Hardiness of Olive Varieties

Cold Hardiness

• Most olive varieties sustain damage to small twigs and stems when temperatures drop below 17 degrees Fahrenheit. At temperatures below 12 F, the damage is severe, and the tree may be killed to the ground at temperatures below 10 F. When killed to the ground, the tree may regrow if the underground roots recover, but the process is slow. You can help young trees survive freezing temperatures by mounding soil around the trunk to a height of about 1.5 feet. Whenever possible, cover the foliage with blankets when temperatures below 17 F threaten. Wait until the tree resumes growth before pruning off frost damage.

Chilling Requirements

• When temperatures drop in autumn, olive trees produce hormones that prevent new growth and induce a state of dormancy that helps the tree survive the winter months. Cold temperatures in winter break down the growth-inhibiting hormones and allow the tree to resume normal growth. Olive trees need 200 to 300 hours of temperatures below 45 F over the winter months to break down the hormones so that they can produce flowers and set fruit. Growth resumes when temperatures rise above 70 F.

Hardy Olive Varieties

• Some varieties stand out for their ability to withstand cold temperatures. Hardy cultivars can withstand temperatures as much as 5 degrees lower than more cold-sensitive varieties without sustaining substantial damage. Hardy varieties include Arbequina, Maurino, Mossion, Aglandau, Pendolino, Ascolano, Picudo, Bouteillan, Picual, Coratina, Hojiblanca and Leccino.

Moderately Hardy and Cold-Sensitive Olive Varieties

• Moderately hardy and cold-sensitive olive varieties are more susceptible to frost damage. Plant these varieties only in areas where temperatures rarely drop below 17 degrees. Moderately hardy cultivars include Kalamon and Picholine, Moraiolo, Empeltre, Frantoio, Taggiasca, Koroneiki and Manzanillo.