Hornbeams are deciduous trees, usually with smooth, gray bark. Imbricate buds have many scales. Leaves are alternate and doubly toothed. Flowers are monoecious and borne in catkins. Fruit is a nutlet subtended on a bract. Buds are usually of two distinct sizes and somewhat angled. Side veins of the leaves are unbranched and run straight to the teeth on the margins. Teeth at the ends of the veins are larger than the teeth between the veins. The bark of the trunk is a smooth, bluish-gray and covers the muscle-like ridges of the trunk. Trunks are usually twisted and fluted.