Gerald L. Klingaman
Plant Common Name
The genus Carya comprises approximately 18 to 22 species of hickories and pecans (experts disagree about the status of some species). Most are large deciduous trees; a few are shrubs. Their areas of origin include Mexico, eastern Asia and the eastern half of North America. They are prized as long-lived, slow growing specimen trees. All have hard, elastic wood that is valuable for furniture making, wood flooring and tool handles, and slow burning hickory wood adds a pleasing flavor to smoked meats. Several species produce edible nuts that are sweet and nutritious.
Mature trees are generally upright with open, rounded crowns. The bark is usually smooth at first but becomes fissured or scaly with age, sometimes breaking off in immense peeling plates. The new twigs may be green, orange, bronze or reddish brown and can have fuzzy, smooth or scaly surface textures. The compound leaves are “odd-pinnate”, which means they have a central stem (rachis) lined with paired leaflets and punctuated with an odd leaflet at the tip. The leaves alternate along the stems and may be aromatic when crushed. The rachis may be smooth, fuzzy or scaly. Fall leaf color varies but is often yellow or burnished shades of orange or brown.
Trees flower in spring on first and second year wood. The small, inconspicuous blooms are pollinated via wind. The trees are monecious and often self-compatible, which means separate male and female flowers occur on the same plant and a tree can pollinate itself. The male flowers are pendent catkins that release copious amounts of pollen that shakes down onto the female flowers. Borne in small terminal spikes, female flowers mature into nuts by fall. The hard-shelled nuts are encased in usually fibrous, four-parted husks. The nuts contain meaty, often sweet seeds that are valuable to wildlife and edible to humans.
Many useful trees are found in this genus. Native Americans collected the nuts of several hickory species for food and oil, including shag-nut hickory (Carya ovata) and pig-nut hickory (Carya glabra), and Cherokees used the inner bark of mockernut hickory (C. alba) and shellbark hickory (C. laciniosa) to make baskets. Pecan (Carya illinoinensis) is likely the most commercially important Carya, valued for its popular nuts and fine wood.
Culture varies from species to species but generally hickories need large open spaces and full sun. The trees form long taproots, so they require deep, rich, upland soils for good root development. Use hickories and pecans in home and commercial orchards, parks, on woodland-urban interfaces and as specimen trees.