Beautiful Fleabane

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.

Erigeron formosissimus is a North American species of flowering plants in the family Asteraceae known by the common name beautiful fleabane.

Erigeron formosissimus is native to the western United States. It has been found in Arizona, New Mexico, Utah, Colorado, Wyoming, the Black Hills of South Dakota, eastern Idaho, and southern Montana.

Erigeron formosissimus is a perennial herb up to 55 centimeters (22 inches) in height, spreading by means of underground rhizomes. It produces 1-6 flower heads per stem, each head as many as 150 white, pink, purple, or blue ray florets surrounding numerous yellow disc florets.

Varieties Erigeron formosissimus var. viscidus (Rydberg) Cronquist - Arizona, Colorado, New Mexico, South Dakota, Wyoming Erigeron formosissimus var. formosissimus - Arizona, Colorado, New Mexico, South Dakota, Utah