Crooked Run Valley
American hornbeam (Carpinus caroliniana)
SCIENTIFIC SYNONYMS: There are no scientific synonyms for
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The currently accepted scientific name for American
hornbeam is Carpinus caroliniana Walt. (Betulaceae). Infrataxa are: 1)
Carpinus caroliniana ssp. caroliniana, and 2) Carpinus caroliniana ssp.
virginiana (Marshall) Furlow.
NATIVE STATUS: Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: American hornbeam
is a native, deciduous small tree. It usually grows 30 to 40 feet (9-12 m) tall.
The bark is thin, close, and usually smooth. The trunk is often crooked, and
is usually coarsely fluted, resembling a flexed muscle. The fruit is a ribbed
nutlet 0.16 to 0.24 inch (4-6 mm) long. It is usually described as slow-
growing and short-lived. The largest American hornbeam on record for
the Southeast was 75 feet (22.8 m) tall, 21.6 (54.8 cm) d.b.h., and 67.8
inches (172.2 cm) in circumference.
REGENERATION PROCESSES: The minimum seed-bearing age of
American hornbeam is 15 years. Production is greatest at 25 to 50 years
and probably ceases at about 75 years. Large seed crops are produced at
3- to 5-year intervals. Seeds are are mainly dispersed by birds, and are
wind blown only a short distance. Seed dormancy may be broken by
stratification. The optimum natural seedbed for American hornbeam is
continuously moist, rich, loamy soil protected from extreme atmospheric
changes. American hornbeam will also establish on leaf litter seedbeds in
deep shade, even when competition is present. Germination occurs from
April to June in the spring following seed maturity. Researchers have found
that seedling survival for American hornbeam is low the first year, but
increases substantially thereafter. Flooding, drought, damping off, proximity
to a conspecific adult, and herbivory were important causes of first year
mortality. Mortality tends to be concentrated in short periods associated
with particular events (flooding, for example). Periods of reduced flooding
allowed American hornbeam seedlings to increase in importance.
SITE CHARACTERISTICS: American hornbeam exhibits its best
growth on rich, moist soils in bottomlands, coves, and lower protected
slopes. It is also common along the borders of streams and swamps
including bay and river swamps in Florida, and is also found in hammocks
in Florida. The best sites for American hornbeam are characterized by
abundant soil moisture but sufficient drainage to prevent saturation and
poor aeration during the growing season. American hornbeam is primarily
found on poorly to imperfectly drained sites, although it grows on well-
drained sites also. American hornbeam has been rated as only weakly
tolerant of flooding, although it occurs on sites that have a high probability
of flooding in any given year.
Maximum elevation for American hornbeam is about 2,900 feet (900 m)
in the southern Appalachians. Its upper elevational range is 3,000 feet
(910 m) in the Great Smoky Mountains, but is more common at about
1,600 feet (490 m). In the Adirondack Mountains, New York, American
hornbeam occurs from 200 to 1,020 feet (60-311 m) elevation.
SUCCESSIONAL STATUS: American hornbeam is tolerant of shade.
It persists in the understory of late seral and climax communities. Shade
tolerance is greatest in American hornbeam seedlings and declines with age.
American hornbeam responds positively to overstory removal. On certain
southern sites, it is so aggressive that it prevents larger species from
regenerating after logging or natural disturbance. In minor streambottoms
American hornbeam and other tolerant subcanopy species are likely to
capture a site once the main canopy is removed. American hornbeam is
classified with species that do not normally invade degraded or newly
aggrading substrates (in relation to stream channelization projects) but
are tolerant of bottomland conditions and have seed that is long-lived
(up to 2 years) and dispersed by wind or water.
American hornbeam was present in the understory of a mixed hardwood
bottomland forest dominated by water oak (Quercus nigra), sweetgum,
cherrybark oak (Quercus falcata var. pagodifolia), and loblolly pine
(Pinus taeda). American hornbeam seedlings and saplings dominated the
reproduction layers in this forest.
SEASONAL DEVELOPMENT: American hornbeam flowers from
March 20 to May 6 in the Southeast, and from April to May in the
northern parts of its range, usually before the leaves are fully grown.
The fruits ripen from August to October in the same season.
GENERAL DISTRIBUTION: The range of American hornbeam
extends from central Maine west to southwestern Quebec, southeastern
Ontario, northern Michigan, and northern Minnesota; south to central
Iowa and eastern Texas; and east to central Florida.
SKY MEADOWS DISTRIBUTION:
Tree specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
HABITAT TYPES AND PLANT COMMUNITIES: American
hornbeam primarily occurs in the understory of bottomland mixed-
hardwood forests, but also occurs in dry-mesic upland hardwood forests.
Understory associates of American hornbeam in all parts of its range
include eastern hophornbeam (Ostrya virginiana), flowering dogwood
(Cornus florida), sassafras (Sassafras albidum), witch-hazel (Hamamelis
virginiana), serviceberries (Amelanchier spp.), and speckled alder (Alnus
rugosa). In the northern parts of its range, understory associates include
striped maple (Acer pennsylvanicum), mountain maple (Acer spicatum),
red mulberry (Morus rubra), pawpaw (Asimina triloba), serviceberries, and
eastern redbud (Cercis canadensis). Southern associates include magnolias
(Magnolia spp.), deciduous holly (Ilex decidua), American holly (Ilex opaca),
winged elm (Ulmus alata), sweetbay (Magnolia virginiana), water-elm
(Planera aquatica), parsley hawthorn (Crataegus marshallii), riverflat
hawthorn (Crataegus opaca), common persimmon (Diospyros virginiana),
and Carolina laurelcherry (Prunus caroliniana).
IMPORTANCE AND USES: American hornbeam is of secondary
importance to wildlife. Ruffed grouse, ring-necked pheasant, and northern
bobwhite eat small quantities of the seeds, buds, and catkins. Seeds are
consumed by yellow-rumped warbler. The seeds are also consumed by
ducks, but usually only when acorn production is limited. Seeds, bark, and
wood are eaten by rabbits, beaver, fox squirrel, and eastern gray squirrel.
White-tailed deer browse the twigs and foliage. American hornbeam has
been reported in wild turkey crops from New York and Pennsylvania.
American hornbeam wood is very hard, heavy, and close-grained. It is
very difficult to work and is used only for tool handles, mallets, and golf
American hornbeam nuts are edible but small and therefore are seldom
collected for food. The leaves of American hornbeam have been used as an