Young olive plants are not entirely hardy but grown in containers plants can be placed outdoors in the summer and brought into a cold greenhouse or conservatory for winter protection. Mature plants are more frost tolerant, and may survive in the open ground, tolerating short exposure to freezing conditions, but suffering damage once temperatures fall below -10°C (14°F).
Pots and compost
Plants are best grown in well crocked pots with a loam-based compost, such as John Innes No 3 adding grit for good drainage. Raise pots on feet for free drainage in wet seasons. Start off with smaller pots, gradually repotting until you reach the largest size that you can move - around 45cm (18in).
Watering and feeding
Although drought tolerant, olives grow and fruit better if watered freely during the growing season. Reduce watering in winter, without allowing the compost to dry out completely. Apply a balanced liquid fertiliser monthly during the growing season.
Pruning
Cut back young plants to encourage a branching habit, selecting three or four shoots to form a main branch framework, reducing these in length. Thin out new shoots each year and cut back when necessary, until a compact plant is produced. Carry out pruning in the spring or early summer.
On mature plants pruning should be kept to a minimum. Old and unproductive wood can be removed to encourage new shoots. Thin out overcrowded or crossing branches.
Fruiting
To flower and fruit successfully olives need at least two months of temperatures below 10°C (50°F) in winter. Avoid prolonged cold weather below 7.5°C (46°F) or winter temperatures above 15.5°C (61°F) as both can prevent successful fruit production.
The flowers are mainly wind pollinated. Most cultivars are self fertile, but by growing more than one cultivar, pollination will be improved.