Avocados originated in Mexico and Central America. The first records of avocados were discovered in Aztec writings, and avocado seeds were discovered buried inside Aztec cities along with other rubble. (The modern name "avocado" actually comes from the Aztec word "ahuacati," meaning testicles, which described how the avocado fruit looked hanging on the tree.) Avocados are now grown in warm and tropical climates around the world.
The preferred climate and zone for avocados is a climate with warm temperatures year-round. The tree is a tropical plant and does not like frost or temperatures under 50 degrees Fahrenheit. Avocado trees prefer high humidity of 60 to 80 percent. They can also grow in dryer climates (with no less than 40 percent humidity), but more problems may occur with the fruit or tree. The tree needs a high level of moisture and plenty of nutrients in the soil.
Mexico, Central America, and some regions of South America have the frost-free climate, high water quality and rich soil necessary to keep avocados healthy. About half of all avocados sold in the United States come from Mexico, with Indonesia and the USA growing an additional third. The rest of Central America and South America make the rest of the percentage of avocados grown for U.S. import.
It is possible to grow avocados in the United States in certain conditions. The best growing zones for avocado trees are U.S. hardiness zones 9 to 11. These zones are frost-free and have relatively even climates. All areas in these zones may not be suitable, however, because avocado trees need moisture and rich soil. Many of the warmer zones in the United States are too dry for avocado growing.
Australia has a large avocado-growing industry, with over 70 varieties grown all over the country. Avocado trees were first introduced to Australia in 1840. The seeds were planted in the royal garden, and it was determined that Australia was an ideal growing climate for avocados. As of 2010, Australia does not export its avocados to any other country, although a plan to export avocados to New Zealand and Asia is in development.
Latitudes at the 0 degree latitudinal mark (right around the equator) grow the healthiest avocados. However, avocado trees can grow between the latitudes of 30 degrees north to 35 degrees south—as far north as Maryland and as far south as South Africa and Australia.