The pistachio, a proud member of the cashew family, is a small tree originating from the Middle East and Central Asia. The tree produces seeds that are popularly consumed as food, especially while traveling long distances.
Pistacia vera often is confused with other varieties in the genus Pistacia that are also recognized as pistachio. These other unique species can be easily distinguished by their present geographic distributions (mostly in the wild) and their much smaller seeds and have a softshell.
As of 2020, Iran accounted for over half the global pistachio production.
Pistachio is exceptionally tolerant of saline soil and is technically a desert plant. It has been recorded to grow well when sprinkled with water having 3,000–4,500 ppm of soluble salts. Pistachio trees are relatively hardy in the right conditions and can withstand temperatures ranging between 14 °F (−10 °C) in winter and 118 °F (48 °C) in summer. They need a sunny position and well-drained soil. Pistachio trees do poorly in high humidity conditions and are receptive to root rot in the wintertime if they get too many rainy months or snow and the soil is not adequately free-draining. Hot, long summers are required for proper Pistachio fruit ripening.
The tree develops up to 33 ft (10 m) tall. It has deciduous pinnate leaves 4–8 inches (10–20 centimeters) long. The plants are dioecious, with separate female and male trees. The flowers are unisexual and apetalous and borne in clean panicles.
The fruit is a drupe, including an elongated seed, which is the safe edible part. Commonly, the seed is a nut, a culinary nut, not a botanical nut as previously thought. The fruit has a cream-colored, hard surface shell. The seed has distinct mauve-colored skin and green flesh (light greenish), with a unique flavor. When the fruit properly ripens, the shell changes from green to an autumnal red/yellow and splits partly open. This is known by the scientists as dehiscence and happens with a loud pop. Splitting open is a trait that humans have selected.[ Commercial cultivars differ in how they split open.
Each pistachio tree presents around 110 lb (50 kilograms) of seeds, or roughly 80,000, every two years.
The pistachio’s shell is typically a beige color, but it is sometimes colored green or red (artificially) in commercial pistachios. Originally, importers applied dye to conceal stains on the shells caused when the seeds were picked by a dirty hand. Most pistachios are now picked by modern machines, and the pistachio seed shells remain unstained, making dyeing useless except to meet fixed consumer expectations.
The pistachio tree is relatively long-lived, possibly up to 350 years or even more. The trees are planted in clean orchards and take about eight years to reach significant production. Production is biennial-bearing or alternate-bearing, meaning the harvest is more abundant in alternate years. Peak production is achieved in around two decades. Trees are usually clipped to size to make the harvest more manageable. One male tree provides enough pollen for seven to eleven drupe-bearing females. Harvesting in Greece and the United States is often performed using tools to shake the tree’s drupes. After drying and hulling, pistachios are sorted according to closed-mouth and open-mouth shells, then processed or roasted by modern machines to produce clean and delicious pistachio kernels.