The Pistachio is a tree up to 10 m tall, native to mountainous regions of central and southwestern Asia.
The fruit is a drupe, containing an elongated seed (a nut in the culinary sense, but not a true botanical nut) with a hard, whitish shell and a striking light green kernel, having a very characteristic flavour.
When the fruit ripens, the shells split open partially. This happens with an audible pop, and legend has it that lovers who stand under a pistachio tree at night and hear the nuts popping open will have good luck.
The kernels are eaten whole, either fresh or roasted and salted, and are also used in ice cream and confections such as baklava.
The shell of the pistachio is naturally a beige colour, but it is sometimes dyed red in commercial pistachios. Originally the red dye was applied by importers to hide stains on the shells caused when the nuts were picked by hand. However most pistachios are now picked by machine and the shells remain unstained, making dyeing unnecessary (except that some consumers have been led to expect red pistachios). Roasted pistachio nuts turn naturally red if they are marinated before in a salt and lemon marinade, or salt and citrus salts.
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.
Pistachio nuts are highly flammable when stored in large quantities, and are prone to self heating and spontaneous combustion.
Source: Wikipedia
