Perennials, 40–250 cm, colonial; long-rhizomatous. Stems 1, erect (straight, ± thin, 2–8 mm diam at base, ± ribbed, red above each node), glabrous or glabrate (very sparsely hispidulous) proximally to ± hispidulous distally. Leaves (crowded, light green, shiny) firm, margins crenulate-serrate or entire, revolute, apices acute to acuminate, mucronate, abaxial faces glabrous or midveins sometimes with hairs apically, adaxial glabrous; basal withering by flowering, subpetiolate (petioles dilated, winged, sheathing), blades spatulate to oblanceolate, 30–100+ × 3–20+ mm, bases attenuate to cuneate, margins remotely crenate-serrate to subentire, apices acute to rounded; proximal cauline withering by flowering, sessile or subpetiolate (petioles widely winged, clasping), blades oblanceolate, 50–150 × 20–30 mm, greatly reduced distally, bases auriculate, clasping, apices acute to acuminate; distal sessile, blades lanceolate to lance-elliptic to oblanceolate, 40–70 × 10–25 mm, little reduced distally, bases auriculate, clasping, margins entire, apices acute to acuminate. Heads in densely paniculiform arrays, branches ascending, densely leafy (branch leaves often overtopping heads). Peduncles 0.2–3+ cm, glabrous or pilose in lines, bracts 4–6, lanceolate-linear, often subtending heads. Involucres campanulate, 6–12 mm. Phyllaries in 4–5(–6) series, linear-lanceolate to linear, slightly unequal, bases indurate 1/5–1/2, margins not scarious (outer) to narrowly scarious, erose, hyaline, sparsely ciliolate, green zones linear-lanceolate, outer sometimes ± foliaceous, apices acute to acuminate or long-acuminate to caudate, faces glabrous. Ray florets 20–40; corollas usually blue to pale lavender, sometimes white, laminae 9–18 × 1.0–1.2 mm. Disc florets 30–50; corollas yellow or cream becoming pink or purple, (4.5–)5–6.4 mm, tubes shorter than funnelform throats, lobes triangular to lanceolate, 0.6–0.9 mm. Cypselae purple or brown, obovoid, oblong or oblanceolate, ± falcate, ± compressed, 1.5–3 mm, 3–4-nerved, faces glabrous or sparsely strigillose; pappi white, 5.2–8 mm. 2n = 16.
Phenology: Flowering Aug–Oct.
Habitat: Open, wet soils, spreading into mesic mineral soils, fens, marshes, wet roadsides
Elevation: 100–400 m
Alta., Man., Ont., Sask., Ga., Iowa, Mich., Minn., Mo., Nebr.
The range of this little known species is badly defined because some specimens attributed to it are in fact white-rayed, glabrate forms of Symphyotrichum puniceum. More work is needed to verify the status of this species.