Environment Planet Earth Identify 6 Common Hickory Species in North America By Steve Nix Steve Nix Writer University of Georgia Steve Nix is a member of the Society of American Foresters and a former forest resources analyst for the state of Alabama. Learn about our editorial process Updated March 30, 2022 Share Twitter Pinterest Email Skapie777 / Getty Images Planet Earth Outdoors Weather Conservation The six most common species of hickory (Carya) trees come from three major groups: shagbark, pignut, and pecan. The shaggy bark is a clear identifier to separate the shagbark group from the pignut group, though some older hickories have slightly scaly bark. Here, we determine how to tell these six common hickory species apart. Common Hickory Characteristics Hickory trees have several common characteristics. The leaves of hickory are mostly alternately placed along the twig, in contrast to a similar-looking ash tree leaf that is in an opposite arrangement. The hickory leaf is always pinnately compound, and the individual leaflets can be finely serrated or toothed. Hickories also have nutritious nut meat that is covered by a very hard shell, which is covered by a splitting husk shell. This fruit is located at the twig tips in clusters of three to five. They are branching flowering catkins just below the emerging new leaf umbrella-like dome in spring. Fruit drops from late summer into autumn. Hickory bark comes in a range of gray colors, and the twigs have a tan, five-sided, or angled soft centers called piths. These large, long-lived, slow-growing deciduous trees are known for being good shade trees and feature golden color in the fall. They are difficult to transplant because of their long taproot and might be hard to find in nurseries. 1 of 6 Shellback Hickory Dan Mullen / Flickr / CC BY-NC-ND 2.0 The shellbark hickory (Carya laciniosa) is a shaggy gray-bark species. This hickory grows up to 75–100 feet tall and can be 50–75 feet wide. Shellback hickory is not tolerant of alkaline soils, drought conditions, salt spray, or salty soils; it requires a big area of well-draining soil. Leaves are in clusters of seven to nine leaflets. Oval nuts have a five- to six-sectioned husk and are the largest of the hickory species. 2 of 6 Mockernut Hickory Melissa McMasters / Flickr / CC BY 2.0 The mockernut hickory (Carya tomentosa) reaches 50–60 feet tall and 20–30 feet wide. This species is tolerant of drought but not poor drainage and is best in slightly acidic soil, as it is intolerant of alkaline soils and salt in the soil. Mockernut hickory leaves are alternate, compound leaves with seven to nine leaflets that are hairy on the underside and on the stalk. The largest will be the terminal leaf. The tree also has nuts that ripen in fall. 3 of 6 Shagbark Hickory Ethan R. / Getty Images Shagbark hickory (Carya ovata) is, as its name suggests, a tree with shaggy bark that peels away in big pieces. Its mature height is 60–80 feet tall, with a 30–50 feet width. Leaves are eight to 14 inches long, featuring five to seven leaflets. The round nut has a four-sectioned husk. Shagbark hickory trees are tolerant of a wide range of conditions, such as drought and acidic or alkaline soil. However, they do need a well-drained, large location free from salty soil. 4 of 6 Pignut Hickory NicoleCastleBrookus / Getty Images The pignut hickory (Carya glabra) is a dark-gray tree that extends to 50–60 feet in height with a spread of 25–35 feet. It does well in a variety of soils, even tolerating salty soil and drought. However, it doesn't do well in areas of poor drainage. As the tree ages, the bark may appear slightly shaggy. Its alternate, compound leaves are 8 to 12 inches long with five to seven leaflets, with the one on the end being the largest. The bitter nuts are pear-shaped and have four ridges on the husks, which do not easily come off of the nut. 5 of 6 Pecan Tree by IAISI / Getty Images The pecan tree (Carya illinoinensis) contains the sweetest nuts of all the hickory trees. It is one of the most important native North American nut trees, though it can be a messy tree to grow due to leaf and fruit drop. Pecan trees grow 70–100 feet tall with a spread of 40–75 feet. The tree is tolerant of acidic soils and only moderately tolerant of alkaline soils. It can handle some poor drainage but not drought, salt spray, or salty soil. The bark is brownish-black, and leaves are 18–24 inches long, containing nine to 17 narrow, long leaflets with a hook shape near each tip. Nuts are cylindrical. 6 of 6 Bitternut Hickory weisschr / Getty Images The bitternut hickory (Carya cordiformis) also commonly called the swamp hickory, loves moist conditions and hates drought and poor drainage, though it can be found in some drier landscapes in addition to its typical low, wet conditions. It needs a large area to grow and can reach 50–70 feet high and 40–50 feet wide when mature. It prefers acidic soil but can tolerate alkaline. It can handle some salt spray but not salty soil. Leaves contain seven to 11 long, narrow leaflets. It grows bitter nuts that are about an inch long and have four-sectioned, thin husks. To identify the tree in winter, look for its bright yellow buds.