Salix hookeriana
Salix arctophila
coastal willow, dune willow, Hooker's willow
arctic willow, northern 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).
prostrate, long-trailing;
branches yellow-brown, red-brown, or green-brown, glabrous;
branchlets yellow-green or yellow-brown to red-brown, (sometimes weakly glaucous), glabrous, (inner membranaceous bud-scale layer free, not separating from outer layer).
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 rudimentary, absent, or foliaceous on early ones, foliaceous or rudimentary on late ones;
petiole 3–7.8–15 mm;
largest medial blade hypostomatous or hemiamphistomatous, elliptic, obovate, broadly elliptic, broadly obovate, subcircular, or oblanceolate, 15–31–60 × 6.5–16–35 mm, 1.2–3–4.3 times as long as wide, base cuneate, convex, or rounded, margins slightly revolute, inconspicuously crenulate or entire, apex usually acute or convex, sometimes rounded, abaxial surface glaucous, glabrous, adaxial slightly or highly glossy, glabrous;
proximal blade margins entire or serrulate;
juvenile blade glabrous.
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 absent, adaxial nectary oblong, square, narrowly oblong, or ovate, 0.4–1 mm;
filaments distinct or connate less than 1/2 their lengths, glabrous, or hairy on proximal 1/2;
anthers ellipsoid or long-cylindrical, 0.5–0.7 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 or narrowly oblong, 0.5–0.9 mm, shorter than stipe;
stipe 0.8–1.4 mm;
ovary pyriform or obclavate, pubescent or short-silky, (refractive), hairs (white, grayish, or ferruginous), crinkled, often refractive, ribbonlike, beak gradually tapering to styles;
ovules 8–16 per ovary;
styles connate or distinct 1/2 their lengths, 0.6–1.4 mm;
stigmas slenderly or broadly cylindrical, 0.24–0.47–0.72 mm.
5–10 mm.
5–9 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 19–54 × 7–16 mm, flowering branchlet 4–20 mm; pistillate densely to moderately densely flowered, slender to subglobose, 30–79(–130 in fruit) × 10–20 mm, flowering branchlet 8–57 mm;
floral bract brown, black, or bicolor, 0.8–2.4 mm, apex rounded or acute, entire, abaxially densely hairy, hairs straight.
= 114.
= 76.
Salix hookeriana
Salix arctophila
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.)
Salix arctophila occurs in western Greenland.
Hybrids:
Salix arctophila forms natural hybrids with S. arctica, S. glauca var. cordifolia, and S. uva-ursi.
Salix arctophila × S. glauca var. cordifolia: Plants with villous leaves and moderately densely hairy branchlets and branches suggest this hybrid. Putative hybrids are rare but have been seen from Kuujjuaq and Ivujivik, Quebec (G. W. Argus, unpubl.), and are reported to be common in West Greenland (T. W. Böcher 1952).
Salix arctophila × S. uva-ursi is a rare hybrid. The plants often have ovaries with patches of hairs, some of which are ribbonlike, as in S. arctophila, but their habit is compact, as in S. uva-ursi, rather than long-trailing as in S. arctophila. Some specimens are infertile and are evidently hybrids, but there is little to confirm S. uva-ursi as the second parent. N. Polunin (1940b) also expressed some uncertainty about plants intermediate between S. arctophila and S. uva-ursi, and A. K. Skvortsov (1971) discounted this hybrid but noted that there were a few somewhat doubtful specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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