Centaurea jacea subsp. nigra
Black knapweed, Black Knapweed
(c) Douglas Goldman, some rights reserved (CC BY-SA), uploaded by Douglas Goldman · licence
Family: Asteraceae · Type: Perennial · Not Native
Centaurea jacea subsp. nigra (Black knapweed) is a non-native California perennial in the Asteraceae family, recognized by dark brown-black fringed appendages, discoid heads, and swollen peduncles.
Black knapweed is a naturalized perennial found in northern California coastal regions, Klamath Ranges, northern Coast Ranges, and California Ranges in disturbed places at elevations below 600 meters. Flowering from August to November, this plant produces purple flowers in distinctive heads with dark brown to black fringed phyllary tips. Growing with erect stems that develop swollen peduncles just below each flower head, it forms dense clusters in open areas. Its leaves are lanceolate, creating a complex texture across the plant's structure. The flower heads feature disk flowers measuring 15 to 18 millimeters long, with intricate dark brown to black appendages that create a striking visual contrast.
Identification and appearance
Key characters: 11 sympatric species; dark brown-black fringed appendages, discoid heads, and swollen peduncles are diagnostic
Habitat and range
Habitat: Disturbed places
Elevation: < 600 m
Outside California: to southern Canada, eastern United States, native to Europe
Bloom period
Centaurea jacea subsp. nigra blooms Aug-Nov.
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 jacea subsp. nigra native to California?
No. Centaurea jacea subsp. nigra is not native to California (recorded as not native).
When does Centaurea jacea subsp. nigra bloom?
Centaurea jacea subsp. nigra blooms Aug-Nov.
What plant family does Centaurea jacea subsp. nigra belong to?
Centaurea jacea subsp. nigra is in the Asteraceae family, genus Centaurea.
What habitat does Centaurea jacea subsp. nigra grow in?
Centaurea jacea subsp. nigra grows in Disturbed places.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.