Perennials, 20–80 cm, colonial; long-rhizomatous. Stems 1–5+, ascending to erect, glabrous or sparsely puberulent. Leaves thin, margins entire, apices acute, faces glabrous or sparsely puberulent; basal persistent, petiolate, blades narrowly elliptic to obovate, 50–150 × 3–15 mm, attenuate, margins entire; proximal cauline sessile or subpetiolate, blades linear to narrowly elliptic, 50–150 × 2–15 mm, bases attenuate or cuneate; distal sessile, blades 30–60 × 2–10 mm, reduced distally, bases cuneate to rounded. Heads in corymbiform to paniculiform arrays, branches usually few. Peduncles sparsely hairy, bracts 0–3+. Involucres campanulate, 5–10 mm. Phyllaries in 3–5 series, narrowly oblong or linear (outer) to linear (inner), unequal, bases indurate, margins entire, green zones elliptic to lanceolate, apices usually acute, sometimes obtuse, faces glabrous or ± puberulent. Ray florets 15–40; corollas violet, laminae 9–15 × 1–2 mm. Disc florets 30-80(–100); corollas yellow, sometimes becoming reddish, 4.5–6 mm, lobes triangular, 0.5–1 mm. Cypselae brown, cylindric to obovoid, not compressed, 2.5–3.5 mm, ± 4-nerved, faces hairy; pappi whitish, 5–7 mm.
Alta., B.C., N.W.T., Calif., Colo., Idaho, Mont., N.Mex., Nev., Oreg., Utah, Wash., Wyo., nw Mexico.
Varieties 3 (3 in the flora).
Symphyotrichum spathulatum is a variable species, widespread in montane regions of western North America. It hybridizes with S. bracteolatum, S. foliaceum, and S. hendersonii.