Plants perennial, glabrous or indistinctly papillose-pubescent, with distinctly tuberous roots and short rhizomes. Stems usually erect, rarely ascending, branched above middle, 25-90(-100) cm. Leaves: ocrea prominent and persistent at maturity, whitish or silvery white, membranous; blade oblong, oblong-elliptic, or obovate-lanceolate, (5-)8-30 × 2-8(-12) cm, base cuneate or narrowly cuneate, margins entire, flat or indistinctly crisped, apex acute or acuminate, rarely obtuse. Inflorescences terminal, occupying distal 1/ 2 of stem, narrowly paniculate, rarely simple. Pedicels articulated near middle or in proximal 1/ 3, filiform, 5-15(-20) mm, articulation indistinct. Flowers 5-20 in whorls; inner tepals oblong-cordate or orbiculate-cordate, 11-16 × 9.5-14 mm, base sinuate or emarginate, margins entire, rarely with few extremely small denticles at base, apex obtuse or subacute; tubercles absent. Achenes brown or reddish brown, 4-5(-7) × 2.5-4.5(-5) mm. 2n = 40.
Rumex hymenosepalus is the only species of subsect. Hymenosepali Rechinger f.
Two varieties have been recognized. The typical variety has achenes 5 mm and ovate-elliptic or oblong-cordate inner tepals with a subacute apex. Variety salinus (A. Nelson) Rechinger f. has larger achenes (to 7 mm) and almost orbiculate inner tepals with an obtuse apex.
Rumex hymenosepalus was reported also from Montana (J. E. Dawson 1979), but no exact localities were given.
FNA 2005, Wiggins 1964, Kearney and Peebles 1969
Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Coarse perennial 30-100 cm tall, with 1-several tuberous roots, glabrous or indistinctly papillose-pubescent. Leaves: Prominent ocrea that is persistent at maturity, whitish or silvery white, membranous; blades oblong to elliptic-oblong, 3-10 cm wide, 10-30 cm long, bases cuneate or narrowly cuneate, margins entire, flat or indistinctly crisped, to sheathing stipules 1-3 cm long. Flowers: Terminal panicle, occupying the upper half of stem; pedicels slender 8-12 mm long, jointed near middle, flowers 5-20 in whorls, outer sepals linear or elliptic, 1.5-2.5 mm long, spreading, inner fruiting tepals cordate-ovate, membranous, reticulate, bright red, 6-14 mm long; flowers January-April. Fruits: Achene brown or reddish brown, shining, 4-5 mm long. Ecology: Found on dry flats and along washes, mostly in gravelly or sandy soil below 6,000 ft (1829 m). Distribution: CA, NV, UT, AZ, s WY, CO, NM, OK, TX; south to n MEX. Notes: Distinct from other Rumex in the region by being a mostly low-desert, upland species growing in dry, often sandy or disturbed areas; it bolts and flowers in early spring, often withering away by summer. The basal rosette is of very large, thick, wavy leaves; the leaf axils do not produce shoots; and the inner tepals (valves), which have 4 wings and tightly contain the seeds, are 10 mm long or longer, have a notch in the top (cordate), and turn red-pinkish with age, making them resemble hanging hearts and giving the inflorescence a red color. Ethnobotany: Used to wash sores, for colds, for ant bites or infected cuts, as a gargle for coughs, as a life medicine, a ceremonial medicine, a lactagogue on breasts, dried and powdered root on burns and other sores, taken for sore throats, used for diarrhea, held in the mouth for sore gums, the stalks and leaves eaten as greens, made into a tea, the seeds are used to make a mush, the stems were baked and eaten, the seeds are roasted, ground, and formed into flat cakes, the roots are chewed like a gum, made into pies, and used for a dye. Etymology: Rumex is the Latin name for docks or sorrels, while hymenosepalus means having membranous sepals in Latin. Synonyms: Rumex hymenosepalus var. euhymenosepalus, R. hymenosepalus var. salinus Editor: SBuckley 2010, FSCoburn 2015