R. Hand, Supplementary notes to the flora of Cyprus VII. in Willdenowia 41. 2011R. D. Meikle, Flora of Cyprus 2. 1985T. Georgiadis & G. Chatzikyriakou, Centaurea akamantis (Compositae), a new species from Cyprus in Willdenowia 23. 1993
1Florets yellow
1'Florets purple, pink or white
2Outer phyllaries with purple spinule; plant arachnoid-villose
2'Outer phyllaries with stiff spine(s); plant thinly pilose, glandular or glabrescent
3Stems winged with decurrent leaf-bases; involucral spines slender
3'Stems not winged; involucral spines stout, rigid
4Involucre conspicuously spinose
4'Involucre unarmed or phyllaries with a very short apical spinule
5Pappus present; involucre width 10-15 mm
5'Pappus lacking; involucre width 3.5-8 mm
6Involucre width 6-7(-8) mm
6'Involucre width 3.5-5(-5.5) mm
7Annuals with conspicuously radiant, bright blue marginal florets; pappus lacking
7'Perennials with thick taproots; marginal florets pink or mauve or conspicuous marginal florets lacking; pappus present
8Acaulescent perennial with very short stems, often stems lacking, but rarely up to 20 cm long; capitula solitary or in subsessile clusters of 4-6
8'Perennial with numerous stems and capitula
9Stem erect; no marginal, radiant florets; ciliate appendages of phyllaries about as long as undivided central part
9'Stem prostrate or drooping (chasmophyte); with conspicuous marginal, radiant florets; ciliate appendages of phyllaries much shorter than undivided central part
10Leaves finely pinnatisect; phyllaries with inconspicuously ciliate appendages; pappus 3-4(-5) mm long
10'Basal leaves lyrate, cauline leaves spathulate to denticulate or lobed; phyllaries with well-developed cilia; pappus up to 2 mm long