JULY Tree of the Month: American Hornbeam - Carpinus Caroliniana

Carpinus caroliniana Walter, or the American Hornbeam, is in my opinion one of the most underrated native tree species. This is an absolutely beautiful tree with delicate looking light green foliage and a strong muscular grey bark that is similar to the Beech family, but in fact is in the Birch Family. Commonly known as Ironwood, as well as Blue Beech, Water Beech, and Musclewood. The name Ironwood is also, and more aptly used for, the American Hop hornbeam or Ostrya virginiana (also in the Birch Family), as well as the Persian Ironwood or Parrotia persica, which is more related to Witch Hazel (Hamamelidaceae) than the Hornbeam. Or many species of tree around the world with an extremely dense hardwood, including one of my personal favorites, Lignum vitae (a South American hardwood also known as Ironwood). This is exactly why Carl Linnaeus invented the scientific Latin binomial system, to avoid the confusion associated with the common names of each tree species. The name Walter is the discoverer of the tree, Thomas Walter, an early American Botanist who is most famous for his book ‘Flora Caroliniana’ (1788).

A slow growing tree that can grow to thirty feet or more in the northeast and maybe upwards of

seventy feet or more with enough time, nobody knows. Apparently, in southern Mexico and Central America this tree grows much larger, due to a more favorable tropical wet climate. But alas we live in the Northeast, and as the trees do, we have to live with the same harsh winter season. The thin simple leaf is a light to medium green color with an alternate growth pattern. The leaves have a serrated, ovate-oblong, acuminate, rounded or even heart shaped form that is very Birch like. The bark is a recognizable smooth grey with a sinewy and muscular growth form that reminds some of a Beech. Even with an extremely tough and hard wood, the younger bark itself is somewhat susceptible to mechanical damage, so climbers tread lightly. Propagation from seed collected prior to fall chill and transplanting with a shallow but wide root ball are recommended

The American Hornbeam is truly a forest understory tree that thrives in exactly that environment, part sun to almost full shade. It seems to do best in moist, slightly acidic and humus rich forest conditions, and especially near streams and river banks. The tree seems to also grow just as well if not better in moist soil sunny locations, and this contributes to a more vibrant fall foliage color of fiery orange-red. There cultivars and related species that can be found, some with upright fastigiate growth to weeping forms and ones with brilliant red fall color (and good luck finding those). The varieties of the genus Carpinus grows throughout the world and is just as valued as any ornamental yard specimen tree.

Written by:  Richard Caldwell, ISA arborist,  20 year tree industry veteran climber