Taxon Report

Cirsium rhothophilum Blake

surf thistle

Print Report

Taxon Summary

Cirsium rhothophilum, commonly known as surf thistle, is a perennial herb in the Asteraceae that is found only in California. It occurs within Coastal bluff scrub, and Coastal dunes, growing at elevations from 3 to 60 meters. Cirsium rhothophilum is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Cirsium rhothophilum Blake
Common Name:	surf thistle
Family:	Asteraceae
Element Code:	PDAST2E2J0
USDA Plants Symbol:	CIRH
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial herb
Blooming Period: Apr-Jun	Apr-Jun
Elevation:	3-60 (10-195)
General Habitats:	Coastal bluff scrub, Coastal dunes
Microhabitat:
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.2
Global Rank:	G1
State Rank:	S1
State List:	CT
Fed List:	None
Other Status:	BLM_S; SB_SBBG
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	21
Element Occurrence Ranks:
Excellent (A)	3
Good (B)	7
Fair (C)	4
Poor (D)	1
None (X)	2
Unknown (U)	4

Location


California Endemic: True
California Counties and Islands: Name (Code)
San Luis Obispo (SLO), Santa Barbara (SBA)
Quads: Name (Quad Code)
Arroyo Grande NE (3512025), Casmalia (3412075), Oceano (3512015), Pismo Beach (3512026), Point Arguello (3412056), Point Conception (3412044), Point Sal (3412086), Surf (3412065)

Threat List Data from the CNDDB


Threat List Total:	10
EOs with Threat Listed:	Total EOs	% of EOs
	16	76 %
Non-native plant impacts	8	38%
ORV activity	6	28%
Foot traffic/trampling	4	19%
Other	3	14%
Development	2	9%
Feral pigs	1	4%
Grazing	1	4%
Insufficient population/stand size	1	4%
Military operations	1	4%
Mining	1	4%

Notes




Threats:
Threatened by vehicles, foot traffic, and non-native plants.
Taxonomy:
See Botanical Gazette 39:45 (1905) for original description.

Selected References

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 1 November 2025].