Erigeron canadensisL.

horseweed

WFO wfo-0000015917 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h

Erigeron canadensis, photographed by Yurii Basov
fig. a Yurii Basov, CC BY 4.0 / 2022-06-11 / obs. 205168356
Erigeron canadensis, photographed by James C. Davis
fig. b James C. Davis, CC BY-SA 4.0 / obs. 204816654
Erigeron canadensis, photographed by Anastasia_Surkova
fig. c Anastasia_Surkova, CC BY 4.0 / obs. 203669387
Erigeron canadensis, photographed by Randy A Nonenmacher
fig. d Randy A Nonenmacher, CC BY 4.0 / obs. 205354198
Erigeron canadensis, photographed by Mila C.
fig. e Mila C., CC BY 4.0 / obs. 201357051
Erigeron canadensis, photographed by Joanna Klukowska
fig. f Joanna Klukowska, CC BY 4.0 / obs. 202167789
Erigeron canadensis, photographed by Юрий Данилевский (Yuriy Danilevsky)
fig. g Юрий Данилевский (Yuriy Danilevsky), CC BY 4.0 / obs. 200991999
Erigeron canadensis, photographed by Валерия Ковалева
fig. h Валерия Ковалева, CC BY 4.0 / obs. 200708198

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.

Confused withby our own model

These are not lookalikes we guessed at. Each one is a species our identification model genuinely mistook for this plant, and how many times. The error rate is published.

Flowering n = 3,299 observations

Peak flowering in Aug, from 3,299 community-annotated observations worldwide. This is a global aggregate, not a forecast for your garden: the same species flowers on different dates in different hemispheres, and citizen-science records cluster near cities, at weekends, and in spring. Where a species has fewer than 30 annotated records we do not draw this chart at all.

Also published as 29 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.

  • Aster canadensis (L.) E.H.L.Krause
  • Caenotus canadensis (L.) Raf.
  • Caenotus pusillus Raf.
  • Conyza canadensis (L.) Cronquist
  • Conyza canadensis var. canadensis
  • Conyza canadensis var. glabrata (A.Gray) Cronquist
  • Conyza canadensis var. pusilla (Nutt.) Cronquist
  • Conyza parva Cronquist
  • Conyzella canadensis Rupr.
  • Erigeron canadense var. pusillus (Nutt.) B.Boivin
  • Erigeron canadensis f. canadensis
  • Erigeron canadensis f. coloratus Fassett
  • Erigeron canadensis var. canadensis
  • Erigeron canadensis var. glabratus A.Gray
  • Erigeron canadensis var. levis Makino
  • Erigeron canadensis var. pusillus (Nutt.) B.Boivin
  • Erigeron canadensis var. strictus Farw.
  • Erigeron myriocephalus Rech.f. & Edelb.
  • Erigeron pusillus Nutt.
  • Erigeron setiferus Post ex Boiss.
  • Erigeron strictus DC.
  • Leptilon canadense (L.) Britton
  • Leptilon canadense (L.) Britton & Brown
  • Leptilon canadense var. canadense

and 5 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.

We publish what we can source and we say so when we cannot. This page has no care advice, no toxicity claim and no native range, because we do not yet have those from a source we can cite.