Centaurea nigrescens Willd.

Perennials, 30–150 cm. Stems 1–few, erect or ascending, openly branched distally, villous to scabrous with septate hairs and loosely tomentose, ± glabrate. Leaves: basal and proximal cauline, petiolate, blades oblanceolate or elliptic, 5–25 cm, margins entire or shallowly dentate to irregularly pinnately lobed; distal cauline sessile, not decurrent, blades linear to lanceolate, gradually smaller, entire or dentate. Heads radiant or discoid, in few-headed corymbiform arrays, borne on leafy-bracted peduncles. Involucres 15–l8 mm, subcylindric to ovoid or campanulate, usually longer than wide, even when pressed. Principal phyllaries: bodies lanceolate to ovate, loosely tomentose or glabrous, usually not fully covered by narrow appendages, these erect, overlapping, dark brown to black, flat, margins pectinately dissected into 6–8 pairs of wiry lobes. Inner phyllaries: tips truncate, irregularly dentate or lobed. Florets 40–100+, all fertile or peripheral sterile; corollas purple (rarely white), those of sterile florets ± expanded and exceeding corollas of fertile florets, those of fertile florets 15–18 mm. Cypselae tan, 2.5–3 mm, finely hairy; pappi 0 or of many unequal, sometimes caducous bristles 0.5–1 mm. 2n = 22 (Hungary), 44 (Hungary; Italy).

It is a Mediterranean climate plant. In Argentina it grows below 500 m above sea level.