Hickory trees (Carya spp.) are found primarily in the Midwest and Upper Midwest, the Southeast and north into New England and beyond. Of the various types of nuts each species produces, only a few are edible by humans. Hickory trees are also grown for shade, for their hard wood, and as a habitat for birds and other small animals.
All hickories reach heights of 50 to 100 feet at maturity with a spread of roughly 40 feet and live for many years. Unless grown commercially, most hickories do not grow in stands but appear individually scattered across a wide area among other trees such as maples, oaks and pines. Most hickories are hardy in U. S. Department of Agriculture plant hardiness zones 4 to 8. They are tolerant of most types of soil but generally prefer rich moist but not soggy well-drained soil in sunny areas that receive some shade. The water hickory (Carya aquatica) stands out among its relatives as the most tolerant of moisture and is found primarily in wet woods from Florida to Texas and north to Virginia and southern Illinois. Once fully established, hickory trees such as shagbark (Carya ovata) and shellbark (Carya laciniosa) live hundreds of years.
The three most commonly grown hickories -- the shellbark, or kingnut (Carya laciniosa), the shagbark (Carya ovata) and Southern shagbark (Carya carolinae-septentrionalis) -- are closely related, and they are distinguished by their leaf composition and nut size. All three have the characteristic shaggy bark from which they get their name, but they are not generally found growing in the same area. The Southern shagbark grows primarily in the southeastern states in areas where large deposits of limestone are found, while the shagbark normally grows on dry ridges. The shellbark prefers rich moist bottomlands. All three species have composite leaves, with five leaves per twig on both shagbarks and seven leaves per twig on the shellbark. Nuts of the Southern shagbark are smallest, and those of the shellbark the largest. All are encased in soft outer husks that split open at maturity revealing hard-shelled nuts with a sweet flavor.
Hickory trees such as the shellbark and shagbark are prized not only for their sweet-tasting nuts but for their wood as well. The very hard durable wood is used extensively to manufacture handles for all types of tools including axes and hammers, and the smoke produced by burning the wood is useful to cook and cure meats. Better grades of hickory wood are also used to build furniture and in the manufacture of wall paneling. Not only are hickory nuts appealing to humans, but squirrels, ducks and turkeys enjoy them, and the shagbark and shellbark's peeling bark provide shelter for bats, moths and squirrels.
Other trees belonging to the hickory family include the bitternut hickory (Carya cordiformis), pignut, or black, hickory (Carya glabra), sand hickory (Carya palida), red hickory (Carya ovalis) and the mockernut hickory (Carya tomentosa). The pecan (Carya illinoinensis) is also a type of hickory, grown commercially for its valuable nuts. Lesser-known hickories include the nutmeg hickory (Carya myristiciformis), whose nuts are edible and whose bark is smooth throughout the tree's life spans and curls as the trees age. Others, such as the scrub hickory (Carya floridana), are more localized and found exclusively in parts of central Florida.