The pistachio is the stone fruit of a deciduous tree. In some aspects, the pistachio tree resembles the almond and walnut trees and belongs to the same family as the walnut. The exact origin of the pistachio nut is not entirely clear. Currently, pistachio trees grow in Afghanistan, Pakistan, India, Iran, Turkey, Greece, Italy and the US. In countries such as Afghanistan, pistachio trees grow in the wild in mountainous regions, where the tree looks more like a bush than a tree.