Cirsium occidentale
Cobweb thistle
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Family: Asteraceae · Type: Herb · Native
Cirsium occidentale (Cobweb thistle) is a native California herb in the Asteraceae family.
Cobweb thistle is a California native biennial found in coastal and interior mountain regions, growing in open grasslands and disturbed areas. Flowering from May to July, this plant produces white to lavender or deep purple flowers in dense, spherical heads 3 to 5 centimeters wide with distinctive cobwebby, interconnected phyllary hairs. Growing 30 to 100 centimeters tall with generally erect, branched stems that are densely gray-white tomentose, it develops a robust and striking appearance. Its leaves are oblanceolate with deeply lobed blades, the lower leaves measuring 10 to 40 centimeters long and having widely triangular lobes with spiny margins. The fruit is a small, 5 to 6 millimeter achene topped with a feathery pappus 15 to 30 millimeters long.
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 occidentale native to California?
Yes. Cirsium occidentale is native to California (recorded as native).
What plant family does Cirsium occidentale belong to?
Cirsium occidentale is in the Asteraceae family, genus Cirsium.
Related species
Other California species in the same genus, family, or bioregion.
- Cirsium occidentale var. californicum — California thistle
- Cirsium occidentale var. candidissimum — Snowy thistle
- Cirsium occidentale var. compactum — Compact cobwebby thistle
- Cirsium occidentale var. coulteri — Coulter's thistle
- Cirsium occidentale var. lucianum — Cuesta ridge thistle
- Cirsium occidentale var. occidentale — Cobwebby thistle
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
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.