General Information on Growing Olives
Ancient olive tree at Pont du Gard in France, pictured in 2008.
Hardiness & Winter Protection
Firstly, it should be said that there are many different cultivated varieties of olives and most are very hardy although some need protection.
Are olive trees hardy in the British Isles?
Although not traditionally regarded as a hardy tree in Britain, olives are known to be growing outdoors successfully in various parts of the country, north and south. In fact the oldest olive tree in Britain is now over 100 years old and fruits in decent summers. Olea europaea 'Peace' is a very large-leaved form and is particularly vigorous which I think that has a lot to do with its success in growing outdoors in various parts of Britain. Its large foliage enables the plant to photosynthesise efficiently and therefore it grows quickly upwards as well as putting its roots down and away from the frost zone at a young age. It also means that the stems fatten up rapidly so it can become strong enough to stand cold winter winds at a young age.
The best chances of success will be by planting your new tree directly in the garden in the spring to summer or planting into a much larger pot in good compost. All evergreen plants in outdoor containers can struggle in severe freezing weather, including some very hardy plants like rhododendrons. If the pot becomes frozen day and night and a breeze is blowing, the plant will continue to loose water through its foliage which cannot be replaced as the water in the pot is frozen solid. Consequently, it will start to use up all the spare moisture in its leaves to survive. Once all that is gone, the leaves are sacrificed as a last desperate act of survival. Container grown olives will behave in the same way and the pot they are growing in should be kept wrapped in severe weather (usually December to February) for the benefit of keeping the exposed roots from freezing. If you have a very tender variety of olive, it must be protected indoors or in a frost-free greenhouse.
When it is finally planted outdoors, choose a sunny place protected from the east and northerly winds. If you have clay soil, you should improve the drainage with plenty of gravel at planting. You can expect flowers in the early summer which will develop fruit, but do not expect the fruit to ripen. Even in hot Mediterranean climates the fruit are not harvested until November or later. The summer of 2006 was hot enough for fruit to develop on some of my trees. Sadly, we still need much more sunshine in Britain before a regular harvest makes it anywhere near the kitchen!
Olive trees have been gaining popularity in Britain in recent years as we have been having consistently warmer winters and there has been an increased realisation have mature trees are quite tough. However, one of the most asked questions is "When can I expect to pick my own olives." Trees can fruit quite easily but the fruit will only ripen in a good summer. So, rather than expect a regular crop you are best taking the approach of 'if it fruits it's bonus'! I have had mixed reports of olive trees producing fruit in the UK and much depends on your locality, soil, shelter etc. But much more depends on the particular variety you are growing. Unfortunately, due to the high demand for plants in recent years, there has been an influx of various unnamed varities arriving into the British Isles, mainly from Italy and Spain, some of which seem to produce fruit and others which don't. I have had some fruit on some of my plants as young as two-years-old. In good summers, the fruit have even turned from green to black. Like many other plants, olives seem to produce more flower when grown in a pot, probably as this restricts the roots. But good flowering then has to be followed by a good summer for any chance of fruit ripening.
There is still much to learn about growing olives in this country and I shall be doing further work on this over the coming years.
Processing the Fruit for Eating
When an olive tree produces ripe fruit, it is not possible to pick it and eat it immediately, as the fruit is far too bitter. They must be cleaned regularly as part of the processing to prepare them for the table. As I understand it, there are various ways of doing this. Basically, having picked the ripe olives, they should be laid in trays of clean water. The water needs to be changed every two or three days until the olives no longer taste bitter. This may take a month or more. Fresh or salty water can be used although I believe the process is quicker when using saline water but the flavour of course will be affected. Finally, the berries can be stored in jars of fresh or salty water and kept in the fridge, or preserved in olive oil which can be flavoured in any number of different preferred ways.
Making Olive Oil
If you are fortunate in having your trees fruit, then it is far easier to produce your own olive oil than processing the fruit for the table. Simply gather your ripe fruit, crush them using a grindstone (which of course we all keep at the back of the garage!), and then squeeze the juice through a press (another everyday object!) Your oil is now ready for use and will initially appear very green. The colour quickly fades to a more golden yellow but its eventual colour will depend on the variety used. Incidentally, it takes about 4.8kg of olives to produce a litre of olive oil. So, what are you waiting for, get bottling and please let me know how you get on!
Some of you may be interested to know that one British farmer is hoping to grow olives commercially in the UK. Mark Diacono has planted 120 olive trees on 17 acres near Honiton in Devon in the last few years. He is hoping to be the first to produce a commercial crop of olive in this country. Interestingly, I have been told of another farmer trying to beat him and also of a Greek family living in London who are already harvesting a small crop from their olive tree(s) at their London home and processing them for sale. If you know any more about this lead, then please do make contact with me. So there really could be a hope for all of us.
Ancient olive trees at Pont du Gard in France, pictured in 2008.
Today there are over 1,000 named varieties of European Olive. Some are hardy and others need winter protection. All will produce an edible olive under favourable conditions, some of which are best harvested when green and others when they have turned black. Even in warm countries, a cold winter can finish off a potential harvest. Many modern varieties are now being bred for colder climates and commercial olive production has moved away from the traditional Mediterranean heartland to new places around the world. Some of the most productive modern groves are now in North and South America, South Africa, Australia and New Zealand.
To order an olive tree please click here.
Caradoc Doy also gives an interesting illustrated talk about olives, for more information please click here.
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Last updated 5th February 2016