Cirsium douglasii var. douglasii
Douglas' swamp thistle
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Family: Asteraceae · Type: Herb · Native
Cirsium douglasii var. douglasii (Douglas' swamp thistle) is a native California herb in the Asteraceae family, recognized by lower elevation coastal range, deeply lobed leaves, and longer spines distinguish it.
Douglas' swamp thistle is a California native perennial found in northern coastal, northern coastal range, northern central coast, San Francisco Bay, and northern south coastal range areas in wet places, occasionally on serpentine, at elevations below 1,400 meters. Flowering from June to August, this plant produces purple flowers in heads 2.5 to 3.5 centimeters long with distinctive spiny characteristics. Growing with stems up to 1.5 meters tall, it develops robust and erect vegetation that spreads broadly in moist environments. Its cauline leaves are deeply lobed with prominent spines on distal leaves measuring 7 to 20 millimeters long, creating a distinctive textured appearance. The dense, spiny leaf structure and tall growth make this thistle a notable inhabitant of California's wet habitats.
Identification and appearance
Key characters: 25 sympatric species; lower elevation coastal range, deeply lobed leaves, and longer spines distinguish it
Habitat and range
Habitat: Wet places, occasionally on serpentine
Elevation: < 1400 m
Bloom period
Cirsium douglasii var. douglasii blooms Jun-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 douglasii var. douglasii native to California?
Yes. Cirsium douglasii var. douglasii is native to California (recorded as native).
When does Cirsium douglasii var. douglasii bloom?
Cirsium douglasii var. douglasii blooms Jun-Aug.
What plant family does Cirsium douglasii var. douglasii belong to?
Cirsium douglasii var. douglasii is in the Asteraceae family, genus Cirsium.
What habitat does Cirsium douglasii var. douglasii grow in?
Cirsium douglasii var. douglasii grows in Wet places, occasionally on serpentine.
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.