Polygonum aviculare or common knotgrass is a plant related to buckwheat and dock. 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.[2][3][4][5][6][7]
| Common knotgrass | |
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Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Polygonaceae |
| Genus: | Polygonum |
| Species: | P. aviculare
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| Binomial name | |
| Polygonum aviculare L. 1753
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| Synonyms[1] | |
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Synonymy
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Description
editCommon knotgrass is an annual, low-prostrate herb with semi-erect, branching stems, which forms patches up to about 2 m across as it matures. It has alternate linear-lanceolate leaves which are longer (7-15 mm) on the main stems than on the branches (3-5 mm). The whole plant is hairless and green, although it may appear mealy due to a powdery mildew,[8] which can give the leaves a whitish appearance.[3][9] The leaves fall early, especially on the main stem. The leaf stalks (petioles) are up to 5 mm long or sometimes absent. Above each leaf there is an ochrea, which is a translucent papery stipule that surrounds the stem.
The inflorescences occur in the leaf axils and consist of a group of 1-6 flowers, each on a very short (1 mm) stalk (pedicel). The flowers are green with white or pink margins, ranging in size from 2 to 4.5 mm. Each flower has five overlapping perianth segments, fused into a cup for about a third of their length, with 8 stamens and 3 carpels.[10][11]
The fruit is a dark brown nut 1.5 - 3.5 mm long with 3 concave sides and a dull, leathery sheen. When ripe it is enclosed in the perianth. 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.[12]
Taxonomy
editThe name "Polygonum" comes from the Ancient Greek for "many knees", in reference to the prominent joints (nodes) along the stem. The specific epithet "aviculare" means "little bird", possibly because the fruits resemble a bird's beak or an egg.[13] Common names include birdweed, pigweed and lowgrass.
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:[1][2][3][9]
- 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
editWidespread and common in Great Britain,[14] Ireland,[14][15] and Scandinavia.[16]
Habitat
editIt is common on roadsides and arable ground in the British Isles.[15]
Ecology
editThe ecological requirements of this species are fairly modest. Its Ellenberg values in Britain are L = 7, F = 5, R = 6, N = 7, and S = 0, [17] which shows that it prefers average light, moisture and fertility, neutral pH and non-saline conditions. However, it can be found on beaches so it must be tolerant of occasional immersion in seawater. Many species of insects feed on knotgrass, including the eponymous Knot Grass moth, Acronicta rumicis, whose larvae are phytophagous on the leaves. The UK's Database of Insects and their Food Plants lists 113 species which are known to feed on this plant in Britain, of which 10 are beetles, 2 are flies, 8 are Hemiptera (bugs and aphids), and the remaining 93 Lepidoptera (butterflies and moths).
Chemistry
editPolygonum aviculare contains the flavonols avicularin, myricitrin and juglanin.[18] The flavanoids astragalin and betmidin, and the lignan aviculin have also been found.[19] The diterpene alkaloid panicudine is another known component.[20]
Fossil record
editOne fossil fruit of Polygonum aviculare has been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland.[21]
Cuisine
editIt 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.
In Vietnam, where it is called rau đắng, it is widely used to prepare soup and hot pot, particularly in the southern region.
In culture
editIn the Harry Potter novels, knotgrass is an ingredient in the magic potion polyjuice.[22]
References
edit- ^ a b The Plant List, Polygonum aviculare L.
- ^ a b Flora of China, Polygonum aviculare Linnaeus, 1753. 萹蓄 bian xu
- ^ a b c Flora of North America, Polygonum aviculare Linnaeus, 1753. Doorweed, knotgrass, renouée des oiseaux
- ^ Atlas of Living Australia, Polygonum aviculare L., Wireweed
- ^ Altervista Flora Italiana, Polygonum aviculare L. includes photos and European distribution map
- ^ Lindau, G. 1894. Beiträge zur argentinischen Flora. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 19(4, Beibl. 48): 8–23 descriptions and geographic information in Latin, commentary in German
- ^ Gibbs Russell, G. E., W. G. M. Welman, E. Retief, K. L. Immelman, G. Germishuizen, B. J. Pienaar, M. Van Wyk & A. Nicholas. 1987. List of species of southern African plants. Memoirs of the Botanical Survey of South Africa 2(1–2): 1–152(pt. 1), 1–270(pt. 2).
- ^ https://www.researchgate.net/publication/338187775 Parasitic activity of powdery mildew (pathogen strain hmlac226) on prostrate knotweed (polygonum aviculare l.) at various locations of Shenyang, northeast China , Iqbal, M. F., Fend, Y. L., Liu, M. C., Lu, X. R., Nasir, M., Sikandar, A., 2019
- ^ a b "Knotgrass: Polygonum aviculare". NatureGate. Retrieved 2013-12-30.
- ^ Sell, Peter; Murrell, Gina (2018). Flora of Great Britain and Ireland, vol. 1. Cambridge: Cambridge University Press. ISBN 978-0-521-55335-3.
- ^ Stace, C.A. (2019). New Flora of the British Isles (4th ed.). Suffolk: C&M Floristics. ISBN 978-1-5272-2630-2.
- ^ Rose, Francis (2006). The Wild Flower Key. London: Frederick Warne. ISBN 978-0-7232-5175-0.
- ^ Stearn, William T. (1980). Botanical Latin: History, Grammar, Syntax, Terminology and Vocabulary. Newton Abbot: David & Charles. ISBN 0-7153-5645-3.
- ^ a b Clapham, A.R. , Tutin, T.G. and Warburg, E.F. 1968. Excursion Flora of the British Isles. Cambridge Press. ISBN 0-521-04656-4
- ^ a b Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press. ISBN 978-185918-4783
- ^ "Knotgrass". Planteværn Online. Aarhus University. Retrieved 1 February 2016.
- ^ Hill, M.O.; Mountford, J.O.; Roy, D.B.; Bunce, R.G.H. (1999). Ellenberg's indicator values for British plants. ECOFACT Volume 2. Technical Annex (PDF). Institute of Terrestrial Ecology. ISBN 1870393481. Retrieved 29 May 2017.
- ^ Xu, Fuquan; Guan, Huashi; Li, Guoqiang; Liu, Hongbing (2009). "LC Method for Analysis of Three Flavonols in Rat Plasma and Urine after Oral Administration of Polygonum aviculare Extract". Chromatographia. 69 (11–12): 1251–1258. doi:10.1365/s10337-009-1088-x. S2CID 93888073.
- ^ Kim, Hyoung Ja; Woo, Eun-Rhan; Park, Hokoon (1994). "A Novel Lignan and Flavonoids from Polygonum aviculare". Journal of Natural Products. 57 (5): 581–586. doi:10.1021/np50107a003.
- ^ Salama, Hediat M.H.; Marraiki, Najat (January 2010). "Antimicrobial activity and phytochemical analyses of Polygonum aviculare L. (Polygonaceae), naturally growing in Egypt". Saudi Journal of Biological Sciences. 17 (1): 57–63. doi:10.1016/j.sjbs.2009.12.009. PMC 3730555. PMID 23961059.
- ^ Łańcucka-Środoniowa M.: Macroscopic plant remains from the freshwater Miocene of the Nowy Sącz Basin (West Carpathians, Poland) [Szczątki makroskopowe roślin z miocenu słodkowodnego Kotliny Sądeckiej (Karpaty Zachodnie, Polska)]. Acta Palaeobotanica 1979 20 (1): 3-117.
- ^ Rowling, J.K. (1998). Harry Potter and the Chamber of Secrets.
External links
edit
- photo of herbarium specimen collected in Nuevo León in Mexico in 1989
- Howard, Michael. Traditional Folk Remedies, (Century, 1987); page 162.