Rumex acetosa ssp. alpestris is a medium-sized herbaceous plant of mountain meadows and shrub tundra in Denali with spear-shaped leaves and an open inflorescence of tiny reddish flowers. Plants grow 30-60 cm high from a short rhizome with both basal and stem leaves. Basal leaves are long-petioled; the stem leaves are shorter and alternately arranged. The leaves are hastate, the base with two triangular lobes pointing out. Stems of Rumex acetosa ssp. alpestris are ridged, with sheathing stipules. The flowers are produced in a terminal inflorescence, open and branched. The species is dioecious, individual plants produce either male or female flowers only. In either case, the tiny flowers have 6 tepals. Male flowers are shed soon after flowering. Female flowers produce winged seeds, also red, 2-3 mm long. Plants look similar to Rumex arcticus, but that species does not have hastate leaves and occurs in wet areas.

This species is perennial and deciduous and greens up after snow melt. Flowering happens in mid-summer.

The species is dioecious. Flowers are wind-pollinated. The fruits are achenes with three winged margins, also wind-dispersed.

Well-drained moist to somewhat dry sites.