Perennials (7–)100–250(–300) cm, cespitose; thickly short-rhizomatous or with stout, branched caudices, sometimes long-rhizomatous. Stems 1–5+, erect (straight to distally flexuous, stout 5–11 mm diam., usually reddish purple), usually densely to sparsely hirsute or hispid, glabrescent, often proximally glabrate, sometimes glabrate. Leaves (dark green, not crowded) thin, margins remotely serrate to sometimes entire, scabrous, apices acute or acuminate to subcaudate, mucronate, abaxial faces glabrate, ± densely pilose along midveins, adaxial glabrate to scabrous; basal withering by flowering, subpetiolate to petiolate (petioles ± winged, bases dilated, sheathing), blades spatulate to oblanceolate or lanceolate, 30–10+ × 3–20+ mm, bases attenuate to cuneate, margins remotely crenate-serrate to denticulate or entire, apices acute or acuminate to rounded; proximal cauline withering by flowering, petiolate to subpetiolate (petioles widely winged, bases auriculate, clasping), blades lanceolate or oblanceolate to oblong, elliptic or elliptic-oblong, (55–)70–200(–220) × 10–40 mm, usually progressively lengthened to mid, bases ± attenuate to cuneate or auriculate and clasping; distal sessile, blades oblanceolate or lanceolate to oblong or elliptic-oblong (sometimes nearly panduriform), 8–160 × 1–40 mm, progressively reduced distally, strongly so and linear in arrays, bases ± strongly auriculate, clasping, margins subentire or entire. Heads in open, paniculiform (often corymbiform-looking) arrays, branches widely spreading to ascending, sparsely to moderately leafy with ± large leaves. Peduncles 0.2–3+ cm, ± hispid or hirsute to villous, bracts 0–3, lanceolate or linear-lanceolate to linear, distal often subtending heads. Involucres campanulate, (6–)8–12(–15) mm. Phyllaries in 4–6 series, oblanceolate-spatulate to linear, subequal, bases indurate 1 / 5 – 1 / 2 , margins not scarious (outer) to narrowly scarious, erose, hyaline, sparsely ciliolate, green zones linear-lanceolate, outer sometimes ± foliaceous, to linear (inner), apices ± spreading at tip when foliaceous, long-acuminate to caudate, mucronate to apiculate, sometimes purplish tinged, faces glabrous or ± hispid. Ray florets 20–50(–60); corollas usually pale to dark blue, lavender or purple, seldom white or pink, laminae (7–)12–18(–21) × (0.9–)1.4–1.8 mm. Disc florets 30–50 (–90); corollas yellow or cream becoming pink or purple, (4.1–)5–6.5 mm, tubes shorter than cylindro-funnelform limbs, lobes triangular, 0.4–1.1 mm. Cypselae purple or brown (nerves stramineous), oblanceoloid, ± falcate, compressed, (2–)2.5–3.5(–4) mm, 3–4-nerved (nerves prominent), faces glabrous or sparsely strigillose; pappi white, 3.8–6 mm.
Wet soils, often peaty, open to moderately shaded, margins of alluvial deciduous woods and alder thickets, swamp margins, edges of bogs, stream and lake shores, marshes, wet meadows; at elevations up to 2,000 metres.
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