Part 1

Forest Trees of Illinois

THIRD EDITION

By Robert H. Mohlenbrock Department of Botany, Southern Illinois University

Photography by John A. Richardson and Robert H. Mohlenbrock Illustrations by Miriam Wysong Meyer and Fredda J. Burton Southern Illinois University

Printed by authority of the State of Illinois Issued by DEPARTMENT OF CONSERVATION Division of Forestry

14 (17943—10M—4-80)

TABLE OF CONTENTS

Acknowledgments 4 Introduction 5 Illustrated Glossary 6 Key to the Trees of Illinois in Spring, Summer, and Fall 9 Key to the Trees of Illinois in Winter 27 Trees of Illinois 38 Special Places to Study Trees 318 White Oak, the State Tree of Illinois 322 Illinois Big Tree Champions 323 Index to Common and Scientific Names 324 District Foresters 330

Acknowledgments

I am grateful to the late Mr. Fred Siemert, State Forester of the Illinois Division of Forestry, for suggesting the need for a new “Forest Trees of Illinois.” The first and second editions of this work have been immensely popular, and the need for a third edition is gratifying.

This third edition is only slightly modified from the second. A few illustrations and bark photographs have been substituted, and the key has been improved in places. New material has been added to the description of the water hickory.

I wish to give thanks to Mr. Al Mickelson of the Illinois Division of Forestry for encouraging this third edition, and to his assistants, Mr. John Sester and Mr. Ernest Kunze, for editing it for publication. Mark Mohlenbrock has redrawn the leaves and fruit illustrated on pages 101 and 169.

Introduction

The initial edition of Forest Trees of Illinois was written in 1927 by W. R. Mattoon and R. B. Miller, two prominent foresters in the state at that time. This was revised in 1955 by Dr. George Damon Fuller, then of the Illinois State Museum, and E. E. Nuuttila, State Forester of Illinois.

In 1973, I prepared the first edition of the new Forest Trees of Illinois with new text, keys, photographs, and illustrations. An updated second edition was published in 1978. Because of the heavy demand for this work, this third edition has been prepared.

Woody plants are usually divided into trees and shrubs, but the difference between these growth forms is not always distinct. In this work, we consider a plant to be of tree stature if it has a single erect trunk which branches above the ground to form a crown. It must have a diameter of at least 3 inches 4½ feet above the ground and an overall height of 12 feet. Some of the plants included in this work are borderline between trees and shrubs. The height of a plant may be influenced by its geography. Thus, the Gray Dogwood (_Cornus racemosa_) in extreme southern Illinois may reach the dimensions of a small tree, but this same species in northern Illinois is also of a shrubby stature.

Almost every kind of plant in the world is known by a Common Name and a Latin Name. The Common Name is the one used locally by residents of the area. It is of limited value because people in different areas sometimes have different names for the same plant. For example, one of the trees in Illinois is known by some as the Ironwood, by others as the Blue Beech, by others as the American Hornbeam, and by still others as the Musclewood Tree. Then again, the name Ironwood applies to at least two different kinds of trees in Illinois. The Latin Name for each kind of tree is known the World over by the same name. Actually, the Latin Name is composed of two words, the genus name, which is always capitalized, and the specific epithet, which is not capitalized.

Of all the kinds of plants in the World, none is so well-loved, so stately and majestic, as a forest tree. More and more people each year are vacationing and seeking outdoor recreation. Many of them “take to the woods” for their leisure, because the forests of our state hold an unending fascination to many who enter them.

Moreover, trees provide us with building material for our homes, shade for our lawns and parks, and hundreds of other products used in our everyday living.

To know the trees we encounter is to enhance our appreciation for them. The purpose of FOREST TREES OF ILLINOIS is to bring to Illinoisans a means of identifying the trees that grow in this state.

Illustrated Glossary

In order to distinguish one kind of tree from another, it is necessary to learn the major characteristics which the forest trees of Illinois may possess. Illustrated below are several of the most commonly encountered characteristics of leaves and twigs. A thorough understanding of these structures will insure a quicker and more accurate identification.

On the pages following the illustrated glossary are keys to the trees of Illinois. A key is a botanical device which enables the user, through proper selection of a series of choices, to identify a specimen at hand. Separate keys are provided for trees during the spring, summer, and autumn seasons and during the winter season. Begin at the first pair of number 1’s, choose the statement that best fits the unknown specimen, and then go to the next pair of statements beneath. Continue this same procedure until the name of the plant is reached.

LEAF FORMS AND ARRANGEMENT SIMPLE PINNATELY COMPOUND PALMATELY COMPOUND DOUBLY PINNATELY COMPOUND OPPOSITE ALTERNATE WHORLED LEAF SHAPES LANCEOLATE OBLANCEOLATE OBLONG ELLIPTICAL OVATE OBOVATE

WINTER TWIG CHARACTERS BUD SCALE TERMINAL BUD LATERAL BUD LEAF SCAR LENTICELS BUNDLE TRACES {LEAF LAYERS} UPPER EPIDERMIS PALISADE LAYER RIBS AND VEINS SPONGY LAYER STOMA LOWER EPIDERMIS LEAF TIPS ACUTE OBTUSE LONG-TAPERING LEAF EDGES PINNATELY LOBED WAVY TOOTHED DOUBLY TOOTHED SMOOTH LEAF BASES HEART-SHAPED TRUNCATE ASYMMETRICAL ROUNDED TAPERING

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.