Salix barclayi is a thicket-forming medium-sized willow shrub of floodplains, subalpine slopes and moist meadows with long-styled catkins. Shrubs grow from 0.5 to 2 m tall. Stems are dark reddish brown and twigs are yellow-green and pubescent. Leaves are hairless, green above, whitish beneath with serrate margins and broad stipules. Willows are dioecious (that is, separate plants produce either male or female flowers) and the flowers highly are reduced and borne in catkins specialized for wind pollination. Catkins are up to 7 cm long, borne on leafy branches and appear at the same time as the leaves. Pistils are hairless and green, but often age to a reddish color, with styles 1-2 mm long. This species can have 'willow rose' galls stimulated by insect parasites. Some key characters which aid in identifying this species are the long, leafy catkin peduncles and the long styles (1-2 mm), but people wishing to make a more certain identification should consult a technical key.
Leaves and catkins develop together and generally appear mid-May to mid-June.
Salix barclayi is dioecious, and insect and wind pollinated. Seeds have attached hairs to aid in wind dissemination. It also readily spreads vegetatively.
Collett (2004) documented some of the various insects and mites that utilize S. barclayi including gall-formers such as: Rabdophaga spp., Euura sp., Pontania sp., and eriophyid mites, leaf skeletonizers from the Chrysomelid family of beetles, and the stem boring beetle, Saperda concolor, as well as many more.
Salix barclayi is useful for revegetation projects (Collett 2004).
Salix barclayi occurs only in western North America, ranging from southern Alaska across southern Yukon through western Canada to Washington state and the northern Rockies southward to Colorado. In Alaska, this species primarily occurs in maritime-influenced southern and western parts of the state. In Denali, S. barclayi occurs occasionally park-wide, but is more common and abundant on the south side of the Alaska Range, particularly in subalpine areas.
Salix barclayi is a thicket forming shrub of the subalpine zone and is found in the park at elevations from 74 m to 1470 m, with an average plot elevation of 770 m. It is more commonly found on south-facing versus north-facing slopes. It prefers moderately sloped sites with an average slope of 11 degrees.