Pistacia vera
Pistacia vera Kerman fruits ripening
Salted roasted pistachio nut with shell
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Sapindales
Family:	Anacardiaceae
Genus:	Pistacia
Species:	P. vera
Binomial name
Pistacia vera

History

The modern pistachio nut P. vera was first cultivated in Western Asia. Its cultivation spread into the Mediterranean world by way of central Iran, where it has long been an important crop. The early 6th-Century manuscript De observatione ciborum (On the observance of foods) by Anthimus implies that pistachio nuts (“pistacia” in vulgar Latin) were well known in Europe by late Roman times.

More recently pistachio has been cultivated commercially in the English speaking world, in Australia, New Mexico, and California. The United States Department of Agriculture introduced the tree in California about 1904, but it was not promoted as a commercial crop until 1929.

Biology

The bush grows up to 10 meters (30 ft) tall. It has deciduous pinnate leaves 10–20 centimeters (4-8 inches) long.

Pistachio is a desert plant, and is highly tolerant of saline soil. It has been reported to grow 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 temperature ranges between −10°C (14°F) in winter to 40°C (104°F) in summer. They need a sunny position and well-drained soil. Pistachio trees do poorly in conditions of high humidity, and are susceptible to root rot in winter if they get too much water and the soil is not sufficiently free draining. Long hot summers are required for proper ripening of the fruit.

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 (see photo). 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.

Cultivation

Commercially prepared pistachios in shells