669 Carpinus carolinianaCommon Names: American hornbeam, musclewood, ironwood, blue beech Family: Betulaceae (birch Family)
American hornbeam is a handsome little deciduous tree that can get as large as 50 ft (15.2 m) tall with a spread of 40 ft (12.2 m). However, they rarely exceed 15-20 ft (4.6-6.1 m) in height. The crown is wide-spreading, flat topped or rounded, and can be symmetrical or irregular. Usually the trunk is crooked and branches out fairly low. The long, slender branches have a zigzag form. The bark is thin and slate gray, and irregularly fluted with smooth, sinewy, muscle-like ripples. The leaves are blue green above and yellowish green below. They are arranged alternately along the twigs. The leaves are oval, 2-4 in (5.1-10.2 cm) in length, 1-2 in (2.5-5.1 cm) wide, long pointed at the tip, and rounded at the base. The margins are doubly toothed and the 10-14 pairs of parallel leaf veins are conspicuous. Male and female flowers are in separate catkins on the same tree. The male catkins are along the branchlets and the female catkins at the branchlet tips. The fruit is a small nut, 1/3 in (0.8 cm) long and attached to the base of a 3-lobed leaflike bract. Several bracts are arranged one above another on a hanging stalk 4-6 in 10.2-15.2 cm) long. The whole affair looks a little like a dangling Japanese pagoda, first green, then becoming yellowish brown as it matures. The leaves turn yellow, orange, red and reddish purple in fall.
American hornbeam, Carpinus caroliniana is a common and widespread understory tree in lowland mixed forests throughout eastern North America from Quebec to Minnesota, south to Florida and eastern Texas, and on into Mexico, Guatemala and Belize. It grows in bottomland forests, swamps and along rivers and streams in association with other deciduous hardwoods including maples, ashes, oaks, birches, alders and hickories.
CultureAmerican hornbeam is a relatively slow growing tree, putting on only a foot or so of new growth per year. Light: American hornbeam does well in shade, but also thrives in sun. Moisture: Although American hornbeam grows naturally in wetlands, once established, it is tolerant of moderate droughts and does fine in well-drained soils. It can tolerate occasional flooding. Hardiness: USDA Zones 3 - 9. Propagation: Fresh seed germinates fairly reliably. Older seed must be cold stratified for 3-4 months before it will germinate.
American hornbeam is an elegant little tree in the woodland garden. It thrives in the shade under larger trees, and requires no attention from its caregiver. For a tree, American hornbeam responds surprisingly well to heavy pruning and can be shaped as a hedge for a screen or used as a formal element in the landscape.
The wood of American hornbeam is heavy, very hard and close grained. It has been used to make bowls and dishes because it does not crack or split, and for tool handles and mallets. It is not important commercially though, because the trees are so small.
American hornbeam belongs in any native plant or woodland garden in the eastern US or Canada. It's a handsome, carefree little tree that thrives in complete shade, and has colorful fall foliage. The unusual fruiting structures always stimulate interest. The long slender zigzag branches make an attractive silhouette in winter. Some people confuse hornbeam with hophornbeam (Ostrya spp.), probably because the leaves and fruiting structures are similar, and certainly because the common names are so similar. In fact, one major field guide to North American trees actually describes the American hornbeam in the first sentence for eastern hophornbeam (O. virginiana)! Talk about getting confused! This is one reason why many prefer the common name, "musclewood," which so aptly describes the trunk and larger limbs of Carpinus, which look like sinewy, flexed muscles. (Hophornbeam has brown, shaggy bark that is not at all fluted or sinewy.) "Hornbeam" comes from the German for "tough tree."
American hornbeam is very similar to European hornbeam (C. betulus), which is used as a street tree and landscape plant, and often pruned as a hedge, in Europe and the US. The European species is a larger tree, has smooth buds, and 3-5 veins on the leaflike bracts around the seeds, whereas the American species has hairy buds and 5-7 veins on the bracts.
Steve Christman 4/11/00, updated 7/27/16