Captivating Carpinus
Maybe you’ve noticed the extreme heat we’ve been dealing with lately. We previously talked about heat-tolerant selections that are capable of thriving even in the hottest of Mid-Atlantic conditions. Still, us lowly humans need to beat the heat somehow, especially if most of our time is spent outdoors whether professionally or recreationally. Where better to find reprieve than under the shelter of a large, shady tree that also has the capacity to house and sustain wildlife? This week, we’re going beneath the cool, shadowy canopies belonging to two members of the Carpinus genus and uncovering some of the lesser-known attributes and interesting facts that make these trees so fascinating.
Criminally underutilized especially considering its tolerance for all types of adversity, our native Carpinus caroliniana is a large, pest and disease-resistant shade tree that is often naturally found along streambanks and low-lying woodlands due to its preference for moist soils and its tolerance of heavy shade. Like its European companion, Carpinus betulus, American hornbeams are often mistaken for beeches due to their similarities. Both beeches and hornbeams are classified under the same family, Betulaceae, each offering unique ecosystem services and physiologically structured with strong, durable wood that has long been used as lumber. The specific epithet for the European hornbeam is, in fact, in reference to these similarities – betulus inferring the Latin term for “beech”. While the shady oasis that both beeches and hornbeams provide is divine, and they can both be found within Mid-Atlantic woodlands freely producing saplings, hornbeams can be identified by their thicker, deeply veined foliage that almost gives the leaves a puckered appearance.
It is these leaves of Carpinus caroliniana that act as a larval host for the caterpillar of the Io moth, a large and ostentatiously colored species of silk moth with overt eyespots on its hind wings. Eastern Tiger Swallowtails, Striped hairstreak butterflies, Red-spotted purple butterflies, and White Admiral butterflies also utilize American hornbeams as one of their chosen larval hosts, and the grazing of their caterpillar babies can occasionally be found on the foliage. Although the male and female catkins are wind-pollinated and do not rely on the assistance of insects, the papery, winged fruit clusters are eaten by various birds and mammals, which in turn help to distribute the next generation of trees far and wide. They are typically light green to chartreuse in hue, contrasting against the darker green foliage during the summer months before the tree transitions to its orangey-red fall colors. The European hornbeam, Carpinus betulus, also produces male and female catkins that develop into nutlets attached to papery bracts, although they tend to be less showy than our native species. In its native range, which spans across much of Europe as far east as Iran, the nutlets are enjoyed by finches and titmouses, and their leaves are eaten by the larvae of native European Lepidopterans, such as the aptly named hornbeam pygmy (Stigmella carpinella), Phyllonorycter esperella, and members of one of the largest moth genus worldwide, Coleophora, of which many species proliferate into North America. Coleophora species moths are important food sources for parasitic braconid wasps, which act as beneficial insects in helping to pluck unwanted caterpillars from gardens, nurseries, and the like. So, the cycle goes.
Beyond providing ecological fodder for wildlife, our two main hornbeams are also ideal for soil stability in areas with periodic flooding. Combined with its penchant for shade, hornbeams tend to thrive in sites where others might suffer from having wet feet and a lack of sunlight. Interestingly, both Carpinus betulus and Carpinus caroliniana are capable of acclimating to sites to sunnier sites as long as the soil retains some moisture, as well as drier sites so long as it has some protective shade. Their tolerance for soil compaction, paired with the availability of columnar varieties such as ‘Franz Fontaine’ and ‘Fastigiata’, make these trees suitable for tight urban sites that call for a tenacious and attractive specimen. Besides providing a shady oasis from the stifling city heat in the summer, hornbeams also give the urban landscape much-needed color come autumn, with the lustrous green foliage transforming into a medley of golden yellows, oranges, scarlet reds and wine burgundies. Like beeches, hornbeams hold their leaves late into winter, creating a textural backdrop of papery brown adornments that rustle gently in chilly breezes. It is during the winter months that the bark of Carpinus caroliniana, specifically, can truly be appreciated. The sinewy, muscle-like formation that the trunk, branches, and smooth bark take give our native American hornbeam one of its alternate common names, musclewood. While these trees tend to be largely deer resistant, come early spring, hungry bunnies and beavers may nibble the young bark of tender, juvenile specimens. However, even as young saplings, musclewood trees provide shelter for a smattering of small mammals, birds, and insects, and shouldn’t be overlooked as an option for woodland gardens, naturalized plantings, and anywhere that wildlife is encouraged to visit.
Make sure to check out our available Carpinus betulus and Carpinus caroliniana selections, all currently ready for sale in #15 and #20 containers. Worried about transplanting? No problem! Our containerized production and subsequent growth of adventitious roots make our trees ready-to-plant without fear of root disturbance.
Genus Coleophora - BugGuide.Net
Phyllonorycter esperella - Wikipedia
Forest Insect Guilds: Patterns of Interaction with Host Trees : Proceedings ... - Google Books
American Hornbeam (Carpinus caroliniana) – Cowling Arboretum – Carleton College
Underutilized Landscape Plant: Carpinus Caroliniana - American Hornbeam (psu.edu)
ENH279/ST120: Carpinus caroliniana: American Hornbeam (ufl.edu)
The Sinewy American Hornbeam — In Defense of Plants
American Hornbeam | Glen Arboretum (towson.edu)
See all our Woody Ornamentals