Description and habitat
American Hophornbeam (Ostyra virginiana), is a deciduous tree in the birch family (Betulaceae) widely distributed throughout the Great Lakes Region. Hophornbeams also occur throughout the eastern United States, occurring as far south of Florida. There are around 9-10 species of Hophornbeam in the world: 3 from North America, 1 from Europe, and the rest from East Asia. This tree is also known as Ironwood due to the texture the bark – among the hardest of any tree species. Hop-hornbeam occupies an intermediate position between the canopy and understory – it is larger than many understory trees (i.e., Blue-beech, Carpinus caroliniana, dogwoods, Cornus sp., and Witch Hazel, Hamamelis virginiana), but smaller than many of the well-known forest canopy trees (i.e., Sugar Maple, Acer saccharum, and Red Oak, Quercus rubra)
The best identification feature for the American Hophornbeam is the bark of mature trees, which is a light grey-brown and is vertically flaking in long-narrow segments. This is unlike most trees in the Great Lakes forests, except White Cedar (Thuja occidentalis), which is coniferous with paler bark, thus easily distinguishable. The leaves are simple and alternately arranged on the twig. They are oval, measuring ~10 cm long and ~4 cm wide, with sharp, doubly toothed leaf margins. Hophornbeam trees are often confused with elm (Ulmus sp.), Yellow Birch (Betula lutea), and blue-beech (Carpinus caroliniana) due to their leaves. Elm leaves are larger, and often asymmetrical compared to hophornbeam, whereas blue beech leaves are smaller in size. Yellow Birch leaves are slightly larger than hophornbeam, but they are often heart-shaped at the base – absent in hophornbeam leaves. The foliage turns a vibrant yellow in the autumn. Throughout the winter, many young hophornbeam saplings retain their dead, brown leaves – a phenomenon known as marcescence. The only other widely marcescent tree species is American Beech, which has slightly paler marcescent leaves than hophornbeam.
Hophornbeam trees are most often witnessed in moist deciduous forests, alongside oaks (Quercus sp.), American Beech (Fagus grandifolia), Sugar Maple, White Ash (Fraxinus americana), and Basswood (Tilia americana). It is often found in mature and old-growth forests. Occasionally, hophornbeam is found in oak-dominated woodland savannas. It is not tolerant of waterlogged soils, thus rarely found in flooded areas, wetlands, or riparian zones. Hophornbeam establishes well in successional forests, but is also quite shade-tolerant, especially as a sapling. Hop-hornbeam has a relatively slow growth rate compared to other tree species.
Wildlife importance
By the end of summer, Hophornbeam produces hop-like clusters of winged-seeds, called nutlets (giving this tree its name). They are consumed by a wide variety of organisms, including squirrels (Sciuridae) and seed-eating birds. The leaves are consumed by insects, including beetles and lepidoptera. A very diverse set of moths feed on hop-hornbeam, including Colorful Zale (Zale aeruginosa), Variegated Snout (Hypena palparia), Eyed Baileya (Baileya ophthalmatica), Pleasant Dagger (Acronicta laetificans), Pale Green (Lithophane viridipallens), Bethune’s Pinions (Lithophane bethunei), Pettit’s Sallow (Pyreferra pettiti), and Quaker Moths (Orthosia sp.).
Fun Facts
- Hophornbeam wood is notoriously difficult to split, due to the very dense, interlocking fibres within the interior of the tree!
- Large hophornbeams are an indicator of healthy forest structure, as they readily proliferate in the dense shade of many closed-canopy deciduous forests, outcompeting weedier tree species in these conditions.
- Hophornbeams are better adapted to ice storms than many of Ontario’s other deciduous trees, a characteristic of dense wood and strong branch attachments!
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University.
Photo Credits (L-R)
Growth Form © Matthew Palarchio
Bark © Matthew Palarchio
Leaves and Fruit © Reuven Martin
Autumn Foliage © Pierre Cartier
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