Plants (15-)30-65 cm. Basal leaves spatulate to oblanceolate, 50-200 × 4-25 mm, faces gray-pubescent. Cauline leaves 8-140 mm, distal usually flagged. Heads 3-30. Involucres: staminate 5-8 mm; pistillate 7-12 mm. Phyllaries distally black, dark brown, light brown, or olivaceous. Corollas: staminate 3.5-5 mm; pistillate 4-6 mm. Cypselae 1-1.5 mm; pappi: pistillate (7-)8-10 mm. 2n = 28, 56. Flowering summer. Alluvial soils in moist willow thickets subject to intermittent flooding along streams, montane to subalpine zone; 0-3000 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Alaska, Colo., Idaho, Mont., Utah, Wash., Wyo.