Cirsium hydrophilum var. hydrophilum
Suisun thistle
(c) Arvel Hernandez, some rights reserved (CC BY), uploaded by Arvel Hernandez · licence
Family: Asteraceae · Type: Herb · Native
Conservation status: CNPS 1B.1 · Endangered
Cirsium hydrophilum var. hydrophilum (Suisun thistle) is a native California herb in the Asteraceae family, recognized by NONE sympatric; geographically isolated in Suisun Marsh tidal habitat.
Suisun thistle is a rare (CNPS 1B.1) California native perennial found in the Deltaic Great Valley region of Suisun Marsh, Solano County, in tidal marsh habitat at sea level. Flowering from June to September, this plant produces purple flowers in thistle heads approximately 2.5 to 3 centimeters long. Growing with stems generally branched in the upper half, it reaches a moderate height with distinctive thistle characteristics. Its leaves are typical of thistles, with spiny edges and a robust green coloration characteristic of marsh environments. The fruit is small, approximately 5 millimeters long and oblong, tapering near the base.
Identification and appearance
Key characters: NONE sympatric; geographically isolated in Suisun Marsh tidal habitat
Habitat and range
Habitat: Tidal marsh
Elevation: +- 0 m.
Bloom period
Cirsium hydrophilum var. hydrophilum blooms Jun-Sep.
Conservation status
CNPS 1B.1 · Endangered
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 hydrophilum var. hydrophilum native to California?
Yes. Cirsium hydrophilum var. hydrophilum is native to California (recorded as native).
When does Cirsium hydrophilum var. hydrophilum bloom?
Cirsium hydrophilum var. hydrophilum blooms Jun-Sep.
What plant family does Cirsium hydrophilum var. hydrophilum belong to?
Cirsium hydrophilum var. hydrophilum is in the Asteraceae family, genus Cirsium.
Is Cirsium hydrophilum var. hydrophilum rare or endangered?
Cirsium hydrophilum var. hydrophilum carries California Rare Plant Rank 1B.1, state rank S1.
What habitat does Cirsium hydrophilum var. hydrophilum grow in?
Cirsium hydrophilum var. hydrophilum grows in Tidal marsh.
Related species
Other California species in the same genus, family, or bioregion.
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.