Cirsium ochrocentrum (yellowspine thistle)

Plate 1 figs. a–h · 8 separate observations

Cirsium ochrocentrum, photographed by Andrew Tree — fig. a Andrew Tree, CC BY 4.0 / 2022-05-25 / obs. 200518333

Cirsium ochrocentrum, photographed by lejones417 — fig. b lejones417, CC BY-SA 4.0 / obs. 138055801

Cirsium ochrocentrum, photographed by Craig Martin — fig. c Craig Martin, CC0 1.0 / obs. 129741479

Cirsium ochrocentrum, photographed by Catherine C. Galley — fig. e Catherine C. Galley, CC BY 4.0 / obs. 79076001

Cirsium ochrocentrum, photographed by CK2AZ — fig. g CK2AZ, CC BY 4.0 / obs. 40893301

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 11 botanical countries

Native distribution of Cirsium ochrocentrum, 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
California	CAL	NORTHERN AMERICA
Colorado	COL
Kansas	KAN
Mexico Northeast	MXE
Nebraska	NEB
New Mexico	NWM
Oklahoma	OKL
South Dakota	SDA
Texas	TEX
Utah	UTA
Wyoming	WYO

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 97 in flower of 136 examined

73%

81%

78%

71%

79%

25%

Proportion of examined Cirsium ochrocentrum in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	2	2	too few examined
Feb	0	0	too few examined
Mar	0	0	too few examined
Apr	2	3	too few examined
May	8	11	73%	43% to 90%
Jun	30	37	81%	66% to 91%
Jul	25	32	78%	61% to 89%
Aug	17	24	71%	51% to 85%
Sep	11	14	79%	52% to 92%
Oct	2	8	25%	7% to 59%
Nov	0	3	too few examined
Dec	0	2	too few examined

Peak flowering in Jun. Each bar is the share of Cirsium ochrocentrum 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. 97 of 136 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 6 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.

Carduus ochrocentrus Greene
Carduus ochrocentrus f. ochrocentrus
Cirsium ochrocentrum subsp. martinii Barlow-Irick
Cirsium ochrocentrum var. townsendii Petr.
Cnicus ochrocentrus A.Gray

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.
Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. 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.