Plants 0.03-0.25 m, not clonal or forming clones by layering. Stems erect, decumbent, or trailing; branches yellow-brown, gray-brown, or red-brown, (strongly glaucous or not, slightly glossy), glabrous; branchlets yellow-brown, red-brown, or violet, (strongly glaucous or not), usually densely villous or pilose (usually appearing unkempt), sometimes glabrous, (inner membranaceous bud-scale layer free, not separating from outer layer). Leaves: stipules absent, rudimentary, or foliaceous (0.2-1.5-10 mm); petiole 2-35 mm, (longer than subtended bud, puberulent or glabrous adaxially); largest medial blade hypostomatous or hemiamphistomatous, narrowly to broadly elliptic, subcircular, circular, oblanceolate, obovate, or broadly obovate, 10-85 × 5.5-60 mm, 1-3.6(-4.9) times as long as wide, base cuneate, convex, or rounded, margins slightly revolute or flat, entire, apex acuminate, acute, convex, or rounded, abaxial surface pilose or midrib sparsely short-silky, or apex long-silky bearded, hairs usually straight or wavy, adaxial slightly glossy or dull, glabrous, pilose or long-silky margin; proximal blade margins entire; juvenile blade glabrous or sparsely villous abaxially, hairs straight, oriented toward apex. Catkins: staminate 14-65 × 5-18 mm, flowering branchlet 2-36 mm; pistillate densely to moderately densely flowered (30+ flowers), slender, stout, or subglobose, 20-145 × 8-22 mm, flowering branchlet 2-40 mm; floral bract brown or black, 1.6-3.7 mm, margins sometimes sinuate, apex broadly rounded, convex, or retuse, entire, sinuate, or 2-fid, abaxially hairy, hairs straight. Staminate flowers: abaxial nectary (0-)0.3-0.8 mm, adaxial nectary narrowly oblong, oblong, or square, 0.5-1.2 mm, nectaries distinct; filaments distinct; anthers ellipsoid, 0.3-0.9 mm. Pistillate flowers: adaxial nectary oblong, ovate, or narrowly oblong, 0.4-1.8 mm, much longer than stipe; stipe 0.2-1.6 mm; ovary obclavate or pyriform, villous, beak abruptly to gradually tapering to or slightly bulged below styles; ovules 12-15 per ovary; styles (connate to distinct 1/2 their lengths), 0.6-2.2 mm; stigmas slenderly cylindrical, 0.35-0.56-0.88(-1.13) mm. Capsules 4-9 mm. 2n = 76, 114. Flowering early Jun-mid Aug. Arctic-alpine, wet to mesic or dry habitats, including hummocks in wet Sphagnum bogs and sedge meadows, polygonal tundra, solifluction slopes, snowbeds, margins of pools, beach ridges, shale and gypsum ridges, gneissic cliffs, colluvial slopes, talus slopes, glacial moraines, imperfectly drained calcareous silty till, muddy salt flats, frost-heaved clay polygons, dry calcareous gravel, coarse sandy soil; 0-2000 m; Greenland; Alta., B.C., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Yukon; Alaska, Wash.; Eurasia (China, Chukotka, Novaya Zemlya, Russian Far East, arctic, e Siberia); Atlantic Islands (Iceland). Salix arctica is polymorphic and nomenclaturally confusing. E. Hultén (1967, 1971) recognized three subspecies: 1) subsp. arctica (circumpolar from Iceland and the Faeroe Islands across northern Russia, Alaska and Canada to Greenland, south to the Hudson Bay shores of Ontario and the Gaspe Peninsula); 2) subsp. crassijulis (a North Pacific race ranging from Kamchatka and the Russian Far East to the Aleutian Islands, south central and southeastern Alaska along the coast to northern Washington); and 3) subsp. torulosa (ranging from the mountains of central Asia to Kamchatka and the Bering Straits, the Brooks Range and the Rocky Mountains in Alaska, south in the cordillera to southern British Columbia and Alberta). While formal recognition of the three races is appealing, they are actually very difficult or impossible to separate morphologically and have strongly overlapping ranges. Some of the variability may be due to environmental modification (D. B. O. Savile 1964; G. W. Argus 1973; J. H. Soper and J. M. Powell 1985). On Attu Island, Alaska, there are plants to 2 m along with dwarf plants (C. Parker, pers. comm.). Their tall stature cannot be accounted for by habitat alone. The possibility that the complex morphological variability within S. arctica may be ecophenic or ecotypic deserves study.

T. E. Dawson (1987) showed that the pistillate-biased sex ratios in Salix arctica are environmentally controlled; pistillate plants are significantly over-represented in mesic-wet, more fertile sites with low soil temperature, whereas staminate plants are predominant in drier, less fertile sites.

The oldest reported age of Salix arctica is 236 years in East Greenland (H. M. Raup 1965) and 85 years on Ellesmere Island (D. B. O. Savile 1979b).

In northern Greenland, Salix arctica is one of the primary foods for musk ox, arctic hare, and collared lemming (D. R. Klein and C. Bay 1991).

Hybrids:

Salix arctica forms natural hybrids with S. arctophila, S. barclayi, S. fuscescens, S. glauca varieties, S. herbacea, S. ovalifolia, S. pedicellaris, S. phlebophylla, S. polaris, S. rotundifolia, and S. stolonifera.

Salix arctica × S. arctophila (S. ×hudsonensis C. K. Schneider) resembles S. arctophila in its trailing habit and toothed leaf margins, and S. arctica in its hairy leaves and petioles, particularly proximal