Cirsium undulatum(Nutt.) Spreng.

wavyleaf thistle

WFO wfo-0000130940 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h

Cirsium undulatum, photographed by Shane Johnson
fig. a Shane Johnson, CC0 1.0 / 2022-06-05 / obs. 204687769
Cirsium undulatum, photographed by Bob Walker
fig. b Bob Walker, CC BY 4.0 / obs. 203540232
Cirsium undulatum, photographed by Shane Johnson
fig. c Shane Johnson, CC0 1.0 / obs. 204552696
Cirsium undulatum, photographed by Shane Johnson
fig. d Shane Johnson, CC0 1.0 / obs. 204678317
Cirsium undulatum, photographed by Shalana Gray
fig. e Shalana Gray, CC BY 4.0 / obs. 204172365
Cirsium undulatum, photographed by Thomas Koffel
fig. f Thomas Koffel, CC BY 4.0 / obs. 204545904
Cirsium undulatum, photographed by Ben Keen
fig. g Ben Keen, CC0 1.0 / obs. 199498043
Cirsium undulatum, photographed by Julia Carr
fig. h Julia Carr, CC0 1.0 / obs. 202774072

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.

Flowering n = 938 observations

Peak flowering in Jun, from 938 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 14 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.

  • Carduus megacephalus (A.Gray) A.Nelson
  • Carduus undulatus Nutt.
  • Carduus undulatus var. undulatus
  • Cirsium megacephalum (A.Gray) Cockerell ex Daniels
  • Cirsium megacephalum (A.Gray) Cockerell
  • Cirsium undulatum f. album Farw.
  • Cirsium undulatum f. undulatum
  • Cirsium undulatum subsp. undulatum
  • Cirsium undulatum var. franktonis B.Boivin
  • Cirsium undulatum var. megacephalum (A.Gray) Fernald
  • Cirsium undulatum var. undulatum
  • Cnicus undulatus A.Gray
  • Cnicus undulatus var. megacephalus A.Gray
  • Cnicus undulatus var. undulatus

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.