
The modern pistachio nut (開心果) was first cultivated in Western Asia, where it has long been an important crop in cooler parts of Iran. Its cultivation spread into the Mediterranean world by way of Syria. The nut was introduced into Italy by the Roman consul in Syria.
More recently, pistachio has been cultivated commercially in Australia, New Mexico and in California where it was introduced in 1854 as a garden tree. It was not promoted as a commercial crop in U.S.A. until 1929. The earliest records of pistachio in English are around roughly year 1400 with the spellings "pistace" and "pistacia". The word pistachio comes from medieval Italian pistacchio, which is from classical Latin
pistacium.
Pistachio is a desert plant, and is highly tolerant of saline soil. It grows well when irrigated with water having 3,000–4,000 ppm of soluble salts. Pistachio trees are fairly hardy in the right conditions, and can survive at temperatures ranging between −10°C (14°F) in winter and 40°C (104°F) in summer. They need much sunshine and well-drained soil. Long hot summers are required for proper ripening of the fruit.
The bush grows up to 10 metres (30 ft) tall. It has deciduous pinnate leaves 10–20 centimetres (4–8 inches) long. The plants are dioecious, with separate male and female trees. The flowers are apetalous and unisexual, and borne in panicles.
The fruit is a drupe, containing an elongated seed, which is the edible portion. The seed, commonly thought of as a nut, is a culinary nut, not a botanical nut. The fruit has a hard, whitish exterior shell. The seed has a mauvish 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 part way open. This is known as dehiscence, and happens with an audible "pop". The splitting open is a trait that has been selected by humans. Commercial cultivars vary in how consistently they split open.
Each pistachio tree averages around 50 kg of seeds, or around 50,000, every two years. The trees are planted in orchards, and take approximately seven to ten years to reach significant production. Production is alternate bearing or biennial bearing, meaning the harvest is heavier in alternate years. Peak production is reached at approximately 20 years. Trees are usually pruned to size to make the harvest easier. One male tree produces enough pollen for eight to twelve nut-bearing females. Harvesting in the United States is often accomplished by using shaking equipment to shake the nuts off the tree.
The photos show the pistachio trees that grow in Sicily, Italy (the thickest tree is the oldest in the area), the green-to-yellow-to-red fruits before they are ripe, the beige-coloured shells and the seeds when the shells are removed.