1 Plants with a mix of alternate and opposite or subopposite leaves; [subgenus Vetrix, section Helix]

1 Plants with all leaves alternate.

  2 Bud apex sharp-pointed; bud scale margin free and overlapping; stamens 3-7 (-9); leaf blades 2.5-16× as long as wide; [subgenus Protitea].

    3 Leaf blades (4-) 7-10 (-16)× as long as wide; leaf abaxial surface glaucous (S. caroliniana) or not (S. nigra); floral bracts deciduous after flowering; plants trees [section Humboldtianae].

      4 Plants trees to 20 m tall; leaves not glaucous beneath (or thinly so); pistils borne on stipes averaging 1 mm long (range 0.5-1.5 mm); stipules usually small and caducous, to 12 mm long; leaf blades avg. 9 (-16)× as long as wide

    3 Leaf blades 2.5-5 (-6)× as long as wide; leaf undersurface glaucous; pistillate bracts deciduous (S. amygdaloides) or persistent (S. floridana) after flowering; plants shrubs or trees.

        5 Leaf apex acuminate to caudate; branchlets yellow; pistillate bracts deciduous after flowering; plants trees, usually 4-20 m tall; [NY and PA west to MO, further north and west; primarily midwestern]; [section Humboldtianae]

        5 Leaf apex acute; branchlets reddish brown or green; pistillate bracts persistent after flowering; plants large shrubs or small trees, usually 2-8 m tall; [rare plant of sphagnous seepages in s. AL, s. GA, and FL]; [section Floridanae]

  2 Bud apex blunt or rounded; bud scale margins fused, thus individual scale margins are not distinct or overlapping; stamens usually 2 (except for S. lucida and S. serissima with 3-10 stamens); leaf blades 2-30× as long as wide; plants short to large shrubs, or trees.

          6 Leaves green or pale green beneath, lacking a glaucous bloom.

             7 Leaves linear to lorate (strap-shaped), (7-) 11-35x as long as wide; leaf margins remotely spinulose-serrulate.

               8 Ovaries glabrous or sparsely long-silky; largest medial blades moderately densely hairy or glabrous; staminate abaxial nectaries present; floral bracts sparsely hairy; capsules (4-) 5-8 (-10) mm; [widespread, including s. TX]

               8 Ovaries moderately to very densely short-silky or villous; largest medial blades moderately to very densely appressed hairy; staminate abaxial nectaries absent; floral bracts moderately to very densely hairy; capsules (2.5-) 4-7 mm; [s. TX]

             7 Leaves narrowly oblong to ovate, oblanceolate to lanceolate, broadly to narrowly elliptic, or sometimes lorate; 1.6-6.2 (-8)x as long as wide; if sometimes lorate or narrowly elliptic, then leaf length never exceeding the leaf width by more than 8x; leaf margins primarily serrate, serrulate, or crenulate but not remotely spinulose-serrulate.

                 9 Stipules not glandular on their margins; pistillate floral bracts present after flowering; petioles not glandular; stamens 2; [subgenus Salix, section Salicaster].

                   10 Stipules on early leaves absent or minute; abaxial leaf surface usually ± glabrous, only thinly glaucous, if at all; leaves with white hairs only (when present); leaf apex usually acuminate, sometimes acute (rarely subcaudate); branches dull or slightly glossy; pistillate catkins stout to globose, 11-22 mm wide; stigma lobes 0.4-0.7 mm long; capsules (6-)7-12 mm long; plants fruiting in late summer or in fall; [mostly exclusive to rich fens and other high pH wetlands; PA northward]

                   10 Stipules on early leaves foliaceous; abaxial leaf surface glabrous, pilose, or moderately densely villous to long-silky; leaves (at least juvenile) with a mix of white and ferruginous hairs; leaf apex usually long-acuminate to caudate; branches slightly to highly glossy; pistillate catkins slender to stout, 7-15 mm wide; stigma lobes 0.2-0.4 mm; capsules 5-7 mm long; plants fruiting in late spring or summer [riparian and gravelly floodplain habitats, stream shores, lake margins, occasionally in fens or marly peatlands; VA northward]

                 9 Apex of petiole without glands (petiole sometimes tomentose or pubescent, but lacking glands); leaf apex rounded, blunt, or acute (sometimes acuminate in S. eriocephala); stamens usually 2; [subgenus Vetrix)

                     11 Leaf blades 2.3-8x as long as wide, the margins serrulate or crenulate; the teeth without glands or if present, very small; stipules not glandular on their margins; pistillate floral bracts densely pubescent, present after flowering; branchlets densely to sparsely puberulent, rarely villous; plants flowering just prior to leaf emergence; [widespread in our area]; [section Cordatae]

                     11 Leaves 1.6-3.2x as long as wide, the margins sharply (sometimes doubly) serrate; the teeth with prominent glands; unfolding leaves with long, dense, silky hairs; branchlets ± villous-pubescent; plants flowering just as leaves emerge; [Great Lakes sand dunes and beaches, limited to Presque Isle, PA in our area]; [section Hastatae]

          6 Leaves glaucous or strongly whitened beneath.

                       12 Leaves 10-35 as long as wide; linear or lorate (strap-shaped); margins entire or remotely spinulose-serrulate; [streams, sandbars, and similar gravelly riparian habitats]; [s. TX, westward].

                          13 Abaxial leaf surface silky or pilose; branchlets densely short-silky-tomentose to short-villous; leaf margins usually entire; plants to 17 m tall

                          13 Abaxial surface glabrous, glabrescent, densely villous, or long- or short-silky; branchlets tomentose or pubescent to glabrescent; leaf margins usually spinulose-serrulate; plants to 10 m tall

                       12 Leaves 2-9x as long as wide; narrowly oblong, narrowly elliptic, elliptic, lanceolate, oblanceolate, obovate, or narrowly ovate; if lorate or narrowly elliptic then l:w ratio not exceeding 9x; leaf margins entire, crenate, crenulate, serrulate, serrate, or irregularly toothed; [in a variety of habitats]; [widespread, including TX].

                            14 Leaf margin crenate, crenulate or entire; if teeth present, then these generally rounded; if teeth are somewhat pointed, then these spaced irregularly and often mixed with crenulate teeth on the same plant; [subgenus Vetrix].

                              15 Leaves without revolute margins, flattened or undulate.

                                16 Leaf blades consistently entire, lacking teeth; leaf surface usually glabrous (very rarely sparsely short-silky)

                                16 Leaf blades with some toothing, usually somewhat crenate, not consistently entire; leaf surface usually at least somewhat pubescent.

                                  17 Leaf blades coriaceous and regularly toothed, strongly glaucous abaxially; leaf margins crenulate or serrulate; aments precocious to coetaneous

                                  17 Leaf blades not coriaceous, with fewer teeth, obscurely or prominently glaucous abaxially; leaf margins mostly crenate, sometimes crenulate, entire, or irregularly serrate; aments precocious (sometimes emerging immediately prior to leaves).

                                    18 Upper (adaxial) surface of leaves usually impressed-veiny, pubescent; proximal blade margins gland-dotted; branchlets pubescent; winter buds red to red-brown

                                    18 Upper surface of leaves less noticeably veiny (or at least not conspicuously impressed veiny), tomentose or glabrous; proximal blade margins not gland-dotted; branchlets glabrate or sometimes with small patches of nodal hairs, but not persistently pubescent; winter buds yellow, yellow-brown or red-brown

                              15 Leaves slightly or strongly revolute along the margins.

                                       19 Leaf margin entire and undulate; plants native shrubs, < 2 m tall (occasionally to 3 m tall); floral bracts 0.8-2 mm long; pistillate aments 1-3.5 cm long; pistils borne on stipes mostly < 2 mm long; staminate aments 0.5-2 cm long.

                                         20 Leaf adaxial surface conspicuously veiny-rugose; leaf abaxial surface densely wooly; catkins 17-39 mm long; filaments glabrous; [fens and other alkaline wetlands]

                                         20 Leaf adaxial surface not veiny-rugose (or only weakly so); leaf abaxial surface whitened, but not wooly; catkins 9-47 mm long; floral bracts 1.2-2 mm long; filaments glabrous or basally pubescent; [forest edges, successional habitats, open sandy or rocky habitats and other similar dry to mesic habitats; associated southward with mafic habitats]

                                           21 Leaves stipulate; leaf blades (5-) avg. 7 (-13) cm long, (12-) avg. 17 (-35) mm wide; staminate aments 1-2 cm long; pistillate aments 2-3.5 cm long; [open, upland habitats, shrubby or rocky balds or rocky, open woodlands, powerline clearings, barrens, woodland borders, fens and grassy balds over mafic rocks (e.g. amphibolite) up to at least 1800m elevation]

                                           21 Leaves exstipulate (without stipules); leaf blades (2.5-) avg. 4 (-5) cm long, (5-) avg. 7 (-10) mm wide; staminate aments 0.5-1.1 cm long; pistillate aments 1-2 cm long; [barrens, glades, rocky or hardpan woodlands, prairies, powerline rights-of-way, rarely in depression ponds]

                                       19 Leaf margin crenate to irregularly serrate (rarely nearly entire), if serrate then the teeth irregularly spaced and not sharply pointed; plants non-native, shrubs to small trees, 3-15 m tall; floral bracts 1-4 mm long; pistillate aments 3-8 cm long; pistils borne on stipes mostly > 2 mm long; staminate aments 2-5 cm long.

                                             22 Trees or tall shrubs, to 15 m tall; decorticated wood of 1-4 year old branches smooth or with a few ridges usually < 5 mm long (striae not dense); floral bracts 2-4 mm long

                                             22 Shrubs, 3-7 (12) m tall; decorticated wood of 1-4 year old branches with numerous prominent ridges (dense striae), many of the ridges longer than 2 cm; floral bracts 1-3 mm long

                                               23 Abaxial leaf surface with a mixture of white and rusty (ferrugineous) hairs; branches yellowish to reddish; plants with single stems or trunks 3-12 m tall

                                               23 Abaxial leaf surface with a mixture of white or gray hairs, without ferrugineous hairs; branches grayish; plants multi-stemmed shrubs to 3-7 m tall

                            14 Leaf margins serrate, serrulate, denticulate, or remotely spinulose-serrulate.

                                                 24 Plants shrubs, to 6 m tall; if large shrubs or small trees then the form vase-like, bushy and upright (not weeping or with strongly pendulous branches); plants clonal and growing in dense patches OR as single-stemmed to clumped shrubs; leaves lacking stomates on the upper surface; catkins precocious to coetaneous [native to our area]; [subgenus Vetrix].

                                                    25 Petioles with one pair (or more) of distal spherical glands.

                                                      26 Leaf abaxial surface thinly glaucous; leaf margins consistently serrate, the apices acuminate, caudate or acute; petioles deeply grooved; branches flexible and sometimes brittle; [plants of rich alkaline wetlands]

                                                      26 Leaf abaxial surface thickly or conspicuously glaucous, sometimes densely obscured by short-silky hairs; leaf margins usually a mix of crenate, crenulate, or serrulate teeth, the apices acute, acuminate or convex; petioles convex, flat, or shallowly grooved; branches highly brittle; [sandy or cobbly river and lake shores, swamps, ditches, fens, other various habitats]

                                                        27 Leaves coriaceous, abaxial surfaces thickly glaucous, the margins mostly obscurely crenate to crenulate, sometimes crenulate-serrulate; staminate catkins emerging before leaves, pistillate as leaves emerge; capsules 5-11 mm long, glabrous; filaments glabrous throughout

                                                        27 Leaves not coriaceous, abaxial surfaces glaucous, sometimes obscured by densely short-silky hairs, the margins serrulate or less often obscurely crenulate (proximal blades sometimes nearly entire); catkins flowering as (coetaneous) or just before leaves emerge; capsules 2.5-4 mm long, pubescent; filaments pubescent

                                                    25 Petioles lacking distal glands.

                                                          28 Leaves lorate, narrowly elliptic, or narrowly oblong; abaxial leaf surfaces glaucous and often sparsely to densely silky pubescent; leaf blade bases cuneate; stipules absent to rudimentary (or distally foliaceous on later stipules); capsules silky-pubescent

                                                            29 Leaf blades 2.5-7 cm long, sometimes nearly entire at the base; stipules absent or minute; branches flexible (not breaking cleanly at junction of annual growth); leaf blades (at least expanding leaves) with ferrugineous and white hairs, the abaxial surface sparely to densely pubescent; capsules 5-9 mm long, beaked; [section Geyerianae]

                                                            29 Leaf blades 4-15 cm long, serrulate to the base; stipules absent or of small glands (rarely to 4 mm long on vigorous shoots); branches brittle (breaking cleanly at junction of annual growth); mature leaves short-sericeous abaxially, but lacking red-brown hairs; capsules 2.5-4 mm long, not beaked [section Griseae]

                                                          28 Leaves narrowly elliptic, elliptic, narrowly oblong, obovate or oblanceolate; abaxial leaf surfaces thickly glaucous and glabrous to sparsely pubescent (thus glaucous surface usually very conspicuous); leaf blade bases cordate, rounded, or broadly cuneate; stipules foliaceous or rudimentary to absent; capsules glabrous.

                                                              30 Stipule apices rounded or acute; mature leaves glabrous or glabrescent abaxially; leaf apices usually acute or acuminate (occasionally rounded); leaf margins serrate or serrulate; floral bracts 0.8-1.5 mm long, with wavy pubescence; anthers 0.4-0.64 mm long; styles 0.3-0.6 mm long; [widespread, section Cordatae]

                                                              30 Stipule apices acute or acuminate; mature leaves glabrous or pilose abaxially, usually strongly glaucous; leaf apices usually acute, sometimes rounded or short-acuminate; leaf margins usually crenulate or crenulate-serrulate; floral bracts 1.5-3 mm long (avg. 1.8 mm), with straight hairs; anthers 0.52-0.76 mm long; styles 0.5-1.3 mm long; [PA northward, section Hastatae]

                                                 24 Plants full-sized trees, usually 10-25 m tall on mature individuals; the form or silhouette often appearing weeping on full-sized trees; catkins coetaneous (occasionally precocious in S. babylonica); [non-native in our area, subgenus Salix]

                                                                 31 Leaf margin coarsely and irregularly serrate; leaves glabrous beneath; leaf blade 4-7 (-10)× as long as wide; petioles (7-) 10-20 mm long, glabrous; [section Salix]

                                                                 31 Leaf margin minutely and uniformly serrulate; leaves long-sericeous or glabrate beneath; leaf blade 5-13× as long as wide; petioles 3-12 mm long, tomentose or sericeous.

                                                                   32 Leaves long-sericeous beneath; branches ascending (rarely pendulous); leaves narrowly lanceolate, with length/width ratio of 5-6.5; petioles 3-6 mm long, sericeous, with spherical glands or lobes distally; flowering branchlets 1-1.5 cm long; [section Salix]

                                                                   32 Leaves glabrate beneath; branches normally pendulous; leaves very narrowly lanceolate, with length/width ratio of 6.5-13; petioles 7-12 mm long, tomentose, eglandular or with spherical glands or lobes distally; flowering branchlets ca. 0.3 cm long; [section Subalbae].

                                                                     33 Branches yellowish, yellow-green, or yellow-brown

                                                                     33 Branches yellow-brown to red-brown, or gray-brown.

                                                                       34 Pistillate catkins on branchlets that are (0-) 2-4 mm long; ovary beak abruptly tapered to styles; anthers 0.4-0.5 mm long

                                                                       34 Pistillate catkins on branchlets that are 3-14 mm long; ovary beak gradually tapered to styles; anthers 0.5-0.8 long.

                                                                         35 Petioles glabrous, pilose, or velvety to glabrescent on the upper surface; branches yellow-brown, gray-brown, or red-brown; staminate catkins loosely flowered, stout, nectaries connate and shallowly cup-shaped

                                                                         35 Petioles short-silky on the upper surface; branches yellow-brown; staminate catkins moderately densely flowered. slender, nectaries distinct