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.Cultivation: Shagbark Hickory prefers full or partial sun, mesic conditions, and deep loam or clay-loam. Conditions that are either moist (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.
Range & 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 floodplain 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 that 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.
Faunal Associations: A large number of insects feed on the wood, foliage, plant juices, and other parts of hickories (Carya spp.). Caterpillars 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,
Catocala angusi
(Angus Underwing), Catocala
judith (Judith Underwing),
and Catocala residua
(Residua Underwing) feed on Shagbark Hickory
exclusively (Wagner et al., 2009). Larvae of several beetles
bore
through the wood or bark of these trees (see Wood-Boring Beetle Table).
Examples of these species include Lepturges
discoidea (Hickory
Saperda), Megacyllene
caryae (Hickory Borer), and Scolytus
quadrispinosus (Hickory Bark Borer). Larvae of the weevil Conotrachelus
aratus (Hickory Shoot Curculio) feed on the shoots of
hickories, while
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
Treehopper Table
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.,
the
aphids Monellia caryella
and Monelliopsis
nigropunctata, the plant bugs
Lygocoris caryae
and Plagiognathus
albatus, and the lace bug
Physatocheila plexus.
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.Photographic Location: Crystal Lake Park in Urbana, Illinois.
Comments: Among the several hickories (Carya spp.) 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 Carya cordiformis (Bitternut 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.