The beaked hazelnut can reach 4–8 metres (13–26 feet) tall with stems 10–25 centimetres (4–9+3⁄4 inches) thick with smooth gray bark, but it can also remain relatively small in the shade of other plants. It typically grows with several trunks.

The leaves are green, rounded oval with a pointed tip, coarsely double-toothed, 5–11 cm (2–4+1⁄4 in) long and 3–8 cm (1+1⁄4–3+1⁄4 in) broad, with soft and hairy undersides.

The male flowers are catkins that form in autumn, pollinating the single female flowers the following spring to allow the fruits to mature through the summer.

The beaked hazelnut is named for its fruit, which is a nut enclosed in a husk with a tubular extension 2–4 cm (3⁄4–1+1⁄2 in) long that resembles a beak. Tiny filaments protrude from the husk and may stick into, and irritate, skin that contacts them. The spherical nuts are small and surrounded by a hard shell. The beaked hazel is the hardiest of all hazel species, surviving temperatures of −50 °C (−58 °F) at its northern limits.

It has a shallow and dense root system which is typically only 15 cm (6 in) deep, with a single taproot which may extend 0.6 m (2 ft) below the surface.

Varieties

There are two varieties, divided by geography:

• Corylus cornuta var. cornuta – Eastern beaked hazel. Small shrub, 4 to 6 m (13 to 20 ft) tall; 'beak' longer, 3 cm (1+1⁄4 in) or more. Occurs from 100–500 m (330–1,640 ft) throughout its range, and up to 1,000 m (3,300 ft) in Alberta.
• Corylus cornuta var. californica – Western beaked hazel or California hazelnut. Large shrub, 4 to 15 m (13 to 49 ft) tall; 'beak' shorter, usually less than 3 cm (1+1⁄4 in). Occurs below 2,100 m (6,900 ft) in California, and below 800 m (2,600 ft) in British Columbia. The Concow tribe called this variety gōm’-he’’-ni (Konkow language). California hazelnut is believed to be resistant to Eastern filbert blight.