- Name also: Wood Sorrel, Alpine Sorrel, Alpine Mountainsorrel, Mountain-sorrel
- Family: Dock Family – Polygonaceae
- Growing form: Perennial herb. Taproot stout, long.
- Height: 10–30 cm (4–12 in.). Stem reddish, hairless, usu. leafless.
- Flower: The greenish perianth consists of two whorls that are of unequal size. Segments of inner whorl are ca. 2–2.5 mm (0.08–0.1 in.) long, erect, broadly obovate, and persist in fruit. Segments of outer whorl ca. 2 mm long, spreading, and narrowly elliptic. Stamens six. Pistil formed from two fused carpels, styles two.
- Leaves: Long-stalked and hairless basal leaves borne in a rosette. Blade roundish to reniform (kidney-shaped), somewhat fleshy, brownish or reddish, margins slightly wavy. Stem leaves usually absent or solitary. Ochrea of stem leaf membranous, short, loose, and brown.
- Fruit: Broad-winged, 3–5 mm long achene with remains of stigmas in the apical notch. When ripe, wings are deep red.
- Habitat: Snow-bed sites, alpine meadows, streamsides.
- Flowering time: June–August.
Worldwide there are only two species in genus Oxyria. The other one, O. sinensis grows in the Himalaya mountains. On the coast of Norway, mountain sorrel pollen has been found in soil layers up to 12,600 years old. Thus, it must have been among the very first plants to follow the retreating ice age glaciers. Another interpretation is that the species survived through the ice age in small areas uncovered by ice.
Mountain sorrel is an edible perennial of the middle part of the alpine tundra zone. Its leaves are acid-tasting and rich in vitamin C. Therefore, they are a popular vegetable among Lapps and Inuits. But it can be dangerous if eaten too much. Oxyria comes from Greek (oxys and aria) meaning acid-tasting. Mountain sorrel is most abundant on nitrogen-rich soil as it can utilise the nitrates in e.g. bird excrement when producing amino acids.