Mat-forming herb with subterranean runners regularly present, thin and with sparse, reduced and bud-shaped leaves, ending in buds developing into leafy rosettes. Leaves basal and on stem. Pale overwintering bulbil-shaped buds at stem bases. Stems up to 10–12 cm, single (rarely 2–3 together), erect, simple, with bulbils in all stem leaf axils, sparsely hairy at base, more densely hairy with glandular, articulate hairs in the upper parts.

Leaves alternate. Basal leaves long-stalked with petioles (0.5)0.7–1.5(2.0) cm, sheathing. Blades 0.4–0.5(0.7) × 0.6–0.8(0.9) cm, palmately lobed, usually with 5 subacute lobes. Stem leaves much smaller and simple or with 1–2 lobes, with one, rarely several, red to purple bulbils in each leaf axil. Leaves with sparse glandular and eglandular hairs, mostly along margins, or glabrous.

One single, terminal flower (very rarely two).

Flower in principle radially symmetric with 5 free sepals and petals but often irregular due to unequal development of petals (and also sepals), half-open with petals erectopatent, never fully patent. Sepals 2–3 × 1.5–2 mm, irregularly ovate, with abundant or sparse glandular hairs, green or tinged reddish but sometimes with white margins (transitional to petals). Petals 3–7 × 2–4 mm, 2–3 times as long as sepals, irregularly narrowly oblong, white with lilac veins, lamina often pale lilac throughout or at least at the base. Stamens 10 or number reduced. Ovary superior, of two carpels with two rooms, split apically, usually only slightly developed.

Fruit a capsule, potentially with numerous seeds, but capsule and seeds very rarely developed.

Vegetative reproduction only, by runners and bulbils. Saxifraga svalbardensis has two modes of vegetative reproduction, both vastly more efficient than the assumedly very rare seed reproduction. Local vegetative reproduction by runners is very efficient, resulting in large, monomorphic stands. Vegetative reproduction by bulbils is the mode for longer distances. Tests have shown that about 90 % of the bulbils sprout after one year cold storage (Alsos et al. 2013). Thus, although they are more fragile than seeds, they provide an efficient way of spread and recruitment. Flowers of this species are assumed to be cross pollinated (Brochmann et al. 1999), but seeds have not been observed in Svalbard.

The species produces large numbers of bulbils that fall to the ground. They may also be eaten by e.g. reindeer or ptarmigan and thereby be spread over longer distance.

Saxifraga svalbardensis and S. cernua are similar. Plants of S. svalbardensis had been identified as S. cernua until the new species S. svalbardensis was described by Øvstedal (1975). The most evident differential character is that S. cernua is almost entirely without runners, whereas S. svalbardensis regularly has very thin runners deep in the moss layer where it grows. This difference results in different growth patterns: where the flowering shoots of S. svalbardensis are rather regularly spaced, those of S. cernua grows much more clumped and irregular. In addition, the flowers of S. cernua are large and regular with white petals, whereas those of S. svalbardensis are smaller and often irregular in size with partly reduced petals with lilac stripes or lilac more or less throughout. Saxifraga cernua grows in a variety of site types, but very rarely in the wet, mossy mires where S. svalbardensis grows. Very small-grown plants of these two species have occasionally been mistaken for S. rivularis and S. hyperborea but the two latter species lack bulbils.

Saxifraga svalbardensis is nearly restricted to wet moss tundra and mossy mires and wetlands, usually growing in and sending its runners through a moist to wet moss mat. Rarely is has been found on wet gravel or sand, without a moss cover. Most sites are on level to slightly sloping ground. Probably indifferent as to soil reaction (pH).

Present in all zones and sections. Locally frequent on Spitsbergen and recorded from Edgeøya, Kong Karls Land and Nordaustlandet, but not from Bjørnøya.

Saxifraga svalbardensis has been considered restricted to Svalbard (i.e., endemic). However, at least one specimen from Russian Novaya Zemlya, collected in 1921 (TROM), has now been identified as belonging to this taxon. The species may have been overlooked in the Russian Arctic.

Saxifraga svalbardensis is similar to S. cernua, both in morphology and in chemical content (anthocyanins, see Andersen & Øvstedal 1983, 1988). It has a hybrid origin from S. cernua and S. rivularis (Øvstedal 1988; Brochmann et al. 1998). At least one other taxon – S. opdalensis A.Blytt in C Norway – has been proposed to have the same parentage but differs consistently in several characters, not least in its regular and always white flowers and its tussocky growth without runners. Whether to treat such plants as hybrids or as one or more hybridogeneous species depends on the authors' taxonomic viewpoints. Authors treating Svalbard plants have mostly accepted S. svalbardensis as species because it is frequent to locally common over large parts of Svalbard, occurs ecologically and mostly also spatially separated from both its proposed parents, is distinctly different morphologically and easily separable from the most similar of its assumed parents, S. cernua, and because it has a habitat different from all its relatives. They have also accepted it as specifically different from S. opdalensis, i.e., thereby accepting two (or more) species within the offspring of one specific parental combination (S. cernua × rivularis). The morphological uniformity of the material of S. svalbardensis in Svalbard, and its restriction to one habitat type different from those of its parents, suggest that there may be very few, perhaps only one, origin of this hybrid species, at least in Svalbard.

Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.

Andersen, Ø.M. & Øvstedal, D.O. 1983. Anthocyanin content in Saxifraga svalbardensis and some allied species. – Biochemical Systematics and Ecology 11: 239–241.

Andersen, Ø.M. & Øvstedal, D.O. 1988. Anthocyanin patterns of European Saxifraga species. – Biochemical Systematics and Ecology 16: 545–550.

Brochmann, C. & Steen, S.W. 1999. Sex and genes in the flora of Svalbard - implications for conservation biology and climate change. – Det Norske Videnskaps-Akademi. I. Matematisk Naturvitenskapelig Klasse, Skrifter, Ny serie 38: 33–72.

Brochmann, C., Xiang, Q.-Y., Brunsfeld, S.J., Soltis, D.E. & Soltis, P.S. 1998. Molecular evidence for polyploid origins in Saxifraga (Saxifragaceae): the narrow arctic endemic S. svalbardensis and its widespread allies. – American Journal of Botany 85: 135–143.

Øvstedal, D.O. 1975. A new Saxifraga from Svalbard. – Astarte 8: 23–27.

Øvstedal, D.O. 1988. Variation within some Nordic Saxifraga species (Saxifragaceae). – Nordic Journal of Botany 18: 171–181.