Description: Annual, biennial or perennial herbs.
Leaves basal or cauline, alternate, entire to pinnatisect.
Heads solitary or in groups of 2 or 3, terminal, sessile or pedunculate, ovoid; involucral bracts multiseriate, unequal, herbaceous, with a scarious or hard comb-like or spiny appendage (absent from innermost bracts); receptacle ± flat, hairy. Florets all tubular, outer sterile, inner bisexual and fertile; corolla with 5 long narrow lobes, those of outer florets often larger, more brightly coloured and spreading. Anthers caudate at base, apical appendage narrow. Style with thickened, often pubescent ring, branches appressed.
Achenes oblong, compressed, asymmetric; pappus 2–many rows of scales or bristles, often reduced or absent.
Distribution and occurrence: World: 500–600 species, Mediterranean region, India, China, North & South America; almost cosmopolitan weed. Australia: 6 species (naturalized), all States except N.T.
Text by L. Murray
Taxon concept:
Taxa not yet included in identification key
Centaurea benedicta,
Centaurea sp. A sensu Murray (1992),
Centaurea stoebe,
Centaurea x moncktonii
| | Key to the species | |
| 1 | Spines on involucral bracts | 2 |
| Spines absent from involucral bracts, appendages of involucral bracts fringed | 5 |
| 2 | Spines on bracts stout, 5–15 mm long | 3 |
| Spines on bracts not stout, usually less than 5 mm long
Back to 1 | 4 |
| 3 | Leaves and stems dark green with coarse, stiff, septate hairs; flowers purple | Centaurea calcitrapa |
| Leaves and stems greyish with long, soft, fine, cobwebby, simple hairs; flowers yellow
Back to 2 | Centaurea solstitialis |
| 4 | Upper cauline leaves lobed; small lateral spines either side of apical spine on bracts; flowers purple | Centaurea species A |
| Upper cauline leaves entire to toothed; small basal spines either side of apical spine on bracts; flowers yellow
Back to 2 | Centaurea melitensis |
| 5 | Appendage margins dissected into short broad teeth, usually brown and darker than the lamina, not obscuring the bract above | Centaurea cyanus |
| Appendage with fine ciliate long margins, as dark or lighter than the lamina, usually covering the base of the bract above
Back to 1 | Centaurea species B |
|
