Cirsium praeteriens
Lost thistle, Lost Thistle
(c) Jacy Chen, some rights reserved (CC BY), uploaded by Jacy Chen · licence
Family: Asteraceae · Type: Herb · Native
Conservation status: CNPS 1A
Cirsium praeteriens (Lost thistle) is a native California herb in the Asteraceae family, recognized by large sessile heads and non-decurrent leaves were distinctive.
Lost thistle is a rare (CNPS 1A) California native perennial herb found in southern San Francisco Bay Area in Santa Clara County at elevations below 100 meters, though presumed extinct with unknown specific habitat. Flowering from June to July, this plant produces white flowers in large heads 3 to 4 centimeters wide, with distinctive hemispheric involucres. Growing with stout, erect stems that are loosely fine-cobwebby and soft-jointed-hairy, it reaches over one meter tall. Its leaves are elliptic to oblanceolate, deeply divided with narrow, rigidly spreading lobes ending in sharp 5 to 15 millimeter spines, with upper leaves clasping the stem. The plant's phyllaries feature narrowly lanceolate outer segments with spreading spine tips, creating a complex and intricate floral structure.
Identification and appearance
Key characters: 16 sympatric species; large sessile heads and non-decurrent leaves were distinctive
Habitat and range
Habitat: Presumed extinct; habitat unknown
Elevation: < 100 m
Bloom period
Cirsium praeteriens blooms Jun-Jul.
Conservation status
CNPS 1A
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 praeteriens native to California?
Yes. Cirsium praeteriens is native to California (recorded as native).
When does Cirsium praeteriens bloom?
Cirsium praeteriens blooms Jun-Jul.
What plant family does Cirsium praeteriens belong to?
Cirsium praeteriens is in the Asteraceae family, genus Cirsium.
Is Cirsium praeteriens rare or endangered?
Cirsium praeteriens carries California Rare Plant Rank 1A, state rank SX.
What habitat does Cirsium praeteriens grow in?
Cirsium praeteriens grows in Presumed extinct; habitat unknown.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.