Leaves broad and flat, never needle-like or scale-like, compound.
1. Leaves alternate.
2. Leaflets 3 _Ptelea trifoliata_
2. Leaflets 5 or more.
3. Main stalk between leaflets winged on either side
_Rhus copallina_
3. Main stalk between leaflets not winged.
4. Leaves with an even number of leaflets, often doubly
compound.
5. Leaflets not more than ½ inch wide.
6. Pods usually 12 inches long or longer, with 6 or more
seeds _Gleditsia triacanthos_
6. Pods 1-2 inches long, with 1-3 seeds _Gleditsia aquatica_
5. Some or all the leaflets at least one inch broad.
7. Leaves doubly compound; leaflets smooth along the edges;
leaves without a foul odor when crushed
_Gymnocladus dioicus_
7. Leaves once compound; leaflets usually with a few coarse
teeth along the edges; leaves with a foul odor when
crushed _Ailanthus altissima_
4. Leaves with an odd number of leaflets, once compound (twice
compound in _Aralia spinosa_, which has prickly leafstalks).
8. Leaflets without teeth along the edges.
9. Leaflets less than 1 inch broad and 2 inches long; twigs
with short spines at base of leaf stalks
_Robinia pseudoacacia_
9. Leaflets up to 4 inches long and up to 2 inches broad;
twigs without spines.
10. Some or all the leaflets alternate; base of leafstalk
conspicuously swollen _Cladrastis lutea_
10. All the leaflets opposite; base of leafstalk not
swollen _Rhus vernix_
8. Leaflets toothed along the edges.
11. Leaves doubly compound, often with small prickles on the
leafstalks and on some of the veins _Aralia spinosa_
11. Leaves once compound, without prickles.
12. All leaves with 11 or more leaflets.
13. Leafstalks and lower surface of leaves completely
smooth _Rhus glabra_
13. Leafstalks and lower surface of leaves (at least on
the veins) hairy.
14. Pith of twigs chambered when cut lengthwise.
15. Pith pale brown; bark dark brown, with roughened
ridges _Juglans nigra_
15. Pith dark brown; bark gray, with smooth ridges
_Juglans cinerea_
14. Pith of twigs solid.
16. Leaves strongly aromatic when crushed; twigs not
covered with velvety hairs.
17. Bud scales with yellow hairs; nut 1½ to 2
times longer than broad _Carya illinoensis_
17. Bud scales without yellow hairs; nut about as
broad as long _Carya aquatica_
16. Leaves not aromatic when crushed; twigs covered
with velvety hairs _Rhus typhina_
12. Some or all leaves with less than 11 leaflets.
18. Buds with 4-6 scales arranged in pairs; most of the
leaves with at least 9 leaflets.
19. Terminal leaflet without a stalk or with a very
short stalk; buds mustard-yellow
_Carya cordiformis_
19. Terminal leaflet with a well-developed stalk; bud
reddish-brown _Carya aquatica_
18. Buds with 6 or more overlapping scales; most of the
leaves with fewer than 9 leaflets (except sometimes
in _Carya tomentosa_ and _Carya laciniosa_), never
with 11 leaflets.
20. Teeth along the leaf margin with small tufts of
hairs _Carya ovata_
20. Teeth along the leaf margin without small tufts of
hairs.
21. Lower surface of leaflets densely and uniformly
hairy.
22. Stalk to which leaflets are attached densely
hairy; bark tight, not shaggy
_Carya tomentosa_
22. Stalk to which leaflets are attached smooth or
sparsely hairy; bark shaggy at maturity
_Carya laciniosa_
21. Lower leaf surface smooth, or with tufts of
hairs in the vein axils, or sometimes sparsely
hairy along the veins.
23. Scales of buds, stalk of leaves, and young
twigs rusty-hairy or -scaly _Carya texana_
23. Rusty hairs and scales not present.
24. Leaflets mostly 5; bud scales without hairs
at the tip; bark tight, not peeling
_Carya glabra_
24. Leaflets mostly 7; bud scales with hairs at
the tip; bark peeling at maturity
_Carya ovalis_
1. Leaves opposite.
25. Leaves palmately compound.
26. Leaflets mostly 7; buds very sticky _Aesculus hippocastanum_
26. Leaflets mostly 5; buds not sticky.
27. Fruit prickly; flowers yellow _Aesculus glabra_
27. Fruit smooth; flowers red _Aesculus discolor_
25. Leaves pinnately compound, or sometimes with only 3 leaflets.
28. Leaflets usually 3, or sometimes 5; twigs green or glaucous
_Acer negundo_
28. Leaflets usually 7 or more, sometimes 5; twigs not green.
29. Some or all of the twigs square _Fraxinus quadrangulata_
29. Stems not square.
30. Leaflets without stalks _Fraxinus nigra_
30. Leaflets stalked.
31. Stalks of the leaflets winged.
_Fraxinus pennsylvanica_ var. _subintegerrima_
31. Twigs and leafstalks smooth
32. Leaflets whitened on the lower surface
_Fraxinus americana_
32. Leaflets green or yellow-brown on the lower surface
_Fraxinus tomentosa_