Tremuloides (Leafy Specimens): Answers to key questions in Conifers & Catkin-Bearing Trees and Shrubs of Saskatchewan, Fascicle 5, Flora of Saskatchewan by George Argus, Vernon Harms, Anna Leighton and Mary Vetter leading to this species. 

	Petioles longer, usual  >= 1 cm and over 1/5 blade length (P. x brayshawii may be an exception); blades usually <= 2 times longer than wide (up to 3 times longer than wide in P. x brayshawii), margins short or long ciliolate (sometimes obscurely so); 3rd year branches shades of gray, grayish yellow, tan, orange or brown; NOT [Petioles short, usually <= 1 cm and to about 1/5 the blade length; blades lanceolate, 2-5 times longer than wide, margins not ciliolate; 3rd year branches whitish tan]
	Petioles strongly flattened laterally at least distally; NOT [Petioles terete, or slightly flattened usually in the same plane as the blade distally (rarely somewhat flattened laterally in P. x jackii)]
	Leaf blade upper surfaces dark green, lower surfaces whitish green and somewhat glaucous, ovate to nearly circular, with apices abruptly short-acuminate, acute to almost rounded; margins of early leaves subentire to evenly and finely crenate-serrate with teeth mostly (12) 18-30 (42) per side and sinuses up to 1 mm deep; bark of lower trunk smooth, becoming shallowly furrowed at base with age; branchlets dark reddish brown; fruiting pedicels normally to 2 mm; terminal buds (2.5) 4-6 (10) mm; catkin rachises sparsely pubescent; NOT [Leaf blades nearly the same color above and below, (light grayish green to bright green on both surfaces, not glaucous below), deltoid to nearly circular, with apices long-acuminate to caudate; margins of early leaves unevenly and coarsely crenate-serrate with teeth mostly fewer than 15 per side (with the largest along lower middle of side) and sinuses (0.4) 0.7-5  (7) mm deep; bark of lower trunk deeply furrowed at all but earliest stages; branchlets olive or yellow-brown; fruiting pedicels normally to 8 mm; terminal buds (5) 8-15 (21) mm; catkin rachises glabrous]

Populus: Answers to key questions in Conifers & Catkin-Bearing Trees and Shrubs of Saskatchewan, Fascicle 5, Flora of Saskatchewan by George Argus, Vernon Harms, Anna Leighton and Mary Vetter leading to this genus.

trees; buds covered by 3-10 scales, usually resinous;  catkins pendulous, sessile; floral bracts deeply cut; perianth reduced to a non-nectariferous, cup-shaped or shallow saucer-shaped floral disc; stamens 6-60 (70); capsules 2-4 valved, narrowly ovoid to spherical, with the floral disc persistent at base; NOT [shrubs or trees; buds covered by 1 scale, not resinous; catkins erect, spreading, or +/- pendulous, sessile or terminating flowering branchlets; floral bracts entire, erose, bifid, or irregularly toothed; perianth reduced to an adaxial nectary (rarely also an abaxial nectary, then the 2 nectaries distinct or connate into a shallow cup); stamens 1, 2, or 3-10; capsules 2-valved, obclavate to ovoid or ellipsoid]