Salix interior
Salix polaris
sandbar willow
polar willow
erect;
branches red-brown, (often glaucous, dull), glabrous;
branchlets brownish, glabrous.
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;
petiole (deeply grooved), 1.3–10 mm, (glabrous adaxially);
largest medial blade (deciduous in autumn, 2 pairs of secondary veins arising at or close to base, arcing toward apex), elliptic, broadly elliptic, obovate, or subcircular, 5–32 × 7–18 mm, 1.1–2.8 times as long as wide, base convex, rounded, or cuneate, margins slightly revolute or flat, entire, ciliate, apex usually rounded or convex, sometimes retuse, abaxial surface (rarely glaucous), glabrous or pilose, adaxial slightly glossy, glabrous;
proximal blade margins entire;
juvenile blade glabrous.
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.
abaxial nectary 0.3–0.7 mm, adaxial nectary oblong, narrowly oblong, square, or ovate, 0.5–1.4 mm, nectaries distinct;
filaments usually distinct, sometimes connate proximally, glabrous;
anthers ellipsoid or ovoid, 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.
abaxial nectaries absent, adaxial nectary narrowly oblong, oblong, or ovate, 0.8–1.8 mm, longer than stipe;
stipe 0.2–0.7 mm;
ovary obclavate or pyriform, densely villous to pilose, hairs flattened, beak gradually tapering to or slightly bulged below styles;
ovules 12–17 per ovary;
styles connate to distinct 1/2 their lengths, 0.7–1.2 mm;
stigmas flat, abaxially non-papillate with pointed tip, or slenderly to broadly cylindrical, 0.3–0.6(–0.7) mm.
(4–)5–8(–10) mm.
4.8–8.25 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.
sometimes from subterminal buds; staminate 9–34 × 6–12 mm, flowering branchlet 1.5–14 mm; pistillate densely or moderately flowered (more than 15 flowers), stout to globose, 10–50 × 7–13 mm, flowering branchlet 1–12 mm;
floral bract brown, black, or bicolor, 1.5–2.5 mm, apex rounded or convex, entire, abaxially sparsely hairy, hairs straight or wavy, (exceeding bract by 0.6–1.12–1.8 mm).
= 38.
= 76, 114.
Salix interior
Salix polaris
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.)
The sectional placement of Salix polaris is uncertain. It was placed in sect. Myrtosalix (G. W. Argus 1997) but more recently Argus et al. (1999) placed it in sect. Herbella. This polyploid species may be an intersectional hybrid.
Hybrids:
Salix polaris forms natural hybrids with S. arctica and perhaps S. rotundifolia.
Salix polaris × S. rotundifolia: This putative hybrid occurs in Alaska and the Yukon. Many plants previously identified as S. rotundifolia but that have ovaries with hairs on the beaks or in patches, leaves not commonly marcescent, and catkins with fewer flowers than in S. polaris may be this hybrid.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC - Local Web sites:
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
