Cirsium scariosum var. scariosum
Elk thistle
(c) Matt Lavin, some rights reserved (CC BY-SA) · licence
Family: Asteraceae · Type: Perennial · Native
Cirsium scariosum var. scariosum (Elk thistle) is a native California perennial in the Asteraceae family, recognized by tall unbranched stems with spike-like head clusters diagnostic.
Elk thistle is a California native perennial found in the Klamath Ranges in meadows and wet soils at elevations around 1,000 meters. Flowering from May to July, this plant produces white flowers in dense clusters with heads 2 to 3.5 centimeters wide. Growing with tall stems 15 to 200 centimeters high, often unbranched and reaching well above surrounding vegetation. Its leaves are uniquely textured, with upper surfaces smooth or sparsely hairy and lower surfaces ranging from smooth to densely woolly. The plant's distinctive involucre features phyllary tips with spines 1 to 8 millimeters long, creating an intricate and textured appearance.
Identification and appearance
Key characters: 17 sympatric species; tall unbranched stems with spike-like head clusters diagnostic
Habitat and range
Habitat: Meadows, wet soil
Elevation: +- 1000 m.
Outside California: to British Columbia, Alberta, Montana, Wyoming, Colorado
Bloom period
Cirsium scariosum var. scariosum blooms May-Jul.
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 scariosum var. scariosum native to California?
Yes. Cirsium scariosum var. scariosum is native to California (recorded as native).
When does Cirsium scariosum var. scariosum bloom?
Cirsium scariosum var. scariosum blooms May-Jul.
What plant family does Cirsium scariosum var. scariosum belong to?
Cirsium scariosum var. scariosum is in the Asteraceae family, genus Cirsium.
What habitat does Cirsium scariosum var. scariosum grow in?
Cirsium scariosum var. scariosum grows in Meadows, wet soil.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.