54. Symphyotrichum welshii (Cronquist) G. L. Nesom, Phytologia. 77: 294. 1995.
Aster welshii Cronquist in A. Cronquist et al., Intermount. Fl. 5: 291, fig. p. 293. 1994
Perennials, 30–100 cm colonial; rhizomes shallow and long, often relatively thick (those of the season each producing a distal rosette near the parent plant). Stems 1–2, ascending to erect (sometimes lax, sometimes reddish), glabrous or sparsely strigoso-villosulous distally (arrays). Leaves (adaxially green, abaxially pale green, sometimes glaucous) thin (proximal) to stiff (distal), margins serrulate (proximal) or entire or nearly so, ± revolute, scabrous, apices mucronulate or sometimes callous-pointed, faces glabrous; basal withering by flowering, petiolate (petioles narrowly winged, sheathing), blades oblanceolate to spatulate, 10–40+ × 4–9+ mm, bases attenuate, margins entire, apices obtuse; proximal cauline withering by flowering, sessile or winged-petiolate, blades lanceolate to oblanceolate, 50–150 × 8–11 mm, bases slightly clasping, margins sparsely serrulate, apices acute; distal sessile, blades linear to linear-lanceolate, 50–130 × 4–6 mm, gradually reduced distally, bases ± clasping, apices acute. Heads in open, slender, leafy, paniculiform or racemiform arrays, branches ascending. Peduncles 0.5–2 cm, scabro-villosulous, bracts linear, scabro-ciliolate. Involucres cylindro-campanulate, 4–7 mm. Phyllaries in 3–4 series, lanceolate (outer) to linear (inner), ± unequal, bases indurate, margins hyaline, erose, distally scabro-ciliolate to ciliolate, green zones ± foliaceous (outer) or lanceolate, apices acute to acuminate, sometimes purplish, faces glabrous. Ray florets 18–25; corollas pink to white, laminae 9–12 × 0.8–1.5 mm. Disc florets 23–60; corollas pale yellow, 3.8–6.4 mm, tubes shorter than funnelform throats, lobes narrowly triangular, 0.4–0.8 mm. Cypselae pinkish tan (nerves stramineous), obovoid, ± compressed, 0.8–1.6 mm, 3–5-nerved, faces sparsely strigillose; pappi white, 2.8–5.3 mm. 2n = 16.
Flowering Aug–Oct. Wet soils in dry areas, hanging gardens, seeps, wet ledges, stream banks; of conservation concern; 1300–2300 m; Ariz., Idaho, Mont., Utah, Wyo.