Centaurea (sect. Phaeopappus) Hoffmann 1895

1 Capitula arranged in a raceme; involucres <15 mm wide; appendages entire or irregularly denticulate C. stapfiana

– Capitula solitary; involucres> 15 mm wide; appendages ciliate............................................................................... 2

2 Appendages never decurrent....................................................................................................................................... 3

– Appendages sometimes shortly decurrent on crenate margins................................................................................... 9

3 Median and upper cauline leaves broadly decurrent.................................................................................................. 4

– Median and upper cauline leaves not decurrent.......................................................................................................... 7

4 Flowers purple............................................................................................................................................ C. handelii

– Flowers yellow or white.............................................................................................................................................. 5

5 Median and upper cauline leaves obtuse at apex; upper cauline leaves slightly longer than capitula; involucres ca. 20 mm long.................................................................................................................................................. C. obtusifolia

– Median and upper cauline leaves acute or acuminate at apex; upper cauline leaves almost shorter than capitula; involucres (25–) 30–40 mm long........................................................................................................................................ 6

6 Plant glabrous; basal and lower leaves undivided; spine 3–7 mm long; achenes brown or dark brown and 6–8 mm long; pappus straw-coloured to brownish, 10–14 mm long..................................................................... C. albonitens

– Plant loosely floccose-tomentose; basal and lower leaves lyrate; spine 5–12 mm long; achenes deep purple and 10– 11 mm long; pappus deep violet, 5–7 mm long....................................................................................... C. heratensis

7 Plant 10–25 cm tall; stem erect to ascending or suberect; basal and lower leaves 10–12 cm long; synflorescence 3–4- cephalous; cilia ca. 1 mm long............................................................................................................... C. microlopha

– Plant 30–70(–80) cm tall; stem erect; basal and lower leaves (22–) 26–40 cm long; synflorescence 1(–2)-cephalous; cilia 3–5 mm long....................................................................................................................................................... 8

8 Plant arachnoid-canescent; all leaves undivided; cauline leaves broadly lanceolate to elliptic, obtuse to subacute at apex; appendages straw-coloured to light brown....................................................................................... C. hellwigii

– Plant tomentose-canescent; basal and lower leaves divided; cauline leaves lanceolate or oblong, short acuminate or mucronate at apex; appendages blackish-brown..................................................................................... C. spectabilis

9 Involucres subglobose, 25–35 mm wide............................................................................................... C. farsistanica

– Involucres oblong or ovoid, (17–) 20–25 mm wide.................................................................................................. 10

10 Flowers purple or dark wine-red............................................................................................................................... 11

– Flowers yellow.......................................................................................................................................................... 12

11 Involucres 20–23 mm long; cilia 5–9 on each side; spine 3–5 mm long, brownish or whitish.................... C. assadii

– Involucres 27–32 mm long; cilia 7–15 on each side; spine (3–) 4–8 mm long, dark brown to blackish................................................................................................................................................................................... C. daralagoezica

12 Terminal spine 4–11 mm long; appendages concealing a major part of phyllaries; leaves almost pinnatisect or pinnatipartite.................................................................................................................................................. C. phaeopappa

– Terminal spine 2–5 mm long; appendages only partly concealing the basal part of phyllaries; leaves often simple or with few divisions..................................................................................................................................................... 13

13 Stem erect; basal leaves shorter than stem; upper cauline leaves shorter than capitula; pappus 13–16 mm long.......................................................................................................................................................................... C. indistincta

– Stem arcuate-ascending or suberect, sometimes strongly abbreviated; basal leaves almost longer than stem; upper cauline leaves longer than capitula; pappus ca. 22–24 mm long................................................................. C. aucheri