- Common name: olive
- Botanical name: Olea europaea
- Family: olive (Oleaceae)
- Type: evergreen shrub or tree
- Fruiting season: autumn
- Flowering season: summer
- Planting time: April or May
- Height: 4 to 10m (15 to 33ft)
- Width: 2 to 10m (7 to 33ft)
- Aspect: sheltered south-facing sun
- Hardiness: H4
- Difficulty: average
The ultimate Mediterranean tree, the olive (Olea europaea) is increasingly popular in the UK for its tolerance of drought. In milder locations, given a sheltered south-facing spot, it is a wonderful garden plant, with silvery evergreen leaves that shimmer in sunlight and glow in moonlight, and – with the right TLC – it may produce a crop of fruit each year.
90% of the world's olives grow in iconic groves around the shores of the Mediterranean sea. Most are farmed and therefore replaced circa 80 years old, but those that are left can reach an incredible age, with some veterans estimated to be 2,000 or more. The older they are, the more characterful their gnarled bark, which bobbles and flows like solidified lava or twists like swollen rope. No wonder olive farmers believe talking to your trees ensures good fruit or oil.
Olives are one of humanity's oldest domesticated crops, potentially grown as far back as 6000 BC in Asia Minor, although some experts believe the Egyptians were the first to graft the wild olive (oleaster). For the old civilisations of the Mediterranean, such as the Phoenicians and the Romans, olive oil was a vast industry, with the city of Rome importing 7.5 million litres of oil per year in the 2nd century AD.
Providing so much (from food and fuel to a base for medicines and cosmetics), capable of living for so long, and the tree that produced light (both via its leaves catching the sun and via its oil in lamps), the olive was regarded as highly sacred. It would become a celestial tree in Jewish, Christian, and Muslim symbolism, and – since oil was so readily presented as a gift and forged good trade ties – it was, and still is, known as the tree of peace.
In the garden, given its preferred conditions, it is a joy all year, with silvery evergreen leaves, ivory summer flowers, and – if you're lucky – delicious smoky olives to eat.
Which olive tree to grow
There are over 700 varieties of the European olive (Olea europaea). Some are more tolerant of the UK climate than others, including 'Arbequina' (a Spanish variety that fruits from a young age) and 'Picual' (a short olive with silver foliage). Both are self-fertile and compact. 'Hojiblanca' is a larger tree and has a whitish sheen on its leaves, which makes it catch the light, but it requires another tree (such as 'Arbequina') in the vicinity for pollination, if you want it to fruit.
If purchasing an imported tree, beware of a disease called Xylella. Symptoms include wilting, yellow leaves, or leaf drop. When purchasing an imported tree, ensure it comes from a low Xylella-risk part of Europe (such as Spain).
How to plant an olive tree
In milder regions: Plant in very well-drained deep ground in April or May, in a sun-baked sheltered spot. If your soil is on the heavy side, either improve drainage by adding lots of sharp sand or plant in raised beds. Fertile soil is also necessary if you want the tree to fruit well.
In cooler regions: Olives can withstand short periods of cold (down to -10°C), but to err on the safe side, grow in pots, so they can be overwintered under cover. Plant a compact form (such as 'Arbequina') with a mix of loam-based John Innes No 3 compost and sharp sand, in a pot with drainage holes, and sit it on a plant caddy, so that it can be wheeled indoors.
How to grow an olive tree
Sunbathing: In the UK, olives fare best in milder regions, where they are most likely to fruit. They demand as much sun as possible, so a south-facing spot is vital.
Shelter: Plant in a site that is shielded from cold winds, and avoid frost pockets. In cooler regions, it's usually best to plant your olive in a container and move it under cover before winter; if you want to plant it in the ground, wrap it in horticultural fleece in late autumn.
Moisture: Olives are extremely drought tolerant, but will require watering until they are established, and older trees benefit from watering during hot, dry weather. They hate sitting in waterlogged soil, so add a generous amount of sand upon planting, if your soil is not already well drained.
Food: If you want your tree to produce fruit, it will need a moderate amount of nitrogen-rich food during late spring or summer. Many olive growers mulch with sheep manure, but chicken manure is also a good source of nitrogen.
Elbow room: Olives appreciate breathing space, so ensure the ground around them is clear of other plants, or, at the least, clear of excessive vegetation.
Aeration: Olive growers scratch the earth around their trees in spring to aerate the soil and lift weeds.
Pruning: There are 1,001 ways to prune an olive. In Tuscany, they religiously shape them into squat, short, bushy trees with one wide trunk. In Provence, the olives are taller, with a trunk that grows into three main branches and enough space to allow a bird to fly between them. And, in Morocco, some farmers don't prune at all. Most growers agree that olives like a haircut and produce more fruit and better fruit as a result. The cutting stimulates growth, more light reaches the plant, and fruit picking is less of a battle. Do it in spring or autumn, focusing on the removal of wood that casts shade, crosses other branches, and has already fruited. Avoid cutting the young, healthy growth, upon which the plant will produce its next crop; take particular care not to damage the tips of those yet-to-fruit stems. Remove the shoots that the plant throws up around the base from its roots.
Harvesting: In mild parts of the UK, olive trees may produce fruit, which can be harvested green in the autumn or black in winter. Olives must be prepared for eating to remove their bitterness. There are a million approaches to this . . . each Mediterranean village has its own method. Score autumn's green olives lightly with a knife, then soak in water for 1 to 2 weeks (change the water every 1 to 2 days); next, brine them (in sterilised jars of salty water) for 2 to 6 months; add whatever you wish to the brine, such as vinegar, green chilli, or lemon.
