonum aviculare'' or common knotgrass is a plant related to

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. The name "buckwheat" is used for several other species, such as ''Fagop ...

and

dock A dock (from Dutch ''dok'') is the area of water between or next to one or a group of human-made structures that are involved in the handling of boats or ships (usually on or near a shore) or such structures themselves. The exact meaning vari ...

. It is also called prostrate knotweed, birdweed, pigweed and lowgrass. It is an annual found in fields and wasteland, with white flowers from June to October. It is widespread across many countries in temperate regions, apparently native to Eurasia, naturalized in temperate parts of the Southern Hemisphere.Flora of China, ''Polygonum aviculare'' Linnaeus, 1753. 萹蓄 bian xu
/ref>Flora of North America, ''Polygonum aviculare'' Linnaeus, 1753. Doorweed, knotgrass, renouée des oiseaux
/ref>

Description

Common knotgrass is an annual herb with a semi-erect stem that may grow from high. The leaves are hairless and short-stalked. They are longish-elliptical with short stalks and rounded bases; the upper ones are few and are linear and stalkless. The

stipules In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole). Stipules are considered part of the anatomy of the leaf of a typical flowering plant, although in many speci ...

are fused into a stem-enclosing, translucent sheath known as an ochrea that is membranous and silvery. The flowers are regular, green with white or pink margins. Each has five

perianth The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla ( petals) or tepals when ...

segments, overlapping at the base, five to eight stamens and three fused carpels. The fruit is a dark brown, three-edged nut. The seeds need light to germinate which is why this plant appears in disturbed soil in locations where its seeds may have lain dormant for years. It is a common carrier of the parasitic pathogen powdery mildew, which can give the leaves a whitish appearance.

Subspecies

''Polygonum aviculare'' has a wide distribution as an arable weed and plant of fields, shingle, sand, roadsides, yards and waste places. There is much morphological variation among different populations and several different sub-species are recognized: * ''Polygonum aviculare ''subsp''. aviculare'' – very widespread *''Polygonum aviculare'' subsp. ''boreale'' (Lange) Karlsson – Greenland, Labrador, Newfoundland, Scandinavia *''Polygonum aviculare'' subsp. ''buxiforme'' (Small) Costea & Tardif – North America * ''Polygonum aviculare'' subsp. ''depressum'' (Meisn.) Arcang. – Europe, North America *''Polygonum aviculare'' var. ''fusco-ochreatum'' (Kom.) A.J.Li – northeastern China, Russian Far East *''Polygonum aviculare'' subsp. ''neglectum'' (Besser) Arcangeli – Europe, North America * ''Polygonum aviculare ''subsp''. rurivagum'' (Jord. ex Boreau) Berher – Europe, North America

Distribution

Widespread and common in

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It ...

Ireland Ireland ( ; ga, Éire ; Ulster-Scots: ) is an island in the North Atlantic Ocean, in north-western Europe. It is separated from Great Britain to its east by the North Channel, the Irish Sea, and St George's Channel. Ireland is the s ...

,Clapham, A.R. , Tutin, T.G. and Warburg, E.F. 1968. ''Excursion Flora of the British Isles''. Cambridge Press. Parnell, J. and Curtis, T. 2012. ''Webb's An Irish Flora.'' Cork University Press. and

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, Norway, and S ...

Habitat

It is common on roadsides and arable ground in the British Isles.

Chemistry

''Polygonum aviculare'' contains the flavonols avicularin, myricitrin and juglanin. The flavanoids astragalin and betmidin, and the lignan

aviculin Aviculin is a lignan. It is bio-active isolate of ''Pseudocydonia sinensis ''Pseudocydonia sinensis'' or Chinese quince () is a deciduous or semi-evergreen tree in the family Rosaceae, native to southern and eastern China. It is the sole spec ...

have also been found. The

diterpene Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being ...

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of simila ...

panicudine is another known component.

Fossil record

One fossil fruit of ''Polygonum aviculare'' has been extracted from borehole samples of the

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million ...

fresh water deposits in Nowy Sacz Basin, West Carpathians,

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...

.Łańcucka-Środoniowa M.: Macroscopic plant remains from the freshwater Miocene of the Nowy Sącz Basin (West Carpathians, Poland) zczątki makroskopowe roślin z miocenu słodkowodnego Kotliny Sądeckiej (Karpaty Zachodnie, Polska) Acta Palaeobotanica 1979 20 (1): 3-117.

Cuisine

It formed a traditional ingredient in porridge consumed by Germanic peoples of western Europe, and has been found in numerous autopsies of peat bodies, including the

Tollund Man The Tollund Man (died 405–380 BC) is a naturally mummified corpse of a man who lived during the 5th century BC, during the period characterised in Scandinavia as the Pre-Roman Iron Age. He was found in 1950, preserved as a bog body, near ...

. In Vietnam, where it is called ''rau đắng'', it is widely used to prepare soup and hot pot, particularly in the southern region.

References

External links

photo of herbarium specimen collected in Nuevo León in Mexico in 1989
* Howard, Michael. ''Traditional Folk Remedies'', (Century, 1987); page 162. {{Taxonbar, from=Q242573 Medicinal plants Flora of North America Flora of Europe Flora of Asia aviculare Plants described in 1753 Taxa named by Carl Linnaeus