Centaurea virgata subsp. squarrosa
Family: Asteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Centaurea virgata subsp. squarrosa is a non-native California herb in the Asteraceae family, recognized by higher elevation (900-1400m), small cylindric heads (7-8mm), and short spines distinguish it.
Squarrose knapweed is a naturalized perennial herb found in the Klamath Ranges, northern California Ranges, northern Sierra Nevada, and Modoc Plateau in disturbed places at elevations of 900 to 1,400 meters. Flowering from June to September, this plant produces pink or pale purple flowers in disciform heads with pale green to straw-colored involucres fringed with delicate spines. Growing with much-branched stems 20 to 50 centimeters tall that emerge from a single base, it develops a loosely tomentose and scabrous appearance. Its lower leaves are deeply 1 to 2 times lobed and up to 15 centimeters long, often absent by flowering time, while upper leaves tend to be entire or shallowly lobed. The fruit develops as a light brown achene approximately 3 millimeters long, topped with short white pappus bristles.
Identification and appearance
Key characters: 10 sympatric species; higher elevation (900-1400m), small cylindric heads (7-8mm), and short spines distinguish it
Habitat and range
Habitat: Disturbed places
Elevation: 900-1400 m
Outside California: native to Asia
Bloom period
Centaurea virgata subsp. squarrosa blooms Jun-Sep.
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 virgata subsp. squarrosa native to California?
No. Centaurea virgata subsp. squarrosa is not native to California (recorded as not native).
When does Centaurea virgata subsp. squarrosa bloom?
Centaurea virgata subsp. squarrosa blooms Jun-Sep.
What plant family does Centaurea virgata subsp. squarrosa belong to?
Centaurea virgata subsp. squarrosa is in the Asteraceae family, genus Centaurea.
Is Centaurea virgata subsp. squarrosa invasive in California?
Centaurea virgata subsp. squarrosa is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Centaurea virgata subsp. squarrosa grow in?
Centaurea virgata subsp. squarrosa grows in Disturbed places.
Related species
Other California species in the same genus, family, or bioregion.
- Centaurea benedicta — Blessed thistle
- Centaurea calcitrapa — Purple star-thistle
- Centaurea cineraria — Dusty miller
- Centaurea cyanus — Bachelor's button
- Centaurea diffusa — Diffuse knapweed
- Centaurea diluta — North african knapweed
- Centromadia fitchii — Spikeweed
- Centromadia parryi — Pappose tarweed
- Centromadia parryi subsp. australis — Southern tarplant
- Centromadia parryi subsp. congdonii — Congdon's tarplant
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.