1 "Shrub < 0.2 m, forming mats by rhizomes or adventitious roots, alpine" 2
1 "Shrub to tree, > 0.2 m, not forming mats, not alpine" 3
2 "Young leaves glabrous; mature leaf blade 6–22 mm, abaxially strongly net-veined, both surfaces glabrous; plant forming mats by rhizomes" "Salix nivalis"
2 "Young leaves hairy; mature leaf blade 19–44 mm, abaxially not strongly net-veined, both surfaces sparsely soft-shaggy-hairy or glabrous in age; plant forming mats by adventitious roots" "Salix petrophila"
3 "Tree; bud scale margins free, overlapping" 4
3 "Low shrub to tree; bud scale margins fused" 5
4 "Leaf blade not glaucous abaxially; twigs ± yellow or yellow-green or ± tan; young leaves white-hairy" "Salix gooddingii"
4 "Leaf blade glaucous abaxially; twigs ± tan; young leaves glabrous or white- or white-and-rusty-hairy" "Salix laevigata"
5 "Petiole generally with glands" 6
5 "Petiole glands 0" 8
6 "Shrub to tree, 0.6–10 m; twigs erect, flexible or brittle at base; petiole glabrous or long-soft-wavy-hairy" "Salix lasiandra"
6 "Tree 7–25 m; twigs pendent or erect, flexible or ± brittle at base; petiole tomentose or silky" 7
7 "Stems, twigs erect to spreading; twigs ± yellow or gray to ± tan, densely silky; petiole silky" "Salix alba"
7 "Stems, twigs pendent; twigs ± tan, short-silky to velvety, glabrous in age (except at nodes); petiole tomentose" "Salix babylonica"
8 "Leaf blade abaxially not glaucous or surface obscured by hair" 9
8 "Leaf blade abaxially glaucous or surface obscured by hair" 13
9 "Leaf entire or ± sparsely short-slender-serrate; plant clonal by root-shoots; petiole glabrous or silky, 2–6 mm" 10
9 "Leaf entire to finely serrate; plant not clonal by root-shoots; petiole soft-shaggy-hairy, tomentose, or velvety, 3–17 mm" 11
10 "Leaf blade linear, length 10–23 × width; young leaves short-silky" "Salix exigua"
10 "Leaf blade linear to narrow-elliptic or -oblanceolate, length 2.8–8.5 × width; young leaves long-soft-wavy-hairy, tomentose, or velvety" "Salix melanopsis"
11 "Leaf blade margins strongly rolled under, especially basally; young leaves abaxially densely silky or woolly" "Salix sitchensis"
11 "Leaf blade margins flat or ± rolled under; young leaves abaxially soft-shaggy-hairy, tomentose, silky, or woolly" 12
12 "Young leaves shaggy-hairy; mature leaf blade abaxially glabrous or soft-shaggy-hairy, adaxially shiny to highly glossy" "Salix boothii"
12 "Young leaves densely tomentose, silky, or woolly; mature leaf blade abaxially tomentose, long-soft-wavy-hairy, woolly-tomentose, silky, or glabrous in age, adaxially dull" "Salix eastwoodiae"
13 "Leaf blade linear, length 6.6–25 × width; plant clonal by root-shoots" "Salix exigua"
13 "Leaf blade narrowly elliptic or wider, length 1.3–8(14.4) × width; plant not clonal by root-shoots (but sometimes clonal by layering or stem fragmentation)" 14
14 "Leaves (at least some) ± opposite" "Salix purpurea"
14 "Leaves alternate" 15
15 "Tree 7–25 m; twigs pendent" "Salix babylonica"
15 "Shrub to tree, 0.2–10 m; twigs erect or decumbent" 16
16 "Leaf blade margins generally strongly rolled under, at least basally" 17
16 "Leaf blade margins flat or ± rolled under" 19
17 "Leaf blade adaxially generally highly glossy" "Salix lasiolepis"
17 "Leaf blade adaxially shiny or dull" 18
18 "Leaf blade abaxially tomentose or woolly or generally sparsely silky, often with white and rusty hairs, glaucous, adaxially shiny" "Salix scouleriana"
18 "Leaf blade abaxially very densely silky or woolly, surface obscured by white hairs, adaxially dull" "Salix sitchensis"
19 "Leaf blade adaxially highly glossy" 20
19 "Leaf blade adaxially dull to shiny" 23
20 "Leaf blade abaxially moderately to densely shaggy, tomentose, or woolly, at least on midrib and veins, rarely ± glabrous" 21
20 "Leaf blade abaxially glabrous (or soon becoming so) to sparsely silky" 22
21 "Twigs generally thinly glaucous; leaf blade abaxially generally woolly or shaggy-hairy, 18–55 wide" "Salix hookeriana"
21 "Twigs not glaucous; leaf blade abaxially generally tomentose, 6–32 mm wide" "Salix lasiolepis"
22 "Petiole tomentose or velvety; leaf blade 35–125 mm; twig hairs spreading; leaf blade glands adaxially submarginal or nearer blade center; 0–2500 m" "Salix lasiolepis"
22 "Petiole sparsely soft-shaggy-hairy; leaf blade 19–75(115) mm; twig hairs appressed or curved toward stem; leaf blade glands generally marginal; 2500–4000 m" "Salix planifolia"
23 "Leaf blade abaxially glabrous, downy, or soft-shaggy-hairy" 24
23 "Leaf blade abaxially long-soft-wavy-hairy, tomentose, silky, or velvety" 34
24 "Leaf blade white- or white-and-rusty-hairy" 25
24 "Leaf blade white-hairy or glabrous" 28
25 "Stipules generally leaf-like; young leaves, mature blades densely silky or generally short-tomentose; 0–2500 m" 26
25 "Stipules 0 or vestigial on first leaves, leaf-like on later leaves or not; young leaves, mature blades generally densely silky; 1400–3600 m" 27
26 "Stipule tip acute; leaf glands submarginal or distinctly on adaxial surface; young leaves thick, yellow-green (or ± red)" "Salix lasiolepis"
26 "Stipule tip convex to rounded; leaf glands marginal; young leaves thin, ± red" "Salix tracyi"
27 "Leaf blade persistently long-(often white-)hairy, 32–89 mm; petiole 3–9 mm; stipules generally 0 or vestigial" "Salix geyeriana"
27 "Leaf blade in age ± glabrous or sparsely short-(generally rusty-)hairy, 44–110 mm; petiole 5–16 mm; stipules vestigial on first leaves, leaf-like on later" "Salix lemmonii"
28 "Stipules 0 or vestigial on first leaves, leaf-like on later" 29
28 "Stipules leaf-like (vestigial or not in Salix bebbiana)" 30
29 "Young leaves, mature blades generally densely silky; twigs generally glaucous; 1450–3600 m" "Salix geyeriana"
29 "Young leaves, mature blades densely silky or generally short-tomentose; twigs not glaucous; 0–2500 m" "Salix lasiolepis"
30 "Leaf blade abaxially generally with raised, net veins, length 1.7–3.9 × width, entire to crenate; young leaves densely silky – n MP" "Salix bebbiana"
30 "Leaf blade abaxially smooth, length 2.2–9.6 × width, generally finely serrate (entire or not in Salix lasiolepis); young leaves generally glabrous or sparsely hairy (densely silky in Salix lasiolepis)" 31
31 "Leaf base wedge-shaped or convex; blade shiny adaxially; twigs tomentose, glabrous in age" "Salix lasiolepis"
31 "Leaf base rounded, subcordate, cordate, or convex; blade dull adaxially; twigs glabrous to sparsely long-soft-wavy-hairy" 32
32 "Twigs yellow-gray or yellow- or gray-brown, not peeling" "Salix lutea"
32 "Twigs generally ± tan, peeling" 33
33 "Leaf blade strap-shaped to narrowly elliptic, length 2.9–6.4 × width, base convex to subcordate; stipule tip rounded to acuminate" "Salix ligulifolia"
33 "Leaf blade narrowly oblong or lanceolate to obovate, length 2.4–4.5 × width, base rounded to cordate; stipule tip convex to rounded" "Salix prolixa"
34 "Twigs glaucous" 35
34 "Twigs not glaucous" 39
35 "Leaf blade dull adaxially" 36
35 "Leaf blade shiny adaxially" 37
36 "Leaf blade abaxially very densely white- or white-and-rusty-silky; young leaves short-silky; twigs brittle at base" "Salix drummondiana"
36 "Leaf blade abaxially sparsely to moderately densely white-silky; young leaves long-silky; twigs flexible at base" "Salix orestera"
37 "Leaf blade hairier abaxially than adaxially (except midrib abaxially ± glabrous), generally densely white-silky to -tomentose; young leaves short-silky" "Salix drummondiana"
37 "Leaf blade equally hairy abaxially and adaxially (midrib abaxially generally ± as hairy as blade), white-, rusty-, or white-and-rusty-hairy, glabrous in age or not; young leaves short- or long-silky" 38
38 "Leaf blade hairs long, generally white or white and rusty, persistent; petiole 2–9 mm; stipules generally 0 or vestigial" "Salix geyeriana"
38 "Leaf blade hairs short, generally rusty, or in age 0; petiole 5–16 mm; stipules vestigial on first leaves, leaf-like on later leaves" "Salix lemmonii"
39 "Young leaves sparsely or moderately hairy; petiole puberulent; twigs soft-shaggy-hairy – n MP" "Salix bebbiana"
39 "Young leaves very densely hairy; petiole tomentose, silky, or velvety; twigs soft-shaggy-hairy, tomentose, silky, velvety, or glabrous in age" 40
40 "Leaf blade elliptic to obovate, length 1.3–2.8 × width; petiole velvety or tomentose; young leaves velvety or silky; leaf tip acute to convex" "Salix delnortensis"
40 "Leaf blade linear to oblanceolate, length 2.8–7.3 × width; petiole tomentose (or silky or velvety in Salix jepsonii); young leaves silky; leaf tip acute to acuminate (convex or not in Salix jepsonii)" 41
41 "Shrub < 1 m, subalpine; leaf blade 10–95 mm; 2100–4000 m" 42
41 "Shrub > 1 m, subalpine and not; leaf blade 32–144 mm; 0–2800 m (to 3400–3600 m in Salix geyeriana, Salix jepsonii, Salix lemmonii)" 43
42 "Leaf blade 10–20 mm, shiny adaxially; petiole silky; young leaves very densely hairy; rare, c SNH (e slope, Mono Co.)" "Salix brachycarpa var. brachycarpa"
42 "Leaf blade 35–95 mm, dull adaxially; petiole soft-shaggy-hairy; young leaves long-silky; not rare, SN, SNE" "Salix orestera"
43 "Leaf blade white-and-rusty-hairy" 44
43 "Leaf blade white-hairy" 46
44 "Stipules generally leaf-like (or vestigial); young leaves, mature blades densely silky or generally short-tomentose; 0–2800 m" "Salix lasiolepis"
44 "Stipules 0 or vestigial on first leaves, generally leaf-like on later; young leaves, mature blades generally densely silky; 1450–3600 m" 45
45 "Leaf blade hairs long (generally white or white and rusty), persistent; petiole 2–9 mm; stipules generally 0 or vestigial" "Salix geyeriana"
45 "Leaf blade hairs short (generally rusty) or 0 in age; petiole 5–16 mm; stipules vestigial on first leaves, leaf-like on later" "Salix lemmonii"
46 "Petiole silky, tomentose, or velvety" 47
46 "Petiole tomentose or soft-shaggy-hairy" 49
47 "Leaf blade generally densely silky on both surfaces, 32–89 mm; stipules generally 0; petiole velvety" "Salix geyeriana"
47 "Leaf blade generally glabrous in age or abaxially hairier, 35–144 mm; stipules generally leaf-like; petiole silky, tomentose, or velvety" 48
48 "Leaf blade abaxially densely silky, adaxially dark green; margin of first leaves on shoot gland-dotted" "Salix jepsonii"
48 "Leaf blade abaxially sparsely or moderately hairy, adaxially not dark green; margin of first leaves on shoot glandless" "Salix lasiolepis"
49 "Leaf blade on both surfaces silky; stipule tip generally acute" "Salix orestera"
49 "Leaf blade abaxially tomentose, adaxially long-soft-wavy-hairy or tomentose; stipule tip generally convex" 50
50 "Leaf blade abaxially generally densely tomentose; twigs generally velvety; on serpentine" "Salix breweri"
50 "Leaf blade abaxially generally sparsely or moderately tomentose; twigs generally sparsely tomentose; on serpentine or not" "Salix lasiolepis"