Isoetes lacustrisL.

lake quillwort

WFO wfo-0001108956 Accepted WFO 2026-06 7 photographs CC BY

Plate 1 figs. a–g · 3 observations

This species has been photographed under an open licence only 3 times, so some figures below are different views of the same plant, taken on the same day, rather than different individuals. They are usually different parts of it: the leaf, the flower, the bark.

Isoetes lacustris, photographed by Valerii Glazunov
fig. a Valerii Glazunov, CC BY 4.0 / 2019-08-14 / obs. 74923730
Isoetes lacustris, photographed by hecklemore
fig. b hecklemore, CC BY 4.0 / obs. 199656325
Isoetes lacustris, photographed by hecklemore
fig. c hecklemore, CC BY 4.0 / obs. 199656357
Isoetes lacustris, photographed by hecklemore
fig. d hecklemore, CC BY 4.0 / obs. 199656393
Isoetes lacustris, photographed by hecklemore
fig. e hecklemore, CC BY 4.0 / obs. 199656256
Isoetes lacustris, photographed by Brandon Corder
fig. f Brandon Corder, CC BY 4.0 / obs. 164770178
Isoetes lacustris, photographed by hecklemore
fig. g hecklemore, CC BY 4.0 / obs. 199656288

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 50 botanical countries

Regions where Isoetes lacustris is native: Morocco, Altay, West Siberia, Austria, Baltic States, Belgium, Bulgaria, Central European Russia, Czechia-Slovakia, Denmark, East European Russia, Finland, Føroyar, France, Germany, Great Britain, Iceland, Ireland, Netherlands, North European Russia, Norway, Poland, Portugal, Spain, Sweden, Switzerland, Connecticut, Greenland, Labrador, Maine, Manitoba, Massachusetts, Michigan, Minnesota, New Brunswick, New Hampshire, New Jersey, New York, Newfoundland, Northwest Territories, Nova Scotia, Ontario, Prince Edward I., Québec, Rhode I., Saskatchewan, Tennessee, Vermont, Virginia, Wisconsin MoroccoAltayWest SiberiaAustriaBaltic StatesBelgiumBulgariaCentral European RussiaCzechia-SlovakiaDenmarkEast European RussiaFinlandFranceGermanyIcelandIrelandNetherlandsNorth European RussiaNorwayPolandPortugalSpainSwedenSwitzerlandConnecticutGreenlandLabradorMaineManitobaMassachusettsMichiganMinnesotaNew BrunswickNew HampshireNew JerseyNew YorkNewfoundlandNorthwest TerritoriesNova ScotiaOntarioPrince Edward I.QuébecSaskatchewanTennesseeVermontVirginiaWisconsin FøroyarRhode I.
Native distribution of Isoetes lacustris, 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
Connecticut CNT NORTHERN AMERICA
Greenland GNL
Labrador LAB
Maine MAI
Manitoba MAN
Massachusetts MAS
Michigan MIC
Minnesota MIN
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New York NWY
Newfoundland NFL
Northwest Territories NWT
Nova Scotia NSC
Ontario ONT
Prince Edward I. PEI
Québec QUE
Rhode I. RHO
Saskatchewan SAS
Tennessee TEN
Vermont VER
Virginia VRG
Wisconsin WIS
Austria AUT EUROPE
Baltic States BLT
Belgium BGM
Bulgaria BUL
Central European Russia RUC
Czechia-Slovakia CZE
Denmark DEN
East European Russia RUE
Finland FIN
Føroyar FOR
France FRA
Germany GER
Great Britain GRB
Iceland ICE
Ireland IRE
Netherlands NET
North European Russia RUN
Norway NOR
Poland POL
Portugal POR
Spain SPA
Sweden SWE
Switzerland SWI
Altay ALT ASIA-TEMPERATE
West Siberia WSB
Morocco MOR AFRICA

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 99 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -15.6 °C -9.9 °C 0.3 °C
Warmest month, mean daily high 14.7 °C 21.6 °C 23.9 °C
Annual rainfall 603 mm 745 mm 1,864 mm
Rainfall in the driest quarter 94 mm 126 mm 323 mm

It is found where winters are severely cold. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 99 research-grade observations of Isoetes lacustris 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 58 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.

  • Calamaria lacustris (L.) Kuntze
  • Calamaria setacea (Lam.) Kuntze
  • Isoetes atrovirens Th.Fr.
  • Isoetes hieroglyphica A.A.Eaton
  • Isoetes lacustris subsp. abbreviata Gand.
  • Isoetes lacustris subsp. arvernensis Gand.
  • Isoetes lacustris subsp. cambrica Gand.
  • Isoetes lacustris subsp. editorum Gand.
  • Isoetes lacustris subsp. errabunda Gand.
  • Isoetes lacustris subsp. hieroglyphica (A.A.Eaton) Taylor & Luebke
  • Isoetes lacustris subsp. lacustris Hook.f.
  • Isoetes lacustris subsp. lamottei Gand.
  • Isoetes lacustris subsp. langei Gand.
  • Isoetes lacustris subsp. latifolia Gand.
  • Isoetes lacustris subsp. noltei Gand.
  • Isoetes lacustris subsp. obscura Gand.
  • Isoetes lacustris subsp. pervaga Gand.
  • Isoetes lacustris subsp. rivalis Gand.
  • Isoetes lacustris subsp. rossica Gand.
  • Isoetes lacustris subsp. scanica Gand.
  • Isoetes lacustris subsp. scotica Gand.
  • Isoetes lacustris subsp. septentrionalis Gand.
  • Isoetes lacustris subsp. spreta Gand.
  • Isoetes lacustris subsp. succedanea Gand.

and 34 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. USDA PLANTS Database. common name, checklist symbol ISLA. public domain. 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.