Bidens beckiiTorr. ex Spreng.

Beck's water-marigold

WFO wfo-0000045262 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Bidens beckii, photographed by Rob Foster
fig. a Rob Foster, CC BY 4.0 / 2021-10-13 / obs. 163584661
Bidens beckii, photographed by Rob Foster
fig. b Rob Foster, CC BY 4.0 / obs. 153106291
Bidens beckii, photographed by Ian Whyte
fig. c Ian Whyte, CC0 1.0 / obs. 171902403
Bidens beckii, photographed by Norma Malinowski
fig. d Norma Malinowski, CC BY 4.0 / obs. 85373163
Bidens beckii, photographed by Mary Krieger
fig. e Mary Krieger, CC BY 4.0 / obs. 49281760
Bidens beckii, photographed by Mary Krieger
fig. f Mary Krieger, CC BY 4.0 / obs. 49273951
Bidens beckii, photographed by Allan Harris
fig. g Allan Harris, CC0 1.0 / obs. 49494386
Bidens beckii, photographed by Mary Krieger
fig. h Mary Krieger, CC BY 4.0 / obs. 23657458

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 28 botanical countries

Regions where Bidens beckii is native: British Columbia, Connecticut, Idaho, Illinois, Indiana, Iowa, Maine, Manitoba, Massachusetts, Michigan, Minnesota, Missouri, Montana, New Brunswick, New Hampshire, New Jersey, New York, Nova Scotia, Ohio, Ontario, Oregon, Pennsylvania, Québec, Rhode I., Saskatchewan, Vermont, Washington, Wisconsin British ColumbiaConnecticutIdahoIllinoisIndianaIowaMaineManitobaMassachusettsMichiganMinnesotaMissouriMontanaNew BrunswickNew HampshireNew JerseyNew YorkNova ScotiaOhioOntarioOregonPennsylvaniaQuébecSaskatchewanVermontWashingtonWisconsin Rhode I.
Native distribution of Bidens beckii, 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
British Columbia BRC NORTHERN AMERICA
Connecticut CNT
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Maine MAI
Manitoba MAN
Massachusetts MAS
Michigan MIC
Minnesota MIN
Missouri MSO
Montana MNT
New Brunswick NBR
New Hampshire NWH
New Jersey NWJ
New York NWY
Nova Scotia NSC
Ohio OHI
Ontario ONT
Oregon ORE
Pennsylvania PEN
Québec QUE
Rhode I. RHO
Saskatchewan SAS
Vermont VER
Washington WAS
Wisconsin WIS

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 46 in flower of 86 examined

Peak flowering in Aug. Each bar is the share of Bidens beckii 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. 46 of 86 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 9 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 5 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.

  • Bidens beckii f. beckii
  • Megalodonta beckii (Torr. ex Spreng.) Greene
  • Megalodonta beckii var. beckii
  • Megalodonta beckii var. hendersonii Sherff
  • Megalodonta beckii var. oregonensis Sherff

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.