Salix hookeriana
Salix athabascensis
coastal willow, dune willow, Hooker's willow
Athabasca willow
branches (highly brittle at base), yellow-brown, gray-brown, red-brown, or violet, not or weakly glaucous, glabrous, tomentose, woolly, or sparsely villous to glabrescent (nodes hairy);
branchlets gray-brown, red-brown, or yellow-brown (sometimes color obscured by hairs), glabrous, pilose, moderately densely villous, tomentose, or woolly, scale with inner membranaceous layer free, (not separating from outer layer).
erect;
branches gray-brown, hairy;
branchlets red-brown, sparsely or moderately densely pubescent, (buds alba-type).
stipules rudimentary or absent on early ones, foliaceous (early deciduous) or rudimentary (sometimes obscured) on late ones, (2.5–7.8–18 mm), apex acuminate, acute, or rounded;
petiole convex to flat, or shallowly grooved adaxially, 4–29 mm, villous, woolly, pilose, or tomentose adaxially;
largest medial blade (sometimes hemiamphistomatous), narrowly to broadly elliptic, oblanceolate, or obovate to broadly obovate, 36–123 × 18–63 mm, 1.5–4.2 times as long as wide, base convex, rounded, subcordate, cordate, or cuneate, margins slightly revolute, crenate, serrate, shallowly serrulate, sinuate, or entire, apex acuminate, acute, or convex, abaxial surface glaucous, pilose, moderately densely tomentose, villous, or woolly, midrib hairy, hairs (white, sometimes also ferruginous), wavy or straight, adaxial highly or slightly glossy, glabrous, pilose, villous, or moderately densely tomentose, midrib and veins hairy (hairs white, sometimes also ferruginous);
proximal blade margins entire or shallowly serrulate;
juvenile blade yellowish, reddish green (sometimes obscured by hairs), pilose or sparsely to densely long-silky, tomentose, woolly, or villous abaxially, hairs white, sometimes also ferruginous, or yellowish.
stipules absent or rudimentary on early ones, usually rudimentary, rarely foliaceous, on late ones;
petiole (shallowly grooved adaxially), 3–10 mm, (puberulent or villous);
largest medial blade oblong, narrowly elliptic, elliptic, oblanceolate, or obovate, 17–50 × 8–18 mm, 1.9–3.2 times as long as wide, base cuneate or convex, margins flat or slightly revolute, entire, apex acuminate or convex, abaxial surface glabrescent or sparsely silky, hairs appressed or somewhat spreading, (usually white, sometimes also ferruginous), straight or wavy, adaxial dull or slightly glossy, glabrous, glabrescent, pilose, or sparsely long-silky along midribs and margin, (hairs usually white, sometimes also ferruginous, appressed);
proximal blade margins entire;
juvenile blade sparsely to moderately densely villous or long-silky abaxially (hairs usually white, sometimes also ferruginous).
adaxial nectary oblong, ovate, or narrowly oblong, 0.5–1.4 mm;
filaments distinct or slightly basally connate, glabrous or hairy on proximal 1/2 or basally;
anthers yellow, cylindrical or ellipsoid, (0.5–)0.7–1 mm.
abaxial nectary (0–)0.3–0.6 mm, adaxial nectary oblong or ovate, 0.4–1.2 mm, nectaries distinct;
filaments distinct, hairy basally or on proximal 1/2;
anthers globose, 0.4–0.6 mm.
adaxial nectary narrowly oblong, oblong, or square, 0.5–1.4 mm, shorter than stipe;
stipe 0.5–1.8(–2.8) mm;
ovary obclavate or pyriform, glabrous, tomentose, villous, or woolly (hairs wavy), beak sometimes abruptly tapering to styles;
ovules 12–20 per ovary;
styles 0.6–2.3 mm;
stigmas broadly to slenderly cylindrical, 0.3–0.8 mm.
abaxial nectary absent, adaxial nectary oblong, 0.4–1.3 mm, shorter than stipe;
stipe 0.8–1.3 mm;
ovary pyriform, very densely long-silky, beak gradually tapering to or slightly bulged below styles;
ovules 6–14 per ovary;
styles 0.5–1 mm;
stigmas flat, abaxially non-papillate with rounded tip, or broadly to slenderly cylindrical, 0.28–0.35–0.48 mm.
5–10 mm.
5.6–7.2 mm.
flowering before or as leaves emerge; staminate slender or stout, 26–73 × 10–27 mm, flowering branchlet 0–10 mm; pistillate densely flowered, slender or stout, 36–92(–140 in fruit) × 10–25 mm, flowering branchlet 0–20 mm;
floral bract brown, black, or bicolor, 1.1–3.6 mm, apex convex, rounded, or acute, abaxially hairy, hairs straight or wavy.
staminate 14–31 × 8–18 mm, flowering branchlet 1.5–9 mm; pistillate loosely flowered, stout to globose, 10–58 × 7–25 mm, flowering branchlet 3.5–26 mm;
floral bract tawny, 1–1.6 mm, apex rounded, entire, abaxially sparsely hairy, almost glabrous, hairs wavy.
= 114.
= 76, 95, 114.
Salix hookeriana
Salix athabascensis
Salix hookeriana is primarily a coastal species occurring from northern California northward to Oregon, Washington, and southern Vancouver Island, with disjunct populations on Queen Charlotte Islands, British Columbia, and northward to Yakatut Bay, Turnagain Arm, and Kodiak, Alaska. It was treated by G. W. Argus (1973) and R. D. Dorn (2000) in a broad sense because of an absence of strong distinguishing characters and intergradation in characters that could be used to divide it. It is highly variable and three very similar taxa have been named: S. amplifolia, S. hookeriana (including vars. tomentosa and laurifolia), and S. piperi. Although extremes of these taxa sometimes are recognizable, the intergradation displayed is so great that even attempts to recognize them as varieties are thwarted. The amplifolia variant in Alaska is characterized by having only white leaf hairs, hairy ovaries, no stipules, and catkins often borne on distinct flowering branchlets, but variation can occur within the same population, and typical S. hookeriana on Vancouver Island sometimes displays the same characteristics. The piperi variant, an inland population in western Oregon and Washington, is usually recognized by local botanists as different from coastal populations. It is characterized by leaves and branchlets soon becoming glabrate and stipules prominent. These characteristics, however, sometimes appear in northern California coastal populations, and some inland populations in Oregon include very hairy individuals that are indistinguishable from coastal variants of S. hookeriana. In general, very hairy populations of S. hookeriana are probably an adaptation to marine coastal environments, but some variation may be due to hybridization and introgression with S. scouleriana. Inland populations suggest the influence of S. lasiolepis. Two hexaploid chromosome numbers reported for S. hookeriana from Vancouver Island (R. L. Taylor and S. Taylor 1977) and Queen Charlotte Islands (R. L. Taylor and G. A. Mulligan 1968), British Columbia, indicate that hybridization has played a role in the evolution of this complex. It is possible that each variant of S. hookeriana has had a different, possibly even recurrent, polyploid origin. Further cytological and genetic study is indicated.
The following comparisons may help to distinguish Salix hookeriana, S. lasiolepis, and S. scouleriana.
Vegetative specimens of Salix hookeriana can be distinguished from S. lasiolepis by having floral buds ellipsoid, beaks distinctly long-tapered, densely long-hairy (villous), red-brown, blades usually pilose, villous, or woolly on abaxial surfaces, usually 18–63 mm wide, and 1.5–4.2 times as long as wide; S. lasiolepis has floral buds ovoid, beaks inconspicuous and blunt, sparsely to moderately densely short-hairy (velvety), yellowish to red-brown, blades usually tomentose on abaxial surfaces, usually 6–32 mm wide, and 3.2–9.6 times as long as wide.
Salix hookeriana is distinguished from S. scouleriana by having branchlets with spreading hairs (woolly or tomentose to glabrate), petioles usually pilose to tomentose, blades typically narrowly elliptic but variable, stigmas 0.3–0.74, short in relation to styles (0.6–2.3 mm), and pistillate nectaries 0.5–1.4 mm, shorter or longer than stipes; S. scouleriana has branchlets usually with short, erect hairs (velutinous), sometimes spreading (villous or tomentose), petioles velvety or villous adaxially, blades typically oblanceolate but variable, stigmas 0.4–1.04 mm, long in relation to styles (0.2–0.6 mm), and pistillate nectaries 0.2–0.8 mm, shorter than stipes.
Hybrids:
Salix hookeriana forms natural hybrids with S. barclayi and S. scouleriana. Variation in some S. hookeriana populations suggests hybridization with S. lasiolepis but no positive identifications have been made. R. D. Dorn (2000) doubted that hybridization in California between these species with different chromosome numbers was possible, but species with different chromosome numbers do hybridize [for example, S. athabascensis (4x) × S. pedicellaris (2x)]; synthetic hybridization studies are indicated.
Salix hookeriana × S. scouleriana: Plants from southern British Columbia with leaves similar to S. hookeriana but with prominent stipules, catkins both erect and recurving, and relatively long stigmas were thought by J. K. Henry (1915) to be this hybrid.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The three polyploid chromosome numbers reported for Salix athabascensis, as well as the presence of leaves with ferruginous hairs, otherwise unknown in sect. Myrtilloides, are indicators of allopolyploidy.
Hybrids:
Salix athabascensis forms natural hybrids with S. pedicellaris. These hybrids combine the characteristics of the parents. The ovaries may be moderately densely villous or glabrous, but commonly have hairs in patches, or the stipes may be hairy and the ovaries glabrous; juvenile blades, and sometimes mature leaves, are hairy with white and ferruginous hairs. Some plants that resemble S. athabascensis have leaves glaucous adaxially, as in S. pedicellaris. The ovaries often appear to be infertile.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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