Polygonum aviculare

Common knotgrass
Least Concern
Least Concern (IUCN 3.1)
(Europe regional assessment)
Secure
Secure (NatureServe)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Polygonaceae
Genus: Polygonum
Species:
P. aviculare
Binomial name
Polygonum aviculare
L. 1753
Synonyms
Synonymy
  • Avicularia vulgaris Didr.
  • Centinodium axillare Montandon
  • Polygonum agreste Sumner, non Polygonum agreste Sumnev.
  • Polygonum aphyllum Krock.
  • Polygonum araraticum Kom.
  • Polygonum berteroi Phil.
  • Polygonum buxiforme Small
  • Polygonum ganderbalense Munshi & Javeid
  • Polygonum heterophyllum Lindm.
  • Polygonum monspeliense Thiéb.-Bern. ex Pers.
  • Polygonum neglectum Besser
  • Polygonum planum Skvortsov
  • Polygonum polyneuron Franch. & Sav.
  • Polygonum prostratum Skvortsov
  • Polygonum procumbens Gilib.
  • Polygonum retinerve Vorosch.
  • Polygonum rubescens Small
  • Polygonum scythicum Klokov
  • Polygonum striatum K. Koch
  • Polygonum uruguense H. Gross
  • Polygonum argenteum Ehrenb. ex Meisn.
  • Polygonum argenteum Skvortsov
  • Polygonum fusco-ochreatum Kom.
  • Polygonum stans Kitag.

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.

Description

Common knotgrass is an annual, low-prostrate herb with semi-erect, branching stems, which forms patches up to about 2 m (6 ft 7 in) across as it matures. It has alternate linear-lanceolate leaves which are longer (7–15 mm (0.28–0.59 in)) on the main stems than on the branches (3–5 mm (0.12–0.20 in)). The whole plant is hairless and green, although it may appear mealy due to a powdery mildew, which can give the leaves a whitish appearance. The leaves fall early, especially on the main stem. The leaf stalks (petioles) are up to 5 mm (0.20 in) 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.

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.

Taxonomy

The 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. 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:

Distribution

Polygonum aviculare is native to Eurasia, but has become a widespread invasive worldwide.

Habitat

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

Ecology

The 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, 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

Polygonum aviculare contains the flavonols avicularin, myricitrin and juglanin. The flavonoids astragalin and betmidin, and the lignan aviculin have also been found. The diterpene alkaloid panicudine is another known component.

Fossil record

One 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.

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.

References

  1. ↑ Khela, S.; Meredith, C.R. (2026). "Polygonum aviculare (Europe assessment)". IUCN Red List of Threatened Species. 2026 e.T203393A209214355. doi:10.2305/IUCN.UK.2026-1.RLTS.T203393A209214355.en. Retrieved 20 August 2026.
  2. ↑ NatureServe. "Polygonum aviculare". NatureServe Explorer. Arlington, Virginia. Retrieved 20 August 2026.
  3. 1 2 The Plant List, Polygonum aviculare L.
  4. 1 2 "Polygonum aviculare Linnaeus, 1753. 萹蓄 bian xu". Flora of China – via eFloras.org, Missouri Botanical Garden, St. Louis, Missouri and Harvard University Herbaria, Cambridge, Massachusetts.
  5. 1 2 3 Flora of North America Editorial Committee (ed.). "Polygonum aviculare Linnaeus, 1753. Doorweed, knotgrass, renouée des oiseaux". Flora of North America North of Mexico (FNA). New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, Missouri and Harvard University Herbaria, Cambridge, Massachusetts.
  6. ↑ "Polygonum aviculare L., Wireweed". Atlas of Living Australia.
  7. ↑ "Polygonum aviculare L." Altervista Flora Italiana.
  8. ↑ Lindau, G. (1894). "Beiträge zur argentinischen Flora". Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie (in Latin and commentary in German). 19 (4, Beibl. 48): 8–23.{{cite journal}}: CS1 maint: unrecognized language (link)
  9. ↑ 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).[page needed]
  10. ↑ Iqbal, M. F.; Fend, Y. L.; Liu, M. C.; Lu, X. R.; Nasir, M.; Sikandar, A. (December 2019). "Parasitic activity of powdery mildew (pathogen strain hmlac226) on prostrate knotweed (Polygonum aviculare L.) at various locations of Shenyang, northeast China". Applied Ecology and Environmental Research. 17 (6): 13384–13394. Bibcode:2019ApEER..1713394I. doi:10.15666/aeer/1706_1338313394.
  11. 1 2 "Knotgrass: Polygonum aviculare". NatureGate. Retrieved 2013-12-30.
  12. ↑ Sell, Peter; Murrell, Gina (2018). Flora of Great Britain and Ireland, vol. 1. Cambridge: Cambridge University Press. ISBN 978-0-521-55335-3.
  13. ↑ Stace, C.A. (2019). New Flora of the British Isles (4th ed.). Suffolk: C&M Floristics. ISBN 978-1-5272-2630-2.
  14. ↑ Rose, Francis (2006). The Wild Flower Key. London: Frederick Warne. ISBN 978-0-7232-5175-0.
  15. ↑ Stearn, William T. (1980). Botanical Latin: History, Grammar, Syntax, Terminology and Vocabulary. Newton Abbot: David & Charles. ISBN 0-7153-5645-3.
  16. ↑ Parnell, J. and Curtis, T. (2012). Webb's An Irish Flora. Cork University Press. ISBN 978-185918-4783.
  17. ↑ 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.
  18. ↑ 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.
  19. ↑ 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. Bibcode:1994JNAtP..57..581K. doi:10.1021/np50107a003.
  20. ↑ 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. Bibcode:2010SJBS...17...57S. doi:10.1016/j.sjbs.2009.12.009. PMC 3730555. PMID 23961059.
  21. ↑ Łańcucka-Środoniowa M. (1979). "Szczątki makroskopowe roślin z miocenu słodkowodnego Kotliny Sądeckiej (Karpaty Zachodnie, Polska)" [Macroscopic plant remains from the freshwater Miocene of the Nowy Sącz Basin (West Carpathians, Poland)]. Acta Palaeobotanica (in Polish). 20 (1): 3–117.
  22. ↑ Nielsen, Nina H.; Henriksen, Peter Steen; Mortensen, Morten Fischer; Enevold, Renée; Mortensen, Martin N.; Scavenius, Carsten; Enghild, Jan J. (2021). "The last meal of Tollund Man: new analyses of his gut content". Antiquity. 95 (383): 1195–1212. doi:10.15184/aqy.2021.98.