Centaurea diffusa Lam.
diffuse knapweed
Asteraceae (Aster family)

Introduction to Vascular Plants


© Bryan Kelly-McArthur     (Photo ID #72692)


E-Flora BC Static Map

Distribution of Centaurea diffusa
Click here to view the full interactive map and legend

Species Information

Annual, biennial or short-lived perennial herb from a taproot; stems erect, branched, sparsely hairy, 10-60 cm tall.
Basal leaves pinnately divided into linear segments, broadly lanceolate in outline, 3.5-20 cm long, 0.5-3.5 cm wide, grey-green, lightly dense-hairy, soon deciduous; stem leaves similar, reduced upwards.
Heads discoid, numerous, solitary at the end of diffuse branches; disk flowers usually creamish, sometimes purplish or pinkish; involucres 8-10 mm tall; involucral bracts broadly lanceolate, leathery, glabrous, with weak spines on the margins, the tips with 1.5-4 mm long spines.
Achenes glabrous; pappus lacking or of minute bristles up to 1 mm long.

SourceThe Illustrated Flora of British Columbia


If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.


Ecological Framework for Centaurea diffusa

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres)
603 260 1772
Slope Gradient (%)
23 0 80

Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]

204 0 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
2 0 5
Modal Nutrient Regime
# of field plots
 species was recorded in:
Modal BEC Zone Class

All BEC Zones (# of stations/zone) species was recorded in

BG(62), ICH(9), IDF(58), PP(75)

Habitat and Range

Dry roadsides, disturbed areas, overgrazed grasslands and shrublands in the steppe and lower montane zones; common in S BC east of the Coast-Cascade Mountains; introduced from the E Mediterranean region.

SourceThe Illustrated Flora of British Columbia


Synonyms and Alternate Names:
Acosta diffusa (Lam.) Soják