Plants perennial, glabrous, with vertical rootstock. Stems usually ascending, usually producing axillary shoots below 1st-order inflorescence or at proximal nodes, 30-50(-60) cm. Leaf blades light or yellowish green, veins scarcely prominent abax-ially, elliptic-lanceolate, occasion-ally lanceolate, 6-12 × (2-)3-6 cm, usually (2-)3(-5) times as long as wide, widest near middle, thin, not coriaceous, base cuneate, margins entire, undulate, apex acute, warty in appearance. Inflorescences terminal and axillary, terminal usually occupying distal 5- 3 of stem, dense or interrupted near base, usually broadly paniculate (branches simple or with few 2d-order branches). Pedicels articulated in proximal 3, filiform (but thickened distally), 3-6 mm, not more than 2-2.5 times as long as inner tepals, articulation indistinctly swollen. Flowers 10-20 in whorls; inner tepals, triangular, broadly triangular, or deltoid, 3-4 × 3.5-4(-5) mm, base truncate, margins entire, apex acute or subacute; tubercle 1, small, narrow, much narrower than inner tepals, smooth to weakly rugose. Achenes not seen. 2n = 20. Flowering late spring-early summer. Wet, alluvial habitats: shores, ditches; 500-1000 m; Wash. Rumex hesperius is a little-known species reported only from a localized area in Washington. According to N. M. Sarkar (1958) it is 'quite distinct from other species' in its general appearance-a small plant with large, broad leaves and compact inflorescences.