Erigeron formosissimus Greene

Variation in vestiture of Erigeron formosissimus is complex, ranging from stems and heads glabrous and densely stipitate-glandular to stems and heads densely hairy and essentially eglandular; intermediates are found over the range of the species. The taxonomic solution of recognizing broadly sympatric varieties within a single species is biologically untenable, and some have treated this as a single entity; the variation is greater than typically occurs within a single species of Erigeron (see comments following 3. E. neomexicanus, where the situation with E. oreophilus is similar).

Perennials, 10–40(–55) cm; rhizomatous, fibrous-rooted, rhizomes variably thick. Stems ascending, densely hirsute to hirsutulous or glabrous, minutely glandular to stipitate-glandular. Leaves basal (persistent) and cauline; basal blades oblanceolate to oblanceolate-spatulate, 20–100(–150) × 4–10(–15) mm, margins entire, closely ciliate, faces glabrous or sparsely hirsute, sometimes sparsely glandular; cauline blades becoming ovate to lanceolate, gradually reduced distally (bases clasping). Heads 1–6. Involucres 5–8 × 10–20 mm. Phyllaries in 2–3 series (greenish), glabrous or hirsuto-villous, densely minutely glandular to stipitate-glandular (glands sometimes obscured by hairs in var. formosissimus). Ray florets 75–150; corollas blue to purple, rarely pink to white, 8–15 mm (ca. 1 mm wide), laminae coiling at tips or not at all. Disc corollas 3.5–4.5 mm. Cypselae (1.3–)1.6–1.9 mm, 2-nerved, faces sparsely strigose; pappi: outer of setae, inner of 15–25 bristles.