Cirsium canescens
Prairie thistle
(c) Harry Podschwit, some rights reserved (CC BY) · licence
Family: Asteraceae · Type: Herb · Not Native
Cirsium canescens (Prairie thistle) is a non-native California herb in the Asteraceae family, recognized by Modoc Plateau habitat and dense gray tomentum with sticky phyllary ridges.
Prairie thistle is a naturalized perennial herb found in the Modoc Plateau in grasslands, arid scrublands, and disturbed areas at elevations of 1,500 to 1,600 meters. Flowering from May to August, this plant produces dull white to lavender-tinged flowers in heads 3 to 4 centimeters wide, arranged in flat-topped clusters. Growing with a single erect stem 20 to 100 centimeters tall, densely covered in fine gray hairs and with few ascending branches. Its leaves are gray-tomentose, with lower leaves up to 25 centimeters long, coarsely toothed or deeply lobed, and upper leaves gradually reduced and becoming bract-like with spiny wings. The involucre has graduated phyllary tips with small 2 to 4 millimeter spines, giving the plant its characteristic thistle-like appearance.
Identification and appearance
Key characters: 14 sympatric species; Modoc Plateau habitat and dense gray tomentum with sticky phyllary ridges
Habitat and range
Habitat: Grassland, arid scrubland, disturbed areas
Elevation: 1500-1600 m
Outside California: native to north-central United States
Bloom period
Cirsium canescens blooms May-Aug.
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 canescens native to California?
No. Cirsium canescens is not native to California (recorded as not native).
When does Cirsium canescens bloom?
Cirsium canescens blooms May-Aug.
What plant family does Cirsium canescens belong to?
Cirsium canescens is in the Asteraceae family, genus Cirsium.
What habitat does Cirsium canescens grow in?
Cirsium canescens grows in Grassland, arid scrubland, disturbed areas.
Related species
Other California species in the same genus, family, or bioregion.
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.