Flower:

Slender, pale clusters (called catkins) up to 3 inches long of male pollen-bearing anthers hang from buds on 1-year-old branches. Female flowers are bud-like with a spray of red styles at the tip, on the same branch as male catkins, single in the axils or at the tip of the branch.

Leaves and stems:

Leaves are simple and alternate, 2½ to 5 inches long, 1¼ to 3 inches wide, oval-elliptic or widest above the middle, with a long or short taper to a sharply pointed tip and a rounded to somewhat heart-shaped base. Edges are sharply double-toothed and may have a few very shallow lobes on the tip half. The upper surface is dark green and sparsely hairy, the lower is paler than the upper surface and hairy along most veins. Leaf stalks are ¼ to ¾ inch long and covered in a mix of soft, white, non-glandular hairs and bristly, dark, glandular hairs.

New twigs are reddish to brown to grayish and densely covered in a mix of soft, white hairs and bristly glandular hairs, becoming smoother the second year.

Older bark is light grayish brown with scattered white lenticels (pores), initially smooth but eventually developing a criss-cross pattern. Stems are multiple from the base, up to 1 inch in diameter, erect with ascending branches, spreading by rhizomes and may form small colonies or dense thickets.

Fruit:

Fruit is a round nut with a hard shell, 1/3 to ½ inch in diameter, enveloped in a pair of bracts that form a stiff, green husk, with up to 5 nuts in a cluster. The husk is up to twice as long as the nut, jagged and ruffled at the tip, and variously covered in a mix of soft, white hairs and glandular hairs that are often red.

The nut becomes exposed as it expands and the bracts spread apart. Nuts and bracts turn an orangy brown when mature in late summer and may persist through fall if not snatched up by wildlife.

Notes:

The nuts are very good eating, though smaller than commercially grown hazelnuts (a.k.a. filberts) so it takes a lot to make a handful. It is usually also a race to beat squirrels and other wildlife to the the punch. It strongly resembles the related Beaked Hazelnut (Corylus cornuta), which lacks glandular hairs on twigs, leaf stalks and husks, and the husks have a distinctive, long beak. The two species' ranges overlap and may be found growing side by side, but Beaked Hazelnut is more common in moister sites and American Hazelnut in drier sites.