Flower:

Male and female flowers are borne separately on the same branch (monoecious). Male flowers are in clusters called catkins, 1½ to 5 inches long, pendulous in flower, in groups of 3 at the base of the current year's new branchlets. Flowers are yellowish-green with up to 10 hairy stamens.

Female flowers are tiny, clustered 2 to 4 at the tip of the current year's new branchlets. Flowers have a stout, yellowish to green, oval to egg-shaped ovary covered in minute hairs and tiny scales, and green stigma at the top.

Leaves and bark:

Leaves are alternate, 12 to 24 inches long, compound with 5 leaflets, rarely 3 or 7. Leaflets are somewhat variable in shape, generally elliptic though may be widest below, at, or above the middle. Leaflets are 2 to 10 inches long, 1 to 5½ inches wide, finely toothed with tufts of minute hairs along the edge, stalkless or nearly so, tapering to rounded at the base, tapering to a pointed tip, often abruptly so. The leaflet pair at the tip is largest, often twice the size of the lowest pair. The upper surface is dark yellow-green and hairless, the lower is paler in color, minutely hairy especially along the veins and variably covered in tiny, round scales. The compound leaf stalk is green and hairy, more densely so on the lower stalk. Hairs and scales may persist or wear off but usually at least a few hairs persist around the leaf edges. Leaves turn golden yellow in fall.

Buds are tan to red-brown to dark brown and variously covered in matted hairs; the terminal bud is oval to egg-shaped with slightly flaring scales and may be nearly ¾ inch long. The inner bud scales greatly expand after bud-break and become quite showy, resembling flower petals. New twigs are brown and minutely hairy with whitish lenticels (pores), becoming hairless the second year.

Older bark is gray and smooth but splits with age, peeling away as narrow vertical strips or broader plates, giving a shaggy appearance. Trunks can reach up to 33 inches diameter at breast height (dbh).

Fruit:

Fruit is oval to round, about 1½ inch diameter, the outer husk quite thick, rough-textured, green turning dark brown, with 4 seams that extend from the tip to all the way to the base. Inside is a sweet nut with a hard shell.

Notes:

Shagbark Hickory is an occasional to common tree found in hardwood forest in the southeast corner of Minnesota, where it reaches the northern edge of its range, though it has been planted farther north. The leaflets that become smaller towards the base of the compound leaf resemble those of the related Juglans (Black Walnut, Butternut) species as well as those of the unrelated Fraxinus (Ash) species, but Juglans have sticky hairs and more numerous leaflets, and Fraxinus have rather different flowers and fruits, and its leaflets are often short-stalked. Mature Shagbark Hickory trees may be most easily distinguished by the shaggy bark, similar only to Silver Maple, and the minute tufts of hairs along the leaflet edge. Bitternut Hickory (Carya cordiformis) has similar fruit and leaves, but almost always has 7 or 9 leaflets in a compound leaf, no hairs along the leaflet edge, and the fruit is bitter and smaller (about 1 inch) with a thinner husk that has 4 distinct ridges. And, of course, it does not have shaggy bark on mature trees. Shagbark and Bitternut Hickory have been reported to hybridize with each other, but no hybrids have been reported in Minnesota. There are 2 recognized varieties of Carya ovata: var. australis limited to regions in the southeast US which lacks scales on leaves, and var. ovata, described above and present in Minnesota.