Tree and Shrub Identification
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Salix Key
This genus is noted for its difficulty. The species hybridize frequently and the characters of many are similar, making separation of the species a matter for the expert. For accurate identification both staminate and pistillate flowers, as well as the leaves and twigs, should be examined in the field and brought into the laboratory for further study. For general information about this genus, see the Salix page.
| 1 | Summit of petiole or its junction with the blade bearing coarse glands; mature leaves coriaceous, lustrous above, acuminate, tapering to petiole, green on both surfaces, with long attenuate tail-like tips | (shining willow) Salix lucida |
| Summit of petiole glandless or only viscid, or, if glandular, with teeth at base of blade and the latter rounded to cordate at base and not highly shining | 2 | |
| 2 (1) | Leaves glabrous | 3 |
| Leaves pubescent, at least beneath | 9 | |
| 3 (2) | Leaves elongate and acuminate or acute, mostly 3-15 cm or more long and one-tenth or two-thirds as broad as long | 4 |
| Leaves shorter and blunt to merely acute, 3-10 cm long, membranaceous, slender petioled, short oval to oblong lanceolate; stipules absent or minute; leaves and buds covered with a resin having a strong balsam odor; branches with shining reddish brown or olivaceous bark; branchlets brittle at base | (balsam willow) Salix pyrifolia | |
| 4 (3) | Leaves subsessile or with petioles rarely 3 mm. long, linear to oblong lanceolate, short acuminate to subacute, with widely spaced (often prolonged) sharp teeth; branchlets brown; plant a colonial stoloniferous shrub or small tree | (sandbar willow) Salix interior |
| Leaves distinctly petioled, the petioles 3 to 30 mm long, the blades narrowly lanceolate to ovate | 5 | |
| 5 (4) | Vigorous vegetative sprouts with conspicuous subpersistent stipules | 6 |
| Vigorous vegetative sprouts usually without stipules or if present, very small and early deciduous | 7 | |
| 6 (5) | Leaves green or merely paler beneath (not whitened), narrowly lanceolate, long attenuate, often falcate, 5 to 10 times as long as broad, finely serrulate; branchlets very brittle at base, the youngest greenish with angles running down from leaf bases | (black willow) Salix nigra |
| Leaves glaucous or whitened beneath, lanceolate to elliptic or narrow obovate, merely acute or acuminate (not long acuminate), tapering to base, irregularly crenate serrate; unfolding leaves with early dropping tawny hairs | (pussy willow) Salix discolor | |
| 7 (5) | Branchlets brittle at base, easily broken off | 8 |
| Branchlets flexible and tenacious, not easily broken off; leaves lanceolate to lance ovate, leathery, with tapering to tailed-attenuate tips, the larger blades 1-5 cm. broad; petioles mostly 1-3 cm long | (peachleaf willow) Salix amygdaloides | |
| 8 (7) | Leaves green on both sides, coarsely undulate serrate, 10-15 cm long and 2.5-4 cm wide; branchlets not "weeping." Introduced | (crack willow) Salix fragilis |
| Leaves whitened or pale beneath, finely serrulate, 2- 12 cm long and 0.5-2 cm broad; the branchlets "weeping," i.e., hanging down. Introduced. | (weeping willow) Salix babylonica | |
| 9 (2) | Lower surface of all or at least young leaves with shiny white silvery pubescence | 10 |
| Lower surfaces of young leaves with opaque tawny hairs which are soon deciduous; leaves bright green above | (pussy willow) Salix discolor | |
| 10 (9) | Leaves subsessile or with petioles rarely 3 mm long, linear to oblong lanceolate, short acuminate to subacute, with widely spaced projecting teeth | (sandbar willow) Salix interior |
| Leaves longer petioled, narrowly lanceolate, tapering to petiole and acuminate tip, finely and regularly serrulate to base, having minute appressed silky pubescence on underside | (silky willow) Salix sericea |
Last Revised: Monday July 30 2007
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