Hardiness Zones for Olive Trees

Winter Hardiness

• Olive trees tolerate winter cold down to about 15 degrees Fahrenheit without sustaining any leaf or branch dieback. This correlates to U.S. Department of Agriculture plant hardiness zones 8b through 10. However, the plants may survive temperatures as low as 10 degrees, but you can expect branches to die back, even as far as the trunk base. Cold-damaged olive trees or shrubs must rejuvenate from the roots in spring. Temperatures colder than 5 F kill roots.

Climate Zones

• In parts of the western United States, where the elevation changes abruptly, applying the USDA hardiness zones is difficult and unreliable. Instead, Sunset climate zones are more frequently used to determine which plants grow well in different areas based on temperatures, elevation, precipitation regimes, seasonal humidity and latitude. Olive trees grow in climate zones 8, 9, 11 through 24, H1 and H2. For good flowering and production of fruits, olive trees must be exposed to winter temperatures below 45 F.

Summer Heat

• Because they are native to the Mediterranean basin, olive trees need sufficient sunlight and summertime heat to develop mature fruits. Cool summers do not result in plump, oily fruits for harvest by early to mid-fall. For consistent fruit production, olives must grow in regions that supply at least 90 days of daytime temperatures above 86 F. They can handle as many as 180 days, according to the American Horticultural Society.

Regional Considerations

• Although drought tolerant, olive trees need some irrigation during the hot, dry summers to remain their healthiest and to prevent any premature loss of developing fruits. The milder climates of California and southern Arizona require some summertime irrigation. Olive trees are winter hardy in the American Southeast, but are not long-term plants nor always bear fruits. Summertime humidity and rains, or acidic, slow-draining soils in this region are not conducive to olive tree growth. If winter cold kills back olive trees, their rejuvenating growth will not bear flowers or fruit. Olive trees bloom on branches that are 1 year old.