The Climate Requirements for Olive Trees

Winter Weather

• Subtropical climates feature long winters with mild temperatures. Winter freezes are rare. Olives are cold hardy in U.S. Department of Agriculture Plant Hardiness Zones 10 and 11, where winter low temperatures average about 30 degrees Fahrenheit, well within the olive tree's tolerance range. Olives bloom in late spring, but only after bathing in warm days and chilly nights all winter long – a process called vernalization. Unexpected late frosts in the cooler portions of the subtropical range can kill the flowers, ruining the fruit crop for the year. Some areas of Zone 11 may not have cold enough winters to stimulate olive production.

Rainfall

• Subtropical climates experience the heaviest periods of rainfall in winter rather than summer. Although the trees normally tolerate dry summers, they grow and produce best in the portions of subtropical areas that receive the most rain annually. Olives need no additional irrigation in subtropical areas that average 15 to 23 inches of rainfall yearly, but produce best in areas that get up to 31 inches. When a subtropical area becomes too dry due to months-long drought or lack of moisture due to cultivation problems, supply the trees with supplemental irrigation.

Summer Weather

• Olive trees prefer summers filled with hot, arid weather. Olives thrive in average summer temperatures of 70 to 80 degrees F. Subtropical areas suitable for growing olives generally exist on the eastern and western borders of continents. In the U.S., the subtropical climate occurs in portions of the Gulf Coast states, Arizona and from Portland, Oregon, down the Pacific coast to California. Brief but intense pop-up thunderstorms often punctuate the otherwise hot, dry summer afternoons.

Microclimates

• Microclimates are pockets of climatic conditions that differ, sometimes dramatically, from the larger climate around them. Microclimates can encompass small spaces, such as an area of the yard that is protected or exposed to sunlight, wind and rain. Low areas may be colder than open areas, making that spot unsuitable for olives. While some microclimates appear on the Hardiness Zone map, many microclimates are too small to show up on the map. Your local extension service office may have information on known microclimates in your area.