Taxon Details

Cirsium rhothophilum

surf thistle

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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:
Name Status:	JEF, FNA, POWO, IPNI, Tropicos

Conservation Status

CA Rare Plant Rank:	1B.2
Fed List:	None
State List:	CT (1990-02-01)
Global Rank:	G1
State Rank:	S1
Other Status:	BLM_S; SB_SBBG
CRPR Changes:
Add Date:	1974-01-01
Date Edited:	2025-10-29

Ecology and Life History

Lifeform: perennial herb

Blooming Period: Apr-Jun

Elevation:
3 - 60 meters
10 - 195 feet

General Habitats:

Coastal bluff scrub
Coastal dunes

Microhabitat Details:

Microhabitat:

Notes

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

Threat List Data from the CNDDB

THREAT LIST:
Threat List Total:	10
	Total EOs	% of EOs
EOs with Threat Listed:	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%

Occurrence Data from the CNDDB

Element Occurrence Ranks:
Total Occurrences:					21
A	B	C	D	X	U
3	7	4	1	2	4

Occurrence Status:
Historical >20 Years	20
Recent <=20 Years	1

Presence:
Presumed Extant	19
Possibly Extirpated	1
Presumed Extirpated	1

Location

California Endemic:

California Island:

States: Name (Code)
California (CA)

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)

Notes:

Definitions of codes following a county and/or quad:
*		Presumed extirpated
(?)		Occurrence confirmed, but possibly extirpated
Quad and county data is imported from the CNDDB. Species may be present in other areas where conditions are favorable. These data should NOT be substituted for pre-project review or for on-site surveys.

Regional Map

Map

Presumed Extant

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CNPS Rare Plant Inventory