Perennial giant-rosette plants to 10 m tall with woody trunks; typically upright and polycarpic, with branching initiated below each terminal inflorescence, sometimes monocarpic or creeping; primary stem 2–12 cm wide, comprised mainly of pith, which provides internal water capacitance; secondary growth produces abundant white wood and a grey, furrowed bark. Seedlings and young plants with leaves commonly constricted toward the base, forming a pseudo-petiole, particularly when growing in partial shade. Developing leaves of mature plants revolutely folded, the upper lamina glabrescent; commonly bathed in mucilage, an ice-nucleating pectinaceous material that in some species is secreted among the leaf bases and may collect in the leaf-rosette. Leaves alternate (although appearing whorled in densely packed leaf-rosettes), to 120 cm long and 35 cm wide, simple, in rosettes of 10–100, with developing leaves often reaching almost mature length in a massive ‘apical bud’ before unfurling to join the leaf-rosette; leaf base wide, sheathing, often with a dense cushion of white trichomes on the upper surface; leaf margin occasionally entire, but usually serrate or dentate, tipped with hydathodes; indumentum of lower lamina comprising multicellular, uniseriate trichomes, variable among species, but generally villose along the lower midvein. Inflorescence to 2.5 m tall, erect, pyramidal-paniculate or cylindrical, densely pubescent to glabrescent; bracteate, with a range of transitional shapes from the mature vegetative leaves subtending the peduncle to the small bracts subtending each capitulum; capitula numerous, with biseriate involucral bracts; outer bracts 5–23, filiform, 5–18 mm long; inner bracts 10–25, narrow to broadly ovate, 11–16 x 2–6 mm, with apical papillae; receptacle nude. Ray florets absent or 6–20, yellow, female, with staminodes sometimes present, ray 2–23 x 2–5 mm; tube 4–8 mm long. Disc florets 30–380, yellow, hermaphrodite, 8–10 mm long; style with a continuous stigmatic surface; anthers non-auriculate, filament collars balusteriform. Achenes glabrous, 8–10-ribbed; pappus of many bristles.
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