Elodea densa (Brazilian waterweed)

Plate 1 figs. a–h · 8 separate observations

Elodea densa, photographed by chiuluan — fig. a chiuluan, CC BY 4.0 / 2022-05-29 / obs. 253904606

Elodea densa, photographed by Doug Miller — fig. b Doug Miller, CC BY 4.0 / obs. 198493391

Elodea densa, photographed by Halema J — fig. c Halema J, CC BY 4.0 / obs. 192752369

Elodea densa, photographed by Malena Lorente — fig. d Malena Lorente, CC BY 4.0 / obs. 192847896

Elodea densa, photographed by Thomas Mesaglio — fig. e Thomas Mesaglio, CC BY 4.0 / obs. 192855504

Elodea densa, photographed by Jon Sullivan — fig. f Jon Sullivan, CC BY 4.0 / obs. 201112579

Elodea densa, photographed by Shaun Lee — fig. g Shaun Lee, CC BY 4.0 / obs. 187198207

Elodea densa, photographed by 葉子 — fig. h 葉子, CC0 1.0 / obs. 184805256

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 5 botanical countries

Native distribution of Elodea 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.

Region	TDWG code	Continent
Argentina Northeast	AGE	SOUTHERN AMERICA
Bolivia	BOL
Brazil South	BZS
Brazil Southeast	BZL
Uruguay	URU

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 95 in flower of 143 examined

78%

55%

80%

73%

67%

71%

70%

61%

55%

64%

81%

Proportion of examined Elodea densa in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	7	9	78%	45% to 94%
Feb	11	20	55%	34% to 74%
Mar	4	5	80%	38% to 96%
Apr	11	15	73%	48% to 89%
May	8	12	67%	39% to 86%
Jun	10	14	71%	45% to 88%
Jul	7	10	70%	40% to 89%
Aug	11	18	61%	39% to 80%
Sep	6	11	55%	28% to 79%
Oct	7	11	64%	35% to 85%
Nov	0	2	too few examined
Dec	13	16	81%	57% to 93%

Peak flowering in Dec. Each bar is the share of Elodea densa 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. 95 of 143 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. One month has fewer than 5 examined observations, so no proportion is drawn for it. 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.

Where it actually grows measured, from 1,178 observations

Condition	5th percentile	Median	95th percentile
Coldest month, mean daily low	-6.0 °C	5.6 °C	13.8 °C
Warmest month, mean daily high	20.5 °C	26.8 °C	32.2 °C
Annual rainfall	541 mm	1,283 mm	3,976 mm
Rainfall in the driest quarter	8 mm	159 mm	697 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 1,178 research-grade observations of Elodea 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. Climate from CHELSA V2.1 (Karger et al. 2017); occurrences from 10.15468/dl.cgje2x.

Also published as 6 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.

Anacharis densa (Planch.) Vict.
Egeria densa Planch.
Elodea canadensis var. gigantea L.H.Bailey
Elodea densa var. longifolia Bonstedt
Philotria densa (Planch.) Small
Udora densa (Planch.) M.R.Almeida

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.
USDA PLANTS Database. common name, checklist symbol EGDE. public domain. 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.