Pistachios grow on trees. They originally grew throughout Asia and the Mediterranean; as of 2014, they also grow in the Western United States. Pistachio trees begin bearing fruit around their fifth to seventh year and produce biennial crops, meaning a large crop one year and a smaller one the next.
When the nuts are ripe, the trees should be harvested quickly. The nuts are then cleaned, roasted and packaged for sale. The sign that pistachios are ripe is that the shells begin to split; this indicates that they are ready for harvest. Depending on the location, pistachio harvest can occur from late August to October.