The American hornbeam (Carpinus caroliniana) is a deciduous hardwood shade tree that's native to eastern North America. It is part of the Betulaceae (birch) family and has several nicknames, including blue beech, muscle beech, water beech, muscletree, musclewood, and ironwood. The reference to muscle relates to the tree's characteristic fluted trunk and branches that look like muscle tissue. Its wood is very strong and sometimes is used to make tools and other implements.
Best planted in the spring, this tree has a slow growth rate, gaining around a foot a year. It produces dark green summer leaves that turn a variegated orange in the fall. Come winter, its blue-gray bark creates a beautiful contrast to the snow in northern climates. The hornbeam is a great tree to add to any landscape, as it's a medium size and resistant to most pests and diseases.
|Botanical Name||Carpinus caroliniana|
|Common Name||American hornbeam, blue beech, musclewood, ironwood, water beech|
|Plant Type||Deciduous tree|
|Mature Size||20 to 25 feet wide and 20 to 35 feet tall|
|Sun Exposure||Part shade to full shade|
|Soil Type||Fertile, moist, well-draining|
|Soil pH||4 to 7.4|
|Hardiness Zones||3 to 9|
|Native Area||North America|
How to Grow American Hornbeam
The American hornbeam looks gorgeous in all seasons. Many gardeners like to use a hornbeam as the focal point in a perennial garden by surrounding it with complementary flowers and mulch. That way, it won't outcompete other trees. Along those lines, remember to consider its mature size when planting. While it's a slow grower (it can take decades to reach its maximum size), this tree might cause crowding problems for neighboring trees down the road. And the tree can be difficult to transplant due to its expansive root system, so you'll want to pick an ideal spot from the start.
For best results, start your American hornbeam from seed on site, or select a young tree from a reputable nursery. This species is highly adaptable and can withstand some flooding, but it has a hard time dealing with drought conditions. Other than providing regular watering, the hornbeam is relatively low-maintenance.
The American hornbeam is commonly found within the understory of hardwood forests, so it can thrive in partial to full shade. It is also quite adaptable and can tolerate full sun. Ideally it should get around four to six hours of light per day.
Hornbeams prefer fertile, moist, well-draining soil with an acidic to neutral soil pH, though they can tolerate slight alkalinity. While they are able to grow in clay soil, loam is best. Poor soil drainage will cause them to grow more slowly.
This tree needs regular watering during dry spells. Installing drip irrigation for summer maintenance is helpful. When the weather is hot and dry, give the tree a deep soak once per week. A layer of mulch over the roots will help to retain soil moisture. To establish the roots of a new tree, keep the ground damp for the first two to three years during the growing season.
Temperature and Humidity
Hornbeams grow in a wide range of climates, from Canada to Florida, so they are tolerant of broad temperature differences and seasonal conditions. However, the species is less common in dry climates; at least moderate humidity is preferred for optimal growth.
American hornbeams typically do not need fertilizer, especially when the ground around the tree has grass that is fertilized.
This tree can form multiple trunks if left to its own devices. So if you'd like your hornbeam to have a single trunk with foliage growing above, make sure to prune it to have only one central leader. Other than that, you generally only have to prune to remove dead or diseased branches.
You can also prune this species to create a formal hedge or living fence. This works well for adding privacy to your yard without the eyesore of a tall fence. Regular pruning will be necessary to maintain the hedge shape.
Common Growing Issues
The American hornbeam is extremely resistant to both pests and diseases, so problems rarely arise. However, hornbeam trees can develop cankers, or dead sections on the bark or branches. And they can present with leaf scorch or leaf spots. Proper maintenance and appropriate water amounts should prevent this. Insects that can affect a hornbeam include maple mealybugs and two-lined chestnut borers. So if you notice damaged foliage, they might be the culprits.
Varieties of American Hornbeam
The American hornbeam has some cultivars with slightly different appearances. They include:
- Carpinus caroliniana 'J.N. Upright': Known as Firespire, this cultivar features brilliant red-orange fall color and grows to around 20 feet tall and 10 feet wide.
- Carpinus caroliniana 'JFS-KW6': This cultivar gets its name, Native Flame, from its bright red fall color. It can reach around 30 feet high and 20 feet wide.
- Carpinus caroliniana 'CCSQU': This cultivar sports yellow-orange fall color. It has an oval shape, reaching around 20 to 30 feet tall and 15 to 20 feet wide.
“Managing Pests in Gardens: Trees and Shrubs: Hornbeam—UC IPM.” Accessed August 11, 2021. http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/hornbeam.html.
Kelby Fite, PhD. “Two-Lined Chestnut Borer.” The Bartlett Lab Staff, n.d. https://www.bartlett.com/resources/two-lined-chestnut-borer.pdf.