Pumila: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 

	shrubs seldom over 2 m high; NOT [trees or tall shrubs 3 m or more high]
	reddish or brown bark; NOT [white, papery bark]
	twig pubescent with scattered hairs; NOT [twig indistinctly puberulent with short hairs]
	twig somewhat glandular; NOT [twig densely glandular]
	petiole under 1 cm long; NOT [petiole 1 cm or more long]
	leaf usually under 3 cm long; NOT [leaf usually over 3 cm long]
	leaf obovate; NOT [leaf orbicular]
	leaves tapering at base; NOT [leaves rounded at base]
	leaf with 10 or more teeth each side; NOT [leaf with 10 or fewer teeth each side]
	leaf with 4 or more lateral veins; NOT [leaf with 3 or fewer lateral veins]
	leaf relatively thick and stiff; NOT [leaf membranous]
	samara wings more than half as wide as nutlet; NOT [samara wings less than half as wide as nutlet]
	samara wings narrower than nutlet; NOT [samara wings at least as wide as nutlet body]

Betula: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 

	staminate flowers usually three in the axils of the catkin bracts; NOT [staminate flowers solitary in the axils of the catkin bracts]
	stamens 2; NOT [stamens 4]
	pistillate catkin elongated; NOT [pistillate flowers few in a short, bud-like catkin]
	bracts of pistillate catkins thin; NOT [bracts of pistillate catkins becoming thick and woody]
	bracts of pistillate catkins deciduous; NOT [bracts of pistillate catkins persistent]
	bracts of pistillate catkins 3-lobed
	fruit a nutlet in the axil of a catkin bract; NOT [fruit a nut enclosed in a hispid, leafy involucre with a long beak]
	fruit often winged

Betulaceae: Answers to key questions in Budd's Flora  leading to this family. 

	shrubs or trees; NOT [herbs]
	flowers with only one floral ring, with sepals but not petals
	male flowers, at least, in catkins or aments; NOT [flowers not in catkins or aments]
	styles 2; NOT [styles 3]
	fruit NOT an acorn
	seeds WITHOUT a tuft of hairs