Öfvers. Kongl. Vetensk.-Akad. Förh. 15: 125. 1858.
Plants (0.3–) 1–3 (–5) m. Stems: branches usually redbrown, sometimes yellowbrown, not to strongly glaucous, glabrous or villous; branchlets yellow-green, yellowbrown, or redbrown, densely villous to pubescent, (buds caprea-type, inner membranaceous bud-scale layer free, separating from outer layer). Leaves: stipules foliaceous, (2–14 mm), apex rounded or acuminate; petiole shallowly grooved, or convex to flat adaxially, 3–14 (–20) mm, villous or pilose adaxially; largest medial blade oblong, narrowly elliptic, elliptic, oblanceolate, or obovate, 33–70 (–100) × 12–35 (–48) mm, 1.6–2.8 (–4) times as long as wide, base usually rounded or convex, sometimes subcordate, margins slightly revolute or flat, serrulate, apex acute, acuminate, or convex, abaxial surface glaucous, glabrous or glabrescent, hairs straight, adaxial slightly glossy or dull, glabrous or pilose, midrib pilose; proximal blade margins serrulate or entire; juvenile blade sometimes reddish, densely villous or glabrous abaxially, hairs white. Catkins flowering as leaves emerge; staminate stout, 13–60 × 10–25 mm, flowering branchlet 0–17 mm; pistillate moderately densely flowered, stout, subglobose, or slender, 26–80 × 9–18 mm, flowering branchlet 4–24 mm; floral bract brown or black, 1.6–2.8 mm, apex acute or rounded, abaxially hairy, hairs straight, wavy, or curly. Staminate flowers: adaxial nectary oblong, 0.5–1 mm; filaments distinct, glabrous; anthers yellow, 0.6–1 mm. Pistillate flowers: adaxial nectary oblong or ovate, 0.4–0.8 mm, shorter than or equal to stipe; stipe 0.4–1.5 mm; ovary obclavate or pyriform, glabrous, beak gradually tapering to styles; ovules 18–24 per ovary; styles 0.6–2.5 mm; stigmas slenderly cylindrical, 0.28–0.48–0.72 mm. Capsules 3–8 mm. 2n = 76 (based on putative Salix barclayi × S. barrattiana, see below).
Phenology: Flowering late May-early Aug.
Habitat: Lake and streamshores, fens, moist to mesic forest openings, subalpine and alpine slopes, glacial moraines
Elevation: 0-2800 m
Alta., B.C., N.W.T., Yukon, Alaska, Idaho, Mont., Oreg., Wash., Wyo.
Vegetative specimens of Salix hastata often are misidentified as S. barclayi. The characters that indicate S. hastata, or sometimes possible hybrids, are the presence of ferruginous hairs on juvenile leaves or adaxial midribs of mature leaves, leaf margins often entire or with teeth present only distally, and buds with inner membranaceous layer not separating from outer layer.
Salix barclayi is distinguished from S. farriae and S. hastata by having bud-scales with inner membranaceous layer separating from outer layer, juvenile blades glabrous, pilose, or moderately densely villous, largest medial blades oblong, narrowly elliptic, elliptic, oblanceolate, or obovate, margins always toothed, pistillate flowering branchlets 4–24 mm, staminate flowering branchlets 0–17 mm, floral bracts brown to black, moderately densely hairy, anthers 0.6–1 mm, styles 0.6–2.5 mm, and stipes 0.4–1.5 mm; S. farriae has bud-scales with inner membranaceous layer separating from outer layer, juvenile blades glabrous or sparsely villous, largest medial blades narrowly elliptic to elliptic, margins usually entire, pistillate flowering branchlets 1.5–14 mm, staminate flowering branchlets 1–5 mm, floral bracts bicolor, brown, or black, sparsely hairy, anthers 0.3–0.6 mm, styles 0.3–1.2 mm, and stipes 0.5–1.2 mm; and S. hastata has bud-scales with inner membranaceous layer not separating from outer layer, juvenile blades sparsely pubescent, largest medial blades narrowly to broadly elliptic, narrowly ovate, or ovate, margins usually entire, pistillate flowering branchlets 1.5–9 mm, staminate flowering branchlets 1–7 mm, floral bracts brown or bicolor, sparsely hairy, anthers 0.4–0.6 mm, styles 0.2–0.48 mm, and stipes 0.4–1.2 mm.
Salix barclayi is morphologically highly variable. While it is possible that much of this variability is inherent, hybridization and introgression have played an important role.
Salix barclayi forms natural hybrids with S. arctica, S. barrattiana, S. brachycarpa, S. cascadensis, S. commutata, S. farriae, S. hastata, S. hookeriana, S. richardsonii, and S. stolonifera.
Salix barclayi × S. barrattiana is characterized by oily buds that stain the pressing paper yellow, and leaves often entire, or nearly so, and closely gland-dotted, and not glaucous abaxially. Some hybrids resemble S. barclayi in having ovaries glabrous and leaves serrulate and slightly glaucous abaxially, while others resemble S. barrattiana in having stipules marcescent and leaves short-hairy on both surfaces and not glaucous abaxially, but it is the presence of the oily buds characteristic of S. barrattiana that indicates their hybridity. The hybrids usually were from populations that included both parents. An important ramification of the discovery of this hybrid is that the specimen on which the chromosome number for S. barclayi (R. D. Dorn 1976) is based is a plant with oily buds, which has leaves with a mixture of weakly developed teeth and closely gland-dotted, entire margins, and is putatively identified as this hybrid. Further chromosome counts for S. barclayi are needed. Hybrids are known in British Columbia from the mountains in the Peace and Liard river basins, and in Mt. Robson National Park. The hybrid should be suspected wherever the parents occur together.
Salix barclayi × S. cascadensis, collected in Washington in alpine mats growing with both parents, has ovaries with hairy beaks indicating hybridization.
Salix barclayi × S. commutata resembles S. barclayi in having leaves glaucous abaxially, and S. commutata in having leaves hairy on both surfaces (northern British Columbia, Unalaska Island, and southeastern Alaska).
Salix barclayi × S. farriae is represented by a series of specimens resembling S. barclayi but with ferruginous hairs on juvenile leaves or on adaxial midribs of mature leaves, found from the Rocky Mountains of Alberta to southern Yukon and adjacent Northwest Territories. Similar specimens from Alaska may be the hybrid S. barclayi × S. hastata. Both of these hybrids require further study. See 63. S. hastata and 64. S. farriae.
Salix barclayi × S. hookeriana hybrids or introgressants at Tanis Lake, Alaska, have subentire leaves and stipes glabrous or hairy.
Salix barclayi × S. richardsonii hybrids and intergrades are relatively common in Alaska, British Columbia, and Yukon. They resemble S. barclayi in having catkins borne on distinct flowering branchlets, small stipules, anthers yellow and longer, and S. richardsonii in having marcescent stipules, branchlets and branches coarsely villous with spreading hairs, pistillate nectaries longer than stipes, and catkins sometimes on relatively short flowering branchlets.
Salix barclayi × S. scouleriana has the general appearance of S. barclayi but the densely hairy ovaries and the relatively long stigmas (0.9–0.92 mm) of S. scouleriana. It was growing with S. barclayi in openings created in white spruce by bark beetles.
Salix barclayi × S. stolonifera is characterized by relatively small leaves with irregularly serrulate margins, some young leaves reddish green, and a prostrate habit (G. W. Argus 1973).
"-0.72mm" is not declared as a valid unit of measurement for this property.