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Carya illinoinensis.jpg
Carya illinoinensis
Morton Arboretum acc. 1082-39*3
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Juglandaceae
Genus: Carya
Section: Carya sect. Apocarya
C. illinoinensis
Binomial name
Carya illinoinensis
Carya illinoinensis range map 1.png
Natural range of Carya illinoinensis
Synonyms [1]
  • Carya oliviformis (Michx.) Nutt.
  • Carya pecan (Marshall) Engl. & Graebn.
  • Hicorius pecan (Marshall) Britton
  • Juglans illinoinensis Wangenh.
  • Juglans oliviformis Michx.
  • Juglans pecan Marshall

The pecan /pɪˈkæn/ (Carya illinoinensis) is a species of hickory native to northern Mexico and the southern United States in the region of the Mississippi River. [1] The tree is cultivated for its seed in the southern United States, primarily in Georgia [2] and Texas, [3] and in Mexico which produces nearly half of the world total. The seed is an edible nut used as a snack and in various recipes, such as praline candy and pecan pie. The pecan, in various aspects, is included in state symbols of Alabama, Arkansas, California, Oklahoma and Texas.



"Pecan" is from an Algonquian word variously referring to pecans, walnuts and hickory nuts. [4] There are many variant pronunciations, some regional and others not. [5] The most common American pronunciation is[ citation needed ] /pɪˈkɑːn/ ; the most common British one is /pɪˈkæn/ . [5] There is little agreement in the United States, even regionally, as to the "correct" pronunciation. [6]


The pecan tree is a large deciduous tree, growing to 20–40 m (66–131 ft) in height, rarely to 44 m (144 ft). [7] 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 12 in) long and 2–6 cm (1–2 12 in) broad. [7]

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 38 in) long and 1.5–3 cm (581 18 in) broad. The outer husk is 3–4 mm (18532 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. [7] [8] [9] [10]


Pecan trees being irrigated in Anthony, New Mexico Irrigating Pecans.jpg
Pecan trees being irrigated in Anthony, New Mexico

Pecans were one of the most recently domesticated major crops. Although wild pecans were well known among native and colonial Americans as a delicacy, the commercial growing of pecans in the United States did not begin until the 1880s. [11] 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. [12] 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 total, similar in volume to the United States, together accounting for 93% of global production. [13] Generally, two or more trees of different cultivars must be present to pollinate each other. [14]

Choosing cultivars can be a complex practice, based on the Alternate Bearing Index (ABI) and their period of pollinating. [14] Commercial growers are most concerned with the ABI, which describes a cultivar's likelihood to bear on alternating years (index of 1.0 signifies 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). [15] State level resources provide recommended varieties for specific regions. [16] [17]

Native pecans in Mexico are adapted from zone 9 to zone 11. [18] 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. [19] [20] 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 Yucatan peninsula while the USDA cultivars have chilling hour requirements greater than occur in much of the region. [21] 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. [22]

Breeding and selection programs

Active breeding and selection is carried out by the USDA Agricultural Research Service with growing locations at Brownwood and College Station, Texas. [23] University of Georgia has a breeding program at the Tifton campus working to select pecan varieties adapted to subtropical southeastern U.S. growing conditions. [2]

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 . [24] 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. [25]

Diseases, pests, and disorders

Pecans are subject to a wide range of 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 currently 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. [26] Similarly, zinc deficiency causes rosetting of the leaves. Various other disorders are documented, including canker disease and shuck decline complex.[ citation needed ]

Food and wood

The seeds of the pecan are edible, with a rich, buttery flavor. They can be eaten fresh or used in cooking, particularly in sweet desserts, such as pecan pie, a traditional Southern U.S. dish. Pecans are a major ingredient in American praline candy. [27]

Pecan wood is used in making furniture and wood flooring, [28] as well as a flavoring fuel for smoking meats, giving grilled foods a sweet and nutty flavor stronger than many fruit woods. [29]


2 pecan nut halves.jpg
Nutritional value per 100 grams
Energy 2,889 kJ (690 kcal)
Starch 0.46
Sugars 3.97
Dietary fiber 9.6
Saturated 6.18
Monounsaturated 40.801
Polyunsaturated 21.614
Vitamins Quantity%DV
Vitamin A equiv.
29 μg
17 μg
Vitamin A 56 IU
Thiamine (B1)
0.66 mg
Riboflavin (B2)
0.13 mg
Niacin (B3)
1.167 mg
Pantothenic acid (B5)
0.863 mg
Vitamin B6
0.21 mg
Folate (B9)
22 μg
Vitamin C
1.1 mg
Vitamin D
0 μg
Vitamin E
1.4 mg
Vitamin K
3.5 μg
Minerals Quantity%DV
70 mg
2.53 mg
121 mg
4.5 mg
277 mg
410 mg
0 mg
4.53 mg
Other constituentsQuantity

Percentages are roughly approximated using US recommendations for adults.
Source: USDA Nutrient Database

A pecan nut is 4% water, 72% fat, 9% protein, and 14% carbohydrates (table). In a 100 g reference amount, pecans provide 691 Calories and a rich source (20% or more of the Daily Value, DV) of total fat, protein, dietary fiber (38% DV), manganese (214% DV), magnesium (34% DV), phosphorus (40% DV), zinc (48% DV), and thiamin (57% DV) (table). [30] Pecans are a moderate source (10-19% DV) of iron and B vitamins. Pecan fat content consists principally of monounsaturated fatty acids, mainly oleic acid (57% of total fat), and the polyunsaturated fatty acid, linoleic acid (30% of total fat). [30]

Evolutionary development

The pecan, Carya illinoinensis, is a member of the Juglandaceae family. Juglandaceae are represented worldwide by between seven and 10 extant genera and more than 60 species. Most of these species are concentrated in the Northern Hemisphere of the New World, but some can be found on every continent except for Antarctica. The first fossil examples of the family appear during the Cretaceous. Differentiation between the subfamilies of Engelhardioideae and Juglandioideae occurred during the early Paleogene, about 64 million years ago. Extant examples of Engelhardioideae are generally tropical and evergreen, while those of Juglandioideae are deciduous and found in more temperate zones. The second major step in the development of pecan was a change from wind-dispersed fruits to animal dispersion. This dispersal strategy coincides with the development of a husk around the fruit and a drastic change in the relative concentrations of fatty acids. The ratio of oleic to linoleic acids are inverted between wind- and animal-dispersed seeds. [31] [32] Further differentiation from other species of Juglandaceae occurred about 44 million years ago during the Eocene. The fruits of the pecan genus Carya differ from those of the walnut genus Juglans only in the formation of the husk of the fruit. The husks of walnuts develop from the bracts, bracteoles, and sepals, or sepals only. The husks of pecans develop from the bracts and the bracteoles only. [32]


Before European settlement, pecans were widely consumed and traded by Native Americans. As a food source, pecans are a natural choice for preagricultural society. As a wild forage, the fruit of the previous growing season is commonly still edible when found on the ground.

Pecans first became known to Europeans in the 16th century. The first Europeans to come into contact with pecans were Spanish explorers in what is now Louisiana, Texas, and Mexico. These Spanish explorers called the pecan, nuez de la arruga, which roughly translates to "wrinkle nut". Because of their familiarity with the genus Juglans , these early explorers referred to the nuts as nogales and nueces, the Spanish terms for "walnut trees" and "fruit of the walnut". They noted the particularly thin shell and acorn-like shape of the fruit, indicating they were indeed referring to pecans. The Spaniards took the pecan into Europe, Asia, and Africa beginning in the 16th century. In 1792, William Bartram reported in his botanical book, Travels, a nut tree, Juglans exalata that some botanists today argue was the American pecan tree, but others argue was hickory, Carya ovata. Pecan trees are native to the United States, and writing about the pecan tree goes back to the nation's founders. Thomas Jefferson planted pecan trees, C. illinoinensis (Illinois nuts), in his nut orchard at his home, Monticello, in Virginia. George Washington reported in his journal that Thomas Jefferson gave him "Illinois nuts", pecans, which Washington then grew at Mount Vernon, his Virginia home.


Pecan is a 32 chromosome species that readily hybridizes with other 32 chromosome members of the Carya genus, such as Carya ovata , Carya laciniosa , Carya cordiformis and has been reported to hybridize with 64 chromosome species such as Carya tomentosa . Most such hybrids are unproductive. Hybrids are referred to as "hicans" to indicate their hybrid origin. [33]


In 1919, the 36th Texas Legislature made the pecan tree the state tree of Texas; in 2001, the pecan was declared the state's official "health nut", and in 2013, pecan pie was made the state's official pie. [34] The town of San Saba, Texas claims to be "The Pecan Capital of the World" and is the site of the "Mother Tree" (c.1850) considered to be the source of the state's production through its progeny. [35] [36] Alabama named the pecan the official state nut in 1982. [37] Arkansas adopted it as the official nut in 2009. [38] California adopted it, along with the almond, pistachio, and walnut, as one of four state nuts in 2017. [39] In 1988, Oklahoma enacted an official state meal which included pecan pie. [40]

Related Research Articles

Drupe Fleshy fruit with hard inner layer (endocarp or stone) surrounding the seed

In botany, a drupe is an indehiscent fruit in which an outer fleshy part surrounds a single shell of hardened endocarp with a seed (kernel) inside. These fruits usually develop from a single carpel, and mostly from flowers with superior ovaries.

<i>Juglans</i> genus of plants

Walnut trees are any species of tree in the plant genus Juglans, the type genus of the family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, 10–40 metres (33–131 ft) tall, with pinnate leaves 200–900 millimetres (7.9–35.4 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya), but not the hickories (Carya) in the same family.

Nut (fruit) In botany, type of dry indehiscent fruit

A nut is a fruit composed of an inedible hard shell and a seed, which is generally edible. In general usage, a wide variety of dried seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent). The translation of "nut" in certain languages frequently requires paraphrases, as the word is ambiguous.

Juglandaceae family of plants

The Juglandaceae are a plant family known as the walnut family. They are trees, or sometimes shrubs, in the order Fagales. Members of this family are native to the Americas, Eurasia, and Southeast Asia.

Hickory Genus of trees

Hickory is a type of tree, comprising the genus Carya, which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mexico, and two to four are from Canada. A number of hickory species are used for products like edible nuts or wood.

<i>Juglans nigra</i> species of plant

Juglans nigra, the eastern American black walnut, is a species of deciduous tree in the walnut family, Juglandaceae, native to North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central Texas. Wild trees in the upper Ottawa Valley may be an isolated native population or may have derived from planted trees.

<i>Carya ovata</i> Species of tree

Carya ovata, the shagbark hickory, is a common hickory in the Eastern United States and southeast Canada. It is a large, deciduous tree, growing well over 100 ft (30 m) tall, and can live more than 350 years. The tallest measured shagbark, located in Savage Gulf, Tennessee, is over 150 ft (46 m) tall. Mature shagbarks are easy to recognize because, as their name implies, they have shaggy bark. This characteristic is, however, only found on mature trees; young specimens have smooth bark.

<i>Carya cordiformis</i> species of plant

Carya cordiformis, the bitternut hickory, also called bitternut or swamp hickory, is a large pecan hickory with commercial stands located mostly north of the other pecan hickories. Bitternut hickory is cut and sold in mixture with the true hickories. It is the shortest-lived of the hickories, living to about 200 years.

<i>Carya glabra</i> species of plant

Carya glabra, the pignut hickory, is a common, but not abundant species of hickory in the oak-hickory forest association in the Eastern United States and Canada. Other common names are pignut, sweet pignut, coast pignut hickory, smoothbark hickory, swamp hickory, and broom hickory. The pear-shaped nut ripens in September and October,has a sweet maple like smell ,and is an important part of the diet of many wild animals. The wood is used for a variety of products, including fuel for home heating.

<i>Carya laciniosa</i> species of plant

Carya laciniosa, the shellbark hickory, in the Juglandaceae or walnut family is also called shagbark hickory, bigleaf shagbark hickory, kingnut, big, bottom, thick, or western shellbark, attesting to some of its characteristics. It is a slow-growing, long-lived tree, hard to transplant because of its long taproot, and subject to insect damage. The nuts, largest of all hickory nuts, are sweet and edible. Wildlife and people harvest most of them; those remaining produce seedling trees readily. The wood is hard, heavy, strong, and very flexible, making it a favored wood for tool handles. A specimen tree has been reported in Missouri with 117 cm (46 in) diameter at breast height, 36.9 m tall, and a spread of 22.6 m.

<i>Carya tomentosa</i> species of plant

Carya tomentosa, is a tree in the Juglandaceae or walnut family. The most abundant of the hickories, common in the eastern half of the US, it is long lived, sometimes reaching the age of 500 years. A straight-growing hickory, a high percentage of its wood is used for products where strength, hardness, and flexibility are needed. The wood makes excellent fuel wood, as well. The leaves turn yellow in Autumn.

<i>Carya myristiciformis</i> species of plant

Carya myristiciformis, the nutmeg hickory, of the Juglandaceae or walnut family, also called swamp hickory or bitter water hickory, is found as small, possibly relict populations across the Southern United States and in northern Mexico on rich moist soils of higher bottom lands and stream banks. Little is known of the growth rate of nutmeg hickory. Logs and lumber are sold mixed with other hickories. The nuts are an oil-rich food for wildlife.

<i>Carya ovalis</i> species of plant

Carya ovalis, the red hickory or sweet pignut hickory, is a fairly uncommon but widespread hickory native to eastern North America. It is typically found growing in dry, well drained sandy upland ridges and sloped woodlands from southern Ontario, Canada, and in the United States east to New Hampshire, south to northern Florida west to eastern Texas and north-west to Nebraska. This species was formerly treated as a variety or northern ecotype of the pignut hickory C. glabra, described as Carya glabra var. odorata. This discrepancy has not yet been completely resolved, and some sources and authors still consider red hickory as a variety or synonym of pignut hickory. However both trees are quite morphologically distinct.

A pecan is a type of nut belonging to either of two species:

The pecan weevil, Curculio caryae is an obligate feeder on the nuts of North American hickories and pecans, most widely recognized as an economically important pest of the pecan, Carya illinoinensis. It has also been observed to infest one Juglans species, the Persian walnut, Juglans regia.

<i>Carya texana</i> Species of tree

Carya texana, or black hickory, for its dark colored bark, is a North American tree in the walnut family, Juglandaceae. It is endemic to the United States, found primarily in the southern Great Plains and the Lower Mississippi Valley. It is an endangered species in Indiana, where it occurs in the southwest corner of the state.

Pecan scab species of fungus

Pecan scab is the most economically significant disease of pecan trees in the southeastern United States. Venturia effusa is a fungal plant pathogen that causes pecan scab. The fungus causes lesions and tissue death on pecan twigs, petioles, leaves, nuts and shucks beginning in early spring, with multiple cycles of infection repeating until late summer. Wind and rain spread the fungus to a susceptible host. Control of the disease is achieved by fungicide, sanitation and, in some cases, quarantine.

The Elliot Pecan, or Elliott Pecan, is a pecan variety planted predominately in Georgia and Florida. The nut is distinguishable by its smooth shell and small, tear-drop shape. The first Elliot tree was a seedling in the lawn of the American lumberman Henry Elliot in Milton, Florida. The Elliot Pecan tree is among the most disease-resistant pecan trees planted in the Southeastern United States.

Pomological Watercolor Collection

The U.S. Department of Agriculture's Pomological Watercolor Collection is an archive of some 7,500 botanical watercolors created for the USDA between the years 1886 and 1942 by around five dozen artists. Housed by the United States National Agricultural Library, it is a unique resource documenting existing fruit and nut cultivars, new introductions, and specimens discovered by USDA's plant explorers, representing 38 plant families in all. It has been called "one of the world's most unusual holdings of late 19th and early 20th century American botanical illustrations".


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