American hornbeam (Carpinus caroliniana), aka ironwood or muscle wood, grows primarily in moist, slightly acidic soils along woodland rivers and streams (USDA hardiness zones 3-9). This native hornbeam adapts to either wet or dry ground as long as soil moisture drains adequately. It copes with tough urban conditions including on non-irrigated parking lots and on the outer edge of rain gardens. It grows equally well in full sun or partial shade.
Its autumn foliage turns intense shades of yellow, orange, and rarely scarlet, depending on soil pH and the provenance of the species. Over the past quarter century Johnson Nursery (primarily wholesale and retail locally) in Menomonee Falls, Wisconsin have selected several good fall red foliage forms. Firespire™ is a grafted clone with semi-upright branching and vibrant red fall color. ‘J N Strain’ is a known seed population which delivers above average red fall leaf color.
Ironwood blooms in spring as separate male and female catkins. In autumn female catkins form showy clusters of winged nutlets, that is an important food resource to numerous forest fauna. Its beech-like muscular bark covers the main trunk and branches as a singular trait in the winter garden.
American hornbeam grows 25-40 feet tall and variable in width depending on cultivar. It commonly grows multi-stemmed and is free of disease and pest problems. The rich green summer and colorful autumn foliage plus attractive gray muscular winter bark makes it an excellent small patio tree. Or mass several together to create a deciduous privacy screen.
American hornbeam is more difficult to transplant than its taller European counterpart (C. betulus).