Flowering and fruit set in olive: a review

Olive is one of the most ancient fruit trees and has been cultivated for its oil for thousands of years. A mature olive tree produces about 500,000 flowers. They are borne on inflorescences termed panicles. The number of flowers and their distribution on the inflorescence are specific for each cultivar but can change from year to year. The flower position on the inflorescence affects its gender and opening day. The flowers are either perfect (hermaphrodite) or staminate (male). Olive flowers are wind-pollinated; however, they are visited by insects. Critical conditions such as strong and dry winds, rain, and high temperature affect pollination and may reduce fruit set. Most olive cultivars are self-incompatible or partially self-compatible and need to be fertilized by compatible pollenisers to ensure acceptable production. Furthermore, some cultivars are cross-incompatible and cannot fertilize each other. The degree of SIin olive is widely influenced by climatic conditions and therefore varies from environment to environment and from year to year. In a year with normal flowering, 1 to 2% of fruit set is enough for a commercial yield. The fruit follows a double sigmoid growth pattern like other drupes and contains quality oil.