Flora of the Southeastern United States
2022 Edition

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Key to Salix

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1 Leaves mostly alternate, but some opposite or subopposite; [subgenus Vetrix, section Helix]
1 Leaves all alternate.
..2 Bud apex sharp-pointed; bud scale margin free and overlapping; leaf blades 2.5-16× as long as wide; [subgenus Protitea].
....3 Leaf blades (4-) 7-10 (-16)× as long as wide; leaf undersurface glaucous or not; [section Humboldtianae].
......4 Leaves glaucous beneath; pistils borne on stipes averaging 2 mm long (range 1-5 mm); stipules usually prominent and persistent, to 15 mm long; leaf blades (4-) avg. 7.5 (-13)× as long as wide
......4 Leaves not (or thinly) glaucous beneath; 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 (4-) avg. 9 (-16)× as long as wide
....3 Leaf blades 2.5-5 (-6)× as long as wide; leaf undersurface glaucous.
........5 Leaf apex acuminate to caudate; branchlets yellow; [midwestern species east and south to KY and WV]; [section Humboldtianae]
........5 Leaf apex acute; branchlets reddish brown or green; [rare plant of sphagnous seepage of s. AL, s.GA, and FL]; [section Floridanae]
..2 Bud apex blunt; bud scale margin fused; leaf blades 2-30× as long as wide.
..........6 Leaves green or pale green beneath.
............7 Leaves linear, (7-) 11-19 (-30)× as long as wide; leaf margin distinctly glandular-denticulate; stomates present on the upper leaf surface; pistils pubescent to glabrescent; stamens 2, the staminate floral bracts tawny, the aments on leafy branches; [subgenus Longifoliae, section Longifoliae]
............7 Leaves lanceolate or elliptic-lanceolate, 2-6× as long as wide; leaf margin serrate; stomates usually absent on the upper leaf surface; pistils glabrous; stamens 3, or if 2 (S. eriocephala), the staminate floral bracts dark brown, the aments sessile with a few leafy bracts.
..............8 Stipules not glandular on their margins; pistillate floral bracts present after flowering; petioles not glandular; stamens 2; [subgenus Vetrix, section Cordatae]
..............8 Stipules glandular on their margins (stipules caducous and often absent in S. pentandra); pistillate floral bracts deciduous after flowering; petioles glandular near the junction with the blade; stamens 3-9; [subgenus Salix, section Salicaster].
................9 Stipules persistent and prominently glandular; young leaves and twigs with reddish-brown hairs, glabrescent or glabrous later; leaves long-acuminate; capsules 5-7 mm long
................9 Stipules caducous, inconspicuously glandular; young leaves and twigs glabrous; leaves short-acuminate; capsules 8-9 mm long
..........6 Leaves glaucous beneath.
..................10 Leaf margin entire or crenate (to slightly and irregularly serrate); [subgenus Vetrix, section Cinerella].
....................11 Leaves glabrate (sparsely pubescent when young), not revolute
....................11 Leaves permanently pubescent, at least on the lower surface (densely villous or tomentose when young), revolute.
......................12 Leaf margin entire and undulate; pistillate aments 1-3.5 cm long; pistils borne on stipes mostly < 2 mm long; staminate aments 0.5-2 cm long; shrubs, < 2 m tall.
........................13 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...
........................13 Leaves exstipulate; 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
......................12 Leaf margin crenate or irregularly serrate (rarely nearly entire); pistillate aments 3-8 cm long; pistils borne on stipes mostly > 2 mm long; staminate aments 2-5 cm long; shrubs to small trees, mostly 3-15 m tall.
..........................14 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
..........................14 Shrubs, 3-7 (12) m tall; decorticated wood of 1-4 year old branches with numerous ridges, many of them longer than 2 cm.
............................15 Leaves tomentose beneath with a mixture of white and rusty hairs
............................15 Leaves tomentose beneath with white or gray hairs
..................10 Leaf margin serrulate or serrate.
..............................16 Shrubs to 6 m tall; leaves lacking stomates on the upper surface; [native to our area]; [subgenus Vetrix].
................................17 Stipules prominent, 5-15 mm long; branches flexible; mature leaves glabrous or glabrescent beneath; staminate aments borne on short, leafy branches; [section Cordatae]
................................17 Stipules absent or of small glands (rarely to 4 mm long on vigorous shoots); branches brittle; mature leaves short-sericeous beneath; staminate aments sessile, sometimes with a few leafy bracts; [section Griseae]
..............................16 Trees; leaves with stomates on the upper surface; [introduced in our area]; [subgenus Salix].
..................................18 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]
..................................18 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.
....................................19 Leaves long-sericeous beneath; branches ascending (rarely pendulous); leaves narrowly lanceolate, with length/width ratio of 5-6.5; petioles 3-6 mm long; petioles 3-6 mm long, sericeous; flowering branchlets 1-1.5 cm long; [section Salix]
....................................19 Leaves glabrate beneath; branches normally pendulous; leaves very narrowly lanceolate, with length/width ratio of 6.5-13; petioles 7-12 mm long; petioles 7-12 mm long, tomentose; flowering branchlets ca. 0.3 cm long; [section Subalbae].
......................................20 Branches yellowish, yellow-green, or yellow-brown
......................................20 Branches yellow-brown to red-brown, or gray-brown.
........................................21 Pistillate catkins on branchlets that are (0-) 2-4 mm long; ovary beak abruptly tapered to styles; anthers 0.4-0.5 mm long
........................................21 Pistillate catkins on branchlets that are 3-14 mm long; ovary beak gradually tapered to styles; anthers 0.5-0.8 long.
..........................................22 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
..........................................22 Petioles short-silky on the upper surface; branches yellow-brown; staminate catkins moderately densely flowered. slender, nectaries distinct