S11 - Session P4 - Evaluating olives for cold hardiness and cultivation in western Oregon

Authors: Neil Bell *, Heather Stoven, Hayley White

Olive ( Olea europaea ) is a broadleaved evergreen tree native to the Mediterranean basin, where it has been cultivated for over 5,000 years. Cultivation of olives spread from the Mediterranean to other parts of the world with a similar climate. In North America, this originally made California the center of olive production. More recently, there has been interest in cultivating olives in non-traditional growing regions in North America, including western Oregon, where a small number of growers are developing a niche market for locally-produced olives for table fruit and oil. The fundamental challenge to growing olives in Oregon is winter cold injury to the woody tissues of the tree. Originating as they do in a relatively mild climate, olives are not adapted to temperatures below approximately -9 o C. Freezes of sufficient severity to damage olives do occur occasionally in western Oregon and observational evidence shows that cultivars vary in their tolerance of cold. In California, a freeze in December, 1990 caused significant damage to olive orchards in the Sacramento Valley and researchers subsequently categorized different cultivars for their susceptibility to this cold event. However, such evidence of injury to the trees themselves in the literature is rare. Where freeze injury data exist, it usually concerns frost damage to flowers, not the woody tissue of the tree. To determine relative cold hardiness of olive cultivars, a new evaluation trial of over 100 cultivars was planted at the North Willamette Research and Extension Center in Aurora, Oregon, USA in mid-July 2021. The cultivars were obtained as cuttings from a collection at the National Clonal Germplasm Repository in Davis, California. The planting is expected to provide data not only on relative cold hardiness of a wide range of cultivars, but also other characteristics such as flowering, fruit set, harvest time and fruit quality attributes.