Yellow or white florets in rather small heads in a wide diffuse panicle.
An erect herb up to about 6 ft. high
Achenes dark-brown, c. 4.5 mm. long including a distinct 1 mm. long beak, c. 1.25 mm. wide, fusiform, 3–4-angled, 1-several-ribbed between the angles, minutely hispidulous; beak slender, discolorous; pappus several-seriate of white barbellate setae c. 5 mm. long.
Corollas 10–12.5 mm. long, blue to purplish; tube c. 5 mm. long, narrowly cylindric, sparsely setulose about the outside of the throat; ligule c. 6.5 mm. long, oblanceolate-lorate, lobes c. 1 mm. long, apically papillose.
Phyllaries 4–5-seriate, purplish, glabrous, ciliolate above; the outermost c. 1.5 mm. long, ovate; the innermost up to c. 12 mm. long, lorate-lanceolate, obtuse to acute.
Capitula numerous stalked; involucres 6–8 mm. long at time of flowering, increasing to c. 12 mm. in fruiting capitula, cylindric to very narrowly campanulate.
Synflorescence elongate-paniculate; branches short, patent and much thinner than the stem axis, sparsely glandular setulose, bracteate; bracts foliaceous.
Leaves cauline somewhat crowded below; the lowermost up to c. 32 x 12 cm., elliptic-lanceolate in outline, grossly lyrate-runcinate, apices acute to obtuse, bases cuneate-attenuate with midrib ± narrowly winged petiole-like and semi-amplexicaul, denticulate on the margins, glabrous or sparsely setose particularly on the midrib and main nerves beneath; the upper leaves decreasing in size towards the stem apex, becoming lanceolate, undivided and sessile, ± sparsely setose.
An erect long-lived giant annual herb, up to 3(3.5) m. tall.
Taproot with several thick ± fleshy lateral roots.
Stem solitary simple up to c. 1.5 cm. in diam., striately ribbed hollow glaucous, sparsely setose below, glabrous above.