Polygonum arenastrumBoreau

common knotweeddoorweedmatweedoval-leaf knotweedovalleaf knotweedprostrate knotweed

WFO wfo-0000488339 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Polygonum arenastrum, photographed by Pavel Kacl
fig. a Pavel Kacl, CC BY 4.0 / 2021-10-10 / obs. 162723755
Polygonum arenastrum, photographed by John Kees
fig. b John Kees, CC0 1.0 / obs. 161543929
Polygonum arenastrum, photographed by Ксения Волянская
fig. c Ксения Волянская, CC BY 4.0 / obs. 159604545
Polygonum arenastrum, photographed by Patrick Meurin
fig. d Patrick Meurin, CC BY 4.0 / obs. 156109781
Polygonum arenastrum, photographed by Alexis Tinker-Tsavalas
fig. e Alexis Tinker-Tsavalas, CC BY 4.0 / obs. 149334018
Polygonum arenastrum, photographed by Robert H. Wardell
fig. f Robert H. Wardell, CC0 1.0 / obs. 147308799
Polygonum arenastrum, photographed by Иван Шихалев
fig. g Иван Шихалев, CC BY 4.0 / obs. 142867635
Polygonum arenastrum, photographed by Leon Perrie
fig. h Leon Perrie, CC BY 4.0 / obs. 112108888

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 70 botanical countries

Regions where Polygonum arenastrum is native: Algeria, Azores, Canary Is., Madeira, Morocco, Tunisia, Afghanistan, Altay, Amur, Buryatiya, Chita, East Aegean Is., Iran, Iraq, Irkutsk, Kamchatka, Khabarovsk, Krasnoyarsk, Kuril Is., Magadan, Manchuria, Mongolia, North Caucasus, Palestine, Primorye, Sakhalin, Sinai, Transcaucasus, Türkiye, Turkmenistan, Tuva, West Siberia, Yakutiya, Pakistan, West Himalaya, Albania, Austria, Baleares, Baltic States, Belarus, Belgium, Bulgaria, Central European Russia, Corse, Czechia-Slovakia, Denmark, East European Russia, Finland, France, Germany, Greece, Hungary, Italy, Kriti, Krym, Netherlands, North European Russia, Northwest European Russia, Norway, NW. Balkan Pen., Portugal, Romania, Sardegna, Sicilia, South European Russia, Spain, Sweden, Switzerland, Türkiye-in-Europe, Ukraine AlgeriaMoroccoTunisiaAfghanistanAltayAmurBuryatiyaChitaEast Aegean Is.IranIraqIrkutskKamchatkaKhabarovskKrasnoyarskMagadanManchuriaMongoliaNorth CaucasusPalestinePrimoryeSakhalinSinaiTranscaucasusTürkiyeTurkmenistanTuvaWest SiberiaYakutiyaPakistanWest HimalayaAlbaniaAustriaBaltic StatesBelarusBelgiumBulgariaCentral European RussiaCorseCzechia-SlovakiaDenmarkEast European RussiaFinlandFranceGermanyGreeceHungaryItalyKritiKrymNetherlandsNorth European RussiaNorthwest European RussiaNorwayNW. Balkan Pen.PortugalRomaniaSiciliaSouth European RussiaSpainSwedenSwitzerlandTürkiye-in-EuropeUkraine AzoresCanary Is.MadeiraBalearesSardegna
Native distribution of Polygonum arenastrum, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows. Regions too small to draw at this scale are marked with a dot.
RegionTDWG codeContinent
Albania ALB EUROPE
Austria AUT
Baleares BAL
Baltic States BLT
Belarus BLR
Belgium BGM
Bulgaria BUL
Central European Russia RUC
Corse COR
Czechia-Slovakia CZE
Denmark DEN
East European Russia RUE
Finland FIN
France FRA
Germany GER
Greece GRC
Hungary HUN
Italy ITA
Kriti KRI
Krym KRY
Netherlands NET
North European Russia RUN
Northwest European Russia RUW
Norway NOR
NW. Balkan Pen. YUG
Portugal POR
Romania ROM
Sardegna SAR
Sicilia SIC
South European Russia RUS
Spain SPA
Sweden SWE
Switzerland SWI
Türkiye-in-Europe TUE
Ukraine UKR
Afghanistan AFG ASIA-TEMPERATE
Altay ALT
Amur AMU
Buryatiya BRY
Chita CTA
East Aegean Is. EAI
Iran IRN
Iraq IRQ
Irkutsk IRK
Kamchatka KAM
Khabarovsk KHA
Krasnoyarsk KRA
Kuril Is. KUR
Magadan MAG
Manchuria CHM
Mongolia MON
North Caucasus NCS
Palestine PAL
Primorye PRM
Sakhalin SAK
Sinai SIN
Transcaucasus TCS
Türkiye TUR
Turkmenistan TKM
Tuva TVA
West Siberia WSB
Yakutiya YAK
Algeria ALG AFRICA
Azores AZO
Canary Is. CNY
Madeira MDR
Morocco MOR
Tunisia TUN
Pakistan PAK ASIA-TROPICAL
West Himalaya WHM

Not drawn on the map: Kuril Is.. We hold no public-domain boundary for this region, so it is listed rather than guessed at.

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Flowering 96 in flower of 108 examined

Peak flowering in Mar. Each bar is the share of Polygonum arenastrum observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 96 of 108 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Also published as 11 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Polygonum acetosellum Klokov
  • Polygonum aequale Lindm.
  • Polygonum arenastrum subsp. calcatum (Lindm.) Wissk.
  • Polygonum arenastrum subsp. microspermum (Jord. ex Boreau) H.Scholz
  • Polygonum aviculare subsp. aequale (Lindm.) Asch. & Graebn.
  • Polygonum aviculare subsp. calcatum (Lindm.) Thell.
  • Polygonum calcatum Lindm.
  • Polygonum ebracteatum Munshi & Javeid
  • Polygonum microspermum Jord. ex Boreau
  • Polygonum montereyense Brenckle
  • Polygonum propinquum Ledeb.

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.