Carduus tenuiflorus
Italian thistle
Family: Asteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Carduus tenuiflorus (Italian thistle) is a non-native California herb in the Asteraceae family, recognized by C. pycnocephalus by glabrous phyllary bases and scarious margins.
Italian thistle is a naturalized annual found in northern coastal, northern coastal ranges, Sierra Nevada foothills, central western, and southwestern California in roadsides, pastures, and disturbed areas at elevations below 1,000 meters. Flowering from April to June, this plant produces pink to purple flowers in clusters of 5 to 20 heads up to 2 centimeters in diameter. Growing with stems 20 to 200 centimeters tall that are widely spiny-winged and either glabrous or slightly woolly, it forms an extensive and aggressive growth habit. Its basal leaves are 10 to 15 centimeters long with 12 to 20 deep lobes, while cauline leaves are slightly tomentose. The fruit is brown, 4 to 5 millimeters long with 10 to 13 prominent veins and a pappus 10 to 15 millimeters in length.
Identification and appearance
Key characters: 3 sympatric species; distinguished from C. pycnocephalus by glabrous phyllary bases and scarious margins
Habitat and range
Habitat: Roadsides, pastures, disturbed areas
Elevation: < 1000 m
Outside California: Oregon, Pennsylvania, native to central Europe
Bloom period
Carduus tenuiflorus blooms Apr-Jun.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Silybum: Carduus has spiny-winged stems and plain leaves; Silybum has smooth stems and white-marbled leaves.; vs Cirsium: Carduus has continuous spiny wings down stems and rough seed bristles; Cirsium lacks stem wings and has feathery seed plumes.; vs Centaurea: Carduus has spiny-winged stems; Centaurea stems lack spiny wings and have bracts with fringed appendages.; vs Sonchus: Carduus has spiny-winged stems and thistle flowers; Sonchus has hollow stems with milky sap and dandelion-like flowers.; vs Blitum: Carduus is a spiny thistle with purple flower heads; Blitum is in the goosefoot family with tiny clustered flowers.
Frequently asked questions
Is Carduus tenuiflorus native to California?
No. Carduus tenuiflorus is not native to California (recorded as not native).
When does Carduus tenuiflorus bloom?
Carduus tenuiflorus blooms Apr-Jun.
What plant family does Carduus tenuiflorus belong to?
Carduus tenuiflorus is in the Asteraceae family, genus Carduus.
Is Carduus tenuiflorus invasive in California?
Carduus tenuiflorus is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Carduus tenuiflorus grow in?
Carduus tenuiflorus grows in Roadsides, pastures, disturbed areas.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.