Sketch Bot. S. Carolina 2: 323. 1823.
Perennials, 20–150 cm; usually rhizomatous and/or lignescent-tuberous-rooted. Stems erect, simple, internodes winged (by decurrent leaf bases), lanate-tomentose and/or glandular. Leaves cauline, alternate; sessile; blades linear to elliptic or obovate, bases decurrent, margins usually serrate to serrulate or denticulate, rarely entire, abaxial faces densely whitish-tomentose [puberulent or glabrescent], adaxial (green) glabrous or glabrescent, both faces usually stipitate- or sessile-glandular. Heads disciform, (sessile) in spiciform arrays (at ends of branches). Involucres cylindro-campanulate to campanulate, 2–3[–5] mm diam. Phyllaries persistent, in 4–6 series, distinct, narrowly lanceolate, unequal (subindurate to scarious). Receptacles flat, epaleate. Ray florets 0. Peripheral (pistillate) florets in 1–3+ series, fertile; corollas yellowish. Inner (functionally staminate [bisexual]) florets [1–]2–15[+]; corollas yellowish, lobes 5. Cypselae cylindric to fusiform, angled or slightly compressed, ribs 6–9 (white, narrow), faces usually sparsely strigose to hispidulous, minutely sessile-glandular between ribs; pappi persistent, of distinct, barbellulate bristles in 1–2 series. x = 10.
North America, South America, Australasia.
Species 17 (2 in the flora).
The 11 primarily South American species of Pterocaulon sect. Pterocaulon have 1–17 functionally staminate florets per head, 1–2-seriate pappi, and hairs of tomentum with the relatively long, aseptate portion arising from clusters of basal cells. The 6 Australasian species of sect. Monenteles (Labillardière) Cabrera have a single functionally staminate floret per head, uniseriate pappi, and hairs of the tomentum equally septate throughout.
|1||Heads in dense, usually continuous, rarely interrupted, narrow, ± ovoid arrays (2–)3–8(–10) cm (axes completely hidden by crowded heads); lengths of leaf blades mostly 2–7 times widths; functionally staminate florets 6–10(–15); flowering May–Jun; Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina||Pterocaulon pycnostachyum|
|1||Heads in open, ± interrupted, ± cylindric arrays (5–)8–20 cm (main axes visible between glomerules of heads); lengths of leaf blades mostly 6–8 times widths; functionally staminate florets 2–4(–5); flowering Aug–Oct; Louisiana, Texas||Pterocaulon virgatum|