Walnut family (Juglandaceae)
This tree is typically 60-80' tall at maturity, forming a straight
trunk 2-3½' across and an ovoid crown. Larger branches in the upper
part of the crown are ascending, while those in the middle part are
widely spreading, and those in the lower part are descending. Smaller
branches and twigs are crooked. Trunk bark is light to medium gray,
rough-textured, fissured, and shaggy from narrow plates that peel away
from the trunk at their tips and/or bottoms. Branch bark is light gray
and more smooth, while the glabrous stout twigs are light gray, light brown, or
reddish brown with scattered white lenticels.
Young shoots that develop from the twigs are light green and
usually pubescent. The compound leaves are odd-pinnate with 5 leaflets
(less often with 3 or 7 leaflets) and about 8-14" long (see photo of Compound
(central stalk) of each compound leaf is light green and either
glabrous or sparsely short-pubescent. At maturity, individual leaflets
are 3-8" long and about one-half as much across; the terminal leaflet
is the largest, while the lowest lateral leaflets (first pair of a
compound leaf) are the smallest. The leaflets are obovate or broadly
elliptic in shape and their margins are serrated; tiny tufts of hair
occur along the teeth of the margins, although these tend to fade away
with age. For mature leaves, the upper leaflet surface is medium to
dark green, shiny, and hairless, while the lower leaflet surface is
pale green, dull, and hairless (or nearly so). Sometimes the lower
leaflet surface of mature leaves has short fine hairs along the veins.
At the base of each leaflet, there is a short petiolule (basal
stalklet) that is light green and either glabrous or short-pubescent.
The petiolules of the lateral leaflets are about 1/8" long, while the
petiolule of each terminal leaflet is about ½" long. The petioles of
the compound leaves are 3-6" long, light green, and either
glabrous or sparsely short-pubescent.
Shagbark Hickory is monoecious,
producing separate male (staminate) and female (pistillate) flowers on
the same tree. The male flowers are produced in drooping yellowish
green catkins near the tips of twigs; these catkins are arranged in
groups of 3 (catkins in each group sharing the same basal stalk) and
they are 3-6" long. Individual male flowers are less than 1/8" across,
consisting of several stamens and an insignificant calyx; each male
flower is partially hidden by a 3-lobed bract. The female flowers are
produced in short greenish spikes (about 1/3" long) at the tips of
young shoots; there is typically 2-3 female flowers per spike.
Individual female flowers are about 1/8" long and ovoid in shape,
consisting of a calyx and a pistil with spreading stigmata at its apex.
The blooming period occurs from mid- to late spring as the leaves
develop. The flowers are cross-pollinated by the wind. Fertile female
flowers are replaced by nearly sessile clusters of 1-3 fruits that
develop during the summer and mature during autumn of the same year.
Individual fruits are 1½-2" long and 1½-2" across (or a little less);
they are globoid to ovoid-globoid in shape. The
thick hairless husks of
the fruits are light green while immature, becoming brownish black at
maturity. Each husk is divided into 4 segments that are indented at
their margins, providing the fruit with a ribbed appearance. The nut of
each fruit is light tan, ovoid-globoid in shape, slightly 4-angled, and
somewhat compressed; the meat of each nut is edible and sweet. The root
system has a deep taproot with spreading lateral roots.
Shagbark Hickory prefers full or partial sun, mesic conditions,
and deep loam or clay-loam. Conditions that are
(but well-drained) or dry-mesic are readily tolerated. It can be
difficult to transplant this tree because of its deep taproot. Growth
and develop are rather slow. Individual trees begin to produce nuts at
about 40 years of age and they may live up to 200-300 years.
& Habitat: The native Shagbark Hickory is
occasional to common in
Illinois, occurring in every county of the state (see Distribution
Map). Habitats include upland woodlands, drier areas of
woodlands, lower wooded slopes, bluffs, and edges of limestone glades.
This tree is often found in upland habitats that are dominated by oaks,
but it also occurs in more mesic habitats where maples and other trees
occur. These habitats usually consist of old-growth woodlands
are little disturbed, although some old trees have persisted in more
disturbed areas. Shagbark Hickory is more resistant to fire than
maples, but less resistant to fire than oaks. Sometimes young seedlings
pioneer in burned-over areas.
Associations: A large number of insects feed on the wood,
plant juices, and other parts of hickories (Carya spp.).
of the butterflies Satyrium
caryaevorum (Hickory Hairstreak) and
Satyrium calanus falacer
(Banded Hairstreak) feed on these trees, as do
caterpillars of many moths (see Moth Table). Among
these moth species,
(Angus Underwing), Catocala
judith (Judith Underwing),
and Catocala residua
(Residua Underwing) feed on Shagbark Hickory
exclusively (Wagner et al., 2009). Larvae of several beetles
through the wood or bark of these trees (see Wood-Boring Beetle Table).
Examples of these species include Lepturges
caryae (Hickory Borer), and Scolytus
quadrispinosus (Hickory Bark Borer). Larvae of the weevil Conotrachelus
aratus (Hickory Shoot Curculio) feed on the shoots of
larvae of the weevil Conotrachelus
hicoriae (Hickory Nut Curculio) feed
on the meat of nuts. A large number of treehopper species have
been observed to feed on Shagbark Hickory (Dennis, 1952); see the
for a list of these species. Other insect feeders
include the leaf beetles Cryptocephalus
guttulatus and Xanthonia
striata, the leafhoppers Eratoneura era and
other Eratoneura spp.,
aphids Monellia caryella
nigropunctata, the plant bugs
albatus, and the lace bug
For a more complete list of insect species that
feed on hickories, see the Insect Table.
Vertebrate animals also use
Shagbark Hickory and other hickories as sources of food. The sweet
edible nuts of Shagbark Hickory are an important source of food for the
Fox Squirrel, Gray Squirrel, Red Squirrel, Southern Flying Squirrel,
and Eastern Chipmunk; these nuts are also consumed by the Black Bear,
Raccoon, and White-Footed Mouse. Among birds, such species as the
Ring-Necked Pheasant, Wild Turkey, Crow, Blue Jay, and Red-Bellied
Woodpecker eat the nuts. These animals help to distribute the nuts to
new locations. White-Tailed Deer browse on the foliage and twigs of
hickories sparingly, while the Cottontail Rabbit gnaws on the bark of
young trees during the winter. Because hickory trees attract so many
insects, they attract many species of flycatchers, vireos, chickadees,
gnatcatchers, warblers, tanagers, and other insectivorous birds that
prefer wooded habitats. Because of the crevices provided by its peeling
bark, Shagbark Hickory in particular provides protective cover for many
insects, particularly during the winter. These bark crevices also
provide summer roosting habitat for the endangered Indiana Bat and
nesting habitat for a small bird, the Brown Creeper.
Location: Crystal Lake Park in Urbana, Illinois.
Among the several hickories (Carya
in Illinois, Shagbark Hickory is one of two species that has older
trees with very shaggy bark. The other species, Kingnut Hickory (Carya laciniosa),
usually has 7 leaflets per compound leaf, while Shagbark Hickory
usually has 5 leaflets. A third species, Carya ovalis
(Sweet Pignut Hickory), occasionally has somewhat shaggy bark, but it
has smaller fruits (less than 1½") than the preceding two species. The
commercially important wood of Shagbark Hickory is highly regarded for
its strength and hardness: It has been used to make furniture,
flooring, tool handles, baseball bats, and other sporting equipment. It
is also an excellent source of firewood. With the possible exception of
Hickory), the range of Shagbark Hickory extends further to the north
than other hickories and it has considerable resistance to the harsh
conditions of winter. This interesting tree should be cultivated in
parks and yards more often than it is.