E-Flora BC: Electronic Atlas of the Flora of British Columbia

Centaurea diffusa Lam.
diffuse knapweed
Asteraceae (Aster family)

Introduction to Vascular Plants

© Bryan Kelly-McArthur  Email the photographer   (Photo ID #72692)

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Distribution of Centaurea diffusa
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Species Information

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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.

Source: The Illustrated Flora of British Columbia

Habitat / 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.

Source: The Illustrated Flora of British Columbia


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) 260 603 1772
Slope Gradient (%) 0 23 80
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 204 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 2 5
Modal Nutrient Regime
Number 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)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Acosta diffusa (Lam.) Soják

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References