Onopordum

Linnaeus

Sp. Pl. 2: 827. 1753

,

Gen. Pl. ed. 5, 359. 1754

Common names: Cotton thistle onoporde
Etymology: Greek onopordon, name for cotton thistle
Treatment appears in FNA Volume 19. Treatment on page 87. Mentioned on page 57, 66, 83, 96.
Biennials, 50–400+ cm, coarse, prickly. Stems usually erect, ± branched, spiny-winged. Leaves basal and cauline; winged-petiolate (basal) or sessile (cauline); blade bases narrowing, margins pinnately lobed or divided and dentate, teeth and lobes tipped with stout spines. Heads discoid, borne singly or in corymbiform arrays; (peduncles 0 or spiny winged). Involucres hemispheric to ovoid or spheric. Phyllaries many in 8–10+ series, linear to ovate, entire, tapered to stiff spines, middle and outer often spreading or reflexed. Receptacles flat to convex, epaleate, not bristly, alveolate with apically fringed pits. Florets many; corollas white or purple, actinomorphic or weakly zygmorphic, tubes slender, throats cylindric or narrowly goblet-shaped, lobes linear; anther bases acute-tailed, apical appendages subulate; style branches: fused portions with minutely hairy nodes, long, cylindric, minutely papillate, distinct portions minute. Cypselae ± cylindric, 4–5-angled, usually ± transversely roughened, glabrous, attachment scars basal; pappi falling in ring, of many barbed or plumose bristles, basally connate. x = 17.

Discussion

Species 25–60 (3 in the flora).

Key

1 Herbage green, ± sticky-glandular Onopordum tauricum
1 Herbage ± canescent-tomentose > 2
2 Leaves dentate to shallowly pinnatifid; phyllaries linear, bases 2–2.5 mm wide. Onopordum acanthium
2 Leaves shallowly to ± deeply 1–2 pinnatifid; phyllaries lanceolate to ovate, bases 3–8 mm wide Onopordum illyricum