Bacopa rotundifolia(Michx.) Wettst.

disk waterhyssop

WFO wfo-0000558323 Accepted WFO 2026-06 6 photographs CC0 / CC BY

Plate 1 figs. a–f · 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.

Bacopa rotundifolia, photographed by Daniel J. Layton
fig. a Daniel J. Layton, CC BY 4.0 / 2022-06-07 / obs. 204237363
Bacopa rotundifolia, photographed by kent ozment
fig. b kent ozment, CC0 1.0 / obs. 162052708
Bacopa rotundifolia, photographed by Katie Kucera
fig. c Katie Kucera, CC BY 4.0 / obs. 170594180
Bacopa rotundifolia, photographed by Daniel J. Layton
fig. d Daniel J. Layton, CC BY 4.0 / obs. 204237385
Bacopa rotundifolia, photographed by kent ozment
fig. e kent ozment, CC0 1.0 / obs. 162052725
Bacopa rotundifolia, photographed by kent ozment
fig. f kent ozment, CC0 1.0 / obs. 162052679

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 39 botanical countries

Regions where Bacopa rotundifolia is native: Alabama, Alberta, Arizona, Arkansas, Colorado, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Mexico Northeast, Mexico Southwest, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Mexico, North Carolina, North Dakota, Oklahoma, Saskatchewan, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin, Wyoming, Argentina Northeast, Argentina Northwest, Bolivia, Brazil West-Central, Honduras, Paraguay AlabamaAlbertaArizonaArkansasColoradoIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMarylandMexico NortheastMexico SouthwestMinnesotaMississippiMissouriMontanaNebraskaNew MexicoNorth CarolinaNorth DakotaOklahomaSaskatchewanSouth CarolinaSouth DakotaTennesseeTexasUtahVirginiaWisconsinWyomingArgentina NortheastArgentina NorthwestBoliviaBrazil West-CentralHondurasParaguay
Native distribution of Bacopa rotundifolia, 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
Alabama ALA NORTHERN AMERICA
Alberta ABT
Arizona ARI
Arkansas ARK
Colorado COL
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Kansas KAN
Kentucky KTY
Louisiana LOU
Maryland MRY
Mexico Northeast MXE
Mexico Southwest MXS
Minnesota MIN
Mississippi MSI
Missouri MSO
Montana MNT
Nebraska NEB
New Mexico NWM
North Carolina NCA
North Dakota NDA
Oklahoma OKL
Saskatchewan SAS
South Carolina SCA
South Dakota SDA
Tennessee TEN
Texas TEX
Utah UTA
Virginia VRG
Wisconsin WIS
Wyoming WYO
Argentina Northeast AGE SOUTHERN AMERICA
Argentina Northwest AGW
Bolivia BOL
Brazil West-Central BZC
Honduras HON
Paraguay PAR

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 53 in flower of 67 examined

Peak flowering in Oct. Each bar is the share of Bacopa rotundifolia 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. 53 of 67 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 7 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 16 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.

  • Bacopa nobsiana H.Mason
  • Bacopa obovata (Raf.) Fernald
  • Bacopa simulans Fernald
  • Bacopa tweediei (Benth.) Parodi
  • Bramia rotundifolia (Michx.) Britton
  • Herpestis rotundifolia (Michx.) Pursh
  • Herpestis rotundifolia C.F.Gaertn.
  • Herpestis tweediei Benth.
  • Herpestis tweedii Benth.
  • Hydranthelium obovatum (Raf.) Pennell
  • Hydranthelium rotundifolium (Michx.) Pennell
  • Macuillamia obovata Raf.
  • Macuillamia rotundifolia (Michx.) Raf.
  • Moniera rotundifolia Michx.
  • Moniera tweedyi Kuntze
  • Ranapalus rotundifolius (Michx.) Pennell

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.