Perennial, rhizomatous,  0.3 – 1.5  m tall herb with glabrous branches from base or above. Leaves undivided to pinnatifid to pinnatipartite, basal and lower  linear-oblanceolate to elliptic, 5 – 25 (-30)   x (1.5-) 2 – 5 (-6)  cm, glabrous,  basally with  rounded, clasping auricles, margins denticulate-mucronate, lateral lobes, when present, 2-5 pairs, lanceolate or triangular-ovate, terminal lobe large, ovate-elliptic; median and upper stem leaves gradually smaller, elliptic-lanceolate, hairy when young. Capitula  180-300-flowered,  2.5 – 4  cm across, on slender, apically  glandular hairy and tomentose peduncles, borne in corymbose synflorescence. Involucre narrowly to broadly campanulate, 1.2 – 1.5 cm long, slightly white tomentose and glandulose below.  Phyllaries 41, all membranous-margined, 3-seriate, densely white tomentose outside, outer ones  lanceolate, 4 – 6 x  c. 1.25 mm, acute, inner phyllaries lanceolate to linear-oblong, 8 – 10 x 1.5 – 2 mm, acuminate at apices. Florets with 7 – 8 mm long, hairy corolla tube and  3.5 – 5  mm long, 5-toothed, ligules yellow. Cypselas  slightly compressed, ellipsoid, (2.5-) 3 – 4  mm long, inconspicuously  5- ribbed on each side, transversely rugose, pale-brownish. Pappus white,  6 – 7.5  (-8.5) mm long, ± persistent.

Sonchus wightianus DC. is well differentiated into 2 subspecies on the basis of the presence or absence of gland-tipped hairs on involucral phyllaries and peduncles.