Taxon Report

Cirsium fontinale Greene var. campylon (H.K. Sharsm.) Keil & C. Turner

Mt. Hamilton thistle

Print Report

Taxon Summary

Cirsium fontinale var. campylon, commonly known as Mt. Hamilton thistle, is a perennial herb in the Asteraceae that is found only in California. It occurs within Chaparral, Cismontane woodland, and Valley and foothill grassland, growing at elevations from 100 to 890 meters. Cirsium fontinale var. campylon is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Cirsium fontinale Greene var. campylon (H.K. Sharsm.) Keil & C. Turner
Common Name:	Mt. Hamilton thistle
Family:	Asteraceae
Element Code:	PDAST2E163
USDA Plants Symbol:	CIFOC
Synonyms/Other Names:	Cirsium campylon H.L. Sharsm.

Ecology and Life History


Lifeform:	perennial herb
Blooming Period: (Feb)Apr-Oct	(Feb)Apr-Oct
Elevation:	100-890 (330-2920)
General Habitats:	Chaparral, Cismontane woodland, Valley and foothill grassland
Microhabitat:	Seeps, Serpentine
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.2
Global Rank:	G2T2
State Rank:	S2
State List:	None
Fed List:	None
Other Status:	BLM_S; SB_CalBG/RSABG
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	36
Element Occurrence Ranks:
Excellent (A)	6
Good (B)	17
Fair (C)	4
Poor (D)	0
None (X)	0
Unknown (U)	9

Location


California Endemic: True
California Counties and Islands: Name (Code)
Alameda (ALA), Santa Clara (SCL), Stanislaus (STA)
Quads: Name (Quad Code)
Cedar Mtn. (3712155), Lick Observatory (3712136), Los Gatos (3712128), Morgan Hill (3712126), Mt. Boardman (3712144), Mt. Madonna (3712116), San Jose East (3712137), Santa Teresa Hills (3712127)

Threat List Data from the CNDDB


Threat List Total:	13
EOs with Threat Listed:	Total EOs	% of EOs
	28	78 %
Grazing	12	33%
Non-native plant impacts	10	27%
Other	7	19%
Road/trail construction/maint.	7	19%
Development	5	13%
Foot traffic/trampling	5	13%
Erosion/runoff	4	11%
Landfill	4	11%
Recreational use (non-ORV)	2	5%
Biocides	1	2%
Surface water diversion	1	2%
Waterway bank protection/maintenance	1	2%
Wood cutting or brush clearing	1	2%

Notes



Threatened by urbanization, trampling, non-native plants, and grazing. Possibly threatened by recreational activities, and erosion. See Phytologia 73(4):312-317 (1992) for revised nomenclature.
Threats:

Taxonomy:

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 26 October 2025].