By Clodagh and Dick Handscombe
Holistic gardeners and authors who have lived in Spain for 25 years.
The basic needs
To ensure the maximum yields each year, subject to seasonal by season weather conditions, you will need to prune, feed and take precautions against potential pest attacks. We suggest that you use ecological methods and products in order to end up with high quality ecological olive oil.
There are four important types of pruning.
Remedial pruning of neglected olive trees
When we took over a long abandoned olive grove we needed to do a 80 to 90 percent pruning the first year.
Regular winter pruning
In the eight weeks after harvesting it is normal to cut out vertical growth which cannot be trained to grow horizontally or weeping, plus weak, deseased and dead growth. This will help channel sap to last year’s growth on which that years olives will form and stimulate new side shoots on which the following years flowers and fruit will form.
Regular spring pruning
Once the new flower buds can be seen a thinning of crowned branches and none flowering growth is made to stimulate larger olives. Depending on the health of the tree this can be a 5 to 20 % pruning.
Removal of suckers
Suckers often sprout up from the lower trunk and shallow roots surrounding the base of the tree. These need to be removed to ensure all sap flows upwards to productive branches.
The main cutting off is in the winter but they are best trimmed off throughout the year when they first appear. Having cut these off some producers cover the base of the tree to stimulate any further shoots to develop as new roots.
Two types of feeding are beneficial. Firstly a late winter root feed using well rotted animal manures, powdered dried manures or proprietary ecological manures. Secondly ecological foliar feeds in early spring summer and autumn.
We suggest you do not water your olive trees except for recently planted young trees and during freak long dry spells. Olive trees are one of the most drought resistant trees.
There are number of pests that can affect yields and the quality of fruit. The most common are as follows.
The olive moth – feeds on flowers, eats kernels and bore into leaves – spray in spring.
The olive fly – infests olives during spring, summer and mostly in autumn – spray three times for greatest effect.
Sooty moulds and scales on leaves and twigs – Spray with a fungicide in winter and early spring.
Olive knot – small tumours on branches and twigs caused by bacteria entering wounds caused by beating olives off the trees, using hand rakes, poor pruning and hail and frosts – prune out badly damaged growth and stop using canes to knock off olives. Spray with a fungicide if a big problem.
Ecological products are available for each and the most convenient can be mixed together to reduce the number of sprayings required.
The three main objectives of harvesting olives are; Pick when ready for preparing eating olives or making olive oil, to cause as little bruising of the fruit as possible and cause as little damage to the trees as possible. Olives for eating need to picked while still firm. Olives for oil can be picked at the same stage or left to fully swell to maximize the overall yields.
Some high quality producers still pick by hand. We follow and recommend this practice for home production. However most olives are allowed to fall naturally or racked, knocked off with long canes, or shaken off with mechanical tree shakers onto nets and then transferred to plastic boxes which hold 20 kilos. In some areas, to reduce harvesting costs, the ground under trees is laid bare by using weed killers two weeks before shaking the olives onto the ground when they are blown or brushed into heaps for sacking. What is done commercially is obviously driven by the increasing cost of agricultural labour.
Yields can vary from 10 to 110 kilos or more per tree depending on the age health and pruning of the tree, and the summer and autumn sunshine and rainfalls.
Pickling olives to eat
See chapter 78 of ‘Growing Healthy Fruit in Spain’ for our favourite methods and recipes.
Producing olive oil
To extract high quality oil from olives they need to be processed as soon after their harvesting as possible to minimise the onset of fermentation that can spoil the taste of the end product.
The process follows the following process. Riddling to remove leaves and stones, washing if allowed to fall on the ground before harvesting, the picking out of obviously bad olives, milling/mashing the olives to create a paste, pressing of the paste to extract the oil and water and then the separation of the oil from the oil/water mix and pouring into storage vessels. Historically earthen ware storage jars or barrels were used but these days quality plastic bottles or storage tanks are used.
There are four possibilities for the processing of your olives to oil.
- Purchase a manually or power operated mill/masher and press yourself or with a group of friends. Small powered presses cost a little over 2000 Euros for processing 40 kilo batches and 8000 Euros for 200 kilo batches.
- Arrange for a friend or local villager to do the pressing for you on in a historic or new old style press. Typically, a minimum of 200 kilos of olives must be delivered to the mill for you to have your olives pressed alone. Smaller quantities would be mixed with other small batches. Typical processing charges are 20 to 25 cents a kilo.
With be an artisan cold pressing and it may be possible to separate the first extra extra virgin oil from the second phase extra virgin and virgin olive oils which are extracted as the press pressure is increased.
- Arrange for a larger agricultural cooperative mill to process your olives mixed in with those of other growers. The quantity of olive oil you receive will be based on the average litres/kilo for the day or an estimate of the yields of the quality of olives you are feeding in. Charges are about the same as for ‘2’.
Old mills will still use a cold process and you will get good quality extra virgin olive oil. New mills may use warmer conditions to increase the speed and extent of extracted oil and deliver you virgin olive oil. Some mills will use hot water and steam to extract the final oil content from the byproduct cake of solids. This refined oil is of high acidity and is blended with better quality olive oil to produce the less expensive olive oils.
Commercially olive oils are classified in descending quality order as Extra Virgin, Virgin, Ordinary Virgin Olive Oil, Olive Oil, Refined Olive oil, Lamp Oil. The ranking of the first three is on the basis of a number of characteristics including taste smell colour and acidity level.
Olive Oil often includes quantities of Refined Oil blended with Virgin Olive Oil.
The standard maximum acceptable acidity levels are 1.0% for extra virgin , 2.0% for virgin and 3.3% for ordinary virgin.
A good yield is a litre of oil from five kilo of olives. A poor yield from poor olives can be as little as a litre from 7 or 8 kilos.
Bottled olive oil is best stored in a cool dark place. Good quality oil can be stored for many years. It is not usual or desirable to add preservatives. Dick remembers being able to share a thirty year old wooden barrel of olive oil found, covered in encrusted dust in a London wine cellar. It was wonderful oil.
Hope the above and the previous January posting helps you get the most out of your olive trees.
(c) Clodagh and Dick Handscombe January 2012.