Salix planifolia
Salix discolor
diamond-leaf willow, plane-leaf willow, tea-leaf willow, tea-leafed willow
American willow, pussy or large pussy willow, pussy willow
(sometimes decumbent);
branches yellow-brown, red-brown, or violet, not to strongly glaucous, glabrous or pubescent;
branchlets yellow-brown, red-brown, or violet, glabrous, pilose, pubescent, moderately densely villous, or short-silky, (buds caprea-type).
branches dark red-brown or yellow-brown, not to strongly glaucous, villous to glabrescent, (peeled wood smooth or striate, striae sometimes very dense, to 10 mm);
branchlets yellowish, red-brown, or yellow-brown, or dark brown, moderately densely velvety, velutinous, or tomentose to glabrescent.
stipules (sometimes marcescent), rudimentary or foliaceous (small and usually brownish) on early ones, rudimentary or foliaceous on late ones, (narrowly ovate to oblong, 1–2.5(–4.5) mm), apex acute;
petiole shallowly grooved adaxially, 2–9(–13) mm, glabrous, pilose, or short-silky adaxially;
largest medial blade (sometimes hemiamphistomatous), narrowly oblong, narrowly elliptic, elliptic, or oblanceolate, 20–36–65 × 5–13–23 mm, 1.7–2.8–4.7 times as long as wide, base cuneate or convex, margins sometimes slightly revolute basally, entire, or, sometimes, crenulate or serrulate, apex acute, acuminate, or convex, abaxial surface glaucous, glabrous or sparsely silky, hairs (white, sometimes also ferruginous) straight or wavy, adaxial highly glossy, glabrous or sparsely short-silky;
proximal blade margins entire;
juvenile blade reddish or yellowish green, glabrous, puberulent, pubescent, or densely long-silky abaxially, hairs white, sometimes also ferruginous.
stipules rudimentary on early ones, foliaceous on late ones, (0.8–12.5 mm), apex acute to acuminate;
petiole convex to flat adaxially, 6–17 mm, tomentose adaxially;
largest medial blade narrowly elliptic, elliptic, oblanceolate, or obovate, 30–80(–135) × 12–33 mm, (2.3–)3–3.5(–4.5) times as long as wide, base convex or cuneate, margins flat, crenate, irregularly toothed, sinuate, or entire, apex acute, convex, or acuminate, abaxial surface glaucous, glabrous, pilose, sparsely pubescent or long-silky, midrib glabrous or densely pubescent, hairs (white, sometimes also ferruginous), wavy, adaxial dull or slightly glossy, glabrous or pilose, (hairs rarely ferruginous);
proximal blade margins entire or serrulate;
juvenile blade reddish or yellowish green, pilose, tomentose or moderately densely short-silky abaxially, hairs white and ferruginous.
adaxial nectary narrowly oblong or oblong, 0.4–1.1 mm;
filaments distinct, glabrous or sparsely hairy basally;
anthers purple turning yellow, shortly cylindrical, 0.5–0.7 mm.
adaxial nectary oblong, 0.6–1.1 mm;
filaments distinct, glabrous or hairy basally;
anthers yellow or purple turning yellow, ellipsoid or short- or long-cylindrical, 0.5–1 mm.
adaxial nectary oblong, square, or ovate, 0.4–1.3 mm, shorter to longer than stipe;
stipe 0.3–0.8 mm;
ovary pyriform, short- to long-silky, sometimes slightly bulged below styles;
ovules 11–16 per ovary;
styles 0.5–2 mm;
stigmas slenderly to broadly cylindrical, 0.36–0.52–1.1 mm.
adaxial nectary oblong or ovate, 0.7–1.3 mm, shorter than stipe;
stipe 1.6–2.7 mm;
ovary obclavate or pyriform, short-silky (hairs straight), beak sometimes slightly bulged below styles;
ovules 6–16 per ovary;
styles 0.3–1 mm;
stigmas slenderly or broadly cylindrical, 0.48–0.64–0.88 mm.
(2.5–)5.5–6 mm.
6–11 mm.
flowering before leaves emerge; staminate stout, subglobose, or globose, 12–41 × 10–20 mm, flowering branchlet 0–4 mm; pistillate densely flowered, slender, or stout to globose, 15–67(–70 in fruit) × 8–18 mm, flowering branchlet 0–6 mm;
floral bract dark brown or black, 1–3.2 mm, apex acute, convex, or rounded, sometimes 2-fid, abaxially hairy, hairs straight.
flowering before leaves emerge; staminate stout or subglobose, 23–52 × 12–22 mm, flowering branchlet 0–3 mm; pistillate densely flowered (loose in fruit), slender or stout, 25–108(–135 in fruit) × 12–33 mm, flowering branchlet 0–10 mm;
floral bract brown, black, or bicolor, 1.4–2.5 mm, apex acute or convex, abaxially hairy, hairs straight.
= 76, 57.
= 76, 95, 114.
Salix planifolia
Salix discolor
Variety monica applies to the diminutive alpine form that sometimes is recognized in the southern Rocky Mountains (S. J. Brunsfeld and F. D. Johnson 1985); it occurs at higher elevations (2200–4000 m) and is characterized by low growth form (0.14–1 m) and smaller, slightly broader leaves. Although it can be distinctive, it is morphologically confluent with the typical species. B. G. O. Floderus (1939) may be correct in characterizing it as an alpine ecotype.
Salix planifolia and S. pulchra are closely related. Their ranges overlap in northwestern Canada, from northern British Columbia across the southern quarter of the Yukon and northeastward into the Great Bear Lake area. Specimens identified as S. pulchra occur as far northeastward as Coppermine and northeast of Bathurst Inlet; S. planifolia has been recognized in the Mackenzie Delta and Eskimo Lake regions, Northwest Territories. Outlying records should be treated with caution because identification of individual specimens out of context may not be definitive. G. W. Argus (1969, 1973) treated these taxa as subspecies based on their intergradation in northwestern British Columbia, their tetraploid chromosome number, and their similar leaf flavonoid chromatographic patterns, but this taxonomy needs reconsideration.
The primary differences between the two species are stipule size, shape, and persistence and the pubescence on juvenile leaves. Stipules of Salix planifolia are oblong to narrowly elliptic or obovate, 0.8–3 mm (or –4.5 mm at Back River, Northwest Territories), distinctly shorter than petioles, and rarely marcescent for more than one year; stipules of S. pulchra are linear to narrowly oblong, 3–32 mm, usually longer than petioles, and usually marcescent for two or more years. Juvenile leaves of S. planifolia are usually more densely hairy, but vary from glabrescent to sparsely or very densely pubescent or long-silky, whereas juvenile leaves of S. pulchra are usually glabrous or, sometimes, sparsely hairy. The occurrence of rhombic mature leaf blades in S. pulchra sometimes is distinctive, but overlap in leaf shape between the two taxa is very great.
The area of geographic overlap in Yukon and western Northwest Territories is large, but evidence suggests that there the two species may be separated by elevation. In the vicinity of Whitehorse, Yukon, Salix pulchra occurs at higher elevations (1400–1900 m) than S. planifolia (ca. 1000 m); no mixed populations were seen. In Nahanni National Park, Northwest Territories, where S. planifolia is more common than S. pulchra, the latter occurs only in alpine and subalpine habitats (1200–1400 m). Evidence from both localities indicates an elevational separation of the two taxa. Within the area of overlap there is little evidence of intergradation except that S. planifolia has stipules that tend to be more marcescent (40% are marcescent) and sometimes longer (2–3.5 mm) than is usual outside the area of overlap. Nevertheless, specimens from the area of overlap can be easily assigned to one taxon or the other with only a few apparent intermediates. The problem in recognizing intermediacy is that there are only a few, variable characters that separate the two. In contrast, in 1973, G. W. Argus described evidence of hybridization and introgression along the Haines Road in northwestern British Columbia. This was based on variation in stipule size, presence, and persistence in what appeared to be a hybrid swarm. Further data are needed to answer questions about actual hybridization. Are the species separated by habitat or elevation, and are there reproductive barriers? Answers could be gained by population studies and controlled hybridization. Until that is done it is best to treat these taxa as species.
See 76. Salix discolor and 95a. S. alaxensis var. alaxensis for comparative descriptions.
Hybrids:
Salix planifolia forms natural hybrids with S. alaxensis var. alaxensis, S. argyrocarpa, S. brachycarpa var. brachycarpa, S. candida, S. drummondiana, S. humilis, S. pellita, S. pulchra, and S. scouleriana. Hybrids with S. glauca var. cordifolia have been reported (C. K. Schneider 1921) but no convincing specimens have been seen.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Salix discolor is introduced in North Carolina.
Vegetative specimens of Salix discolor can be difficult to distinguish from S. planifolia, but there are two, somewhat variable, characters that can be used. Salix discolor usually has leaves dull adaxially, with arcuate secondary veins widely and irregularly spaced; S. planifolia has leaves slightly or highly glossy adaxially, with straight secondary veins closely and regularly spaced.
Salix discolor in northeastern United States can be difficult to distinguish from widely naturalized S. atrocinerea and S. cinerea. Useful diagnostic characters are: tertiary leaf veins, which are irregular in S. discolor but close and parallel in introduced species, and raised striae on peeled 3–5-year old branches, which are absent or indistinct and relatively short in S. discolor, but long and very prominent in the introductions.
Hybrids:
Salix discolor forms natural hybrids with S. humilis, S. interior, S. myricoides, S. pellita, and S. planifolia. Reports of hybrids with S. candida and S. eriocephala (M. L. Fernald 1950), and S. bebbiana and S. pyrifolia (C. K. Schneider 1921; Fernald), are not based on convincing specimens. Synthetic hybrids with S. bebbiana could not be made (G. W. Argus 1974; A. Mosseler 1990) and those made with S. eriocephala had low seed viability (Mosseler).
Salix discolor × S. humilis has tomentose leaves of S. humilis and longer catkins and styles of S. discolor (G. W. Argus 1986). These species readily hybridize and produce abundant seed (Argus 1974). The hybrids are fertile and backcross. Specimens of S. discolor with densely villous branchlets may be hybrids or introgressants with S. humilis. The two species usually are ecologically isolated; S. discolor occurs in wetland thickets and S. humilis in dry, sandy upland forests. Where the two habitats come into proximity, hybrids occur but large swarms have not been observed.
Salix discolor × S. myricoides (S. ×laurentiana Fernald, syn. S. paraleuca Fernald) usually resembles S. myricoides but has hairy ovaries (R. D. Dorn 1975, 1976). This hybrid was originally described as a species, from lower St. Lawrence River, Quebec. Its most distinctive feature is that hairs appear on ovaries in patches, at the base or, sometimes, only on the stipes. A similar ovary indumentum pattern appears in other hybrids or species of hybrid origin, e.g., S. hookeriana. Characteristics of S. discolor found in S. ×laurentiana include epidermis with gray-margined splits, leaf margins entire or sinuate, leaves with 2–4 teeth per cm, anthers yellow or purple, filaments hairy on proximal half or basally, ovaries hairy, greenish brown or green with red sutures, and adaxial pistillate nectaries ovate. Characteristics of S. myricoides include inner bud-scale membranes separating from the outer ones, stipules more prominent, catkins on distinct flowering branchlets, and longer styles sometimes distinct about half their lengths. This hybrid occurs throughout the area of overlap of the parents. All three taxa often are intermixed but few hybrids seem to produce well-developed seed.
Salix discolor × S. pellita (S. ×pedunculata Fernald) is characterized by juvenile leaves with infolded or sometimes revolute margins, ovaries with patches of hairs relatively short, flattened, crinkled, and refractive, and catkins borne on distinct flowering branchlets 2–10 mm. This sporadic hybrid does not seem to be fertile. It occurs in Newfoundland, Quebec, and Saskatchewan. Although it has been collected at few localities, it probably is more common and should be expected wherever the two species grow together. The type and other collections compare very well with synthetic hybrids (A. Mosseler 1990), which were reported to show a high hybridization success rate, high F1 pollen viability, and high seedling viability. It was suggested that variability within these species may be due to interspecific gene flow. In interpreting the parentage of the wild hybrids it is not possible to rule out hybridization of S. planifolia or S. myricoides with S. pellita, or that these hybrids may be S. myricoides × S. planifolia, as suggested by B. G. O. Floderus (1939). Salix ×pellicolor Lepage is a later synonym of this hybrid.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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