The tree grows up to 10 metres (33 feet) tall. It hasdeciduous,pinnate leaves 10–20 centimetres (4–8 inches) long. The plants aredioecious, with separate male and female trees. The flowers areapetalous andunisexual and borne inpanicles.[4]
Pistachios growing inIran in 2007. The fruits have not yet begun to open.
The fruit is adrupe, containing an elongatedseed, which is the edible portion. The seed, commonly thought of as a nut, is aculinary nut, not abotanical nut. The fruit has a hard, cream-colored exterior shell. The seed has a mauve-colored skin and light green flesh, with a distinctive flavor. When the fruit ripens, the shell changes from green to an autumnal yellow/red and abruptly splits partly open. This is known asdehiscence and happens with an audible pop. Humans selected the trait of splitting open.[5] Commercialcultivars vary in how consistently they split open.
Each mature pistachio tree averages around 50 kilograms (110 pounds) of seeds, or around 50,000 seeds, every two years.[6]
Pistachio is a desert plant and is highly tolerant ofsaline soil. It has been reported to grow well when irrigated with water having 3,000–4,000 ppm of soluble salts.[8] Pistachio trees are fairly hardy in the right conditions and can survive temperatures ranging between −10 °C (14 °F) in winter and 48 °C (118 °F) in summer. They need a sunny position and well-drained soil. Pistachio trees do poorly in high humidity conditions and are susceptible toroot rot in winter if they get too much water and the soil is not sufficiently free-draining.[9] Long, hot summers are required for proper ripening of the fruit.[10]
The pistachio tree may live up to 300 years.[11] The trees are planted inorchards, and take around 7 to 10 years to reach significant production. Production is alternate-bearing orbiennial-bearing, meaning the harvest is heavier in alternate years. Peak production is reached around 20 years. Trees are usually pruned to size to make the harvest easier. One male tree produces enough pollen for 8 to 12 drupe-bearing females. Harvesting in the United States and Greece is often accomplished using equipment to shake the drupes off the tree. After hulling and drying, pistachios are sorted according to open-mouth and closed-mouth shells, then roasted or processed by special machines to produce pistachio kernels.[citation needed]
Archaeological evidence shows that pistachio seeds were a common food as early as 6750 BCE.[16] The earliest archeological evidence of pistachio consumption goes back to the Bronze Age Central Asia and comes fromDjarkutan, modern Uzbekistan.[17][18]
The Romans introduced pistachio trees from Asia to Europe in the first century AD. They are cultivated across Southern Europe and North Africa.[19]
The manuscriptDe observatione ciborum (On the Observance of Foods) byAnthimus,[23] from the early sixth century, implies thatpistacia remained well-known in Europe inlate antiquity.
An article on pistachio tree cultivation was brought down inIbn al-'Awwam's 12th-century agricultural work,Book on Agriculture.[24]
Archaeologists have found evidence from excavations atJarmo in northeastern Iraq for the consumption of Atlantic pistachio.[16]
Pistachio trees are vulnerable to numerous diseases and infestation by insects such asLeptoglossus clypealis in North America.[25] Among these is infection by the fungusBotryosphaeria, which causes panicle and shootblight (symptoms include death of the flowers and youngshoots), and can damage entire pistachio orchards.[26] In 2004, the rapidly growing pistachio industry in California was threatened by panicle and shoot blight first discovered in 1984.[27] In 2011,anthracnose fungus caused a sudden 50% loss in the Australian pistachio harvest.[28] Several years of severe drought in Iran around 2008 to 2015 caused significant declines in production.[29]
In 2022, world production of pistachios was one million tonnes (2.2 billion pounds), with the United States, Iran, and Turkey together accounting for 88% of the total (table). The state of California produces 98% of the pistachios grown in United States, with more than 485,000 acres devoted to the crop in 2020, mostly in theSan Joaquin Valley, contributing $5.2 billion to the state's economy.[31]Fresno County alone accounted for about 40% of U.S. pistachio production in 2021, with a value of $722 million.[32]
Italy produces a small quantity of pistachios, with thePistacchio di Bronte (pistachios fromBronte town)DOP-protected.[33]
In the 19th century, the pistachio was cultivated commercially in parts of the English-speaking world, including Australia and the United States, in the states ofNew Mexico[8] and California, where it had been introduced as a garden tree in 1854.[34]
In 1969 and 1971, changes to the tax code in the United States eliminatedtax shelters foralmonds andcitrus fruits. That encouraged California farmers to plant pistachio trees because they were still eligible for such tax breaks. In 1972, theShah of Iran began a school breakfast program that included packets of pistachios. This resulted in a decline in pistachio exports from Iran, resulting in increased prices in other countries and additional incentives to plant pistachio trees in California.[37] The first commercial pistachio harvest in California took place in 1976.[38] The Shah was forced into exile in January 1979 during theIranian Revolution, resulting in an end to trade between the United States and Iran, providing additional incentives for American farmers to plant dramatically more pistachio trees.[37]
By 2008, U.S. pistachio production rivaled that of Iran. Drought and cold weather in Iran led to severe declines in production, while U.S. production was increasing. At that time, pistachios were Iran's second-most important export product, after the oil and gas sector.[39]
By 2020, there were 150,000 pistachio farmers in Iran, approximately 70% of whom were small-scale producers using inefficient manual picking and processing techniques. There were 950 far larger U.S. producers, using highly efficient mechanized production techniques. The U.S. and Iran control 70% of the world export market, with the U.S. in the lead. Worldwide demand exceeds production, so both countries can sell to various export markets.[38]
As with other tree seeds,aflatoxin is found in poorly harvested or processed pistachios. Aflatoxins are potentcarcinogenic chemicals produced by molds such asAspergillus flavus andA. parasiticus. The mold contamination may occur from soil or poor storage and be spread by pests. High levels of mold growth typically appear as gray to black filament-like growth. Eating mold-infected and aflatoxin-contaminated pistachios is unsafe.[40] Aflatoxin contamination is a frequent risk, particularly in warmer and humid environments. Food contaminated with aflatoxins has caused frequent outbreaks of acute illnesses in parts of the world. In some cases, such as in Kenya, this has led to several deaths.[41]
Pistachio shells typically split naturally before harvest, with a hull covering the intact seeds. The hull protects the kernel from invasion by molds and insects, but this hull protection can be damaged in the orchard by poor orchard management practices, by birds, or after harvest, which makes exposure to contamination much easier. Some pistachios undergo a so-called "early split", wherein both the hull and the shell split. Damage or early splits can lead to aflatoxin contamination.[42] In some cases, a harvest may be treated to keep contamination below strict food safety thresholds; in other cases, an entire batch of pistachios must be destroyed because of aflatoxin contamination.
Large quantities of pistachios are self-heating in the presence of moisture due to their high oil content in addition to naturally occurringlipases, and canspontaneously combust if stored with a combustible fabric such asjute.[44]
The shell of the pistachio is naturally a beige color, but it may be dyed red or green in commercial pistachios. Originally, dye was applied to hide stains on the shells caused when the nuts were picked by hand.[51] In the 21st century, most pistachios are harvested by machine and the shells remain unstained.[51]
In July 2003, the United StatesFood and Drug Administration approved the first qualifiedhealth claim specific to consumption of seeds (including pistachios) to lower the risk ofheart disease: "Scientific evidence suggests but does not prove that eating 1.5 ounces (42.5 g) per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease".[56] Although a typical serving of pistachios supplies substantial food energy (nutrition table), their consumption in normal amounts is not associated with weight gain orobesity.[54]
One review found that pistachio consumption loweredblood pressure in persons withoutdiabetes mellitus.[57] A 2021 review found that pistachio consumption for three months or less significantly reducedtriglyceride levels.[58]
^Participants of the FFI/IUCN SSC Central Asian regional tree Red Listing workshop, Bishkek, Kyrgyzstan (11–13 July 2006) (2007).Pistacia vera. The IUCN Red List of Threatened Species 2007: e.T63497A12670823.doi:10.2305/IUCN.UK.2007.RLTS.T63497A12670823.en
^"pistachio".Cambridge Dictionary. CUP. Retrieved17 February 2024.
^Considine, Douglas M.; Considine, Glenn D. (1995).Van Nostrand's Scientific Encyclopedia (8th ed.). Boston, MA s.l: Springer US. p. 556.ISBN978-1-4757-6918-0.
^abcEsteban Herrera (1997)Growing pistachios in New Mexico, New Mexico State University, Cooperative Extension Service, Circular 532[1]Archived 20 July 2011 at theWayback Machine
^Marks, Gil (2010).Encyclopedia of Jewish Food. HMH.ISBN978-0544186316.These pale green nuts covered with a papery skin grow on a small deciduous tree native to Persia, the area that still produces the best pistachios.
^V. Tavallali and M. Rahemi (2007)."Effects of Rootstock on Nutrient Acquisition by Leaf, Kernel and Quality of Pistachio (Pistacia vera L.)"(PDF).American-Eurasian J. Agric. & Environ. Sci.2 (3):240–246.S2CID7346114. Archived fromthe original(PDF) on 24 February 2019.Native P. vera forests are located in north eastern part of Iran particularly in Sarakhs region. This native P. vera originates from cultivated pistachio trees in Iran [1]. P. mutica is a wild species indigenous to Iran that grows with almonds, oak, and other forest trees and is common to most Alpine regions.
^Rieger, Mark (2012)."Pistachio –pistacia vera".Mark's Fruit Crops. University of Georgia. Archived fromthe original on 30 October 2014. Retrieved16 January 2023.
^Shaker Ardakai, A.; Mir Damadiha, F.; Salehi, F.; Shahedi, M.; Kabir, G. H.; Javan Shah, A.; et al. (2007)."Pistachio Halva Production".Document Number: 29328. Iran Pistachio Research Institute. Archived fromthe original on 31 December 2018. Retrieved4 May 2011.
