This attractive shade tree has a long, straight trunk and tall, somewhat narrow crown that displays striking yellow foliage in the fall. Its open habit and patterned bark are of interest in the winter. It has an extremely high wildlife value, and its strong, durable wood has a long history of use for a variety of products. It grows slowly up to 80 feet tall in a variety of average to dry soils and full or part sun. It occurs in well-drained to dry soils and, less commonly, in moist soils, and it is tolerant to drought. Native to the southern and eastern US, pignut hickory is mostly found in the unglaciated eastern part of Ohio, especially in the lower Ohio River Basin. It’s the hickory most commonly found in the Appalachian forests, especially on the drier soils of the upper slopes. One notable pest is the hickory bark beetle, which is responsible for hickory wilt; however, pignut hickory is resistant to verticillium wilt.
The edible nuts are bitter to humans, but squirrels and other wildlife consume them for their high nutritional content. The kernel is exceptionally high in crude fat, and hickory nuts represent up to a quarter of the foods eaten by several squirrel species. Some sources say the common name reflects the nut’s bitter taste (“fit to be eaten only by pigs and other animals”) rather than its physical profile, which looks like a tiny pig’s face and snoot (uky.edu/hort).
The wood of hickory is famously heavy and tough, and it torques and twists without splintering. It’s “stronger than steel, yet more elastic, less brittle and less conductive of heat,” according to the University of Kentucky's College of Agriculture. Because of these qualities, it’s often used for making sporting goods and tool handles. Pioneers used the dense wood as fuel, and hickory’s low rate of heat conductivity made hickory the wood of choice for wagon wheels and sulkies for harness horses. It was used to make automobile parts in the early days of that industry.
The genus name, Carya, is from karya, the Greek name for the walnut tree. The species name, glabra, means glabrous or smooth, referring to the foliage and new growth of the twigs. Early settlers, who also called the tree "broom hickory," made brooms from narrow splits of the wood (wildflower.org). Although only a few hickory species exist outside of eastern North America (in eastern Asia), fossils indicate that hickories were once found in central Europe, China, and the former Soviet Union. Pignut hickory is not to be confused with the least-common hickory species, sweet pignut (C. ovalis), which has sweeter nuts and shaggier bark.
Native habitats include dry ridgetops and slopes, moist sites in mountains, and hickory-and-oak communities. Useful as a shade tree in large yards or parks, in woodlands, and in drought-tolerant gardens. Like other large trees, it produces a significant amount of litter through branch, leaf, and nut drop. Deep tap roots make it difficult to transplant once established.
Plant Characteristics:
Grows 50-60' tall and 25-35' wide.
Prefers full or part sun.
Grows in dry to average, acidic to alkaline, well-drained soils, including sandy, loamy, or clay. Tolerates occasional drought.
Blooms appear April-May. Very small female flowers are a green pistil with a few bracts. Male flowers are drooping, yellow-green catkins 2-4” long. Oval-shaped, 1-3” fruits have green husks that turn brown as they ripen. In October, the dry husks pull away from the nut in 4 sections. Husks of pignut hickory split only to the middle and tend to cling to the nut.
Alternate, 8-12” compound leaves have 5-7 leaflets with sharply serrated margins. The lower 2 leaflets are one-third the size of the upper 3 leaflets with the terminal leaflet being the largest. Medium green leaves have paler undersides. Fall color is clear yellow.
Bark is smooth and gray-brown when young. Mature trees have irregular, rounded ridges that form diamonds and x’s. Smaller branches and twigs are often crooked.
Wildlife Value:
Host plant for 231 species of Lepidoptera larvae, including hickory horndevil, tuliptree silkmoth, luna and polyphemus moths, and eastern tiger butterfly. Nuts and flowers are eaten by wild turkeys and several species of song birds. Nuts and bark are eaten by foxes, rabbits, and raccoons. Small mammals eat the nuts and leaves, and deer occasionally browse hickory leaves, twigs, and nuts (USDA.gov).
Medicinal, Edible, and Other Uses:
Native Americans made a tea from the bark to treat rheumatism and arthritis.
The nuts may best be left to wildlife due to their high tannin content and bitter flavor. Native Americans mixed the nut oil with food as a flavoring agent and mashed the nuts to use in bread and other foods.
Native Americans used the wood for making bows. The inner bark is used for finishing basket rims and for weaving a chair seat that will last for hundreds of years (theonefeather.com/2012/10/30/gettin-wild-hickory-nuts/). The wood can be used to smoke meat.