code in the United States eliminated tax shelters for almonds and citrus fruits. That encouraged California farmers to plant pistachio trees, because they were still eligible for such tax breaks. In 1972, the Shah of Iran began a school breakfast program that included packets of pistachios. This resulted in a decline of pistachio exports from Iran, resulting in increased prices in other countries and additional incentives to plant pistachio trees in California. The first commercial pistachio harvest in California took place in 1976. The Shah was forced into exile in January, 1979 during the Iranian Revolution, resulting in an end to trade between the United States, providing additional incentives for American farmers to plant dramatically more pistachio trees. By 2008, U.S. pistachio production rivaled that of Iran. Drought and unusually cold weather in Iran led to severe declines in production there, while U.S. production was increasing. At that time, pistachios were Iran's #2 export product, after the oil and gas sector. By 2020, there were 150,000 pistachio farmers in Iran, approximately 70% of whom were small-scale producers using inefficient manual picking and processing techniques. There were 950 far larger U.S. producers, using highly efficient mechanized production techniques. Between them, the U.S. and Iran control 70% of the world export market, with the U.S. in the lead. Worldwide demand exceeds production, so both countries have the ability to sell their production to various export markets. In 2021, Fresno County, California accounted for about 40% of U.S. pistachio production, with a value of $722 million. Botany Habitat Pistachio is a desert plant and is highly tolerant of saline soil. It has been reported to grow well when irrigated with water having 3,000–4,000 ppm of soluble salts. Pistachio trees are fairly hardy in the right conditions and can survive temperatures ranging between in winter and in summer. They need a sunny position and well-drained soil. Pistachio trees do poorly in conditions of high humidity and are susceptible to root rot in winter if they get too much water and the soil is not sufficiently free-draining. Long, hot summers are required for proper ripening of the fruit. Characteristics The tree grows up to tall. It has deciduous, pinnate leaves long. The plants are dioecious, with separate male and female trees. The flowers are apetalous and unisexual and borne in panicles. The fruit is a drupe, containing an elongated seed, which is the edible portion.