Most species of hickory can be easily determined in the field using a combination of key characteristics. Detailed botanical descriptions of species are beyond the scope of this text but are provided by Sargent (1922). Following is an abbreviated dichotomous key which is based on the field characteristics which are most reliable, in the author's experience. More information concerning distinctions between similar species will be provided in subsequent text.

1a. Nuts cut in cross section have prominent cavities in the shell walls and middle septum (lacunae) often filled with powdery, rust-colored, very bitter material (Section Apocarya)................................................................. 2

1b. Nuts cut in cross section have woody shells without prominent cavities in the shell wall and middle septum (Section Carya).................................................................... 5

Section Apocarya

2a. Buds tan to black, outer bud scales not leaf-like. Commonly 11 (may be more) leaflets per compound leaf. Leaflets assymetrical (falcate)........................ 3

2b. Buds bright yellow or yellow-orange, outer bud scales leaf-like. Commonly 9 (or fewer) leaflets per compound leaf (rarely 11). Leaflets symmetrical (rarely falcate) ....................................................................................................................4

3a. Nuts more or less circular in cross-section. Shell usually tan with dark stripes at apex, speckles at base, smooth or slightly ribbed, winter buds tan to brown, plump..........................................................................................C. illinoinensis

3b. Nuts compressed. Shell dark, prominently ribbed and very rough. Kernel convoluted, very bitter. Winter buds very dark black, acute...........C. aquatica

4a. Wings on husk sutures from middle to apex. Nut a slightly compressed sphere with a prominently pointed tip..........................................C. cordiformis

4b. Wings on husk sutures from apex to base of nut. Nuts round, lacking prominent tip at apex.........................................................................Carya palmeri

Section Carya

5a. Dense tufts of hairs near the tips of the serrations on the leaf edge. ...............................................................................................................C. ovata

5b. Lacking dense tufts of hairs at the tips of the leaf serrations..........................6

6a. Lower leaf surfaces velvety with dense pubescence. Twigs stout. Terminal buds very large (1-2 cm in length)..........................................................................7

6b. Lower leaf surfaces not velvety with dense pubescence. Twigs slender. Terminal bud usually less than 1 cm in length.......................................................8

7a. Outer terminal bud scales persistent. Current season's shoots hair-less, orange or tan in color, often with rachises persistent after leaflets drop. Bark of mature trees shedding in plates......................................................C. laciniosa

7b. Outer terminal bud scales shed in autumn. Current season's shoots pubescent. Bark of mature trees furrowed or ridged, tight...........C. tomentosa

8a. Leaf rachis and midrib covered with curly fascicles of hairs.......Carya pallida

8b. Leaf rachis and midrib either hairless or pubescent with single hairs...........9

9a. Terminal bud and lower leaf surfaces densely covered with scales.............10

9b. terminal buds and lower leaf surfaces hairless or variously pubescent, but without abundant scales......................................................................................12

10a. Bark of mature trees shedding in plates. Lower leaf surfaces shiny, silver in spring to bronze in autumn, covered with dense peltate scales. ..............................................................................................C. myristiciformis

10b. Bark of mature trees tight, smooth to furrowed but not shedding in plates. Lower leaf surfaces densly covered with rust colored wavy-margined peltate scales...................................................................................................................11

11a. Trees found west of the Mississippi River.................................Carya texana

11b. Trees of the Florida sand scrub, often small, multi-trunked. .........................................................................................................Carya floridana

12a. Shuck smooth, splitting to middle of nut only or to base along one suture. Bark of mature trees tight, not shedding in long thin plates................Carya glabra

12b. Shuck warty, splitting to base along 3-4 sutures. Bark of mature trees often "scaly", shedding in long thin plates....................................................Carya ovalis