150. Erigeron gracilis Rydberg, Mem. New York Bot. Gard. 1: 404. 1900.
Erigeron ursinus D. C. Eaton var. gracilis (Rydberg) A. Nelson
Perennials, 5–20 cm; rhizomatous, fibrous-rooted, forming diffuse systems of slender, rhizomelike caudex branches. Stems ascending (bases usually purplish), glabrous or sparsely strigose (or hairs loosely spreading), eglandular. Leaves basal (persistent) and cauline; basal (purplish) and proximal cauline blades oblanceolate to oblong, 20–40(–90) × 1–3(–5) mm, cauline reduced distally, margins entire, glabrous or sparsely strigose (or hairs loosely spreading), eglandular. Heads 1. Involucres 5–7.5 × 10–15 mm. Phyllaries in 2–3(–4) series (margins and tips often purplish, loose, linear-lanceolate, apices spreading), sparsely strigoso-hirsute to strigose (hairs appressed or slightly loose), sometimes minutely glandular. Ray florets 40–100; corollas blue to pinkish purple, 7–14 mm, laminae not coiling or reflexing. Disc corollas 4.1–5.6 mm. Cypselae 2 mm, 2-nerved, faces sparsely strigose; pappi: outer of setae, inner of 14–21 bristles. 2n = 18.
Flowering Jun–Aug. Moist slopes, creek bottoms, sagebrush meadows; 2200–2400 m; Idaho, Mont., Wyo.
Erigeron gracilis "differs from E. ursinus in the strigose and scarcely glandular pubescence of the involucre, narrower and less herbaceous phyllaries, narrower and on the average longer disc-corollas, simple or nearly simple pappus, narrower ligules, on the average, and ordinarily narrower and slightly hairier leaves. E. gracilis grows at lower elevations than E. ursinus, in a drier habitat, and has a much more restricted range" (A. Cronquist 1947, p. 162). The two species are sympatric in northwestern Wyoming.