Groenlandia densa(L.) Fourr.

Opposite-leaved Pondweedopposite-leaved pondweed

WFO wfo-0000771226 Accepted WFO 2026-06 8 photographs CC BY

Plate 1 figs. a–h · 8 separate observations

Groenlandia densa, photographed by Julien Renoult
fig. a Julien Renoult, CC BY 4.0 / 2022-04-18 / obs. 189078097
Groenlandia densa, photographed by David Delon
fig. b David Delon, CC BY 4.0 / obs. 183013940
Groenlandia densa, photographed by David Delon
fig. c David Delon, CC BY 4.0 / obs. 182245245
Groenlandia densa, photographed by David Delon
fig. d David Delon, CC BY 4.0 / obs. 168422606
Groenlandia densa, photographed by Yves Bas
fig. e Yves Bas, CC BY 4.0 / obs. 120927021
Groenlandia densa, photographed by Bastien Alegot
fig. f Bastien Alegot, CC BY 4.0 / obs. 119885068
Groenlandia densa, photographed by Yves Bas
fig. g Yves Bas, CC BY 4.0 / obs. 76493171
Groenlandia densa, photographed by Elina Zepp
fig. h Elina Zepp, CC BY 4.0 / obs. 178035899

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 33 botanical countries

Regions where Groenlandia densa is native: Algeria, Morocco, Tunisia, Iran, Lebanon-Syria, North Caucasus, Palestine, Transcaucasus, Türkiye, West Himalaya, Albania, Austria, Baltic States, Belgium, Bulgaria, Czechia-Slovakia, Denmark, France, Germany, Great Britain, Greece, Hungary, Ireland, Italy, Netherlands, NW. Balkan Pen., Poland, Portugal, Romania, Sicilia, Spain, Switzerland, Türkiye-in-Europe AlgeriaMoroccoTunisiaIranLebanon-SyriaNorth CaucasusPalestineTranscaucasusTürkiyeWest HimalayaAlbaniaAustriaBaltic StatesBelgiumBulgariaCzechia-SlovakiaDenmarkFranceGermanyGreeceHungaryIrelandItalyNetherlandsNW. Balkan Pen.PolandPortugalRomaniaSiciliaSpainSwitzerlandTürkiye-in-Europe
Native distribution of Groenlandia densa, 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.
RegionTDWG codeContinent
Albania ALB EUROPE
Austria AUT
Baltic States BLT
Belgium BGM
Bulgaria BUL
Czechia-Slovakia CZE
Denmark DEN
France FRA
Germany GER
Great Britain GRB
Greece GRC
Hungary HUN
Ireland IRE
Italy ITA
Netherlands NET
NW. Balkan Pen. YUG
Poland POL
Portugal POR
Romania ROM
Sicilia SIC
Spain SPA
Switzerland SWI
Türkiye-in-Europe TUE
Iran IRN ASIA-TEMPERATE
Lebanon-Syria LBS
North Caucasus NCS
Palestine PAL
Transcaucasus TCS
Türkiye TUR
Algeria ALG AFRICA
Morocco MOR
Tunisia TUN
West Himalaya WHM ASIA-TROPICAL

Not drawn on the map: Great Britain. 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.

Where it actually grows measured, from 346 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -8.2 °C -0.4 °C 5.5 °C
Warmest month, mean daily high 19.4 °C 25.7 °C 30.0 °C
Annual rainfall 593 mm 942 mm 1,530 mm
Rainfall in the driest quarter 53 mm 144 mm 287 mm

It is found where winters bring hard frost. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 346 research-grade observations of Groenlandia densa that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one.

Also published as 36 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.

  • Buccaferrea densa (L.) Bubani
  • Potamogeton densus L.
  • Potamogeton densus f. major Cham. & Schltdl.
  • Potamogeton densus f. major Cham. & Schltdl.
  • Potamogeton densus f. minor Cham. & Schltdl.
  • Potamogeton densus f. minor Cham. & Schltdl.
  • Potamogeton densus f. oppositifolius (DC.) Rchb.
  • Potamogeton densus f. setaceus (L.) Rchb.
  • Potamogeton densus subsp. oppositifolius (DC.) Bonnier & Layens
  • Potamogeton densus subsp. serratus (L.) Arcang.
  • Potamogeton densus subsp. serratus (L.) K.Richt.
  • Potamogeton densus subsp. setaceus (L.) K.Richt.
  • Potamogeton densus var. angustifolius Wallr.
  • Potamogeton densus var. angustifolius Mert. & W.D.J.Koch
  • Potamogeton densus var. lanceolatus Gaudin
  • Potamogeton densus var. lancifolius Mert. & W.D.J.Koch
  • Potamogeton densus var. latifolius Wallr.
  • Potamogeton densus var. latifolius Roth
  • Potamogeton densus var. laxifolius Gren. & Godr.
  • Potamogeton densus var. laxus Opiz
  • Potamogeton densus var. major G.Mey.
  • Potamogeton densus var. oppositifolius DC. ex Rchb.
  • Potamogeton densus var. pauciflorus Lam. ex Vayr.
  • Potamogeton densus var. rigidus Opiz

and 12 more.

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.