The olive tree is a native of the chaparral regions of the Mediterranean where the oil from its fruits have fueled the diets of many great, early civilizations. Unlike most other fruit trees, olives are very long-lived and produce better with age, so ancient groves across countries such as Greece, Italy, Israel and Turkey. Trees as old as 1800 years still produce bumper crops of olives. Contemporary groves also exist worldwide, where the climate permits. In the North America, California is the center for olive production. Olive trees develop low branches that support a dense cover of small, lance-shaped, gray-green leaves with whitish undersides. These remain evergreen all season. As the trees age, the grey trunks become quite gnarled and attractive. Olives are slow growing and usually take between five and eight years before they are fruitful. Mature specimens produce clusters of small, fragrant, white flowers in the spring. The flowers give way to the familiar olive fruits. Some cultivars are self-fruitful, others set more fruit with cross pollination and a few ornamental selections are sterile and fruitless. Those grown for their fruits are typically harvested in late fall or winter.