Mediterranean Garden Society

Olive Cultivation

The photograph at the top of this page shows olives harvested and ready to take to the mill (Photo Yvonne Barton)

The most popular article in the MGS journal, The Mediterranean Garden, has proved to be one about pruning olive trees. It seems that gardening in a Mediterranean country goes hand in hand with growing olives – from planting a new grove to tackling one or two neglected trees. So here in their entirety are two articles about olive cultivation which have appeared in TMG.

Olive Oil Production by Brian Chatterton
From The Mediterranean Garden No 34 July 2003

Organic Olives by Chevrel Traher
FromThe Mediterranean Garden No 47 January 2007

For additional reports and articles on this subject please check out the (non-responsive) MGS Archive.

Olive Oil Production

by Brian Chatterton
From The Mediterranean Garden No 41 July 2004

The production of olive oil is a mystery. Unlike vines where teams of pickers or large machines bring in the vintage, the picking of olives is an inconspicuous operation. Pruning is the same. Vines are transformed from a tangled mass of twigs to neat pared rows of almost identical vines. One rarely sees the olive pruner at work. Perhaps there is a ladder propped against a tree and one sees some prunings on the ground before they are burnt or mulched. It would be a mistake to be fooled into believing that this is a night time operation carried out by elves. In fact the classic olive grove is the result of care and attention over many years. The olive trees in Umbria and Tuscany are not by any stretch of the imagination a natural landscape. The untended olive is an untidy bush and it is only through pruning that it has form.

The Italian olive oil industry is an eclectic blend of the traditional and the modern. While the traditional techniques receive the greatest attention in marketing, the reality behind the scenes is often the most modern technology. Landcare in the olive grove has been slow to adopt more modern ideas. Most Italian olive groves are cultivated in the spring to kill the weeds and reserve the moisture for the tree. Over the years the fertility and structure of the soil is destroyed by this excessive cultivation. Heavy rainfall runs off and carries the soil with it. This problem has been reduced to a limited extent by terracing but the basic structure of the soil remains a disgrace. Some growers cultivate the soil in the autumn as well as the spring in a vain attempt to break open the soil and allow more rain to penetrate; I say "vain attempt" because cultivation can be effective for a few weeks but over the years the extra cultivation is even more destructive of the soil structure.

An olive grove in late spring on the Mediterranean island of Rhodes, covered with asphodels and annual wild chrysanthemums. (Photo Alisdair Aird)

Abandoned groves
Today many olive groves have been abandoned or at least are no longer cultivated in this destructive manner. More environmentally aware olive growers have allowed the grass to grow back and provide protection for the soil against erosion. The easy management option is to go through the grove with a mower or better a trincatore or mulcher in late spring and mulch down the grass and olive prunings. This will keep the grove tidy, reduce the fire risk and leave the ground reasonably clear for the autumn picking. If you have your own equipment for mowing or mulching you can mow the grass two or three times over the spring period. Keeping the grass down more frequently will encourage the growth of naturally occurring clovers, medics and vetches that are shaded out by the tall grass. These legumes fix nitrogen from the air and add fertility to the soil but are suppressed by grass. To encourage the legumes further, it is a good idea to apply some phosphate fertiliser during winter. The phosphate fertiliser and nitrogen produced by the pasture legumes will fertilise the olive trees.

If your grove is still cultivated or has only been abandoned over the last five years, very little herbage of any type will grow. The cultivation over decades has not only destroyed the structure of the soil but also the reserves of seeds in the soil. In these circumstances you can speed up the recovery process by sowing some medic and clover seed. For those living in Italy, these seeds can be ordered from your local consorzio who in turn will need to contact a seed merchant in Sardinia who specialises in seed legume mixtures; readers elsewhere will find their own local suppliers.

Summer is the period when little happens in the olive grove. I have many enquiries from Australia and New Zealand from growers wishing to claim tax relief on their European holidays by including a study session on an Italian olive grove in summer. I reply that this would be as interesting as watching paint dry and about as instructive.  While summer is a period of little activity for the grower, the dreaded olive fly can be munching into your olives. The olive fly is a tiny midge that lays its eggs on the olive during the summer. The eggs hatch into grubs that burrow through the olive. The tell-tale sign is tiny air holes and of course if you break open the olive there is the little grub. The olive fly is a permanent problem at low altitudes as the eggs over-winter in these warmer zones. At higher altitudes the eggs are killed by the cold and the fly must re-infect each year. We have never had any olive fly damage in our grove which is at 550 metres. The grubs eat the olives and reduce the yield but they also allow mould to enter and this can give your oil a mouldy taste. The most popular form of control is traps. The difficulty is that the flies are spread from property to property and must therefore be controlled by the collective action of many growers. I would suggest that a small contribution to a group scheme is a cheap and effective means of control.

The other great hazard of summer is hail and there is nothing one can do to avoid that. While hail is one of the many hazards of the long-suffering olive grower, the late summer thunderstorms are welcomed for their rain. The olive starts to produce oil in September and October in considerable qualities and the trees benefit from rain at this time. 

By the end of summer herbaceous plants in the Mediterranean olive groves are parched dry, but the deep-rooted olive trees still find the moisture they need to stay green and ripen their fruits (Photo Alisdair Aird)

Time of picking
Picking in our zone begins in November when all the summer visitors have returned to their heated city apartments. The date for picking the olives varies from year to year but only by a few days. This is quite different from the grape harvest and is not determined by the same criteria. Traditionally, in our zone the olive harvest began on 25th November or St Catherine's Day. Olive growers in other parts of the world such as Australia who are without an olive-growing tradition find the idea of picking on a Saint's day a fascinating piece of folk farming that has no relevance in a modern scientific world. Scientific research does support the idea of a fixed day, if not precisely 25th November. The reasoning goes like this. The olives accumulate large amounts of oil in September and October. In November the rate of accumulation slows as the days become cooler and shorter. The olives begin to change colour but this is of no significance as green olives make the best oil with the most flavour. In December oil accumulation stops and the olives begin to fall to the ground. They fall slowly at first but the rate accelerates week by week until the losses are very substantial. The date you start is determined by when you will finish. This may sound rather strange but if the olives fall on the ground they are wasted. Not only is it unbelievably laborious to pick up fallen olives but they will ruin your oil as they have started to break down and have high acidity. No more oil is being produced in December and the oil you already have is falling on the ground. It is obvious that you should try to finish the harvest before there are too many olives lost on the ground. One works backwards. The last two weeks in November probably have the best combination of high oil and low fruit loss. Further back in the first half of November there is virtually no fruit loss but less oil will have accumulated in the fruit. During the 15 years we have been growing olives we have noticed that the harvest has become earlier. Growers are more interested in quality than quantity and the early picked olives have more flavour. We usually begin to pick our olives in the first or second week of November, that is, about two weeks before St Catherine's day. These are all dates for our zone. In your area picking could be some weeks earlier or even later. Friends who grow olives in the Chianti area, for example, pick their olives two weeks before we do. The same principle applies of a fixed date that only varies by a few days from year to year.

The oil percentage
When you are at the frantoio or oil press waiting for your olives to be pressed all the talk is about the oil percentage. Mine went 14%, what did you get? The old-timers will reminisce about the harvests in their youth when they got 20% and even more. They picked late – well into December and even January. Don't be fooled. They may have got high percentages of oil but they did not get any more oil as so many olives had fallen on the ground. If they picked them up the quality would have been very poor indeed. The reason for the late picking was the slow pressing. The frantoio could not handle the crop and the olives were left to wait in the loft over the frantoio – sometimes for weeks until they were mouldy. Given that choice, it was better to leave the olives on the tree until time was available at the frantoio. Oil percentages vary by as much as 5% from year to year. They are therefore useless as an indication of maturity. You can delay harvest until you have achieved a certain target oil percentage but you would be foolish to do so as many olives may have fallen on the ground. You will have a lower yield in spite of the higher oil percentage and the quality will also be poorer.

Nets placed around an olive tree whilst picking using a mechanical picker (Photo Yvonne Barton)

How to pick
We have now become such an urban society that old rural skills are forgotten and despised. It is thought that any fool can pick grapes or olives. Having picked many hundreds of tonnes of grapes myself over many years, I know that this is not true. I continue to marvel that amateur pickers can pick so few grapes and yet apparently look busy. No doubt our local contadini think the same about my olive picking. The most important thing is to have good olives to pick. Even a veteran Italian picker will pick very little on unpruned trees where the few olives are scattered all over the tree. One needs a net under the tree to catch the fruit. In the past they used many types of material but I recommend a proper olive-picking net made from knitted nylon that absorbs the energy of the olive when it drops and reduces the amount of bouncing and rolling. On a really steep slope you will still need to prop up the net. The nets come in all sizes. There is no point in dragging a huge net around small trees, but on the other hand the net must be big enough to catch all the olives. For mature trees a net of between 6 and 8 metres square is used and for young trees one of 4 metres square. The picking action is to pull your fingers down the twig and strip the olives off without the leaves. One can also use a small rake.  Most small growers still pick by hand but machines are becoming more common. The only machine worth considering for the small grower with a few dozen trees is the electric one run from a car battery. I have no personal experience so I cannot recommend them. When the olives have been picked on to the net you roll them into a corner and pick out the twigs and leaves with olives attached. Do not worry too much about the other leaves as they will be removed by the vacuum at the frantoio. Where olives and leaves are still attached they will go through the cleaner into the press; as it is better not to have leaves in the oil, try to remove most of them at the picking stage. From the net they go into crates. The crates have mesh sides to allow air through. Good air circulation will reduce the chance of mould. Do not use solid-sided crates for this reason. In the past the olives went into trays and were then transferred to sacks for the journey to the frantoio but this involved pointless double handling. The olives were often squashed in the sacks.

Crates of olives ready to go to the mill (Photo Yvonne Barton)

How much do olives yield? How long is a piece of string? The bottom of the scale is easy – nothing. Unfortunately that is quite common. Our best trees yield 40 kg each and have on rare occasions yielded more, even as much as 60 kg. We have seen irrigated olive trees in Tunisia that yield 400 kg each. Over the whole of our grove we average 8 to 10 kg a tree. If the oil percentage is 14% this translates into a little more than one litre of oil per tree.

Leaves removed from olives at the mill(Photo Yvonne Barton)

To the frantoio
Fifteen years ago when we first started to pick our olives all the local growers took their olives to the frantoio at the end of the harvest. Naturally we did the same. Since then we have come to realise that olives lose their flavour if they are stored for two to three weeks. The rule of thumb I learnt from an expert at the University of Perugia is that half the flavour is lost in a week and another half of what is left in another week. Given that we pick for a couple of weeks, that is more that we can afford to lose. We now try to take the olives to the frantoio every three or four days. That means they are on average stored for only two days. If we are picking good trees and are not interrupted by rain, snow or fog we can pick 80 kg of olives a day on good trees, or about 300 kg in four days. This is about the minimum amount our frantoio will take as a separate batch but the rule in each frantoio varies. You will need to balance the amount needed for a batch against the time it takes and whether you can work with a neighbour to form a bigger picking team. The olives are pressed at the frantoio; and most presses are now able to keep each batch separate so you take home your own oil and gloat over it. Quality is more important for the small grower than for the commercial one. For the commercial grower it is a question of costs and returns. For example, mechanical picking is carried out later than hand picking because the fruit are too difficult to detach by shaking. Late picking by machine may be cheap but the quality of the oil is lower. For the small producer the objective is to produce the best possible oil for your own use in sufficient quantity for yourself and some friends. The quality is determined overall by the variety of olive tree, the soil and the climate. The main ways of improving the flavour within these constraints is to prune well, to pick early and to take your olives to the frantoio every few days.
© Brian Chatterton

Organic Olives

by Chevrel Traher
The Mediterranean Garden No. 47 January 2007

Near Canakkale, 9 km from Troy and across the Dardanelles from Gallipoli, I run an olive grove of almost 6,000 trees on calcareous soils, which forms part of a 150 Ha organic farm. The trees are mostly elderly, dating from before the exchange of populations between Greece and Turkey in 1924, and have survived since then on a regime of neglect and picking-by-beating. From time to time some of them have been butchered in the name of rejuvenation (or ‘pruning’), and the general condition is poor. Yields are variable and currently average around 10kg per tree, which, if you know your olives, you will realise is pathetic (optimum yields should be approximately 45 kg per tree – more than four times what we are getting). 
The trees were last sprayed for olive fly in August 2004. The decision to turn the land into an organic farm was taken in November 2004, and the trees are therefore ‘in conversion to organic’ until the end of the 2006 crop – after which they became fully organic olives.

The great threat to olive crops being the ubiquitous olive fly, the priority was to instigate a management programme which would deal with this minute but hugely threatening pest. For control of the olive fly we chose to use the Spanish olive fly trap. This consists of a clear plastic (PET) 1.5-litre bottle, into which holes of 5mm diameter are drilled around the top part (we use a soldering iron for this, with a metal template which fits around the top of the bottle as a guide – and to prevent soldering ones’ fingers). These holes are for the flies to come into the trap. The bottle is then filled with 1 litre of ammonium bicarbonate solution, the cap screwed back on, and each tree gets a trap. We hang them with a plastic-coated steel wire hooked around a convenient branch in the shade. The flies simply adore the delicious scent of the solution inside the bottles (it smells something like lavatory cleaner to us humans) and fly from miles around in search of the source. Once inside the bottle, they can’t find their way out again, because all of the attractant smells are inside (and they are quite busy drowning in the solution).

As for results, this is a debatable issue. The olives picked in 2004 were riddled and pockmarked with olive fly damage – despite the fact that they had in fact been sprayed! The olives picked in 2005, after a season with fly traps, were 95% clean. I wonder if this was due to the success of the fly traps, or whether it was the absence of pesticide which enabled the population of olive fly predators (whatever creature eats olive flies) to multiply and hunt them down. The fact is that although our traps caught many olive flies they also trapped many other insects, some unidentified, but the overall numbers were smaller than we expected. If anyone is interested in studying this subject with us, he or she is most welcome. 

Olive blossom in Umbria, Italy (Photo Yvonne Barton)

With the fly issue more or less under control, the next critical factor for olives is water. We don’t expect rain in Canakkale from April until November or December. The critical issue for our particular trees is that the last rain falls before the flowers can open, and the first rain in the autumn is usually after (or during) harvest. The local people tell us categorically that olives must not be watered. However, the truth is that though olive trees can survive drought, they do like a drink now and again (don’t we all…). So we water 6000 trees during May and June. It takes 6 weeks with 4 ladies working 6 days a week, and we give approximately 100 litres of water per tree, although larger trees get more. In other words, 600+ tons of water. The critical factor about watering in May is that if the trees are irrigated at the point of fruit-setting (between flower and fruit), it encourages them to ‘set’ a larger quantity of fruits per tree. In August, we repeat the whole process all over again. The August-September watering encourages swelling of the fruit. Once again, the timing is important: too early and the water is wasted; too late and the oil content is lowered. With so many trees, and such a long period thus required for each operation, some trees get watered too early and some rather late – but the overall effect is to increase the total tonnage of fruit, which is beneficial.

During 2005 none of the trees were pruned – the weather was bad, and we were too busy doing other things… But in 2006 we started a 5-year programme for pruning the trees. This year, only ‘escapees’ were cut – two or three branches per tree. These are the branches that are rising vertically upwards and out of the tree canopy. They are too high up and difficult to pick, and their removal allows more light penetration into the body of the tree. Four boys with chainsaws and hand tools cut and collected approximately 12,000 olive branches in 28 days, working flat out. The net result from this first phase of the programme is to bring down the overall height of the canopies, which will make picking that much easier. The second phase next year was thinning the bunches of new growth, singling out a few strong leaders for the future. During the third year it was again top-growth which was reduced, and so on, until we achieve happy and contented, conveniently shaped and sized olive trees. Insaallah, as the locals say.

As for climate, in Canakkale we are borderline for olive-growing. Once every 100 years or so, temperatures reach minus 12 degrees Celsius. Once every 50 years or so, statistically, temperatures reach minus 6, and temperatures of zero to minus 4 are expected routinely every two or three years. The winter of 2003 (before we started) was a 100-year statistic. 185 trees were killed during that winter on this particular plot, all in one field which is fairly flat and low-lying, and seems to have acted as a cold-sink. We cleared the stumps to plant apples and other fruit trees. The winter of 2004 was a 50-year statistic. Some trees lost the ends of their branches.  The winter of 2005 was a 100-year statistic again (bring on global warming!) with a low one Friday night of minus 12 degrees. We didn’t lose a single tree – twelve 20-ton truck-loads of bark mulch, and any other mulching materials which could be found, had been spread around as many trees as possible, as a thick mulch. Perhaps it helped – who knows? Or perhaps the fact that we are not ploughing the ground, but rather trying to encourage a natural meadow around and among the trees, meant that the weed cover trapped sufficient snow to protect the trees from freezing. Another opportunity for a research project, perhaps?

Previously, almost the only management technique applied to these trees was routine ploughing of the entire soil area. In my view, this was a diabolical approach – removing the vegetative ground cover, exposing the soil to wind and water erosion, increasing the evaporation of soil moisture content, depleting soil condition and resources, causing damage to the roots, and destroying the natural habitat for any creature which might otherwise have taken part in the local ecosystem. The stories in the village that there is treasure buried on this land (by the Greeks) may also have something to do with this practice!

The new approach of maintaining the vegetative groundcover as a meadow system is radical indeed: no more digging for treasure, for one thing. The idea of mulching each and every tree with a 10cm thickness of wood chips is further evidence of our new-fangled madness – but add to that the hanging of plastic bottles in the trees, watering twice a year and harvesting by hand (no beating), and you begin to see how and why the villagers were convinced of my complete craziness. This year, however, I noticed that in one field on the other side of the valley the olive trees had been mulched with straw and compost – so the crazy ideas are being watched and copied, by at least one person.

Harvesting is done entirely by hand. With 40 workers and everyone else who could be mustered it took two months in 2005. A lot of cajoling of the hired help, picnics in the fields, getting caught in the rainstorm: it all adds up to the fact that we had a lot of fun amid the hard physical labour. We plan to make the next harvest even more fun, and to invite as many people as possible to come and join in the experience for a few days each – having some ‘visitor’ pickers seems to encourage the hired help to work more efficiently!

The management of all these issues ultimately leads to one overall objective, that of increasing the overall yield. If we can raise the average yield to 25 kg per tree within 3-5 years, this will be a success! At the same time, regular and careful management to reduce the biennial periodicity of fruiting will also benefit the project. In the future I also hope to find others who will join the team here and take an active part in the analysis of the efficacy of our efforts, in order to create effective guidelines for future programmes.
© Chevrel Traher

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