Mat-forming prostrate dwarf shrub with extensive below and above ground branched rhizomes and stems, may form carpets of 1 m² but usually smaller. The subterranean stems often coarse, 5–7 mm thick, and blackish brown; the above ground stems usually more slender, ca. 2–4 mm thick, and reddish brown, glabrous. Dormant buds 1–1.5 × 0.5–1 mm, bud scale (one per bud) broad and obtuse, often pinkish. Shoots at or above ground level, ascending to 5(10) cm.
Leaves alternate. Petiole from very short to about half as long as blade, (0.3)0.4–1.0 cm, glabrous or with soft, white hairs to 1–2 mm. Blades to 3 × 2 cm, oblong or occasionally orbicular, with margins entire and slightly reflexed, obtuse, not notched; upper surface dark green, dull, glabrous or sparsely pubescent; lower surface nearly white (with bloom) and glabrous to moderately pubescent with hairs up to 2 mm; young leaves often densely pubescent but the hairs are lost with age. Veins pinnate, often conspicuously impressed on upper surface (‘reticulata’), always distinctly raised on lower surface, usually pink (and contrasting with the waxy white surface between veins).
The inflorescences of Salix are more or less dense, pedunculate, many-flowered spikes. The plants are unisexual. The flowers are without any perianth but supported by bracts. The male flower consists of 2 stamens (in all arctic species, 1–5 or rarely more in some southern species) and a scale-like gland between the stamens and the spike mid axis. The female flower consists of a sessile or short-stalked, fused gynoecium of 2 carpels, with a style and a stigma with 2–4 branches, and a gland similar to that of the male flower.
Spikes small, compact or loose, few-flowered on densely pubescent peduncles 0.8–2.0 cm, terminal on short shoots, appearing at the same time as the leaves. Bracts 1.5–2.0 × 1.0–1.2 mm, oblong, broadly oblong or orbicular, obtuse or sometimes retuse, brown or purple, pubescent in the margins and on the ventral surface, dorsal surface more or less glabrous. Male spikes 0.5–1.2 × 0.3–0.5 cm, with 8–20 flowers. Anthers bright red before flowering, yellow at flowering. Female spikes 0.8–1.5 × 0.4–0.6 cm, with 10–30 flowers. Gynoecium densely white-hirsute, dark red; styles dark red, cleft to base into four stigmatic branches.
The fruit is a one-roomed, dark reddish-brown capsule covered by white hairs. It contains numerous seeds with long hairs facilitating dispersal.
Sexual reproduction by seeds; very local vegetative reproduction by fragmentation of mats. Strictly outcrossing due to being dioecious. Probably pollinated by both wind and insects. Seed set is regular. Salix seeds is rumoured to lose their germination ability fairly rapidly (reportedly within days rather than weeks).
The seeds have long hairs and are dispersed by wind, probably over some distance.
Three dwarf willows are present in Svalbard: Salix herbacea, S. polaris and S. reticulata. Salix reticulata differs from the two others by being larger, having thick leaves with a network of veins impressed on the upper surface (‘reticulata’) and sharply raised on the lower surface, and by an obvious colour difference between the dark green upper leaf surface and the nearly white lower surface.
Sheltered heaths and mossy meadows with well-drained soils, usually with a favourable exposure. The species is not very demanding as to basic substrates but is absent from areas with acidic substrates only.
Moderately thermophilous. Middle and northern arctic tundra zones; weakly oceanic to weakly continental sections. Rather frequent on Bjørnøya (Engelskjøn & Schweitzer 1970; mapped from 18 sites). Otherwise known from the western and central parts of Spitsbergen from Sørkapp Land north to Liefdefjorden (Haakon VII Land) but frequent only in the Bellsund area, around the middle and inner Isfjorden, and in the Kongsfjorden area.
Salix reticulata is nearly circumpolar and arctic–alpine but absent from all of Greenland. The connection of the Svalbard population is therefore to the east (Russia) or south (Fennoscandia).
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Engelskjøn, T. & Schweitzer, H.J. 1970. Studies on the flora of Bear Island (Bjørnøya). I. Vascular plants. – Astarte 3: 1–36.
