Silky willow is a shrub with unisexual catkins (aka aments) 1-4 cm. Pistillate catkins have pubescent ovaries and styles less than 0.5mm long. Staminate catkins have 2 filaments, yellow anthers less than 0.7mm, and develop on branchlets with green bracts. Its fruits are ovoid-oblong, 3-5mm, blunt, silky, with long, soft, slender hairs. Leaves are alternate, narrowly lanceolate to lanceolate, 6-14cm long by 1-3cm wide, gradually tapering to a sharp point, forming concave sides along the tip, wedge-shaped at the base, closely glandular-serrate, dark green and minutely hairy to smooth above, waxy-white and silky below.
This genus is notoriously difficult to distinguish to the specific level when not in flower.