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.