Salix alaxensis is a tall willow shrub, the leaves with a distinctive white felt-like underside. This species commonly occurs in early successional habitats on floodplains and in steep gullies in the mountains. Individuals may grow up to 10 m tall. Leaves are oblanceolate-elliptic in shape, margins entire or undulating. The underside of leaves, as well as young twigs and branches are characteristically felt-like or wooly, in contrast to the dark green upper leaf surfaces. The stipules are persistent and densely hairy. Willows are dioecious (separate plants producing either male or female flowers only), the flowers highly reduced and borne in catkins. The catkins appear before leaves, and are sessile; female catkins are relatively large (6-15 cm). The fruits are pubescent capsules with long styles. Floral bracts are long-hairy, acute, and black tipped. This species of willow is recognizable by its large dark green leaves with a felt-like, densely white hairy surface below.
Catkins generally appear mid-April to mid-May, leaves appear in early May (Collett 2004).
Salix alaxensis is dioecious, and insect and wind pollinated. Seeds have attached hairs to aid in wind dissemination. Salix alaxensis can also spread vegetatively as broken branches readily take root.
Collett (2004) documented a variety of insects that utilize S. alaxensis including gall-formers such as: Rabdophaga spp., Euura sp., and Pontia sp., the Rusty tussock moth Orgyia antiqua, and a stem boring beetle Saperda concolor, plus many more. 'Diamond willows' also form with this species, which is caused the canker fungus Valsa sordida.
Salix alaxensis has a wide variety of traditional uses as food, medicine, construction materials, and firewood. Like all willows, the fresh bark of S. alaxensis contains salicin, a precursor to aspirin and has traditionally been used as pain and fever reliever. The fresh inner bark has long been a food source for indigenous peoples throughout its range. Young buds and shoots are said to be sweet and have a watermelon or cucumber taste. Willow suckers (long straight branches) have long been utilized for constructions of baskets, crab pots, furniture and other objects. Above the northern treeline, S. alaxensis is the largest (living) source of wood available for fires. S. alaxensis has been used for streambank restoration as cuttings can be directly planted and take root.
Salix alaxensis is a widespread amphi-Beringian species ranging from Siberia, across Alaska to Yukon and Nunavut (including the Arctic Islands), and southward to B.C. and Alberta. Salix alaxensis' eastern range stretches to Manitoba and Quebec, but does not reach the continental U.S. This species occurs in suitable habitat throughout Alaska, and also Denali, occurring on both sides of the Alaska Range.
Salix alaxensis occurs in Denali National Park at a wide variety of elevations 89 m to 1577 m with the average plot elevation at 732 m. This species does not exhibit any obvious preference in slope or aspect.