Pistachios are seeds of a fruit, not true nuts.

The pistachio tree is called Pistacia vera. It belongs to the same plant family as cashews and mangoes. Botanists define a true nut as a dry fruit with a shell that does not open on its own. Acorns and chestnuts are examples of true nuts.Pistachios are different because they are drupes. A drupe has a fleshy outer layer and a hard inner shell. As the fruit ripens, the outer skin dries out. The inner shell then splits open naturally. This process is called dehiscence.The split in the shell makes it easy for people to reach the seed. Pistachio trees grow slowly and take 7 to 10 years to produce a large crop. They reach their peak production around age 20. Most pistachios come from the United States and Iran.California produced over 1 billion pounds of pistachios in 2020. The green color in the seed comes from chlorophyll. This is the same chemical plants use to turn sunlight into food. The purple colors come from anthocyanins, which are natural pigments found in many fruits.