Onopordum illyricum
Illyrian thistle
(c) Zac Peterson, some rights reserved (CC BY), uploaded by Zac Peterson · licence
Family: Asteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Onopordum illyricum (Illyrian thistle) is a non-native California herb in the Asteraceae family, recognized by geographic restriction, leaf dissection, flower size, and pappus color.
Illyrian thistle is a naturalized biennial found in southern San Francisco Bay disturbed sites at elevations below 500 meters. Flowering from June to July, this plant produces striking purple flowers with glandular-puberulent lobes in large heads up to 25 decimeters tall. Growing with a canescent-tomentose appearance, the plant has deeply pinnately lobed leaves with 8 to 10 pairs of triangular lobes. Its extensive leaves can reach 1 to 5 decimeters long, creating a dramatic silvery-gray architectural form with spiny, intricate leaf edges. The fruit is small, approximately 4 to 5 millimeters long, with a white pappus 10 to 12 millimeters in length.
Identification and appearance
Key characters: 1 sympatric species; key features are geographic restriction, leaf dissection, flower size, and pappus color
Habitat and range
Habitat: Disturbed sites
Elevation: < 500 m
Outside California: native to southeastern Europe
Bloom period
Onopordum illyricum blooms Jun-Jul.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Cirsium: Native and other thistles have a receptacle densely covered with soft bristly hairs; Onopordum's receptacle is naked and honeycombed (pitted), without bristles.; vs Carduus: Carduus has a bristly receptacle and a pappus of simple barbed hairs; Onopordum has a naked fleshy receptacle and a broadly gray-cottony plant with spiny-winged stems.; vs Silybum: Milk thistle has shiny green leaves boldly marbled with white veins; Onopordum leaves are uniformly gray-woolly, not marbled.; vs Arctium: Burdock heads have hooked, burr-forming phyllaries and broad unspined leaves; Onopordum has straight spine-tipped phyllaries and spiny gray leaves.; vs Centaurea: Star-thistles have leathery spine-tipped phyllaries but soft, unspined leaf blades; Onopordum has broad continuous spiny wings running down the stem and cottony spiny leaves.
Frequently asked questions
Is Onopordum illyricum native to California?
No. Onopordum illyricum is not native to California (recorded as not native).
When does Onopordum illyricum bloom?
Onopordum illyricum blooms Jun-Jul.
What plant family does Onopordum illyricum belong to?
Onopordum illyricum is in the Asteraceae family, genus Onopordum.
Is Onopordum illyricum invasive in California?
Onopordum illyricum is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Onopordum illyricum grow in?
Onopordum illyricum grows in Disturbed sites.
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.