Salix humboldtiana
Salix irrorata
Humboldt's willow
blue-stem willow, dewy-stem willow
branches (highly brittle or not at base), red-brown to violet, usually glaucous, glabrous;
branchlets yellow-brown, (strongly glaucous or not), glabrous, sparsely velvety, or tomentose.
stipules absent or rudimentary on early ones, foliaceous or rudimentary on late ones, apex acute;
petiole convex to flat adaxially, 4–14 mm, velvety adaxially;
largest medial blade lorate, narrowly oblong, narrowly elliptic, or narrowly oblanceolate, 47–115 × 8–22 mm, 3.5–7.7 times as long as wide, base cuneate or convex, margins flat to slightly revolute, entire and gland-dotted, serrulate or crenate, apex acuminate, acute, or convex, abaxial surface glaucous, glabrous, sparsely tomentose, or short-silky, hairs wavy, adaxial slightly to highly glossy, glabrous or pilose;
proximal blade margins entire or serrulate;
juvenile blade yellowish green or reddish, glabrous or sparsely villous abaxially, hairs white.
adaxial nectary narrowly oblong to oblong, 0.3–0.8 mm;
filaments connate less than to more than 1/2 their lengths;
anthers yellow or purple turning yellow, ellipsoid or shortly cylindrical, 0.4–0.7 mm.
adaxial nectary narrowly oblong to oblong, 0.3–0.7 mm;
stipe 0.4–1 mm;
ovary pyriform, beak slightly bulged below styles;
ovules 9–12 per ovary;
styles 0.3–0.9 mm;
stigmas flat, abaxially non-papillate with rounded tip, 0.15–0.28–0.6 mm.
3.5–4 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 before or just before leaves emerge; staminate stout or subglobose, 15–34 × 8–22 mm, flowering branchlet 0(–2) mm; pistillate densely flowered, stout or slender, 14–43 × 7–12 mm, flowering branchlet 0–4 mm;
floral bract brown or black, 1.3–2.5 mm, apex rounded, abaxially hairy, hairs straight or wavy.
= 38.
Salix humboldtiana
Salix irrorata
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 irrorata is very closely related to S. lasiolepis. The two are here maintained as separate species primarily because S. irrorata is a diploid and S. lasiolepis a tetraploid, and also because of their largely allopatric ranges (G. W. Argus 2007). Studies of sawflies (Euura Newman) by P. W. Price (pers. comm.) show that the same species of Euura can successfully reproduce on either willow. The only morphological character that separates the two is that in S. irrorata branchlets and branches are very strongly glaucous, whereas in S. lasiolepis they are not glaucous. Some plants have weakly glaucous stems (wax not visible except by polishing or only as sparkling crystals); this may be infraspecific variability or evidence of hybridization.
Hybrids:
Salix irrorata forms natural hybrids with S. drummondiana, S. geyeriana, and S. lasiolepis var. lasiolepis.
Salix irrorata × S. lasiolepis var. lasiolepis: This putative hybrid occurs in Arizona and New Mexico. It is characterized mainly by weakly glaucous branches.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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