Arbust. Amer., 37. 1785.
Shrubs or trees, open-spreading, 4–8 (–15) m. Bark light to dark-brown, smooth. Branches ascending; twigs glabrous to sparsely pubescent, sometimes with glandular-hairs. Winter buds containing inflorescences ovoid, 3–5 × 3–4 mm, acute. Leaves: petiole glabrous to moderately pubescent, with or without glandular-hairs. Leaf-blade nearly orbiculate to narrowly ovate or ovate-oblong, often nearly angular and slightly lobulate near apex, 4–10 × 3.5–12 cm, thin to leathery, base narrowly cordate to narrowly rounded, margins coarsely and often irregularly doubly serrate, apex obtuse to acute or acuminate; surfaces abaxially glabrous to moderately pubescent, usually pubescent on major veins and in vein-axils. Inflorescences: staminate catkins lateral along branchlets on short-shoots, usually in clusters of 2–3, 4–6 × 0.5–0.8 cm; peduncles 0.5–10 mm. Nuts in clusters of 2–6, completely concealed; bracts bristly, connate at summit, lengthened into extended tubular beak.
|1||Leaf blade ovate to narrowly elliptic, apex distinctly acuminate; twigs and petioles without glandular hairs; involucral tubular beak 2 times or more length of fruit; small to large shrubs of e, c, n North America.||Corylus cornuta subsp. cornuta|
|1||Leaf blade nearly orbiculate or broadly elliptic, apex broadly acute to obtuse; twigs and petioles usually bearing glandular hairs; involucral tubular beak less than 2 times length of fruit; large shrubs or small trees of Pacific coastal region of North America.||Corylus cornuta subsp. californica|
"lengthened" is not a number."thin" is not a number.