Eden horticulturalist Shirley Walker takes a detailed look at the olive tree and shares her tips on how to grow your own at home.
The history of the olive tree
My love affair with the olive began many years ago on the Ionian island of Paxos. I was captivated by this ancient and beautiful tree, brought to the island by the Venetians in the 15th century. The history of the olive, however, stretches back much further and it has become one of the most powerful symbols of the Ancient World.
The olive has been a part of everyday life in the eastern Mediterranean since the beginnings of civilisation more than 6,000 years ago, but began life as a sprawling, spiny shrub in the Levant (present day Syria and Lebanon). Thousands of years of selection and breeding have turned it into the productive tree we know today. The olive is now an integral part of the Mediterranean landscape and the most important economic plant in the region with 800 million trees in cultivation.
Botanical details of the olive tree
In spring the silvery canopy is covered in tiny flowers, like scattered stars, and the swaying branches protect a wealth of spring bulbs and wildflowers beneath, like cyclamen, poppies, field marigolds, purple viper’s bugloss and tassel hyacinths. During the long, hot Mediterranean summer the trees become heavy with fruit, ripening from green to black as the winter approaches.
Olive trees are extremely tough and can withstand searing heat, drought, fire and temperatures as low as -7oC for short periods. I really admire Mediterranean plants because they have adapted over thousands of years to cope with extreme climatic conditions, poor soils and the effects of fire. Many plants, including the olive have the capacity to regenerate from the base when damaged by fire – that’s how the olive came by its name ‘tree of eternity’.
Our olive grove in the Mediterranean Biome at Eden contains some old, gnarled specimens but these are mere juveniles compared with some you find in the Mediterranean region – many are more than 1,000 years old. Carbon dating of old specimens in Lebanon has revealed trees several thousand years old. I find it amazing that these trees have been producing fruit and giving oil since Biblical times!
Growing your own olive tree at home
This wonderful, evergreen tree will add a touch of the Mediterranean to any garden and when I’m working in the Biome I am frequently asked how to care for them. Here are some questions and answers:
Can I grow an olive tree successfully in a container?
Certainly, olives do well in containers. When you buy your tree, pot it on into a larger pot, preferably terracotta rather than plastic and use a loam- based compost like a John Innes no. 3. Add 20% horticultural grit to improve the drainage. Place in a sunny position, keep the soil moist during the growing season and feed with a balanced liquid fertiliser once a month. In winter you can reduce watering but don’t allow the compost to dry out completely.
Can I plant my olive tree outdoors?
Olive trees are tougher than you think but try and choose a sunny, sheltered, well-drained position and plant in spring, after the risk of frost has passed, but before the end of June to give the tree plenty of time to establish before the following winter.
Will my olive tree need pruning?
Olives grow very slowly so don’t require much pruning when young. Container-grown plants tend to grow quicker, so if the canopy becomes dense, remove some of the branches to let more light into the centre. Keep an eye on the shape of the tree and remove any dead or diseased wood.
Will my olive tree produce fruit?
Trees should begin producing fruit at about three to five years old. Most olive varieties are self-fertile but they are wind pollinated so will need to be outdoors when in flower. (We use a leaf-blower to pollinate our olive trees in the Biome!) Olives need a two-month cold spell in winter and fluctuating day/night temperatures to initiate flowering and fruiting, so keep container-grown trees in an unheated conservatory or greenhouse, with plenty of light. Olive trees flower and fruit on one-year-old wood.
What are the best cultivars for growing outdoors in the UK?
- Arbequina is a small tree from Catalonia in northern Spain, with a weeping habit, ideal for small gardens.
Cipressino originated in Puglia, Italy, and is a vigorous tree with an upright habit. Its name comes from its similarity to the Italian cypress.
- Leccino comes from Tuscany, Italy, and is a popular, widely planted variety with an open, pendulous habit. It is easy to grow and will tolerate a wide range of temperatures.
- Picual is an extremely hardy and vigorous tree requiring regular pruning. It originates in Andalusia, Spain.
- Pendolino is a small, compact, weeping form with architectural appeal from Tuscany, Italy. It will need a pollinator to provide fruit as unlike most olives, this one is self-sterile.
My favourite culinary tip
Try pot-roasting a chicken with plenty of black olives, sliced leeks and peppers, rosemary, lemon juice and olive oil.