Annuals or biennials, (30-)50-85 cm; fibrous-rooted. Stems erect or ascending (usually 1, sometimes 2-5), densely and closely white-pannose. Leaves basal and cauline, basal usually withering before flowering, blades oblanceolate to oblanceolate-spatulate, 5-9 cm × 6-18 mm (gradually smaller distally, margins closely undulate, nearly crenulate; distal cauline linear-lanceolate to linear-oblanceolate, apices long-acute; sessile clusters of smaller leaves produced in axils of mid and distal cauline leaves), faces bicolor, abaxial closely white-pannose, adaxial glabrous (shiny). Heads in interrupted, spiciform arrays (8-)16-30 cm × 10-14 mm (pressed; sometimes with ascending, lateral branches, glomerules usually subtended by ± patent linear bracts longer than the glomerules). Involucres cylindro-campanulate, 3-3.5 mm, bases glabrous. Phyllaries in 4-6 series, outer ovate to oblong, lengths ¹/3-¹/2 inner, apices acute-acuminate, inner narrowly oblong, laminae brownish to tan (not purplish), apices acuminate-apiculate. Florets: bisexual (2-)3; all corollas yellowish distally. Cypselae (tan) 0.5-0.6 mm.

Flowering (Jun-)Jul-Aug(-Oct). Open sites, sandy soil, roadsides, fields, open woods, dunes; 0-10 m; introduced; Ala., Fla., Ga., N.C., S.C.; South America; naturalized in New Zealand, Australia, Java.

Gamochaeta simplicicaulis was reported from North America by G. L. Nesom (1999b, 2000b) as an apparently recent adventive.