The Plants of Michigan

Salicaceae, the Willow Family

Trees or shrubs, with dioecious flowers in catkins.

1a. Leaves less than twice as long as broad, on petioles 3 cm. long or more — 2.
1b. Leaves more than twice as long as broad, on petioles 2.5 cm. long or less. (The genus Salix, or Willow, contains about 30 species in Michigan, of which only the commoner are mentioned here. For the others the Manuals should be consulted.) — 8.
2a. Petioles strongly flattened laterally — 3.
2b. Petioles not flattened laterally — 6.
3a. Leaves broadly ovate or nearly circular — 4.
3b. Leaves broadly triangular or deltoid in shape — 5.
4a. Leaves coarsely toothed	Large-toothed Aspen, Populus grandidentata.
4b. Leaves finely crenulate or serrate	Quaking Aspen, Populus tremuloides.
5a. Tree with narrow spire-shape crown	Lombardy Poplar, Populus nigra var. italica.
5b. Tree with spreading crown	Cottonwood, Populus deltoides.
6a. Lower side of leaf densely tomentose	White Poplar, Populus alba.
6b. Lower side of leaf glabrous or nearly so — 7.
7a. Petioles glabrous	Balsam Poplar, Populus balsamifera.
7b. Petioles ciliate	Balm of Gilead, Populus candicans.
8a. Trees — 9.
8b. Shrubs — 13.
9a. Petioles without glands — 10.
9b. Petioles with glands — 11.
10a. Petiole short (about 5 mm.), broad and flat	Black Willow, Salix nigra.
10b. Petiole slender, about 10-20 mm. long	Peach-leaved Willow, Salix amygdaloides.
11a. Leaves green beneath	Crack Willow, Salix fragilis.
11b. Leaves pale beneath — 12.
12a. Branches and twigs conspicuously drooping	Weeping Willow, Salix babylonica.
12b. Branches and twigs not conspicuously drooping, yellow	Yellow Willow, Salix alba var. vitellina.
13a. Shrubs of bogs — 14.
13b. Plants of sand-dunes along the Great Lakes — 15.
13c. Plants of dry upland hills — 16.
13d. Plants of wet ground, river-banks, and swamps — 17.
14a. Leaves densely white-tomentose beneath	Willow, Salix candida.
14b. Leaves pale beneath but not tomentose	Willow, Salix serissima.
14c. Leaves glabrous and green beneath	Willow, Salix pedicellaris.
15a. Leaves linear	Willow, Salix longifolia.
15b. Leaves ovate-lanceolate, tomentose beneath	Willow, Salix syrticola.
15c. Leaves ovate-lanceolate, glabrous	Willow, Salix glaucophylla.
16a. Leaves about 3 times as long as broad	Willow, Salix rostrata.
16b. Leaves narrower, nearly sessile	Willow, Salix tristis.
16c. Leaves narrower, distinctly petioled	Willow, Salix humilis.
17a. Leaves linear or nearly so	Willow, Salix longifolia.
17b. Leaves shining	Willow, Salix lucida.
17c. Leaves silky	Willow, Salix sericea.
17d. Leaves not as in the preceding 3 species — 18.
18a. Leaves rounded at base	Willow, Salix cordata.
18b. Leaves acute at base — 19.
19a. Leaves finely serrulate	Willow, Salix petiolaris.
19b. Leaves remotely serrate or nearly entire	Willow, Salix discolor.