About 20 species of evergreen trees and shrubs native to the Old World. The common olive is cultivated widely for the edible and oil-rich fruit. This plant grows to 25 feet tall and produces oblong, glossy, black fruits to 1 1/2 inch long. Olives attain great age if given a deep, fertile and well-drained soil. It was during late 1800s that the suitability of California was recognized for the cultivation of olives. Today, in California and Arizona, this plant is not only cultivated for its fruit, but also as an ornamental plant, and has become a source of concern for people with allergies.