Flora of North America species comparison

The Ohio occurrence of Salix cinerea is based on information from T. Cooperrider (pers. comm.).

Salix cinerea and S. atrocinerea are very closely related. Their occurrence in the flora area, as naturalized introductions, is not well understood, probably because they usually are introduced under the name S. caprea, and that species often is not treated in North American floristic literature (e.g., C. K. Schneider 1921; M. L. Fernald 1950). They probably are introductions of long-standing brought to the New World for their value as ornamentals and bee-plants. Salix atrocinerea was first documented in the southeastern United States (G. W. Argus 1986) after plants with ferruginous hairs and prominently striate wood were found in North Carolina; since that time, it has been found in other states and provinces. In the northeastern states, S. atrocinerea and S. cinerea are thought to be invasive species. The species do reproduce by seed and hundreds of seedlings were observed in a drained reservoir (A. Zinovjev, pers. comm.) and on sandy pond shores (T. Rawinski, pers. comm.), where they are thought to compete with native species.

The presence of long, prominent, striae on the peeled wood of 4–5 year old branches is commonly used in European literature (K. H. Rechinger 1993; A. K. Skvortsov 1999) to separate Salix cinerea and S. atrocinerea from S. caprea etc., in which the wood is smooth or with fewer, shorter striae. In the flora area, long striae also occur in S. bebbiana, S. discolor, and S. humilis, but usually they are not as long as or as prominent in S. cinerea and S. atrocinerea. Some floras (e.g., F. Martini and P. Paiero 1988) use the relative prominence of striae to separate S. cinerea and S. atrocinerea, but their separation remains difficult. The presence of ferruginous hairs on the leaves of S. atrocinerea is the best diagnostic characteristic, but they are not always present or easily observed. For a comparison of these species, see the key to species under subg. Vetrix. For further discussion of morphologies, see Salix ×smithiana Willdenow [p. 132] and 76. S. discolor.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Vegetative specimens of Salix hastata often are misidentified as S. barclayi. The characters that indicate S. hastata, or sometimes possible hybrids, are the presence of ferruginous hairs on juvenile leaves or adaxial midribs of mature leaves, leaf margins often entire or with teeth present only distally, and buds with inner membranaceous layer not separating from outer layer.

Salix barclayi is distinguished from S. farriae and S. hastata by having bud-scales with inner membranaceous layer separating from outer layer, juvenile blades glabrous, pilose, or moderately densely villous, largest medial blades oblong, narrowly elliptic, elliptic, oblanceolate, or obovate, margins always toothed, pistillate flowering branchlets 4–24 mm, staminate flowering branchlets 0–17 mm, floral bracts brown to black, moderately densely hairy, anthers 0.6–1 mm, styles 0.6–2.5 mm, and stipes 0.4–1.5 mm; S. farriae has bud-scales with inner membranaceous layer separating from outer layer, juvenile blades glabrous or sparsely villous, largest medial blades narrowly elliptic to elliptic, margins usually entire, pistillate flowering branchlets 1.5–14 mm, staminate flowering branchlets 1–5 mm, floral bracts bicolor, brown, or black, sparsely hairy, anthers 0.3–0.6 mm, styles 0.3–1.2 mm, and stipes 0.5–1.2 mm; and S. hastata has bud-scales with inner membranaceous layer not separating from outer layer, juvenile blades sparsely pubescent, largest medial blades narrowly to broadly elliptic, narrowly ovate, or ovate, margins usually entire, pistillate flowering branchlets 1.5–9 mm, staminate flowering branchlets 1–7 mm, floral bracts brown or bicolor, sparsely hairy, anthers 0.4–0.6 mm, styles 0.2–0.48 mm, and stipes 0.4–1.2 mm.

Hybrids:

Salix barclayi is morphologically highly variable. While it is possible that much of this variability is inherent, hybridization and introgression have played an important role.

Salix barclayi forms natural hybrids with S. arctica, S. barrattiana, S. brachycarpa, S. cascadensis, S. commutata, S. farriae, S. hastata, S. hookeriana, S. richardsonii, and S. stolonifera.

Salix barclayi × S. barrattiana is characterized by oily buds that stain the pressing paper yellow, and leaves often entire, or nearly so, and closely gland-dotted, and not glaucous abaxially. Some hybrids resemble S. barclayi in having ovaries glabrous and leaves serrulate and slightly glaucous abaxially, while others resemble S. barrattiana in having stipules marcescent and leaves short-hairy on both surfaces and not glaucous abaxially, but it is the presence of the oily buds characteristic of S. barrattiana that indicates their hybridity. The hybrids usually were from populations that included both parents. An important ramification of the discovery of this hybrid is that the specimen on which the chromosome number for S. barclayi (R. D. Dorn 1976) is based is a plant with oily buds, which has leaves with a mixture of weakly developed teeth and closely gland-dotted, entire margins, and is putatively identified as this hybrid. Further chromosome counts for S. barclayi are needed. Hybrids are known in British Columbia from the mountains in the Peace and Liard river basins, and in Mt. Robson National Park. The hybrid should be suspected wherever the parents occur together.

Salix barclayi × S. cascadensis, collected in Washington in alpine mats growing with both parents, has ovaries with hairy beaks indicating hybridization.

Salix barclayi × S. commutata resembles S. barclayi in having leaves glaucous abaxially, and S. commutata in having leaves hairy on both surfaces (northern British Columbia, Unalaska Island, and southeastern Alaska).

Salix barclayi × S. farriae is represented by a series of specimens resembling S. barclayi but with ferruginous hairs on juvenile leaves or on adaxial midribs of mature leaves, found from the Rocky Mountains of Alberta to southern Yukon and adjacent Northwest Territories. Similar specimens from Alaska may be the hybrid S. barclayi × S. hastata. Both of these hybrids require further study. See 63. S. hastata and 64. S. farriae.

Salix barclayi × S. hookeriana hybrids or introgressants at Tanis Lake, Alaska, have subentire leaves and stipes glabrous or hairy.

Salix barclayi × S. richardsonii hybrids and intergrades are relatively common in Alaska, British Columbia, and Yukon. They resemble S. barclayi in having catkins borne on distinct flowering branchlets, small stipules, anthers yellow and longer, and S. richardsonii in having marcescent stipules, branchlets and branches coarsely villous with spreading hairs, pistillate nectaries longer than stipes, and catkins sometimes on relatively short flowering branchlets.

Salix barclayi × S. scouleriana has the general appearance of S. barclayi but the densely hairy ovaries and the relatively long stigmas (0.9–0.92 mm) of S. scouleriana. It was growing with S. barclayi in openings created in white spruce by bark beetles.

Salix barclayi × S. stolonifera is characterized by relatively small leaves with irregularly serrulate margins, some young leaves reddish green, and a prostrate habit (G. W. Argus 1973).

(Discussion copyrighted by Flora of North America; reprinted with permission.)