Salix humboldtiana
Salix herbacea
Humboldt's willow
snow-bed willow
erect;
branches red-brown to violet, (sometimes weakly glaucous), glabrous;
branchlets yellow-brown or red-brown, glabrous.
stipules absent;
petiole (convex or flat to deeply grooved adaxially), 1.5–6(–7) mm;
largest medial blade (2 pairs of secondary veins arising at or close to base, arcing) circular, subcircular or broadly elliptic, 6–21(–34) × 6–17(–31) mm, 0.9–1.4 times as long as wide, base usually subcordate or cordate, sometimes convex or rounded, margins flat, crenulate or crenate, apex rounded, convex, retuse, or toothed, abaxial surface (not glaucous), glabrous, adaxial slightly glossy to almost dull, glabrous;
proximal blade margins crenulate;
juvenile blade glabrous.
abaxial nectary 0.5–0.8 mm, adaxial nectary oblong or ovate, 0.6–1.1 mm, nectaries distinct, or connate and shallowly cup-shaped;
filaments distinct, glabrous, or hairy on proximal 1/2;
anthers shortly cylindrical or globose, 0.3–0.6 mm.
abaxial nectary (0–)0.2–0.3 mm, adaxial nectary narrowly oblong or oblong, 0.3–1.1 mm, longer or shorter than stipe, nectaries distinct or connate and shallowly cup-shaped;
stipe 0.3–1.1 mm;
ovary pyriform or ovoid, glabrous, beak abruptly tapering to styles;
ovules 11–18 per ovary;
styles connate to distinct, 0.2–0.4 mm;
stigmas broadly cylindrical or 2 plump lobes, 0.08–0.24–0.32 mm.
2.2–7.5 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.
from subterminal buds;
staminate 3–7.5 × 1.5–5 mm, flowering branchlet 0.3–2 mm;
pistillate loosely flowered (2–11 flowers), stout to globose, 3.3–13 × 2–10 mm, flowering branchlet 0.8–3.5 mm;
floral bract tawny, light rose, or brown, 0.5–1.5 mm, margins ciliate, apex rounded, retuse, or truncate, entire, abaxially glabrous.
= 38.
Salix humboldtiana
Salix herbacea
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 herbacea is the only willow with an amphi-Atlantic distribution. Disjunct populations occur as far west as Great Bear and Great Slave lakes, Northwest Territories. Macrofossils show that, during the late-Wisconsinan period, it occurred in North America along the glacial margin between Minnesota (R. G. Baker et al. 1999) and Cambridge, Massachusetts (G. W. Argus and M. B. Davis 1962). D. J. Beerling (1998) provided a comprehensive review of its biology and ecology.
Hybrids:
Salix herbacea forms natural hybrids with S. arctica, S. argyrocarpa, S. fuscescens, and S. uva-ursi.
Salix herbacea × S. uva-ursi (S. ×peasei Fernald) was described from Mt. Washington, New Hampshire, but occurs also in northern Quebec (G. W. Argus, unpubl.). It is morphologically intermediate between the parents. Its distinctly crenulate, broadly obovate leaves are similar to those of S. herbacea, its catkins are smaller and have fewer flowers than those of S. uva-ursi but more flowers than those of S. herbacea, its leaves are sparsely glaucous abaxially, and it has stems stouter than those of S. uva-ursi.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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