1a.

Leaf scars opposite, nearly opposite, or in whorls of 3 or more

2

1b.

Leaf scars alternate or elongate shoots (sometimes clustered or nearly opposite at the tips or on slow-growing shoots)

21

2a.

Climbing or straggling vines with weak wood

3

2b.

Erect trees or shrubs

4

3a.

Leaf petioles persisting; internodes solid; stem with several prominent ridges

Clematis

3b.

No petioles present in winter; internodes hollow; stem not prominently ridged

Lonicera

4a.

Leaf scars in whorls of 3 or more at most nodes; twigs stout with somewhat swollen nodes

Catalpa

4b.

Leaf scars generally opposite; nodes not swollen

5

5a.

Twigs and buds densely covered with silvery-white peltate scales

Shepherdia

5b.

Twigs smooth or covered only with hairs, not with dense peltate scales

6

6a.

Vascular bundle scars one, or very numerous and joined in a line or crescent

7

6b.

Vascular bundle scars 3-7, separate and distinct

12

7a.

Leaf scars ending in 2 prominent lines running down green, slender twigs; pith hollow or chambered; buds football shaped with thin scales

Forsythia

8a.

Twigs greenish or reddish, often with 2-4 wings

Euonymus

8b.

Twigs gray or brown, not winged

9

9a.

Leaf scars prominently raised and connected by distinct stipular scars encircling twig

Symphoricarpos

9b.

Leaf scars not prominently raised; stipular scars faint or absent

10

10a.

Some twigs tipped with short  thorns; buds appressed to twigs, black, and acute

Rhamnus

10b.

No thorns present; buds spreading or obtuse

11

11a.

Bundle scars in crescent or U shape; buds solitary, broadly rounded; terminal bud rarely missing

Fraxinus

11b.

Bundle scars in a straight line; buds often in 3’s, elongate, pointed; terminal bud often missing

Syringa

12a.

Buds imbedded under the leaf scars, scarcely visible until late winter

Philadelphus

12b.

Buds apparently above leaf axils

13