American Hornbeam (Carpinus caroliniana)

American Hornbeam, Blue Beech, Hornbeam, Ironwood, Musclewood, Muscle Wood, Water Beech

A lovely shade tree suitable for most settings, American hornbeams are compact trees that fit the scale of the average home landscape perfectly. The hornbeam tree info in this article will help you decide whether the tree is right for you, and tell you how to care for it.

I. Appearance and Characteristics 

Carpinus caroliniana, the American hornbeam, is a small hardwood understory tree in the genus Carpinus. American hornbeam is also known as blue-beech, ironwood, musclewood and muscle beech. It is native to eastern North America, from Minnesota and southern Ontario east to Maine, and south to eastern Texas and northern Florida. It also grows in Canada (southwest Quebec and southeast Ontario). It occurs naturally in shaded areas with moist soil, particularly near the banks of streams or rivers, and is often a natural constituent understory species of the riverine and maritime forests of eastern temperate North America.

Carpinus caroliniana (American hornbeam) is a small tree reaching heights of 10–15 meters (35–50 ft), rarely 20 meters (65 ft), and often has a fluted and crooked trunk. The bark is smooth and greenish-grey, becoming shallowly fissured in all old trees. The leaves are alternate, 3–12 centimeters (1+1⁄4–4+3⁄4 in) long, with prominent veins giving a distinctive corrugated texture, and a serrated margin. The male and female catkins appear in spring at the same time as the leaves. The fruit is a small 7–8-millimeter (9⁄32–5⁄16-inch) long nut, partially surrounded by a three- to seven-pointed leafy involucre 2–3 centimeters (3⁄4–1+1⁄4 in) long; it matures in autumn. The seeds often do not germinate till the spring of the second year after maturating.

  • Bark: On old trees near the base, furrowed. Young trees and branches are smooth, dark bluish gray, sometimes furrowed, light and dark gray. Branchlets at first pale green, changing to reddish brown, ultimately dull gray.
  • Wood: Light brown, sapwood nearly white; heavy, hard, close-grained, very strong. Used for levers, handles of tools. Specific gravity, 0.7286; density 45.41 pounds per cubic foot (0.7274 g/cm3).
  • Winter buds: Ovate, acute, chestnut brown, 1⁄8 inch (3 mm) long. Inner scales enlarge when spring growth begins. No terminal bud is formed.
  • Leaves: Alternate, two to four inches long, ovate-oblong, rounded, wedge-shaped, or rarely subcordate and often unequal at base, sharply and doubly serrate, acute or acuminate. They come out of the bud pale bronze green and hairy; when fully grown they are dull deep green above, paler beneath; feather-veined, midrib and veins very prominent on the underside. In autumn bright red, deep scarlet and orange. Petioles are short, slender, and hairy. Stipules caducous.
  • Flowers: April. Monoecious, without petals, the staminate spike naked in pendulous catkins (aments). The staminate ament buds are axillary and form in the autumn. During the winter they resemble leaf-buds, only twice as large. They begin to lengthen very early in the spring, and when full grown are about 1+1⁄2 inches (4cm) long. The staminate flower is composed of three to twenty stamens crowded on a hairy torus, adnate to the base of a broadly ovate, acute boot-shaped scale, green below the middle, bright red at apex. The pistillate aments are one-half to three-fourths of an inch long with ovate, acute, hairy, green scales and bright scarlet styles.
  • Fruit: Clusters of involucres, hanging from the ends of leafy branches. Each involucre slightly encloses a small oval nut. The involucres are short stalked, usually three-lobed, though one lobe is often wanting; halberd-shaped, coarsely serrated on one margin, or entire.

II. Types 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.

III. How to Grow and Care

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 extensive root system, so you’ll want to pick an ideal spot from the start.

Sunlight

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.

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.

Watering

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.

Soil

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.

Fertilizing

Although American hornbeam can grow well on its own, you should fertilize the plant if it’s young. Spread an organic fertilizer around the young tree during the spring, at the beginning of the growing season. Cut back on fertilizing as the plant grows older unless its growth becomes stunted.

Planting Instructions

Dig a planting hole that is at least twice as wide as the root ball and has the same depth. Position the tree in the planting hole so the top of the root ball is level with the surrounding grade. Backfill with the original soil. Water well and continue to water the newly planted tree deeply and regularly during the first growing season. If deer tend to browse in your yard, protect the young tree with a tree guard for the first couple of growing seasons. 

Plant trees 20 to 35 feet apart.

Pruning

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.

Propagation

The propagation of American hornbeam is not recommended for home gardeners. The seeds need to be collected while green and require several months of moist treatment. Propagating the tree vegetatively is also better left to nursery trade professionals. In addition, some of the popular cultivars are protected by plant patents.

Potting and Repotting 

Although this is a slow-growing tree, it is not suitable to be grown in a container.

Pests and Diseases

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.1 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.2 So if you notice damaged foliage, they might be the culprits.

IV. Uses and Benefits 

American hornbeam is a wonderfully compact and shade-providing understory tree that is somewhat common in yards and parks. It is primarily prized for its natural umbrella-like shape and lovely fall foliage. As a low-maintenance and manageably-sized tree, american hornbeam is perfectly suitable for smaller lawns and along walkways. Plant alongside red oaks, American holly, flowering dogwood, or sweet gum trees for extra value.

The wood is heavy and hard, and is used for tool handles, longbows, walking sticks, walking canes and golf clubs.

V. American Hornbeam Companion Plants

  • Common Witch Hazel

For a native plant landscape, choose Hamamelis virginiana, a North American witch hazel species. It is the most attractive in the fall when it blooms yellow and develops brilliant golden fall foliage. The shrub grows 12 feet tall and wide. Zone 3-8.

  • Serviceberry

These small trees and large shrubs in the Amalanchier genus thrive through all four seasons. Serviceberries show off their blossoms—which are usually white but may also be pink or yellow—just before their blue-green foliage emerges in early spring, offering some of the first sources of nectar for pollinators. Serviceberry sizes vary greatly, ranging from a low-growing 6-foot shrub to a 25-feet- tall and wide tree-like shrub. Zone 2-9.

  • Eastern Redbud

Unlike the American hornbeam, Cercis canadensis grows quickly, reaching seven to 10 feet in height in as little as five or six years. The small lavender-pink, white, or magenta blooms appear on the tree in March and April. In the fall the heart-shaped leaves turn golden. Zone 4-9.

American Hornbeam (Carpinus caroliniana) Details

Common name American Hornbeam, Blue Beech, Hornbeam, Ironwood, Musclewood, Muscle Wood, Water Beech
Botanical name Carpinus caroliniana
Plant type Native Plant
Hardiness zone 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Slow
Harvest time Fall
Height 20 ft. 0 in. - 30 ft. 0 in.
Width 20 ft. 0 in. - 30 ft. 0 in.
Sunlight Deep shade (Less than 2 hours to no direct sunlight)
Soil condition Clay
Flower color Gold/Yellow
Leaf color Gold/Yellow