Flora of North America species comparison

Gamochaeta calviceps is recognized by its subpannose cauline and foliar indument (perhaps intermediate between the looser tomentum of G. antillana and the tight, pannose covering of G. argyrinea) and the contrast of its spatulate proximal leaves with the much narrower cauline ones, glabrous or glabrescent involucres, and phyllaries in 5–7 series, lacking purple color, the outer and mid with acute-acuminate apices commonly becoming subulate (by inrolled margins). The distal cauline leaves usually are folded along the midveins (at least when pressed). The relatively late flowering also is distinctive. Plants on the Atlantic coastal plain usually produce 2–3 bisexual florets per head, those on the Gulf coast 3–4.

Heads of older plants are borne in paniculiform arrays resulting from development of lateral branches, the heads usually on evident peduncles and with very little tomentum at the base of the outer phyllaries, thus appearing discrete. In early-season plants, lateral branches may not have formed or lengthened and the arrays of heads may appear continuous-cylindric at stem apices; in such plants, the species can usually still be recognized by the relatively numerous, relatively shorter, axillary shoots along the main stems.

(Discussion copyrighted by Flora of North America; reprinted with permission.)