Group 1: Leaf scars opposite

1. Twigs angled, surfaces nearly flat; twigs and stems green to ground level or nearly to ground level...Euonymus americanus

1’. Twigs round, surfaces not flat; twigs and stems often brown, gray, or maroon to ground level (Acer negundo saplings usually have green stems nearly to ground level but their stems are round)...2.

2. Stipular scars prominent...Staphylea trifolia

2’. Stipular scars inconspicuous or lacking (transverse lines joining adjacent leaf scars may resemble stipular scars)...3.

3. Vascular bundle scars > 6...4.

4. Buds with about 6 pairs of scales...Aesculus sylvatica

4’. Buds with 2-3 pairs of scales...5.

5. Upper edge of largest leaf scars deeply notched; twigs glabrous; plant of dry soils...Fraxinus americana

5’. Upper edge of all leaf scars straight or only slightly notched; twigs glabrous or pubescent; plant of wet or inundated soil...Fraxinus pennsylvanica or F. caroliniana

3’. Vascular bundle scars 1-5 or not discernable...6.

6. Terminal bud scales keeled, distinctly sharply pointed...Chionanthus virginicus

6’. Terminal bud scales not keeled, if pointed not distinctly so...7.

7. Axillary bud scales woody / leathery; pith spongy and white...Sambucus canadensis

7’. Axillary bud scales not woody / leathery; pith spongy and white or otherwise...8.

8. Axillary buds sunken into stem tissue...Cephalanthus occidentalis

8’. Axillary buds not sunken (may be obscured by petiole bases or leaf scars)...9.

9. Axillary buds usually partly or totally obscured by petiole bases or leaf scars...Cornus florida

9’. Axillary buds not obscured...10.

10. Axillary buds valvate (only two scales enclose valvate bud)...11.

11. Line connecting opposite leaf scars projected upward into ridge...Acer negundo

11’. Line between opposite leaf scars not evident or, if evident, then not projected upward into ridge...12.

12. Pith of year-old stem brown...Cornus amomum

12’. Pith white...13.

13. Bud scales covered with dense, velvety, reddish hairs...Viburnum rufidulum

13’. Bud scales smooth or hairs not velvety or reddish...14.

14. Buds dark brown, gray or black; twigs rigid...Viburnum prunifolium

14’. Buds rusty – colored; twigs often flexuous...Viburnum nudum

10’. Axillary buds imbricate (a bud composed of two valvate scales and two small basal scales is imbricate)...15.

15. Twigs green to red/pink...16.

16. Line connecting opposite leaf scars projected upward into ridge...Acer negundo

16’. Line connecting opposite leaf scars straight or nearly so...Acer rubrum

15’. Twigs brown to gray...17.

17. Twigs hairy...18.

18. Twig hairs radially branched...Viburnum dentatum

18’. Twig hairs unbranched...Viburnum acerifolium

17’. Twigs smooth...19.

19. Axillary buds appressed against twig...Viburnum rafinesquianum

19’. Axillary buds divergent...20.

20. Leaf scars small, vertically narrow; vascular bundle scars 3-5, distinct...Acer floridanum [=A. barbatum]

20’. Leaf scars relatively large, vertically elongate; vascular bundle scars >6, but often small and indistinct, arranged in a horseshoe or U-shape...21.

21. Upper edge of largest leaf scars deeply notched; plant of dry soils...Fraxinus americana

21’. Upper edge of all leaf scars straight or only slightly notched; plant of wet or inundated soil...Fraxinus pennsylvanica or F. caroliniana