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.)

Salix farriae is a cordilleran species ranging from Wyoming to central British Columbia with disjunct occurrences in northwestern British Columbia, western Northwest Territories, and southern Yukon. It is related to S. hastata, an amphiberingian species ranging from Scandinavia to southwestern Yukon and northwestern Northwest Territories. There may be reasons for treating these slightly different plants as S. hastata var. farriae, but R. D. Dorn (1975) maintained them as a species based on flavonoid differences. In a phenetic study (G. W. Argus 2007), the two taxa had dissimilarity values at the same level as other closely related species. They are treated here as species, primarily because their ranges are disjunct. They can be separated as follows:

Salix farriae is distinguished from S. hastata by having largest medial blades narrowly elliptic to elliptic, pistillate nectaries oblong or ovate, stipules on early leaves absent or rudimentary (sometimes foliaceous), branches strongly to weakly glaucous or not, floral bract apices rounded, and plants of the cordillera in Alberta and British Columbia, in Idaho, Montana, Oregon, and Wyoming; S. hastata has largest medial blades narrowly elliptic to broadly elliptic or broadly obovate, pistillate nectaries square, stipules on early leaves foliaceous (sometimes rudimentary), branches not glaucous, floral bract apices acute or rounded, and plants of Alaska, Northwest Territories, and Yukon.

Salix farriae and S. barclayi are sympatric in western Canada and the Pacific Northwest, where they are difficult to separate. Salix farriae can often be recognized by its largest medial leaves with at least some minute, ferruginous hairs on the adaxial midrib or blade surfaces; ferruginous hairs do not occur in S. barclayi. Its leaf margins also tend to be more nearly entire, but relatively short teeth are not infrequent. Such plants are sometimes interpreted as intergrades between S. farriae and S. barclayi (R. D. Dorn 1975). The variable leaf toothing also occurs in S. hastata and may not be a reliable indicator of intergradation. Salix farriae also differs from S. barclayi in usually having shorter anthers, 0.3–0.6 mm versus 0.6–1 mm in S. barclayi. See 61. S. barclayi.

Hybrids:

Salix farriae forms natural hybrids with S. barclayi.

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