Annuals, 6-40 cm; taprooted. Stems erect to decumbent-ascending, loosely arachnose-tomentose. Leaves basal and cauline, basal usually withering before flowering, blades spatulate to oblanceolate, narrowly lanceolate, linear-oblanceolate, or linear, 2-3(-4) cm × 2-3.5(-5) mm (distal rarely folded along midveins), faces concolor, loosely tomentose. Heads initially in uninterrupted, cylindro-spiciform arrays (1-)3-4(-10) cm × 8-12 mm (pressed), usually becoming glomerulate-interrupted in late flowering (equally leafy-bracted throughout, bracts linear to narrowly lanceolate, smaller distally). Involucres campanulate, 2.5-3 mm, bases sparsely arachnose. Phyllaries in 3-4(-5) series, outer ovate-lanceolate, lengths ¹/2-²/3 inner, apices (sometimes purplish-tinged) narrowly to broadly acute, inner usually purple (immediately beyond stereome and along proximal margins), oblong, laminae usually purple (at stereome and along proximal margins), apices (whitish, tinged with brown) rounded-obtuse. Florets: bisexual 3-5; all corollas usually purple distally. Cypselae (tan) 0.4-0.5 mm.

Flowering (Feb-)Mar-May, sometimes later with moisture. Open sites in sandy soils, commonly in roadsides and other disturbed sites, stream and pond banks; 10-100 m; Ala., Ark., Fla., Ga., La., Miss., N.C., Okla., S.C., Tenn., Tex., Va.; South America; Europe; New Zealand.

Gamochaeta antillana and G. calviceps have been combined in concept and often misidentified as Gamochaeta falcata (Lamarck) Cabrera; the latter name applies to a South American species that has not been recorded from the flora area. Gamochaeta subfalcata, which has been attributed to the United States (e.g., S. E. Freire and L. Iharlegui 1997), almost certainly applies to the same species as G. antillana.