Hickories are trees in the genus Carya; they are related to walnuts and are valued both for their nuts and their strong, versatile hardwood. Hickory trees are divided into three groups: pignut, shagbark and pecan. All three groups are represented among the nine species of hickory native to Illinois.
The black hickory (Carya texana) is also commonly called Texas hickory. It is hardy in U.S Department of Agriculture hardiness zones 5 to 8. It is most common west of the Mississippi River, but its native range extends through southern Illinois and as far east as Indiana. It is a relatively small tree, typically reaching a height of 25 to 50 feet, although in ideal conditions it can grow as tall as 100 feet. Black hickory is characterized by dark brown or black bark that develops fissures as the tree matures.
Pignut, Mockernut and Red Hickories
The pignut hickory (Carya glabra) is larger than the black hickory, often reaching 50 to 65 feet in height with a spread of 30 to 40 feet; large specimens can grow as tall as 120 feet. The red hickory (Carya ovalis) is very similar to the pignut hickory, and the two are sometimes considered a single species. The mockernut hickory (Carya tomentosa) is similar in size, and mature trees of both species have a coarse, oval-shaped canopy. Like the black hickory, these hickories have tight bark rather than the exfoliating bark of shagbark hickories. Pignut hickory is hardy in USDA zones 5 to 9, and mockernut hickory is hardy in USDA zones 4 to 9.
Shagbark and Shellbark Hickories
The shagbark hickory (Carya ovata) is a large tree, commonly reaching 100 feet in height with a 60-foot spread. It is easily identified by its bark, which in mature trees develops deep vertical fissures and peels away from the trunk in long strips. The shellbark hickory (Carya laciniosa) is smaller, reaching about 80 feet in height; it develops similar fissures in its bark, but the bark usually does not peel away the same way it does in shagbark trees. The shagbark hickory is hardy in USDA zones 4 to 8, and the shellbark is hardy in USDA zones 5 to 8.
The pecan (Carya illinoensis) is the largest of the hickory trees, with a typical height of 70 to 100 feet and a spread of 75 feet; the trunks of large pecan trees can reach 6 feet in diameter. The related water hickory (Carya aquatica) is slightly smaller, and the bitternut hickory (Carya cordiformis), another pecan hickory, is smaller still, reaching only about 80 feet in height. The pecan is hardy in USDA zones 5b through 9a, the bitternut hickory in USDA zones 3 through 7, and water hickories in USDA zones 4 to 9.
- University of Illinois Extension: Illinois Forest Facts
- Illinois State Museum: Black Hickory
- Forrest Keeling: Carya texana
- USDA Forest Service: Carya glabra
- North Carolina State University: Carya tomentosa
- Ohio DNR: Shagbark Hickory
- Ohio DNR: Shellbark Hickory
- USDA Forest Service: Carya illinoensis
- Ohio DNR: Bitternut Hickory
- Texas A&M University: Water Hickory
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