Salix interior
Salix sericea
sandbar willow
silky willow
branches (highly brittle at base), gray-brown or violet, not glaucous, tomentose to glabrescent;
branchlets red-brown, violet, or mottled yellow-brown, sparsely to densely velvety.
stipules absent or rudimentary on early ones, rudimentary or foliaceous on late ones;
petiole 1–5(–9) mm, glabrous or sparsely villous adaxially;
largest medial blade linear to lorate, 60–160 × 4–11 mm, (6.5–)11–19(–31) times as long as wide, base cuneate, margins flat, remotely spinulose-serrulate (teeth 2–5 per cm), apex acute or subacuminate, abaxial surface thinly glaucous, densely villous or long-silky to glabrescent, adaxial slightly glossy, pilose or densely villous to glabrescent;
proximal blade margins entire;
juvenile blade reddish or yellowish green, moderately densely to sparsely long-silky abaxially.
stipules absent or rudimentary on early ones, late ones 1.2–4 mm, apex acute or acuminate;
petiole convex to flat, or shallowly grooved adaxially, 3.5–12(–21) mm, (sometimes 2 spherical glands distally), velvety adaxially;
largest medial blade lorate, narrowly oblong, or narrowly elliptic, (48–)54–82–100(–125) × (7–)9–16.7–25 mm, base cuneate or convex, margins flat, serrulate or crenulate, apex acute, acuminate, or convex, abaxial surface glaucous (sometimes obscured by hairs), densely short-silky, hairs straight, adaxial dull, sparsely pubescent to glabrescent;
proximal blade margins entire;
juvenile blade reddish or yellowish green, very densely short-silky abaxially, hairs white, sometimes also ferruginous.
abaxial nectary 0.5–1.1 mm, adaxial nectary ovate, narrowly oblong, or flask-shaped, 0.6–1.4 mm, nectaries distinct;
filaments hairy;
anthers 0.4–0.9 mm.
adaxial nectary ovate to oblong, 0.3–0.8 mm;
filaments distinct or connate less than 1/2 their lengths;
anthers purple turning yellow, 0.4–0.6 mm.
adaxial nectary narrowly oblong, 0.4–1.1 mm, shorter to longer than stipe;
stipe 0.4–0.8 mm;
ovary obclavate to pyriform, glabrous, glabrescent, or long-silky, beak abruptly tapering to styles;
ovules 16–36 per ovary;
styles 0–0.2 mm;
stigmas flat, abaxially non-papillate with pointed tip, or broadly cylindrical, 0.3–0.7 mm.
adaxial nectary oblong, ovate, or flask-shaped, 0.4–0.7 mm;
ovary ovoid, beak abruptly tapering to styles;
ovules 6 per ovary;
styles 0.2–0.4 mm.
(4–)5–8(–10) mm.
2.5–4 mm.
(flowering throughout season); staminate 20–61 × 4–10 mm, flowering branchlet 3–20 mm; pistillate loosely flowered, slender or stout, 20–67 × 5–9 mm, flowering branchlet 3–19 mm;
floral bract (sometimes greenish), 1.5–3.5 mm, apex acute, acuminate, or rounded, entire, erose, or toothed, abaxially hairy either proximally or distally, hairs wavy.
flowering as or just before leaves emerge; staminate stout, 13.5–40 × 4–9 mm, flowering branchlet 0–2 mm; pistillate loosely to moderately densely flowered, slender to stout, 18–43 × 5–12 mm, flowering branchlet 1–3 mm;
floral bract dark brown, black, or bicolor, 0.8–1.5 mm, apex rounded, abaxially hairy, hairs straight or wavy.
= 38.
Salix interior
Salix sericea
Sometimes Salix interior is treated as a subspecies of S. exigua (R. D. Dorn 1998). Salix exigua and S. interior hybridize and apparently intergrade in the western Great Plains; because the area of overlap is relatively small and distinctiveness of the two taxa is not compromised by hybridization and introgression, it is best to treat them as separate species.
Leaves on sylleptic shoots are usually very densely silky. Salix interior sometimes has shoots that arise from buds on either side of the normal axillary bud. They do not seem to be directly related to the stipules because they are enclosed by the petiole. Catkins with both staminate and pistillate flowers are rare in S. interior, but a Quebec specimen had some catkins predominantly pistillate and others staminate; most were a mixture. The flowers were not teratological, but a mature capsule contained aborted ovules.
Hybrids:
Salix interior forms natural hybrids with S. exigua var. exigua. Controlled pollinations using S. interior (as S. exigua) from southern Ontario (A. Mosseler 1990) successfully produced F1 hybrids with S. bebbiana, S. discolor, S. eriocephala, and S. petiolaris. Seed production was usually relatively low, except in crosses with S. discolor. In general, F1 viability was relatively low in crosses with these members of subg. Vetrix. No seeds were produced in crosses with members of subgenera Protitea or Salix. Morphology of the hybrids usually was intermediate between the two parents, but when S. petiolaris was used as the maternal parent, the F1s more closely resembled that species. J. Salick and E. Pfeffer (1999) extended these findings to show that, although crosses between S. interior (as S. exigua) and S. eriocephala are partially sterile, their clonal growth parameters (sprouting, shoot length, and biomass production) are strong and thus permit these partially sterile hybrids to exist as successful individuals and perhaps to “... make a contribution to interspecific gene flow over time.” Of particular taxonomic interest is that, in this cross, the staminate parent has a significant influence on leaf shape, whereas in the cross S. eriocephala × S. petiolaris it is the pistillate parent that is significant for leaf shape. Relatively few hybrids resembling those produced by Mosseler have been recognized in nature, but it is possible that the unusually broadly leaved plants named S. interior var. exterior and var. wheeleri, from northern Maine, Nebraska, New York, and West Virginia, and probably elsewhere, may be hybrids. Phenological isolation may be strong enough to prevent crosses in nature (A. Mosseler and C. S. Papadopol 1989) with the earlier flowering S. eriocephala and S. petiolaris, a barrier that even an occasional period of overlap cannot breach.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Some specimens of Salix sericea are difficult to separate from S. petiolaris (G. W. Argus 1986). Salix sericea can be distinguished from S. petiolaris in having branches highly brittle at base, stipules on early leaves rudimentary or absent, on late leaves usually foliaceous, juvenile blades usually with white hairs, rarely some ferruginous, ovaries ovoid, beaks abruptly tapering to styles, and capsules 2.5–4 mm; S. petiolaris has branches flexible at base, stipules on all leaves absent or rudimentary, juvenile blades usually with conspicuous ferruginous hairs, ovaries pyriform, beaks gradually tapering to styles, and capsules 5–9 mm.
See 68. Salix eriocephala for comments on differences.
Hybrids:
Salix sericea forms natural hybrids with S. eriocephala and S. petiolaris. Reports of hybrids with S. humilis (C. K. Schneider 1921; M. L. Fernald 1950) are not based on convincing specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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