The pecan (/pɪˈkæn/ pih-KAN, also US: /pɪˈkɑːn, ˈpiːkæn/ pih-KAHN, PEE-kan, UK: /ˈpiːkən/ PEE-kən; Carya illinoinensis) is a species of hickory native to the southern United States and northern Mexico in the region of the Mississippi River.[2]
The tree is cultivated for its seed primarily in the U.S. states of Georgia,[3] New Mexico,[4] and Texas,[5] and in Mexico. The seed is an edible nut used as a snack and in various recipes, such as praline candy and pecan pie. The pecan is the state nut of Alabama, Arkansas, California, Texas and Louisiana, and is also the state tree of Texas.
Pecan derives from an Algonquian word variously referring to pecans, walnuts, and hickory nuts.[6] There are many pronunciations, some regional and others not.[7] There is little agreement in the United States regarding the "correct" pronunciation, even regionally.[8]
In 1927, however, the National Pecan Growers Association acknowledged variant pronunciations while designating one as official and correct: "pronounced as though spelled pea-con ... those in the habit of using any other pronunciation therefore be requested henceforth to adopt exclusively the pronunciation above specified above and hereby adopted by the Association."[9]
The pecan tree is a large deciduous tree, growing to 20–40 m (66–131 ft) in height, rarely to 44 m (144 ft).[10] It typically has a spread of 12–23 m (39–75 ft) with a trunk up to 2 m (6 ft 7 in) diameter. A 10-year-old sapling grown in optimal conditions will stand about 5 m (16 ft) tall. The leaves are alternate, 30–45 cm (12–18 in) long, and pinnate with 9–17 leaflets, each leaflet 5–12 cm (2–4+1⁄2 in) long and 2–6 cm (1–2+1⁄2 in) broad.[10]
A pecan, like the fruit of all other members of the hickory genus, is not truly a nut but is technically a drupe, a fruit with a single stone or pit, surrounded by a husk. The husks are produced from the exocarp tissue of the flower, while the part known as the nut develops from the endocarp and contains the seed. The husk itself is aeneous, that is, brassy greenish-gold in color, oval to oblong in shape, 2.6–6 cm (1–2+3⁄8 in) long and 1.5–3 cm (5⁄8–1+1⁄8 in) broad. The outer husk is 3–4 mm (1⁄8–5⁄32 in) thick, starts out green, and turns brown at maturity, at which time it splits off in four sections to release the thin-shelled seed.[10][11][12][13]
Pecans are one of the most recently domesticated of the major crops. Although wild pecans were well known among native and colonial Americans as a delicacy, the commercial growth of pecans in the United States did not begin until the 1880s.[14] As of 2014, the United States produced an annual crop of 119.8 million kilograms (264.2 million pounds), with 75% of the total crop produced in Georgia, New Mexico and Texas.[4] They can be grown from USDA hardiness zones approximately 5 to 9, and grow best where summers are long, hot and humid. The nut harvest for growers is typically around mid-October.
Outside the United States, Mexico produces nearly half of the world's total, similar in volume to the United States, together accounting for 93% of global production.[15] Pecan trees require large quantities of water during the growing season, and most orchards in the region use flood irrigation to optimize consumptive water use and production of mature pecans.[16] Generally, two or more trees of different cultivars must be present to pollinate each other.[17]
Choosing cultivars can be a complex practice, based on the Alternate Bearing Index (ABI) and their period of pollinating.[17] Commercial growers are most concerned with the ABI, which describes a cultivar's likelihood to bear on alternating years (index of 1.0 signifies the highest likelihood of bearing little to nothing every other year). The period of pollination groups all cultivars into two families: those that shed pollen before they can receive pollen (protandrous) and those that shed pollen after becoming receptive to pollen (protogynous).[18] State-level resources provide recommended varieties for specific regions.[19][20]
Native pecans in Mexico are adapted from zone 9 to zone 11.[21] Little or no breeding work has been done with these populations. A few selections from native stands have been made, such as Frutosa and Norteña, which are recommended for cultivation in Mexico.[22][23] Improved varieties recommended for cultivation in Mexico are USDA-developed cultivars. This represents a gap in breeding development given that native pecans can be cultivated at least down to the Yucatán peninsula while the USDA cultivars have chilling hour requirements greater than those occurring in much of the region.[24] Some regions of the U.S. such as parts of Florida and Puerto Rico are zone 10 or higher, and these regions have limited options for pecan cultivation. 'Western' is the only commonly available variety that can make a crop in low-chill zones.[25]
Active breeding and selection is carried out by the USDA Agricultural Research Service with growing locations at Brownwood and College Station, Texas.[5] University of Georgia has a breeding program at the Tifton campus working on selecting pecan varieties adapted to subtropical southeastern U.S. growing conditions.[3]
While selection work has been done since the late 19th century, most acreage of pecans grown today is of older cultivars, such as 'Stuart', 'Schley', 'Elliott', and 'Desirable', with known flaws but also with known production potential. Cultivars such as 'Elliot' are increasing in popularity due to resistance to pecan scab.[26] The long cycle time for pecan trees plus financial considerations dictate that new varieties go through an extensive vetting process before being widely planted. Numerous varieties produce well in Texas but fail in the Southeastern U.S. due to increased disease pressure. Selection programs are ongoing at the state level, with Alabama, Arkansas, Florida, Georgia, Kansas, Missouri, New Mexico, and others having trial plantings.
Varieties adapted from the southern tier of states north through some parts of Iowa and even into southern Canada are available from nurseries. Production potential drops significantly when planted further north than Tennessee. Most breeding efforts for northern-adapted varieties have not been on a large enough scale to significantly affect production. Varieties that are available and adapted (e.g., 'Major', 'Martzahn', 'Witte', 'Greenriver', 'Mullahy', and 'Posey') in zones 6 and farther north are almost entirely selections from wild stands. Kanza, a northern-adapted release from the USDA breeding program, is a grafted pecan having high productivity and quality, and cold tolerance.[27]
Pecans are subject to various diseases, pests, and physiological disorders that can limit tree growth and fruit production. These range from scab to hickory shuckworm to shuck decline.
Pecans are prone to infection by bacteria and fungi such as pecan scab, especially in humid conditions. Scab is the most destructive disease affecting pecan trees, untreated with fungicides. Recommendations for preventive spray materials and schedules are available from state-level resources.
Various insects feed on the leaves, stems, and developing nuts. These include ambrosia beetles, twig girdlers, pecan nut casebearer, hickory shuckworm, phylloxera, curculio, weevils, and several aphid species.
In the Southeastern United States, nickel deficiency in C. illinoinensis produces a disorder called "mouse-ear" in trees fertilized with urea.[28] Similarly, zinc deficiency causes rosetting of the leaves. Various other disorders are documented, including canker disease and shuck decline complex.[citation needed]
Pecan seeds are edible, with a rich, buttery flavor. They can be eaten fresh, roasted or used in cooking,[29] particularly in sweet desserts, such as pecan pie, a traditional Southern U.S. dish. Butter pecan is also a common flavor in cookies, cakes, and ice creams. Pecans are a significant ingredient in American praline candy.[30] Other applications of cooking with pecans include pecan oil and pecan butter.
Pecan wood is used in making furniture and wood flooring,[31] as well as flavoring fuel for smoking meats, giving grilled foods a sweet and nutty flavor stronger than many fruit woods.[32]