- Name also: Purple Mountain Saxifrage
- Family: Saxifrage Family – Saxifragaceae
- Growing form: Perennial herb. Taproot strong. Tufted, sometimes a cushion plant–mat-forming. Forms stands.
- Height: 2–5 cm (0.8–2 in.). Stem woody, limp–ascending. Flowering shoots densely leaved, flowerless runner shoots rare and small-leaved.
- Flower: Corolla regular (actinomorphic), purple–reddish violet, approx. 1 cm (0.4 in.) wide; petals five, 5–10 mm (0.2–0.4 in.) long. Sepals 5. Stamens 10, anthers blue. Styles 2, fused at base. Flowers solitary terminating stems, fragrant.
- Leaves: Opposite in 4 rows, stalkless, overwintering. Blade ovate–obovate, with entire and ciliate margins, fleshy, rigid, bluish green, often lime-flecked.
- Fruit: 2-parted capsule.
- Habitat: Fellside snow-bed sites, stream banks, wet rock surfaces, Lappish rock faces, rocky places, gravels, fell heaths. Calcicole.
- Flowering time: June–July.
Purple saxifrage is very impressive when it is in flower. It opens its flowers on south-facing ridges as soon as spring arrives in the fells, but plants on north-facing slopes emerge from under the snow late and don’t bloom until the middle of July. The species even grows on the highest fells of the Halti ridge, and outwith the Lappish “arm” of Finland there are a few stands in Inari Lapland.
Purple saxifrage is demanding and only grows in calciferous soils. The plant has a group of cells at the tip of the leaves that secrete water, thus dripping calciferous water onto the hummock. In lime-rich areas the plant gradually gets covered in a white covering of lime deposits. This kind of coating has been observed to be advantageous to the plant: it decreases evaporation, protects against excessive solar radiation and protects the leaf margins from the wind. Purple saxifrage grows on fell heaths and forms mat-like stands, sometimes resembling real cushion plants. In Finland, in keeping with its scientific name oppositifolia, the plant has opposite leaves, but an alternate-leaved version can be found e.g. in the Pyrenees.
As purple saxifrage grows broadly also in more southern mountainous areas, it has been chosen for international monitoring to help study the climate and its relation to the plant’s flowering time. A rapid warming of the climate can be especially destructive to fell plants. Purple saxifrage grows in the highest parts of the fell zone, where only a few flowers survive. As Finland’s only purple-lowered saxifrage, this species cannot be confused with any other saxifrage. It bears closest resemblance to moss campion (Silene acaulis), although its leaves are thin and needle-like.