1	Buds scales imbricate; leaf blades ovate, < 3 × as long as broad, bases truncate to broadly rounded, slightly cordate; inflorescences pendulous; stamens 5−80	Populus heterophylla Fig. 197
–	Bud scales 1; leaf blades lanceolate, > 3 × as long as broad, bases cuneate, not cordate; inflorescences erect or spreading; stamens 1−9	2
2	Mature leaf undersides glaucous, glabrous to sparsely pubescent, blades (4−) average 7.5 (−13) × as long as wide; stipules usually prominent and persisting, to 15 mm long	Salix caroliniana Fig. 198
–	Mature leaf undersides green, not glaucous, glabrous, blades (4−) average 9 (−16) × as long as wide; stipules not persisting, to 12 mm long	Salix nigra Fig. 199

Key adapted from Godfrey and Wooten (1981), Argus et al. (2010), and Weakley (2012).