Olea europaea aka Olive

Olea europaea, the common olive, belongs to the olive family. This evergreen tree grows slowly and can also form a shrub. Its native range includes the Mediterranean, Africa, and parts of Asia. People have grown olives for food for thousands of years. Wild plants grow in woods and scrub on dry, rocky ground. Garden trees reach 20–30 feet [6.1–9.1 metres] tall. Their crowns spread 15–25 feet [4.6–7.6 metres] wide. RHS gives a smaller spread of 5–8 feet [1.5–2.5 metres].

The crown starts rounded and grows less even with age. Young trees have smooth, pale gray bark. Older trunks and branches twist and develop deep grooves. The leathery leaves grow in pairs along the stems. They have oval or narrow, lance-shaped blades. Their upper sides look gray-green, while fine hairs silver the undersides. Small white flowers grow in clusters where leaves meet stems. They have a scent and bloom from June to July. Each oval fruit is a drupe with one hard pit. Green fruits turn purple-black as they ripen in fall.

Give olives full sun and deep, fertile soil that drains well. They grow in sand, loam, or clay with good drainage. They also accept acid, neutral, and alkaline soil. Hot, dry summers and mild, wet winters suit them best. Established trees can cope with drought. The species grows outdoors in USDA zones 8–10. RHS rates its UK hardiness as H4. In colder areas, growers use greenhouses or cool indoor winter quarters. Indoor container care can be difficult. Trees need about two cool winter months to flower. Two different pollinizers can improve fruit yields.

Gardeners grow olives for fruit, evergreen cover, and their aged trunks. They also suit coastal gardens, courtyards, containers, and bonsai. Fallen fruit can make a mess on paving. Birds and small mammals spread the seeds. Trees can form dense stands outside their native range. Reports record invasion in Australia, New Zealand, Hawaii, and southern California. People cure the fruit for food and press it for oil. PFAF also lists leaves and sweet sap as edible. It reports no known hazards. Brined olives can contain much salt. Other uses include medicine, fuel, dyes, wood, and soil protection.

Scale insects may attack the tree. Other problems include olive knot, verticillium wilt, and root rot. RHS also lists olive scab and occasional honey fungus. It flags olives as high-risk hosts for Xylella fastidiosa.