American hornbeam is a tall shrub or small tree, to 35 feet tall, with pendulous branches and a gray trunk that is fluted into musclelike ridges.
Leaves are simple, alternate, 2–5 inches long, 1–2 inches wide, with upper surface bluish green, dull; undersurface paler, mostly smooth, or with hairs in vein axils only, margins with small sharp teeth.
Bark is smooth, tight, thin, bluish gray, sometimes blotched, fluted into muscle-like ridges, hence the other common name, “musclewood.”
Twigs are slender, gray or red, zigzag, with small buds.
Flowers April–May; in catkins, with male and female on the same twig.
Fruit in long, hanging clusters of paired 3-lobed bracts (modified leaves), with each pair of bracts having a nutlet at its base.