Forest Trees of Illinois (Third Edition)

by Robert H. Mohlenbrock

Key to the Trees of Illinois in Spring, Summer, and Fall

1. Leaves needle-like or scale-like [Group A] 1. Leaves broad and flat, never needle-like or scale-like. 2. Leaves compound (divided into 3 or more leaflets) [Group B] 2. Leaves simple. 3. Leaves opposite or whorled [Group C] 3. Leaves alternate. 4. Leaves neither toothed nor lobed [Group D] 4. Leaves toothed or lobed or both. 5. Leaves toothed but not lobed [Group E] 5. Leaves lobed [Group F]

GROUP A

Leaves needle-like or scale-like, often evergreen.

1. Leaves in clusters of 2 or more. 2. Leaves in clusters of 10 or more, falling off during autumn. 3. Leaves blue-green; cone-scales smooth [Larix laricina] 3. Leaves bright green; cone-scales hairy [Larix decidua] 2. Leaves in clusters of 2-5, evergreen. 4. Leaves in clusters of 5 [Pinus strobus] 4. Leaves in clusters of 2-3. 5. Leaves in clusters of 2. 6. Most or all the leaves less than 3 inches long, usually twisted. 7. Leaves up to 1½ inches long; sheath at base of leaves not longer than ⅛ inch [Pinus banksiana] 7. Leaves 2-3 inches long; sheath at base of leaves at least ⅓ inch long [Pinus sylvestris] 6. Most or all the leaves longer than 3 inches, rarely twisted. 8. Leaves mostly less than 5 inches long; cone-scale with a small spine [Pinus echinata] 8. Leaves mostly more than 5 inches long; cone-scale without a spine [Pinus resinosa] 5. Leaves in clusters of 3. 9. Leaves flexible, mostly less than 5 inches long; sheath at base of leaves about ¼ inch long [Pinus echinata] 9. Leaves stiff, mostly more than 5 inches long; sheath at base of leaves about 1 inch long [Pinus taeda] 1. Leaves solitary. 10. Leaves evergreen, of 2 types, some of them scale-like and about ⅛ inch long, some of them needle-like and up to ⅓ inch long [Juniperus virginiana] 10. Leaves falling off in autumn, all needle-like, usually at least ½ inch long. 11. Leaves 3-angled. 12. Leaves blue-green [Larix laricina] 12. Leaves bright green [Larix decidua] 11. Leaves flat [Taxodium distichum]

GROUP B

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]

GROUP C

Leaves broad and flat, never needle-like or scale-like, simple, opposite or whorled.

1. Leaves (or some of them) in whorls of 3. 2. Leaves with a bad odor when crushed; flowers with conspicuous purple spots [Catalpa bignonioides] 2. Leaves without a bad odor when crushed; flowers merely lined with purple [Catalpa speciosa] 1. Leaves opposite. 3. Leaves at least 6 inches long and 6 inches broad, heart-shaped at the base, never palmately lobed [Paulownia tomentosa] 3. Leaves usually less than 6 inches long and 6 inches broad, not heart-shaped at the base or, if slightly heart-shaped, then also palmately lobed. 4. Leaves palmately lobed. 5. Leafstalk with milky sap when broken [Acer platanoides] 5. Leafstalk without milky sap. 6. Areas between leaf lobes mostly V-shaped; leaves usually silvery or white on the lower surface. 7. Leaves deeply divided, the areas between the lobes extending more than half-way to the midvein [Acer saccharinum] 7. Leaves shallowly divided, the areas between the lobes extending less than half-way to the midvein. 8. Leaves completely covered with a white felt on the lower surface [Acer rubrum var. drummondii] 8. Leaves smooth or sparsely hairy on the lower leaf surface [Acer rubrum] 6. Areas between leaf lobes mostly U-shaped; leaves green or paler on the lower surface, not white or silvery. 9. Leaves with the edges drooping. 10. Leaves green on the lower surface; small leafy outgrowths sometimes present at the base of the leafstalk [Acer nigrum] 10. Leaves grayish on the lower surface; small leafy outgrowths at the base of the leafstalk absent [Acer barbatum] 9. Leaves flat, the edges not drooping [Acer saccharum]

4. Leaves not lobed. 11. Leaves toothed along the edges. 12. Edges of leaves regularly toothed from tip of leaf to base; leaves usually short-pointed or rounded at the tip. 13. Buds, leafstalks, and veins on the lower surface of the leaf covered with rusty hairs [Viburnum rufidulum] 13. Buds, leafstalks, and veins on the lower surface of the leaf without rusty hairs. 14. Leaf stalks wavy along the edges [Viburnum lentago] 14. Leaf stalks not wavy along the edges. 15. Branches spine-tipped [Rhamnus cathartica] 15. Branches not spine-tipped [Viburnum prunifolium] 12. Edges of leaves toothed only above the middle of the leaf; leaves tapering to a long point [Forestiera acuminata] 11. Leaves not toothed along the edges. 16. Upper surface of leaves rough to the touch [Cornus drummondii] 16. Upper surface of leaves smooth. 17. Leaves with deeply impressed veins on the upper surface; lower surface of leaves gray or whitish. 18. Leaves often nearly as broad as long; flowers surrounded by 4 large, white bracts; berries red; twigs green [Cornus florida] 18. Leaves longer than broad; flowers not surrounded by 4 large, white bracts; berries white; twigs gray [Cornus racemosa] 17. Leaves without deeply impressed veins; leaves often paler on the lower surface, but not gray or whitish [Forestiera acuminata]

GROUP D

Leaves broad and flat, never needle-like or scale-like, simple, alternate, neither toothed nor lobed.

1. Most or all of the leaves more than six inches long. 2. Leaves long-tapering to the base; winter buds elongated, about ⅛ inch long, covered with reddish-brown hairs [Asimina triloba] 2. Leaves rounded or only short-tapering to the base; winter buds either ½ inch long and white-hairy, or rounded and yellow. 3. Leafstalks usually more than 1½ inches long, hairy; buds nearly round, yellow [Nyssa aquatica] 3. Leafstalks usually less than 1½ inches long, smooth; buds elongated, white-hairy [Magnolia acuminata] 1. Most or all of the leaves less than six inches long. 4. Leafstalks with milky sap; twigs usually bearing small spines near the point of the leaf attachment [Maclura pomifera] 4. Leafstalks without milky sap; twigs not spiny. 5. Leaves spicy-aromatic when crushed, twigs green [Sassafras albidum] 5. Leaves not spicy-aromatic when crushed; twigs usually not green. 6. Leaves distinctly asymmetrical at base, usually obviously 3-nerved from the base. 7. Leaves usually at least twice longer than broad, rounded at the base [Celtis laevigata] 7. Leaves usually less than twice longer than broad, more or less heart-shaped at the base [Celtis tenuifolia] 6. Leaves symmetrical at the base, with a single main vein. 8. Leaves heart-shaped at the base, about as broad as long [Cercis canadensis] 8. Leaves rounded or tapering to the base, longer than broad. 9. Many of the leaves clustered near the tips of the twigs. 10. Leaves abruptly short-pointed at the tip [Nyssa sylvatica] 10. Leaves tapering to the tip. 11. Veins of leaf deeply impressed, strongly arching toward the tip of the leaf; fruit a berry [Cornus alternifolia] 11. Veins of leaf not deeply impressed nor strongly arching toward the tip of the leaf; fruit an acorn. 12. Lower surface of leaves hairy; leafstalk usually hairy; leaves usually one inch wide or wider [Quercus imbricaria] 12. Lower surface of leaves smooth except for the veins; leafstalk usually smooth; leaves usually less than one inch wide [Quercus phellos] 9. Leaves not clustered near the tips of the twigs. 13. Leaves usually with 10 or more pairs of veins; leafstalks often 1½ inches long or longer [Nyssa aquatica] 13. Leaves usually with 6-8 pairs of veins; leafstalks rarely as long as 1½ inches. 14. Leaves abruptly contracted to a short point at the tip. 15. Leaves usually about twice as long as broad; fruit an orange berry about 1 inch in diameter [Diospyros virginiana] 15. Leaves usually less than twice as long as broad; fruit a blue berry up to ½ inch in diameter [Nyssa sylvatica] 14. Leaves gradually tapering to the tip [Rhamnus caroliniana]

GROUP E

Leaves broad and flat, never needle-like or scale-like; leaves simple, alternate, toothed but not lobed.

1. Leaves asymmetrical at the base. 2. Leaves with 3 main veins arising from the base of the blade. 3. Edge of leaf with low, rounded teeth or merely wavy [Hamamelis virginiana] 3. Edge of leaf sharply or finely toothed. 4. Most of all the leafstalks less than one inch long; trunk usually warty. 5. Upper surface of leaf very rough to the touch; leaves thick and leathery. 6. Leaves tapering to a long point at the tip; most or all of the blades 3 inches long or longer [Celtis occidentalis] 6. Leaves tapering to a short point at the tip; most or all of the blades less than 3 inches long [Celtis tenuifolia] 5. Upper surface of leaf smooth or only slightly rough to the touch; leaves thin and membranaceous. 7. Leaves at least three times longer than broad [Celtis laevigata] 7. Leaves less than three times longer than broad. 8. Some or all the leaves 3 inches long or longer [Celtis occidentalis] 8. Leaves less than 3 inches long [Celtis tenuifolia] 4. Leafstalks more than 1 inch long. 9. Leaves smooth on the lower surface except for small tufts of hairs where the veins meet [Tilia americana] 9. Leaves hairy on the lower surface. 10. Lower surface of leaves white [Tilia heterophylla] 10. Lower surface of leaves green [Tilia americana]

2. Leaves with one main vein arising from the base of the blade. 11. Some of the twigs with corky wings. 12. Some or all the leaves four inches long or longer; leaf-stalks more than ⅛ inch long [Ulmus thomasii] 12. None of the leaves four inches long; leafstalks up to ⅛ inch long [Ulmus alata] 11. Twigs without corky wings. 13. Leaves very rough-hairy to the touch [Ulmus rubra] 13. Leaves smooth or soft to the touch. 14. Edge of leaf doubly toothed (each tooth divided into a second small tooth). 15. Leaves distinctly one-sided at the base; leafstalks often smooth [Ulmus americana] 15. Leaves only slightly one-sided at the base; leafstalks hairy. 16. Bark of trunk with sinewy ridges; fruit enclosed in flat, 3-lobed bracts; lower lateral veins of leaf unbranched [Carpinus caroliniana] 16. Bark of trunk broken into scales; fruit surrounded by inflated, bladdery bracts; lower lateral veins of leaf branched [Ostrya virginiana] 14. Edge of leaf singly toothed. 17. Leaves smooth on the lower surface; leafstalks smooth [Ulmus pumila] 17. Leaves hairy on the lower surface, at least where the veins meet; leafstalks usually hairy [Planera aquatica] 1. Leaves symmetrical at the base. 18. Leaves with 2-4 irregular teeth along the edges. 19. Leaves usually with 10 or more pairs of veins; leaf stalks often 1½ inches long or longer [Nyssa aquatica] 19. Leaves usually with 6-8 pairs of veins; leaf stalks rarely as long as 1½ inches [Nyssa sylvatica] 18. Leaves more regularly toothed with more than 4 teeth along the edges. 20. Leafstalks with milky sap when broken. 21. Leaf stalks and lower surface of leaf with long hairs [Broussonetia papyrifera] 21. Leaf stalks and lower surface of leaf smooth or with short hairs. 22. Lower leaf surface hairy between the veins [Morus rubra] 22. Lower leaf surface smooth or hairy only on the veins [Morus alba] 20. Leafstalks without milky sap when broken. 23. Leaves at least 4 times as long as broad. 24. Leafstalks less than ⅛ inch long; leaves irregularly toothed along the edges [Salix interior] 24. Leafstalks more than ⅛ inch long; leaves regularly toothed along the edges. 25. Leaves green on the lower surface [Salix nigra] 25. Leaves whitish on the lower surface. 26. Each leaf with a pair of leaf-like stipules at the base of the leafstalk [Salix caroliniana] 26. Each leaf without a pair of leaf-like stipules [Salix amygdaloides] 23. Leaves less than 4 times as long as broad. 27. Leaves as broad as long or broader. 28. Leaf stalks not flattened. 29. Leaves strongly whitened on the lower surface, not heart-shaped at the base [Populus alba] 29. Leaves not strongly whitened on the lower leaf surface, heart-shaped at the base [Populus heterophylla] 28. Leaf stalks flattened. 30. Leaves basically triangular in shape, coarsely toothed [Populus deltoides] 30. Leaves basically ovate or spherical, coarsely or finely toothed. 31. Leaves with 20 or more fine teeth along the edges [Populus tremuloides] 31. Leaves with up to 15 coarse teeth along the edges. [Populus grandidentata] 27. Leaves longer than broad. 32. Twigs usually with sharp spines. 33. Leaves broadest below the middle; fruit a small apple. 34. Many of the leaves narrowly oblong to narrowly elliptic [Malus angustifolia] 34. Most of the leaves ovate to oval to broadly lance-shaped. 35. Twigs and young leaves densely hairy [Malus ioensis] 35. Twigs and young leaves smooth or nearly so [Malus coronaria] 33. Leaves broadest at or above the middle; fruit a hawthorn. 36. Leaves broadest at the middle; leafstalks one inch long or longer [Crataegus viridis] 36. Leaves broadest above the middle; leafstalks up to ¾ inch long. 37. Leaves leathery, smooth on both surfaces [Crataegus crus-galli] 37. Leaves not leathery, usually somewhat hairy on the lower surface [Crataegus punctata] 32. Twigs not spiny. 38. Some of the twigs with corky wings. 39. Some or all the leaves 4 inches long or longer; leafstalks more than ⅛ inch long [Ulmus thomasii] 39. None of the leaves 4 inches long; leafstalks up to ⅛ inch long [Ulmus alata] 38. None of the twigs with corky wings. 40. Individual teeth along edge of the leaf at least ¼ inch long. 41. Most of the veins not reaching to the tip of each leaf; lower surface of leaf usually silvery-white [Quercus bicolor] 41. Most of the veins projecting to the tip of each leaf; lower surface of leaf green or pale, but usually not silvery-white. 42. Leaves usually with sharp-pointed teeth. 43. Fruit an acorn; lower leaf surface usually covered with very short hairs [Quercus muhlenbergii] 43. Fruit enclosed in a prickly bur; lower leaf surface smooth or nearly so [Castanea dentata] 42. Leaves usually with somewhat rounded teeth. 44. Cup of acorn at least 1 inch across; trunk whitish to gray [Quercus michauxii] 44. Cup of acorn less than 1 inch across; trunk brown to black [Quercus prinus] 40. Individual teeth along edge of leaf up to ⅛ inch long. 45. Some of the leaves produced from short, stubby shoots along the main twigs [Ilex decidua] 45. Twigs without short, stubby side shoots. 46. Leafstalks with 1 or more small glands (“bumps”), usually near the point of attachment to the blade. 47. Each tooth along the edge of the leaf bearing a small, reddish-brown gland. 48. Some or all leaves one inch broad or broader. 49. Leaves flat [Prunus hortulana] 49. Leaves more or less folded down the middle [Prunus munsoniana] 48. None of the leaves as much as one inch broad [Prunus angustifolia] 47. Teeth along the edge of the leaf not bearing a gland. 50. Leaves usually with a dull, wrinkled surface; fruit a plum [Prunus americana] 50. Leaves usually appearing smooth and rather shiny; fruit an elongated cluster of small cherries. 51. Teeth along edge of leaf curving inward, usually rather blunt [Prunus serotina] 51. Teeth along edge of leaf pointing outward, usually sharp-pointed [Prunus virginiana] 46. Leafstalks not bearing glands. 52. Leaves doubly toothed along the edges. 53. Bark peeling off into papery strips or layers; leaves usually about two-thirds as broad as long or broader. 54. Bark yellowish, silvery-gray, or creamy-white. 55. Bark yellowish or silvery-gray; leaves with 8 or more pairs of veins [Betula lutea] 55. Bark creamy-white; leaves with no more than 7 pairs of veins [Betula papyrifera] 54. Bark reddish-brown [Betula nigra] 53. Bark broken into small plates, or smooth and sinewy, not peeling off into papery strips or layers. 56. Bark of trunk with sinewy ridges; fruit enclosed in flat, 3-lobed bracts; lower lateral veins of leaf unbranched [Carpinus caroliniana] 56. Bark of trunk broken into scales; fruit enclosed in inflated, bladdery bracts; lower lateral veins of leaf branched [Ostrya virginiana] 52. Leaves singly toothed along the edges. 57. Leaves heart-shaped at the base. 58. Leaves up to six inches long and nearly as broad [Populus heterophylla] 58. Leaves not more than four inches long and about half as broad. 59. Leaves bronze as they unfold; leafstalk smooth [Amelanchier laevis] 59. Leaves densely white-hairy as they unfold; leafstalk somewhat hairy [Amelanchier arborea] 57. Leaves rounded or tapering to the base, not heart-shaped. 60. Teeth along edge of leaf widely spaced, at least ¼ inch apart [Fagus grandifolia] 60. Teeth along edge of leaf closely and regularly spaced. 61. Leafstalk hairy; fruit fleshy. 62. Leaves shiny on the upper surface; leafstalks ½ inch long or longer [Rhamnus caroliniana] 62. Leaves dull on the upper surface; leafstalks up to ¼ inch long [Planera aquatica] 61. Leafstalk smooth at maturity; fruit dry and variously winged. 63. Some of the leaves three inches long or longer; fruit 4-winged or a woody “cone.” 64. Leaves pointed at the tip; fruit 4-winged [Halesia carolina] 64. Leaves rounded at the tip; fruit a woody “cone” [Alnus glutinosa] 63. Leaves less than 3 inches long; fruit surrounded by a flat wing [Ulmus pumila]

GROUP F

Leaves broad and flat, never needle-like or scale-like; leaves simple, alternate, lobed.

1. Leafstalks with milky sap when broken. 2. Leafstalks and lower surface of leaf with long hairs [Broussonetia papyrifera] 2. Leafstalks and lower surface of leaf smooth or with short hairs. 3. Lower leaf surface hairy between the veins [Morus rubra] 3. Lower leaf surface smooth or hairy only on the veins [Morus alba] 1. Leafstalks without milky sap when broken. 4. Twigs usually with sharp spines. 5. Leaves broadest at the middle or above the middle. 6. Leaves broadest at the middle; lower surface of leaf smooth except for a few tufts of hairs near the veins [Crataegus viridis] 6. Leaves broadest above the middle; lower surface of leaf hairy throughout [Crataegus punctata] 5. Leaves broadest below the middle. 7. Leaves hairy throughout on the lower surface. 8. Leaves mostly tapering to the base; fruit a crab apple [Malus ioensis] 8. Leaves rounded at the base; fruit a hawthorn. 9. Fruit with pitted seeds; flowers appearing in late May and June [Crataegus calpodendron] 9. Fruit without pitted seeds; flowers appearing in April or early May [Crataegus mollis] 7. Leaves smooth on the lower surface or hairy only on the veins. 10. Leaves tapering to the base. 11. Leaves oval to ovate to broadly lance-shaped [Malus coronaria] 11. Leaves narrowly oblong to narrowly elliptic [Malus angustifolia] 10. Leaves rounded at the base. 12. Leaves blue-green; fruit spherical or nearly so [Crataegus pruinosa] 12. Leaves green; fruit shaped like a little apple [Malus coronaria] 4. Twigs without spines. 13. Leaves star-shaped [Liquidambar styraciflua] 13. Leaves not star-shaped. 14. Leaves 4-lobed, smooth on both surfaces [Liriodendron tulipifera] 14. Leaves more than 4-lobed, hairy on one or both surfaces. 15. Leaves palmately lobed and veined. 16. Leaves densely coated with white felt on the lower surface [Populus alba] 16. Leaves without a coat of white felt on the lower surface [Platanus occidentalis] 15. Leaves pinnately lobed and veined. 17. Lobes of leaf with bristle-tips. 18. Leaves broadest above the middle [Quercus marilandica] 18. Leaves broadest at or below the middle. 19. Leaves hairy throughout on the lower surface. 20. Lower surface of leaves with gray hairs; base of leaf blade usually broadly rounded. 21. Leaves with 5-11 more or less equal lobes, the uppermost lobe not strongly curved [Quercus pagodaefolia] 21. Leaves with 3-5 more or less unequal lobes, the uppermost lobes often strongly curved [Quercus falcata] 20. Lower surface of leaves with rusty hairs; base of leaf blade not broadly rounded [Quercus velutina] 19. Leaves smooth on the lower surface or hairy only next to the veins. 22. Leaves divided less than halfway to the middle. 23. Leafstalks hairy; buds hairy, gray [Quercus velutina] 23. Leafstalks smooth; buds smooth, reddish-brown [Quercus rubra] 22. Leaves divided more than halfway to the middle. 24. Leafstalks hairy; cup of acorn fringed around the edge [Quercus velutina] 24. Leafstalks smooth; cup of acorn not fringed around the edge. 25. Lower surface of leaves with large tufts of hairs in the vein axils. 26. Cup of acorn saucer-shaped. 27. Cup of acorn up to ½ inch broad. [Quercus palustris] 27. Cup of acorn more than ½ inch broad [Quercus shumardii] 26. Cup of acorn top-shaped. 28. Cup of acorn enclosing about ⅓ the nut at most [Quercus shumardii] 28. Cup of acorn enclosing more than one-third of the nut [Quercus ellipsoidalis] 25. Lower surface of leaves smooth or with small tufts in hairs in the vein axils [Quercus coccinea] 17. Lobes of leaf with round tips, not bristle-tipped. 29. Leaves smooth on the lower surface [Quercus alba] 29. Leaves hairy on the lower surface. 30. Upper three lobes of leaf squarish, forming a cross; twigs hairy [Quercus stellata] 30. Leaves without three squarish lobes at the upper end; twigs smooth or nearly so. 31. Edge of acorn cup with a fringe [Quercus macrocarpa] 31. Edge of acorn cup not fringed [Quercus lyrata]