(Based on leaves and fruit)

• a.—Leaves simple.
• b.—Leaves needle-shaped, awl-shaped, or scale-like, usually evergreen; fruit a cone or berry-like.
• c.—Leaves in bundles of 2-many; fruit a cone.
• Leaves in bundles of 2-5, evergreen
• Pinus, p. 13.
• Leaves in clusters of 8-many on short spur-like branchlets, deciduous in autumn
• Larix, p. 13.
• c.—Leaves not in bundles, solitary.
• d.—Leaves alternate or whorled.
• Leaves 4-angled, harsh, needle-shaped
• Picea, p. 13.
• Leaves flat, whitened beneath, ½-1¼ inches long, sessile, aromatic; cones 2-4 inches long with deciduous scales; bark of twigs smooth, and on old trunks with raised resin-filled blisters
• Abies, p. 14.
• Leaves two-fifths to one-half inch long, short-petioled, flat and whitened beneath; cones about ¾ inch long with persistent scales; bark of twigs rough
• Tsuga, p. 14.
• d.—Leaves opposite.
• Leaves scale-like, decurrent on the stem, all of one kind; twigs flattened; fruit a small elongated cone with 8-12 over-lapping scales
• Thuja, p. 14.
• Leaves of two kinds, either scale-like or awl-shaped, not decurrent on the stem; twigs nearly terete; fruit a bluish, berry-like strobile
• Juniperus, p. 14.
• b.—Leaves flat and broad, usually deciduous.
• c.—Leaves alternate or clustered.
• d.—Leaves without lobes.
• e.—Leaves with margins entire or slightly undulate.
• f.—Leaves deciduous.
• Leaves 2-5 inches long, oval; fruit an ovoid, blue berry-like drupe, borne 1-3 in a drooping cluster
• Nyssa, p. 25.
• Leaves 2-5 inches long, ovate; fruit a spherical, blue berry-like drupe, borne many in an upright cyme, (Cornus alternifolia)
• Cornus, p. 25.
• Leaves 4-6 inches long, oval; fruit an edible berry ¾-1¼ inches in diameter
• Diospyros, p. 26.
• Leaves 4-12 inches long, obovate-lanceolate; fruit banana-like, 3-5 inches long, with many flattened seeds in the yellow flesh
• Asimina, p. 20.
• Leaves 6-24 inches long, ovate-obovate; fruit a cone-like or cucumber-like cylindrical mass 2-4 inches long
• Magnolia, p. 20.
• Leaves 3-5 inches long, heart-shaped; fruit a pod 2-3 inches long
• Cercis, p. 23.
• Leaves 4-6 inches long, oblong-lanceolate; fruit an acorn (Quercus imbricaria)
• Quercus, p. 17.
• f.—Leaves evergreen.
• Leaves 3-4 inches long; fruit many dry spherical capsules in a corymb
• Kalmia, p. 26.
• Leaves 4-11 inches long, evergreen; fruit an oblong, dry capsule, several in umbel-like clusters
• Rhododendron, p. 26.
• e.—Leaves with margins toothed.
• f.—Branches armed with stiff, sharp thorns.
• Leaves 1-3 inches long, serrate or doubly serrate; fruit a small pome
• Crataegus, p. 22.
• f.—Branches not armed with thorns.
• g.—Base of leaf decidedly oblique.
• Leaf-blade broad, heart-shaped, serrate; fruit a spherical woody drupe on stalks attached to an oblong bract
• Tilia, p. 25.
• Leaf-blade oval, doubly-serrate, primary veins straight; fruit an oval samara
• Ulmus, p. 19.
• Leaves 2-4 inches long, serrate; fruit a small sweet purple drupe
• Celtis, p. 19.
• g.—Base of leaf nearly symmetrical.
• h.—Teeth coarse, 2-5 to the inch.
• Leaves smooth, oval, 3-5 inches long; fruit a small bur with weak prickles and 3-faced nuts ½-¾ inch long
• Fagus, p. 17.
• Leaves 6-8 inches long; fruit a bur with stiff prickles and 1-3 rounded, brown nuts
• Castanea, p. 17.
• Leaves 2-4 inches long, broadly ovate to sub-orbicular; fruit a small capsule falling in spring
• Populus, p. 15.
• Leaves 4-8 inches long, lanceolate to obovate; fruit an acorn
• Quercus, p. 17.
• Leaves wavy-toothed with sharp spines, evergreen; fruit a small red drupe
• Ilex, p. 24.
• Leaves 4-6 inches long, oval; fruit a short woody pod with black seeds
• Hamamelis, p. 21.
• h.—Teeth fine, 6-many to the inch.
• i.—Leaves not doubly serrate.
• Leaves 1½-2 inches long, nearly as broad, tremulous on long petioles; fruit a small capsule. (P. tremuloides)
• Populus, p. 15.
• Leaves 2-6 inches long, often narrow; twigs easily separated at the joints; fruit a small capsule
• Salix, p. 14.
• Leaves 5-7 inches long, 1½-2½ inches wide, very smooth; bark acid; fruit a 5-valved capsule borne in clusters
• Oxydendrum, p. 26.
• Leaves 2-5 inches long, ovate to lanceolate; bark often bitter; fruit a drupe
• Prunus, p. 22.
• Leaves 3-4 inches long; fruit a red berry-like pome in clusters
• Amelanchier, p. 22.
• Leaves 3-5 inches long, nearly as wide, often heart-shaped, sometimes 2-5-lobed; fruit oblong, about 1 inch long, composed of many small drupes
• Morus, p. 19.
• Leaves 3-4 inches long, often doubly serrate or lobed on sterile shoots; fruit a greenish-yellow pome about 1 inch in diameter
• Pyrus, p. 21.
• Leaves 4-6 inches long, ovate-lanceolate; fruit 1-2 inches long, dry, 4-winged
• Halesia, p. 26.
• Leaves 4-5 inches long, ovate; fruit scarlet berry-like drupes on short stems and scattered along the branches (Ilex monticola)
• Ilex, p. 24.
• Leaves 2-5 inches long; fruit cone-like, containing many dry scales (B. lenta)
• Betula, p. 16.
• i.—Leaves doubly serrate.
• Leaves 2-4 inches long, thin; fruit a small nut enclosed in a halberd-shaped leaf-like involucre; trunk smooth and fluted
• Carpinus, p. 16.
• Leaves 3-5 inches long; fruit hop-like, composed of several inflated bracts overlapping and each containing a flat seed; bark brown with loose scales
• Ostrya, p. 16.
• Leaves 2-4 inches long; bark peeling off in papery scales; fruit oblong or ovate, 1-2 inches long, composed of numerous 3-lobed scales, bearing winged nuts
• Betula, p. 16.
• Leaves 1-3 inches long, sometimes serrate or lobed; twigs armed with stiff thorns; fruit a hard pome
• Crataegus, p. 22.
• Leaves 3-4 inches long, often serrate or lobed; fruit a sour yellowish pome about 1 inch in diameter
• Pyrus, p. 21.
• d.—Leaves lobed.
• e.—Margins of lobes entire.
• Leaves oval often without lobes or with 2-3 lobes, smooth, aromatic; fruit a dark blue drupe borne on a thickened red stem
• Sassafras, p. 21.
• Leaves broadly ovate, with truncate apex, 2 apical and 2-4 basal lobes; fruit a cone-like aggregate of dry, lance-shaped carpels
• Liriodendron, p. 20.
• Leaves variously lobed, some with bristle-tipped teeth; fruit an acorn
• Quercus, p. 17.
• e.—Margins of lobes not entire.
• Leaves thick, glossy, star-shaped, with fine pointed serrate lobes; fruit a pendulous spiny spherical head about 1 inch thick, composed of numerous capsules
• Liquidambar, p. 21.
• Leaves oval, pointed, often without lobes, thin, margins serrate or doubly serrate; fruit a yellowish pome 1-1½ inches thick
• Pyrus, p. 21.
• Leaves oval, pointed, often without lobes, thin, margins serrate or doubly serrate; fruit a pome about two-fifths of an inch thick, often red; twigs armed with thorns
• Crataegus, p. 22.
• Leaves often broadly ovate and not lobed, sometimes with 2-5 lobes, serrate; fruit oblong, about 1 inch long, an aggregate of many small dark purple drupes
• Morus, p. 19.
• Leaves nearly round in outline, 3-5 lobed, coarse sinuate-toothed; fruit a round pendulous head 1 inch thick; composed of many hairy achenes
• Platanus, p. 21.
• c.—Leaves opposite.
• d.—Leaf margins entire or slightly undulate.
• Leaves 3-5 inches long, ovate; fruit a bright red ovoid drupe, two-fifths inch long in small bunches
• Cornus, p. 25.
• Leaves 4-8 inches long, ovate; fruit a dark blue ovoid drupe, ¾ of an inch long, in drooping, loose clusters
• Chionanthus, p. 27.
• d.—Leaf margins not entire.
• Leaves 3-5 lobed, finely or coarsely toothed, fruit a drooping samara
• Acer, p. 24.
• Leaves not lobed, 1-3 inches long, oval, finely toothed; fruit a dark blue drupe borne in clusters
• Viburnum, p. 27.
• a.—Leaves compound.
• b.—Leaves alternate.
• c.—Margins of leaflets entire.
• Leaves pinnate, 8-14 inches long; fruit a pod 2-4 inches long; limbs bearing short spines in pairs at the nodes
• Robinia, p. 23.
• Leaves 3-foliate; fruit a samara, winged all around, in drooping clusters
• Ptelea, p. 23.
• Leaves pinnate with 9-21 leaflets; fruit small, red or white dry drupes in dense upright or loose drooping clusters
• Rhus, p. 23.
• c.—Margins of leaflets not entire.
• Leaves pinnate with 11-23 serrate leaflets; fruit a large sculptured nut
• Juglans, p. 15.
• Leaves odd-pinnate, with 3-11 leaflets; fruit a smooth or angled nut
• Carya, p. 15.
• Leaves odd-pinnate, with 13-17 lance-shaped leaflets; fruit a small red acid pome, borne many in a flat-topped cluster. (Pyrus Americana)
• Pyrus, p. 21.
• Leaves doubly compound with many ovate serrate leaflets; fruit a small ovoid black berry in large branching clusters; twigs and trunk armed with sharp spines
• Aralia, p. 25.
• b.—Leaves opposite.
• c.—Leaves pinnate, fruit a samara.
• Leaflets, 3-5, samaras paired
• Acer, p. 24.
• Leaflets, 5-11, samaras, not paired
• Fraxinus, p. 26.
• c.—Leaves digitate, fruit a globular capsule containing large brown nuts
• Aesculus, p. 25.