UW-Stevens Point Freckmann Herbarium:

Winter Key to Some Common Genera of Deciduous Woody Plants of the Upper Midwest

55a.		Stipule scars present	56
55b.		Stipule scars absent	75
	56a.	Terminal bud present	57
	56b.	Terminal buds absent	63
57a.		Buds stalked	58
57b.		Buds sessile in leaf axils	59
	58a	Buds scurfy or sticky; pith triangular in cross-section; catkins or woody "cones" often present	Alnus
	58b.	Buds densely short hairy, pith round in cross-section; no catkins	Hamamelis
59a.		Buds without scales; embryonic leaves visible	Rhamnus
59b.		Buds scales present	60
	60a.	Twigs smooth, shiny; catkins often present; bark often with wintergreen flavor	Betula
	60b.	Twigs shiny or dull; no catkins ; twigs with bitter almond taste or without taste	61
61a.		Low weak shrubs; last season's growth branched	Ceanothus
61b.		Trees or large shrubs; last season's growth not branched	62
	62a	Stipule scars slightly above leaf scars; lowermost bud-scale lateral; twigs sometimes bitter-almond taste	Prunus
	62b.	Stipule scars lateral; lowermost bud scale facing outward; linticels weak; buds sometimes sticky; twigs without flavor	Populus
63a.		Stipule scars encircling stems; leaf scars nearly encircling bud	Platanus
63b.		Stipule scars not encircling stem; leaf scar not encircling bud	64
	64a.	Buds naked, exposed embryonic leaves	Rhamnus
	64b.	At least one bud scale present covering embryonic leaves	65
65a.		One hood-like bud scale with suture down inner side of bud; twigs often slender and flexible	Salix
65b.		Two or more bud scales present	66
	66a.	Two or three visible bud scales	67
	66b.	Four to many bud scales	69
67a.		Accessory buds present above axillary buds; twigs coarsely striate; shrubs	Amorpha
67b.		No accessory buds normally present; twigs not striate; mostly trees	68
	68a.	Buds reddish, broadly ovate; twigs zig-zag, lacking very prominent lenticels; no catkin	Tilia
	68b.	Buds brownish, acute; twigs straight, with very prominent lenticels; catkins often present	Betula