Salix humboldtiana
Salix sericea
Humboldt's willow
silky willow
branches (highly brittle at base), gray-brown or violet, not glaucous, tomentose to glabrescent;
branchlets red-brown, violet, or mottled yellow-brown, sparsely to densely velvety.
stipules absent or rudimentary on early ones, late ones 1.2–4 mm, apex acute or acuminate;
petiole convex to flat, or shallowly grooved adaxially, 3.5–12(–21) mm, (sometimes 2 spherical glands distally), velvety adaxially;
largest medial blade lorate, narrowly oblong, or narrowly elliptic, (48–)54–82–100(–125) × (7–)9–16.7–25 mm, base cuneate or convex, margins flat, serrulate or crenulate, apex acute, acuminate, or convex, abaxial surface glaucous (sometimes obscured by hairs), densely short-silky, hairs straight, adaxial dull, sparsely pubescent to glabrescent;
proximal blade margins entire;
juvenile blade reddish or yellowish green, very densely short-silky abaxially, hairs white, sometimes also ferruginous.
adaxial nectary ovate to oblong, 0.3–0.8 mm;
filaments distinct or connate less than 1/2 their lengths;
anthers purple turning yellow, 0.4–0.6 mm.
adaxial nectary oblong, ovate, or flask-shaped, 0.4–0.7 mm;
ovary ovoid, beak abruptly tapering to styles;
ovules 6 per ovary;
styles 0.2–0.4 mm.
2.5–4 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.
flowering as or just before leaves emerge; staminate stout, 13.5–40 × 4–9 mm, flowering branchlet 0–2 mm; pistillate loosely to moderately densely flowered, slender to stout, 18–43 × 5–12 mm, flowering branchlet 1–3 mm;
floral bract dark brown, black, or bicolor, 0.8–1.5 mm, apex rounded, abaxially hairy, hairs straight or wavy.
Salix humboldtiana
Salix sericea
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.)
Some specimens of Salix sericea are difficult to separate from S. petiolaris (G. W. Argus 1986). Salix sericea can be distinguished from S. petiolaris in having branches highly brittle at base, stipules on early leaves rudimentary or absent, on late leaves usually foliaceous, juvenile blades usually with white hairs, rarely some ferruginous, ovaries ovoid, beaks abruptly tapering to styles, and capsules 2.5–4 mm; S. petiolaris has branches flexible at base, stipules on all leaves absent or rudimentary, juvenile blades usually with conspicuous ferruginous hairs, ovaries pyriform, beaks gradually tapering to styles, and capsules 5–9 mm.
See 68. Salix eriocephala for comments on differences.
Hybrids:
Salix sericea forms natural hybrids with S. eriocephala and S. petiolaris. Reports of hybrids with S. humilis (C. K. Schneider 1921; M. L. Fernald 1950) are not based on convincing specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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