Plants perennial, glabrous, with vertical rootstock. Stems usually erect, occasionally ascending, usually producing axillary shoots below 1st-order inflorescence or at proximal nodes, 15-40(-60) cm. Leaf blades lanceolate or linear-lanceolate, 6-15 × 2-3 cm, usually ca. 4-5 times as long as wide, widest near middle or slightly towards base, usually thin, base cuneate, margin entire, flat, rarely indistinctly undulate, apex acute. Inflorescences terminal and axillary, terminal usually occupying distal 1/ 1/ 3 of stem, dense or occasionally slightly interrupted at base, usually broadly paniculate (branches normally simple and crowded). Pedicels articulated in proximal 1/3 or almost near base, filiform (but thickened distally, 4-7 mm, not more than 2-2.5 times as long as inner tepals, articulation indistinctly or evidently swollen. Flowers 10-25 in whorls; inner tepals deltoid or broadly ovate-deltoid, 2.5-3 × 2.5-3 mm, base truncate or indistinctly cordate, margins entire, apex acute, rarely subacute; tubercles absent. Achenes dark reddish brown or almost black, 1.8-2 × 1-1.3 mm. 2n = 40. Flowering late spring-summer. Shores of rivers and streams, wet meadows, rocky slopes; 1000-3500 m; Alta.; Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wyo. The names Rumex mexicanus and R. salicifolius in the broad sense often have been applied to R. utahensis.
Records of 'narrow-leaved forms' of Rumex utahensis from Yukon (E. Hultén 1968) probably refer to R. hultenii Tzvelev (see comments under 27. R. sibiricus) or R. sibiricus in the narrow sense.