Perennials, 15-40 cm (rhizomes slender). Stems 1-8, branches ascending, ± tomentose. Leaves green (at least cauline) at flowering; blades oblong-oblanceolate, 3-6 cm, margins entire or toothed (teeth remote, faces tomentose). Heads borne singly or clustered along stems and branches. Peduncles 2-10 mm (glabrous). Calyculi of (4-6) appressed bractlets (unequal, lengths to 1/2 phyllaries). Involucres 8-10 mm (phyllaries 5, glabrous). Florets 5(-6). Cypselae tan, 4-4.4 mm, faces smooth, grooved; pappi of 30-40, white bristles (persistent), wholly plumose. 2n = 16.
Flowering Jul-Aug. Spring-flooded flat, gravel stream beds. of conservation concern; 2000-2300 m; Wyo.
Stephanomeria fluminea is known only from northwestern Wyoming. Its habitat is unique among all species of the genus. The plants grow on impermanent, raised cobble benches in flat, gravel beds of creeks that flood and churn after spring snowmelt.