ASHS 2025 Conference

Global olive oil production tripled over the past six decades to 2.76 million tons in the 2022/23 year. California is the largest producer of olive oil in the United States, and its planting is increasing at an estimated rate of 3000 acres per year. Most of the new plantings for oil in California are in hedgerows under intensive management either in a super high (SHD) or medium (MD) density systems. Of these plantings, an estimated ~80% is ‘Arbequina’, ~15% ‘Arbosana’, and ~5% ‘Koroneiki’. As expected, the industry is continuously searching for novel cultivars that can improve field and oil productivity, EVOO quality, as well as increase economic returns for their operation. With industry support, a trial was planted at the Wolfskill Experimental Orchard in Winters, CA in 2019. Four acres were planted at a density of 620 trees per acre, at 5 feet between trees and 14 feet between rows. ‘Arbequina’, ‘Arbosana’, and ‘Koroneiki’ were planted alongside two new cultivars, ‘Lecciana’ and ‘Sikitita’, and one numbered selection, Agromillora ‘9805-01’. The orchard was planted with five complete replicates of the six cultivars, each cultivar row was randomized within each replicate, with the exception of ‘Lecciana’ which was planted one year later in 2020. Seasonal and cumulative yield were measured from the 2021 through the 2024 growing seasons; while fruit weight, oil content, basal shoot prevalence, and maturity index were measured over the 2023 and 2024 growing seasons. The entire orchard was managed following industry agronomic practices for all replicates. During the four years ‘Koroneiki’ had the greatest cumulative yield on average, followed by ‘Arbequina’ and ‘Arbosana’, ‘Lecciana’, ‘9805-01’, and ‘Sikitita’ (16.60, 13.38, 13.37, 10.61, 8.17 and 7.76 tons per acre respectively). Alternate bearing behavior was more prevalent for ‘9805-01’ and ‘Sikitita’ and ‘Sikitita’ took an additional year to come into production. The results, including seasonal yield, oil content, basal shoot prevalence, and fruit weight, show why ‘Arbequina’, ‘Arbosana’, and ‘Koroneiki’ are still the prevalent cultivars grown in California for SHD plantings. In our trial, ‘Arbosana’ and ‘Koroneiki’ performed as well or better than ‘Arbequina’, but growers in California have planted less of those two cultivars due to concerns with disease resistance and vigor management over time across the different climatic conditions of the state. Our research shows that further evaluation of novel cultivars is essential for a growing industry.