Salix humboldtiana
Salix niphoclada
Humboldt's willow
barren-ground willow, snow willow
erect, decumbent, or trailing;
branches gray-brown, yellow-brown, or red-brown, pilose, villous, or long-silky to glabrescent;
branchlets violet, red-brown, or yellow-brown, pilose, densely villous, long-silky, or tomentose.
stipules (sometimes marcescent), foliaceous, (sometimes obscured by hairs);
petiole (shallowly grooved adaxially), 2–5.5 mm, (usually shorter than or barely exceeding subtended bud, villous adaxially);
largest medial blade hypostomatous or amphistomatous, narrowly oblong, narrowly to broadly elliptic, lanceolate, or obovate, 13–64 × 6–22 mm, 1.6–5.5 times as long as wide, base convex, margins slightly revolute, entire (obscured by hairs), apex acuminate or acute, abaxial surface densely villous or woolly to pilose, hairs straight or wavy, adaxial slightly glossy, moderately densely to sparsely villous;
proximal blade margins entire;
juvenile blade abaxially densely long-silky.
abaxial nectary 0.5–1.2 mm, adaxial nectary narrowly oblong to ovate or flask-shaped, 0.5–1.5 mm, nectaries distinct or connate and cup-shaped;
filaments distinct, glabrous, or sparsely hairy on proximal 1/2;
anthers ellipsoid or globose, 0.3–0.5 mm.
abaxial nectary rarely present, 0.7 mm, adaxial nectary narrowly oblong, ovoid, or flask-shaped, 0.5–2 mm, longer than stipe;
stipe 0–0.5 mm;
ovary pyriform, very densely villous or long-silky, beak slightly bulged below or abruptly tapering to styles;
ovules 8–20 per ovary;
styles connate to almost distinct, 0.2–0.8 mm;
stigmas slenderly to broadly cylindrical, 0.2–0.36–0.6 mm.
4–6 mm.
humboldtiana Willdenow: Humboldt willow is not known to occur in the flora area.
is characterized by: trees, 4–25 m;
branches highly brittle at base, bud-scale margins distinct and overlapping adaxially;
stipules on late leaves rudimentary or foliaceous;
largest medial leaf blade usually linear, abaxial surface not glaucous, adaxial dull;
pistillate bract deciduous after flowering;
stamens 3–7;
capsules with distinct, often raised, white veins.;
it occurs throughout much of Mexico to central Chile.
staminate 12–42 × 4–14 mm, flowering branchlet 0–20 mm;
pistillate densely flowered, slender, stout, or subglobose, 16–69 × 4–13 mm, flowering branchlet 4–30 mm;
floral bract tawny, brown, or black, 1.2–3.2 mm, apex rounded, entire, abaxially sparsely to moderately densely hairy, hairs wavy.
Salix humboldtiana
Salix niphoclada
Salix humboldtiana is closely related to S. nigra in its generally narrow leaf blades, which are not glaucous abaxially. The two differ in the following characters: S. humboldtiana has leaf blades linear to sometimes narrowly oblong (10–28.6 times as long as wide), ovaries usually ovoid to ellipsoid, ovary walls often stomatiferous and with raised, white veins, and capsule valves relatively thick, slightly recurved. S. nigra has leaf blades usually narrowly lanceolate (6–13 times as long as wide), ovaries pyriform to obclavate, ovary walls neither stomatiferous nor notably veined, and capsule valves relatively thin and strongly recurved. Both species occur in Chihuahua, Mexico.
The report by R. I. Lonard et al. (1991) that specimens identified as Salix nigra from the lower Rio Grande, Texas, resemble S. humboldtiana in having strongly veined capsules suggests that S. humboldtiana, or intergrades with that species, may occur in Texas. Attempts to locate a voucher specimen were unsuccessful; because strongly veined capsules are diagnostic, further field study is indicated.
An earlier name, Salix chilensis Molina, has been applied to this species; it does not seem to pertain to this taxon (C. K. Schneider 1918).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Salix niphoclada was treated as S. brachycarpa subsp. niphoclada (G. W. Argus 1965, 1973) because where the ranges of the two taxa overlap in northern British Columbia they appeared to intergrade. Species rank is used here, however, because there is no evidence to suggest that intergradation is common or extends beyond the small area of overlap.
Salix brachycarpa var. fullertonensis, which mainly occurs in southern Nunavut and the western side of Hudson Bay, is characterized by smaller leaves and catkins, broad, reddish floral bracts, and more sparsely hairy branchlets (G. W. Argus 1965). Its intergradation with S. niphoclada is so extensive that it is not recognized here as a separate taxon.
Hybrids:
Salix niphoclada forms natural hybrids with S. glauca var. acutifolia and S. setchelliana.
Salix niphoclada × S. setchelliana is a putative hybrid from Sheep Mountain, Kluane, Yukon, at 1180 m. It resembles S. niphoclada in leaf shape and indumentum, stigmas 0.6 mm, floral bracts oblong, 1.8 mm, and in the shape and length of pistillate catkins, but it has the glabrous, reddish ovaries of S. setchelliana. Both putative parents occur in the area.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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