Centaurea solstitialis
Yellow star-thistle, Yellow Star-Thistle
Family: Asteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Centaurea solstitialis (Yellow star-thistle) is a non-native California herb in the Asteraceae family, recognized by yellow flowers with long stout spines (10-25mm) and winged stems.
Yellow star-thistle is a naturalized annual found in California's coastal foothills, Mediterranean province, and western Mojave Desert in disturbed grasslands, roadsides, and woodlands at elevations below 1,300 meters. Flowering from May to October, this invasive plant produces distinctive yellow flowers in spiny, straw-colored heads with central spines 10 to 25 millimeters long. Growing 1 to 10 decimeters tall with a rounded, bushy form, the plant has gray-tomentose stems that are winged and branched throughout. Its lower leaves are deeply lobed or dissected, often withering by flowering time, while upper leaves are linear and long-decurrent with bristly undersides. The fruit is small, 2 to 3 millimeters long, with dark brown outer seeds and fine white pappus bristles.
Identification and appearance
Key characters: 15 sympatric species; yellow flowers with long stout spines (10-25mm) and winged stems are diagnostic
Habitat and range
Habitat: Invasive, roadsides, disturbed grassland or woodland
Elevation: < 1300 m
Outside California: native to southern Europe
Bloom period
Centaurea solstitialis blooms May-Oct.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Cirsium: Cirsium bracts taper to simple spines; Centaurea bract tips expanded with fringed/toothed edges; vs Carduus: Carduus bracts spine-tipped but not fringed; Centaurea bract appendages distinctly fringed or toothed; vs Jacobaea: Jacobaea has obvious yellow ray flowers; Centaurea lacks true rays (all tubular flowers); vs Silybum: Silybum has white-veined leaves and simple spine-tipped bracts; Centaurea bracts ornately fringed; vs Eriophorum: Eriophorum is a sedge with grass-like leaves and cottony heads; Centaurea is a branched herb
Frequently asked questions
Is Centaurea solstitialis native to California?
No. Centaurea solstitialis is not native to California (recorded as not native).
When does Centaurea solstitialis bloom?
Centaurea solstitialis blooms May-Oct.
What plant family does Centaurea solstitialis belong to?
Centaurea solstitialis is in the Asteraceae family, genus Centaurea.
Is Centaurea solstitialis invasive in California?
Centaurea solstitialis is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Centaurea solstitialis grow in?
Centaurea solstitialis grows in Invasive, roadsides, disturbed grassland or woodland.
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.