Pistachios (Pistacia vera). The pistachio is a tree seed or, botanically, a drupe. Roasted pistachios have a bright green flesh and a distinctive flavour that has many culinary uses as a snack and flavouring. With a worldwide production of 1.4 million tonnes, 72 percent comes from Iran and the USA. Each tree produces around 50 kilos. The shells that have opened when harvested are roasted for the snack market while closed shells are processed for their kernels. Shells are sometimes dyed. The distinctive colour is used as a colour description. While they have many health benefits pistachios, a relative of cashews, can cause a nut allergy that seems to be increasing at a global scale.