American Hornbeam

American Hornbeam Carpinus carolinianaHornbeam (Carpinus caroliniana) is an attractive small tree that is common, but not abundant in its natural range.  It has many common names, the most common include: blue beech because of its very smooth gray bark, and musclewood referring to its muscle-like branches which are irregularly fluted.

Habitat: Grows on moist, rocky, wooded slopes. Commonly found in NE Iowa

American hornbeam leaves
American Hornbeam Leaves - Photo by Paul Wray, Iowa State University

Hardiness: Zones 3 through 9

Growth Rate: Slow

Mature Shape: Symmetrical canopy with a smooth outline; ovular dense crown

Height: 25-35 feet

Width: 15-25 feet

Site Requirements: Prefers deep, fertile, moist, acidic soil and grows best in partial shade, but will grow in full sun. Not drought-tolerant.

Leaves: Alternate, simple, double-toothed with equal leaf base

Flowering Dates: April - June

Seed Dispersal Dates: November - Spring

Seed Bearing Age: 15 Years; Peaks at age 25-50; Ceasing around 75 years

Seed Bearing Frequency: 3-5 years

Seed Stratification: Seeds need stratification for 2 months at 40°F

American hornbeam fruit
American Hornbeam Fruit - Photo by Paul Wray, Iowa State University

Hornbeam has alternate simple leaves, with fine teeth and tapering to a sharp point. Winter twigs are very fine reddish brown in color with three bundle scars. It is a member of the birch family and will have the male catkin flower buds present in the winter months. The fruit is a small nut about 1/3” in diameter, lying at the base of 3-lobed leafy bract; the fruits are clustered on a hanging stalk. The bark is thin, slate gray to light gray in color and very tight, seldom forming any ridges or breaking into plates.

It is native to the eastern third of Iowa and can also be found growing up the Iowa and Des Moines rivers. It is a common, but not abundant tree, often growing in multiple stem clumps. Like ironwood, it is very shade tolerant and thrives in the understory of our upland oak-hickory woodlands. It prefers a moister site than Ironwood and will often be located on north and east slopes or on the upper stream terraces.

It is a small tree, seldom reaching a foot in diameter or more than 30 feet tall. The wood is very tough with exceptional strength characteristics and has been used for tool handles and other minor uses requiring tough wood. Because it is such a small tree, its commercial value for lumber is almost non existent. It does have high density and makes excellent firewood. 

It has great potential as an ornamental tree, because of its gray fluted stems and good reddish-orange fall color. It is somewhat difficult to transplant and does best in a moist, sheltered location of the landscape and will tolerate some shading.


American hornbeam flowers
American Hornbeam Fruit - Photo by Paul Wray, Iowa State University

American hornbeam bark
American Hornbeam Bark - Photo by Paul Wray, Iowa State University