Plate 1 figs. a–h · 8 separate observations
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 78 botanical countries
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 344 observations
| Condition | 5th percentile | Median | 95th percentile |
|---|---|---|---|
| Coldest month, mean daily low | -14.6 °C | -5.1 °C | 16.6 °C |
| Warmest month, mean daily high | 23.0 °C | 27.6 °C | 34.6 °C |
| Annual rainfall | 461 mm | 997 mm | 1,601 mm |
| Rainfall in the driest quarter | 3 mm | 155 mm | 264 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 344 research-grade observations of Potamogeton illinoensis 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 Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one.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 19 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.
- Potamogeton angustifolius var. connecticutensis (J.W.Robbins) A.Benn.
- Potamogeton brasiliensis (A.Benn.) A.Benn.
- Potamogeton curvatus A.Benn.
- Potamogeton dunicola Tur
- Potamogeton elipticus Larrañaga
- Potamogeton fragillimus Hagstr.
- Potamogeton illinoensis f. homophyllus Hagstr.
- Potamogeton illinoensis f. rosulatus Hagstr.
- Potamogeton linearis Larrañaga
- Potamogeton lucens subsp. brasiliensis A.Benn.
- Potamogeton lucens var. connecticutensis J.W.Robbins
- Potamogeton lucens var. floridanus A.Benn.
- Potamogeton macrophylloides Hagstr.
- Potamogeton pedersenii Tur
- Potamogeton pulchelliformis Hagstr.
- Potamogeton zizii var. connecticutensis (J.W.Robbins) Morong
- Potamogeton zizii var. gracilis A.Benn.
- Potamogeton zizii var. porrectifolius A.Benn.
- Potamogeton ziziiformis Hagstr.
Sourcesevery claim on this page
- World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
- iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
- Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
- 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.