The pistachio is not a nut in the botanical sense but a stone fruit of the dioecious pistachio tree. The foliate tree can grow up to 12 metres high and live for up to 300 years. Its roots reach depths of 15 metres.

Pistachios grow in heavy grape-like clusters, and like almonds, are surrounded by a fleshy hull. The hulls contain the oval, yellow-green pistachio kernels, which ripen within a thin, wooden shell. The nuts mature in late summer or early autumn. Their hulls become rosy and their inner shells split along their sutures.

As pistachio trees are dioecious they produce male and female flowers on separate trees. This means that both male and female trees must be present for pollination, or, alternatively, branches from male trees must be grafted onto female trees. Pollen is carried from male to female flowers by the wind, not by bees. Pollination generally takes place between March and April.

Pistachios grow best in a desert-type climate with hot days and cold nights. Pistachio trees require approximately 1,000 hours of temperatures at 7°C or below to ensure the required kernel dormancy. A mild winter, frost in spring or heavy rainfall during pollination can reduce yield.