- Name also: White Dryas, White Dryad, Eightpetal Mountain-avens
- Family: Rose Family – Rosaceae
- Growing form: Dwarf shrub, basal part woody. Forms dense, mat-like stands.
- Height: 5–10 cm (2–4 in.), extends after flowering.
- Flower: Corolla regular (actinomorphic), white–slightly yellowish, approx. 2.5–3.5 cm (1–1.4 in.) broad; petals usually eight, 8–15 mm (0.32–0.6 in.) long, round-tipped. Calyx 8-lobed, hairy, also with glandular hairs. Stamens many. Gynoecium separate, pistils several. Flowers solitary.
- Leaves: In basal rosette, quite long-stalked, overwintering. Blade elliptic–quite ovate, with glandular teeth, leathery, dark green on top, shiny, underside white-felted, with revolute margins.
- Fruit: Achene tipped with 20–35 mm (0.8–0.14 in.) long, hairy, greyish flying hairs.
- Habitat: Rich fell moors, sometimes barren moors, gravels, rocky outcrops, sometimes in the coniferous forest zone. Calciphile.
- Flowering time: (June–)July–August.
Mountain avens has been chosen to represent Finnish fell flora, although it is rare in the wild. The large size and whiteness of its flower enchants fell walkers with their own special style. It is only common around the fells close to Kilpisjärvi, although there are smaller stands in the Saariselkä and Pallas-Ounas area, as well as on the fells of Inari and Utsjoki. An ancient, separate stand survives on the canyon walls of Kuusamo.
The form of mountain avens’ leaves is like a smaller version of oak leaves, which has led to its scientific name: the classical Greek word drys means ‘small oak’. Thanks to its distinctive leaves the species has become a guide fossil for the tundra phase of the late Ice Age: it has provided a lot of help in comparing the age of strata of bedrock that are located far away from each other. Mountain avens fossils have been found on the Karelian Isthmus, the Baltic countries and southern Sweden. Finds point to the fact that in the late Ice Age, when the continental ice plate was melting, these areas were covered in tundra plants. The two cold phases within the melting phase in the Ice Age have been named the younger and older Dryas periods after mountain avens.
Despite its herb-like appearance, mountain avens is a dwarf shrub with a woody base. In the most favourable habitats it can grow up to a square metre wide and live up to 100 years. Mountain avens is the national flower of Island.