Olea europaea
Family: Oleaceae

Olea includes some 20 species of evergreen trees and shrubs, including the common olive, Olea europaea, which is native to the Mediter­ranean, and cultivated for several thousand years for the extraction of olive oil as well as for its fruit. These trees have small, leathery, green leaves and creamy white flowers, followed by the fruit. They are adaptable, very long lived, and cultivated in many regions of the world. The oil is extracted from the ripe fruit and is used in food preparation, medicine and the manufacture of toiletries and cosmetics. Both the green fruits and the fully ripened, black fruits are preserved and pickled, either plain or stuffed with pimento, nuts or anchovies.

Species

Olea europaea is a tree growing 6-12 m (20-40 ft) tall, with narrow, leathery leaves which are dull green above and silvery beneath. The insignificant flowers are cream in colour and are followed by the fruits. Traditionally grown varieties include 'Sevillano', 'Verdale' and 'Manzanillo', while 'Mission' and University of California selections (marketed as 'UC' fol­lowed by a number) are newer varieties which have a wider range of climatic tolerance as well as possessing good bearing characteristics. Varieties grown more specifically for oil extrac­tion include 'Bouquetier' and 'Correggiola'.

Olea europaea subspecies africana grows around 8 m (26 ft) in height and has darker, glossy, green leaves and fleshy fruit which is edible but without the flavor and succulence of the European olive. It has become naturalized in many areas and can become quite invasive.

Cultivation

In climates subject to hard frosts, grow in a cool greenhouse or conservatory in a large pot or tub of soil-based potting compost. Where it is possible to grow olives outdoors, win­ters must be cool enough to provide the chilling needed to induce flowering, but temperatures of less than -9°C (16°F) can kill these trees.

Long, hot summers are necessary for proper growth and development of the fruit. Inland areas where humidity is low appear to be more suitable than coastal regions. Deep, well-drained soils are ideal and olives grow well in soils that are slightly alkaline or even with some salinity. Although these trees are drought tolerant once established, adequate water is needed throughout the grow­ing season to ensure good fruit development.

Seedling-grown trees may take eight to ten years to produce a crop, while some types may pro-duce only every second year. Propagation is by budding in late summer to early autumn, grafting in spring or from semi-hardwood cuttings taken from midsummer onwards. Olives are relatively free from pests and diseases but they are prone to attack by scale insects, especially when grown under glass.

Climate

Zone 9.