Part 1

Clair A. Brown Harold E. Grelen

IDENTIFYING HARDWOODS GROWING ON PINE SITES

Southern Forest Experiment Station U.S. Department of Agriculture, Forest Service General Technical Report SO-15

Acknowledgments

The authors thank Bryan A. Jowers, Glendale, California, for the excellent winter silhouettes. For help in obtaining specimens or photographs of species not easily accessible to us, we thank the following: Roger W. Barbour, University of Kentucky; William Harlow, College of Environmental Science and Forestry, State University of New York; Richard Johnson, Caroline Dormon Nature Preserve; Betty E. Lemon, University of Southwestern Louisiana; R. Dale Thomas, Northeast Louisiana University; and Lino Della-Bianca and Edwin R. Lawson of the U.S. Forest Service.

Summary

This publication illustrates and describes 26 hardwood species or varieties, including 16 oaks and hickories, with photographs of leaves, bark, buds, flowers, and fruits. Line drawings feature the winter silhouette of each species and a key is included to assist in identification.

US. Department of Agriculture Forest Service General Technical Report SO-15

Identifying Hardwoods Growing On Pine Sites

_CLAIR A. BROWN_ Professor Emeritus, Department of Botany Louisiana State University Baton Rouge, Louisiana

_HAROLD E. GRELEN_ Principal Range Scientist Southern Forest Experiment Station Forest Service—USDA Pineville, Louisiana

1977

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Contents

Page Overview of Southern Hardwoods 1 Key to Hardwoods 6 Species Described and Illustrated Mockernut hickory 10 Pignut hickory 12 Shagbark hickory 14 Bitternut hickory 16 Southern red oak 18 Cherrybark oak 20 Black oak 22 Scarlet oak 24 Northern red oak 26 Shumard oak 28 Blackjack oak 30 Laurel oak 32 Water oak 34 White oak 36 Post oak 38 Chestnut oak 40 Winged elm 42 American elm 44 Sugarberry 46 Yellow-poplar 48 Sweetbay 50 Sweetgum 52 Red maple 54 Black tupelo 56 White ash 58 Green ash 60 Selected References 63 Glossary 65 Index 69

Overview of Southern Hardwoods

Throughout the South some 49 billion cubic feet of small, low-quality hardwoods are growing on southern pine sites[1] (Staff, For. Resour. Res. Work Unit 1976). This material is usually wasted; if the site is prepared for regeneration to pine, the hardwoods there are destroyed. Research is underway to find economical methods of harvesting and utilizing these hardwoods. The descriptions, key, and illustrations in this book should help wood utilization researchers, especially those new to the South, to identify the most prevalent hardwood species on southern pine sites (Table 1).

Table 1.—_Important hardwoods on southern pine sites, ranked according to percentage of total hardwood volume_

Percentages were derived from Staff, For. Resour. Res. Work Unit (1976).

Nomenclature used herein follows Little (1953).

_Species_ _Percent_

Sweetgum _Liquidambar styraciflua_ L. 13.2 White oak _Quercus alba_ L. 12.3 Hickory _Carya_ spp. 8.5 Southern red oak _Quercus falcata_ Michx. 8.1 Post oak _Quercus stellata_ Wangenh. 7.0 Yellow-poplar _Liriodendron tulipifera_ L. 7.0 Black tupelo _Nyssa sylvatica_ Marsh. 5.5 Water oak _Quercus nigra_ L. 4.7 Black oak _Quercus velutina_ Lam. 4.0 Scarlet oak _Quercus coccinea_ Muenchh. 3.6 Red maple _Acer rubrum_ L. 3.6 Chestnut oak _Quercus prinus_ L. 2.9 Northern red oak _Quercus rubra_ L. 2.4 Laurel oak _Quercus laurifolia_ Michx. 1.4 Elm _Ulmus_ spp. 1.4 Cherrybark oak _Quercus falcata_ var. _pagodaefolia_ Ell. 1.2 Ash _Fraxinus_ spp. .9 Sweetbay _Magnolia virginiana_ L. .6 Shumard oak _Quercus shumardii_ Buckl. .2 Hackberry _Celtis_ spp. .1 Other hardwoods including blackjack oak (_Quercus 11.4 marilandica_ Muenchh.) Total hardwoods 100.0

Hickories have alternate compound leaves with 5 to 13 leaflets. They are monoecious; that is, the stamens and pistil are borne in separate flowers on the same plant. Flowers generally develop after the leaves are three-fourths to full grown. Staminate flowers are in catkins, which occur on last year’s wood and usually have three branches. The stalkless pistillate flowers are in several-flowered spikes at the apex of the current season’s growth. Catkins last from 10 days to 3 weeks and are usually not useful in distinguishing the species. The fruit, however, is widely used for identification. The husk may be very thin (about 1 mm), moderately thick (3 to 5 mm), or very thick (more than 5 mm). Similarly, the shell may be thin, moderately thick, or very thick. The meat varies from sweet to bitter. Upon drying, the husk usually separates along sutures and frees the nut. In some species the husk partly splits at the sutures but still encloses the nut when it falls. Such nuts are usually sterile, because the meat is seldom filled out.

For identification purposes use nuts from the ground with caution; if more than one species grows in the vicinity, the fruits could be mixed. Also some trees shed defective or sterile fruits early, and these fruits are often different in shape and size from typical fruit.

Hickories are generally divided into true hickories, which have overlapping (imbricate) bud scales, and pecan hickories, which have valvate bud scales. True hickories are divided into those with tight bark and those with loose bark. Mockernut Hickory, _Carya tomentosa_ Nutt., a tight bark species, has very pubescent leaves, large buds, and a thick husk over a large nut. Pignut Hickory, _C. glabra_ (Mill.) Sweet, also a tight bark hickory, has three to nine glabrous leaflets and a tardily dehiscing husk about 3 mm thick. Shagbark Hickory, _C. ovata_ (Mill.) K. Koch, is one of the few species with bark in thin, loose plates. It has small buds and usually has five leaflets. Bitternut Hickory, _C. cordiformis_ (Wangenh.) K. Koch, belongs to the pecan hickory group and has yellow buds with valvate scales. It also has tight bark, thin four-winged husks, thin shells, and bitter meat.

Oaks are also monoecious, and staminate flowers are in drooping catkins, which consist of a central, flexible axis with sessile, apetalous and pubescent flowers. They are most abundant on the developing new twigs. Although catkins vary among oaks, they are usually not used as distinguishing characteristics because they last only 2 to 3 weeks. Pistillate flowers occur on wood of the previous season and in leaf axils of twigs. In red oaks, however, pistillate flowers on current twigs do not mature until the second fall.

The fruit, a nut or acorn, consists of the seed enclosed in a shell. The nut is seated in a cup consisting of many scales. At maturity nuts are shed from the tree by shrinkage of the cup (dehydration). Considerable variation in mature acorn size occurs among trees of a species, notably in water oak, willow oak, and white oak.

Differences in foliage within a species also complicate identification. Apparently because lower leaves receive less sunlight they differ in size and appearance from those in the middle or upper crown. Most taxonomists prefer a specimen from the upper half of the crown because they consider leaves from this area typical for the species. To get such specimens easily, use a tree pruner and take leaves from at least 20 to 30 feet off the ground or collect them from freshly felled trees. Moreover, foliage of seedlings and small saplings often differs from that of mature trees, and spring and summer growth flushes on the same branch often appear markedly different. This seasonal variation has been noted for many oaks, including laurel, post, blackjack, and especially water oak. For example, by late March or April, water oak leaves reach their normal size and shape—obovate with a wavy apex; the second flush of growth, which starts in late April or May, produces lobed leaves.

Identification is further complicated because hybrids commonly occur among the oaks.

The oaks are divided into two main groups: the white oaks and the red (or black) oaks. The white oaks have leaves with rounded lobes and no bristles; acorns mature the first fall, and the inner surface of the shell is glabrous. White oak, chestnut oak, and post oak belong to this group. The red oak group is characterized by bristle-tipped leaf lobes in such species as Shumard, southern red, northern red, cherrybark, and black oak. The red oak group also includes non-lobed species such as water, laurel, and willow oak, which usually have entire margins. Blackjack oak leaves usually lack lobes and bristles, but leaves with terminal lobes occasionally occur and may have one bristle per lobe. Acorns mature the second fall, and the inner surface of the shell is pubescent.

Southern Red Oak, _Quercus falcata_ Michx., and its variety Cherrybark Oak, _Q. falcata_ var. _pagodaefolia_ Ell., have almost identical acorns, but they can be distinguished by other characteristics. The leaf base of southern red oak is somewhat bell-shaped, but that of cherrybark is not. Southern red oak forms heavy ridges of bark; cherrybark does not.

The distinctive feature of Black Oak, _Q. velutina_ Lam., is its yellow-orange inner bark. Its leaves take three forms. Seedlings to small saplings have a “bear-paw” leaf with only a suggestion of lobing. Lower leaves on large trees also have little lobing, but leaves from the middle and upper crown are clearly lobed. The uppermost leaves, which have seven lobes and deep sinuses, are usually illustrated as typical.

Scarlet, _Q. coccinea_ Muenchh., Northern Red, _Q. rubra_ L., and Shumard Oak, _Q. shumardii_ Buckl., are difficult to distinguish. Northern red oak leaves have shallow sinuses and a dull-green upper surface with little or no pubescence in the vein axils on the underside. Shumard oak leaves have a glossier surface, shallow to deep sinuses that are usually wider than the adjacent lobes, and definite hairiness at the vein axils. The sinuses of scarlet oak are also usually wider than their adjacent lobes, which are usually toothed. Both Shumard and scarlet oak have outstanding fall coloration.

Blackjack Oak, _Q. marilandica_ Muenchh., can be recognized by its leathery, usually entire, broadly obovate leaf, which has a rusty undersurface. The branches are stout, irregular, gnarled, drooping to horizontal.

Laurel Oak, _Q. laurifolia_ Michx., and Water Oak, _Q. nigra_ L., are similar in size and shape, but water oak has oblong-obovate or spatula-shaped leaves gradually narrowed to a wedge-shaped base. Laurel oak leaves are elliptic to oblong-ovate. Laurel oaks tend to shed leaves late and thus may retain about 30 to 50 percent of their lower leaves after water oaks are bare. Some recent authors separate the laurel oaks into two species, upland laurel oak, _Q. hemisphaerica_ Bartr., and swamp laurel oak, _Q. laurifolia_ Michx.

White Oak, _Q. alba_ L., has a thin, light green leaf with a light glaucous bloom at maturity; it is oblong or ovate, with rounded lobes and three to five narrow sinuses extending nearly to the mid-rib. The cup scales of the acorn-cup are heavy and distinct.

Post Oak, _Q. stellata_ Wangenh., has stout, irregular branches. The leathery leaves are usually five-lobed; usually the two side lobes are at right angles to the central axis, thus forming a cross-shaped leaf.

Chestnut Oak, _Q. prinus_ L., resembles swamp chestnut oak, _Q. michauxii_ Nutt., a commercially important tree southwide. Chestnut oak is primarily a northeastern tree, extending into the South along the Appalachian highlands into northern Georgia and Alabama where its range overlaps that of swamp chestnut oak, and its leaves lack the dense pubescence found on those of swamp chestnut oak.

Common elms include American Elm, _Ulmus americana_ L., and Winged Elm, _U. alata_ Michx. Both bloom after a freeze breaks dormancy. For example, if a killing frost occurs in the last week of November or the first week of December, American elm will bloom the first week of January. If no killing frost occurs by early December. American elm may not bloom until the third week of January. Winged elm usually blooms 10 days to 2 weeks later than American elm. Small winged elm trees frequently have a corky outgrowth on opposite sides of twigs at least 3 years old. Mature trees often lack this characteristic. The American elm leaf has unequal basal lobing and pubescent or ciliate samaras about 12 mm in diameter; winged elm has a smaller leaf with round to acute leaf bases and a very ciliate samara about 8 mm long.

Young Sugarberry, _Celtis laevigata_ Willd., and Hackberry, _C. occidentalis_ L., trees are readily recognized by a whitish to light gray bark dotted with small corky warts. Older trees often have relatively smooth, light to medium gray bark. Leaf margins of sugarberry are usually entire or indistinctly toothed; the upper half of hackberry leaves are usually conspicuously serrate. Both species produce tiny flowers on the new growth when the leaves are about half normal size. The fruit of sugarberry is orange-red to black; that of hackberry is dark red to nearly black at maturity.

Yellow-poplar, _Liriodendron tulipifera_ L., or tulip tree, has alternate, four- to six-lobed leaves with truncate to distinctly notched apices, a unique feature among American trees. The flowers are tulip-like with red markings on a greenish-yellow background. The fruit is a cone-like aggregate of samaras.

Sweetbay, _Magnolia virginiana_ L., produces moderate-sized trunks on uplands or numerous pole-like suckers in branch bottoms. It is evergreen in the southern part of its range and deciduous in the northern portion. A wind blowing in the crown will expose the silvery underside of the leaves. The white flowers, about 5 to 10 cm in diameter, open for the first time about 3 p.m. and close about 9 p.m. They reopen the next morning and shed their stamens. The fruit is a green pickle-like aggregate of follicles that splits open to reveal red seeds. Sweetbay and yellow-poplar, both members of the Magnolia family, have stipule scars circling the twigs.

Sweetgum, _Liquidambar styraciflua_ L., or redgum, is easily recognized by its alternate, star-shaped, palmately lobed leaves. Some trees have corky outgrowths on the small branches. Its flower consists of several round clusters of stamens arranged in a raceme and a stalked pistillate head that develops into a spiny, woody fruit containing many seeds.

Red Maple, _Acer rubrum_ L., has simple, opposite leaves that are usually glaucous and pubescent. The flowers appear in early February and the fruit is a double samara. The variety _A. rubrum_ var. _drummondii_ (Hook. and Arn.) Sarg., which has densely matted white hairs on the undersides of young leaves, grows in swamps throughout the South. Leaves may have three to five lobes, but southern trees are predominantly three-lobed. For this reason, some authors recognize the southern form as _A. rubrum_ var. _tridens_ Woods.

The leaves of Black Tupelo (blackgum) _Nyssa sylvatica_ Marsh., are alternate, elliptical to obovate, and become spotted early in their development, turning purplish in September before their early shedding. The flowers are small, inconspicuous, and produce a blue-black fruit.

Two of the most common ashes are White Ash, _Fraxinus americana_ L., and Green Ash, _F. pennsylvanica_ Marsh. The most reliable distinction between the two species appears to be samara differences. White ash has a plump, short seed end with the wing practically terminal, whereas green ash has a slender seed end and the wing extends more than halfway down the seed end. White ash usually has a rounded leaflet base, but green ash has wedge-shaped leaflet bases. The undersurfaces of fresh white ash leaves are white, but the color is difficult to detect on dry specimens. Green ash leaves are green on both surfaces, although somewhat paler on undersurfaces.

Key To Hardwoods

The key is composed of paired statements, one true and one false for any given specimen. The guide numbers at the end of statements are used to locate the next pair. Follow the true statements until you come to a common name. If you have made no mistake in interpreting the paired statements, you should arrive at the correct identity of the specimen. Then check the text and illustration.