Pistachio

Sowing: Pistachio is grown from seed, sown directly or raised as transplants after soaking seed for 24 hours and sowing about an inch deep, with germination favoured by soil temperatures of 68–77°F (20–25°C). Young trees are set out in full sun and well-drained, sandy to loamy soil of neutral to slightly alkaline pH, spaced 15–20 feet apart to allow the canopy to develop, and staked while establishing. Because the trees are dioecious, both male and female trees are needed for fruit to form, and long, hot summers are required for the nuts to ripen properly.

Watering: Soil is kept moist through the first year while young trees establish, but mature trees are highly drought-tolerant and need little irrigation thereafter; too much water in poorly drained soil predisposes the roots to rot. A balanced fertilizer is applied each spring, and pruning is done in late winter to shape the tree and remove dead or crossing wood. Trees take roughly seven to ten years to reach significant production and bear in an alternate pattern, cropping heavily one year and lightly the next.

Pistachio trees are vulnerable to root rot over winter if the soil does not drain freely and the roots sit in excess water. Aphids and scale insects are common pests, which can be managed with treatments such as neem oil or horticultural soap.

Harvest: Nuts are picked in late summer to early fall once the hulls have split open, and picking is done in two or three stages, or "hands," since fruit on a tree does not all ripen at once; the first hand is usually taken once 60–70% of the fruits have ripened. Ripe nuts must not be left to fall to the ground, where soil microorganisms can contaminate them, so they are shaken from the branches by hand or mechanically into nets or bins, then sorted and dried or peeled within 10–12 hours to prevent quality loss.

Storage: Once dried, pistachios keep in an airtight container in a cool, dark place for up to six months, or can be refrigerated or frozen for up to a year; nuts left in the shell keep longer than shelled ones.

Culinary: Pistachio seeds are eaten raw, roasted, or salted, and are used in desserts, chocolate, candy, ice cream, baked goods, and savory dishes, as well as blended into pastes, butters, and sauces. As a tree nut, pistachio is classed as a priority allergen.

Medicinal: The Assyrians are recorded to have used pistachios as medicines, aphrodisiacs, and antidotes.

Pistachio is native to western Asia, and its consumption is attested as far back as 300,000 years ago, with charred remains recovered from Mousterian levels at Kebara Cave in Israel. Cultivated pistachio remains dating from the sixth millennium BC have been found in Afghanistan and southeastern Iran, close to where the species grew wild, marking the likely region of early cultivation. From there it was widely grown in the ancient Persian Empire before cultivation gradually spread west, reaching Italy from Syria around the first century AD and then other Mediterranean lands and Europe through trade. Over the course of domestication, humans selected for the trait of the fruit splitting open at ripening.