A N F Keys
1 Blades ovate to deltate, rarely twice as long as wide; petioles usually 20−55 mm long; involucre surrounding base of flower; nectaries absent; stamens 8−55; immature fruit ovoid to broadly ellipsoid, 3(−4)-valved, 6.5−8 mm diameter .. Populus
1' Blades lanceolate or oblanceolate to elliptic or linear, usually at least four times as long as wide; petioles < 20 mm long; involucre absent; nectaries present on staminate and pistillate flowers; stamens 2−8; immature fruit lanceoloid, 2-valved, < 2 mm diameter .. Salix
Populus L.
POPLAR, COTTONWOOD, ASPEN
1 Petiole strongly compressed side-to-side approaching blade; blades green but slightly paler on lower surface; staminate inflorescence 12−15 mm diameter; ovary spheroid, 2 mm diameter, shallowly 3-lobed, glabrous .. Populus fremontii subsp. fremontii [pics]
1' Petiole cylindric approaching blade; blades somewhat glaucous and whitish on lower surface; staminate inflorescence 6−10 mm diameter; ovary broadly ovoid, 3−4 mm diameter, 6-ribbed, villous .. Populus trichocarpa [pics]
1 Conspicuously clonal; blades linear to narrowly oblanceolate or narrowly lanceolate, never exceeding 8 mm diameter, when young silvery sericeous; stamens 2 .. Salix exigua var. hindsiana [pics]
1' Growing as individual trees or shrubs; blades lanceolate or narrowly elliptic to oblanceolate or oblong, most leaves at least 8 mm diameter, when young glabrous or finely pubescent but not sericeous
2 Flowering mostly before leaves; leaves lacking resin glands on stipules, petioles, and blades (vestigial stipules sometimes glandlike); immature capsules 3.5−5.5 mm long
3 Petioles ± cylindric; blades with sunken minor veins on upper surface; staminate flower with 2 stamens and bractlet subtending flower dark brown; bud scale caplike with fused margins .. Salix lasiolepis [pics]
3' Petioles channeled to midpoint and channel conspicuously hairy; blades ± smooth minor veins on upper surface; staminate flower with 3−5 stamens and bractlet subtending flower light green to light greenish yellow; bud scale free and overlapping .. Salix laevigata [pics]
2' Flowering with leaves or after appearance of leaves; leaves with resin glands on stipules, petioles, or blades (including conic teeth on margins); staminate flower with 3 or more stamens; immature capsules 6−9 mm long
4 Blades distinctly glaucous on lower surface; stipules persistent; staminate flowers with 3−5 stamens and nectaries dull yellow to orange-yellow; bud scale caplike with fused margins .. Salix lasiandra var. lasiandra [pics]
4' Blades bright green on both surfaces (never glaucous); stipules early-deciduous; staminate flowers with (4−)5−8 stamens and nectaries dark red (purple); bud scale free and overlapping .. Salix gooddingii [pics]
The text of the above keys used with permission from
A Naturalist's Flora of the Santa Monica Mountains and Simi Hills, California
© Copyright
Barry A. Prigge and Arthur C. Gibson
2013