Cirsium fontinale var. campylon
Mount hamilton thistle, Mount Hamilton Fountain Thistle
(c) Madeleine Claire, some rights reserved (CC BY), uploaded by Madeleine Claire · licence
Family: Asteraceae · Type: Herb · Native
Conservation status: CNPS 1B.2
Cirsium fontinale var. campylon (Mount hamilton thistle) is a native California herb in the Asteraceae family, recognized by serpentine seeps, permanently nodding heads with recurved phyllaries, long spines.
Mount hamilton thistle is a rare (CNPS 1B.2) California native perennial found in eastern San Francisco Bay Area bioregion in serpentine seeps and streams at elevations below 750 meters. Flowering from March to October, this plant produces white to purple flowers in distinctive nodding heads with intricate phyllary structures. Growing up to 2 meters tall with green stems, it develops a robust form with densely cobwebby leaves covered in velvety hairs. Its leaves feature longer spines to 18 millimeters, with cauline leaves particularly notable for their complex texture and defensive spiny margins. The plant's uniquely structured flower heads include 65 to 85 phyllaries, with outer phyllaries up to 30 millimeters long and strongly recurved.
Identification and appearance
Key characters: 16 sympatric species; serpentine seeps, permanently nodding heads with recurved phyllaries, long spines
Habitat and range
Habitat: Serpentine seeps and streams
Elevation: < 750 m
California counties: Santa Clara, Stanislaus, Alameda
Bloom period
Cirsium fontinale var. campylon blooms Mar-Oct.
Conservation status
CNPS 1B.2
How to tell it apart
vs Carduus: Cirsium has fluffy, feathery seed tufts; Carduus has rough bristles or no pappus and continuous spiny wings down the stem.; vs Silybum: Cirsium leaves are plain green; Silybum has bright white marbling along the leaf veins.; vs Sonchus: Cirsium has thistle-type flowers with spine-tipped bracts; Sonchus has dandelion-like flowers and milky sap.; vs Cynara: Cirsium heads are 1-6 cm across; Cynara heads are massive (4-15 cm, tennis ball sized) with fleshy bases.; vs Centaurea: Cirsium has linear bracts without appendages; Centaurea bracts have fringed or comb-like tips.
Frequently asked questions
Is Cirsium fontinale var. campylon native to California?
Yes. Cirsium fontinale var. campylon is native to California (recorded as native).
When does Cirsium fontinale var. campylon bloom?
Cirsium fontinale var. campylon blooms Mar-Oct.
Where in California does Cirsium fontinale var. campylon grow?
Cirsium fontinale var. campylon occurs in Santa Clara, Stanislaus, Alameda, at elevations of < 750 m.
What plant family does Cirsium fontinale var. campylon belong to?
Cirsium fontinale var. campylon is in the Asteraceae family, genus Cirsium.
Is Cirsium fontinale var. campylon rare or endangered?
Cirsium fontinale var. campylon carries California Rare Plant Rank 1B.2, state rank S2.
Related species
Other California species in the same genus, family, or bioregion.
- Cirsium fontinale var. fontinale — Fountain thistle
- Cirsium fontinale var. obispoense — Chorro creek bog thistle
- Cirsium hydrophilum — Suisun thistle
- Cirsium hydrophilum var. hydrophilum — Suisun thistle
- Cirsium hydrophilum var. vaseyi — Mount tamalpais thistle
- Cirsium inamoenum var. inamoenum — Greene's thistle
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.