According to global rankings, Iran ranks third in the world’s walnut production. The first country is China and the second country is America. After Iran, Turkey, Mexico and Ukraine are ranked third. Of course, Iran ranked fourteenth in 1992, but with the increase in production, it has reached the third rank. With this account, Iran ranks second in the production of walnuts in Asia. There are walnut trees over 300 years old in traditional and old gardens of Iran, and this shows the age of this tree in Iran. Walnut grows mostly in cold and dry areas, but extreme cold and heat causes serious damage to it. The provinces of Hamadan, Fars and Kurdistan are important hubs of walnut production in the country.