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- growing olives in New Zealand
- harvesting and pressing the crop
- expected oil yields
- identifying and storing extra virgin olive oil
- health benefits of extra virgin olive oil
- sources of information about the New Zealand olive industry
What is the minimum economic size of an olive grove?
The industry is still at a reasonably early phase of its development and it is not possible at this time to state the number of trees that constitute an economically viable grove. While those with smaller groves are likely to have lower start-up and maintenance costs than those with bigger (say over 1000 trees), it may prove more financially challenging to market the oil as a sole label. For this reason, smaller growers in particular may wish to look at joining or developing co-operative marketing companies. It is very useful to talk early on with other growers about the financial issues involved in olive growing and marketing.
Where are olives grown in New Zealand?
It is possible to grow olives in most regions of New Zealand. Currently, the main producing areas are Northland, Waiheke Island, Hawkes Bay, Wairarapa, Kapiti, Nelson, Marlborough and Canterbury, but there are also smaller numbers of growers in the Waikato, Bay of Plenty, Gisborne and Central Otago.
However, as the ONZ manual, Best Practices for Olive Growing In New Zealand notes, intending growers need to look carefully at a range of factors relating to the choice of site, such as general climatic factors, including hours of sunlight, which decreases as you move south; soil factors; the orientation of the site to the north; micro climates, likelihood of severe frosts, and so on. More detailed information about these issues are discussed in the Manual.
Best Practices for Olive Growing in New Zealand is available only to ONZ members. An account of topics covered in the manual is on the Growing Olives page.
What type of soil do I need to grow olives successfully?
Olives prefer well-drained, stony or rocky soil. Poorly drained soils can result in water logging, root rot and fungal diseases.
What should my spacing be between trees?
Traditional spacing is 6m x 5m or 6m x 6m. A key reason for using a wide spacing is that this contributes to a reduction of fungal diseases in the grove as it means that there is a lot of wind movement between the cultivars. It also means that, once the trees grow, they do not grow into each other. This makes grove management and picking difficult.
What types of olives should I plant?
There are about 10-12 varietals of olives available in New Zealand. You will need to determine, first, what cultivars do best in the region where you have or will have your grove. It is very useful to talk with other growers about the range of cultivars they have in their groves; what they see as the pros and cons of growing these types, and which types do best. Remember, though, that you will need to take microclimates into account in interpreting this advice. Trees that do very well in one grove may not do as well in a grove close by because of microclimatic features.
Second, you need to decide is whether you are planning to produce only olive oil or only table olives, or a combination of both. There are some varietals that are much better for table olives than for pressing.
What type of climate do I need to plant olive trees?
The trees do best in a warm climate with no frost and well-drained soil.
What type of temperatures will olive trees withstand in the winter months?
Olive trees will typically withstand temperatures down to –0.2C. However, if the temperature drops below this, bark splitting can occur and those affected trees can take a long time to recover their vigour. Some varietals withstand lower temperatures than others.
When I prune my trees, how does this affect them?
Pruning is critical to maintaining the health and productivity of the trees. You will find some very helpful practical information about pruning in Best Practices for Olive Growing in New Zealand. Your regional branch is also likely to run pruning workshops for their members.
What types of fertilizers should I use on my olive grove?
It is important that you do not apply any nutrients to the soil until you have done a soil test (recommended time in early spring). The lab will analyse your samples and advise you of: (a) the levels of nutrients already in the soil that are necessary for olive cultivars; (b) what their current levels of availability to the trees are; and (c) what actions you should take to remedy any deficits.
It is good practice to do a soil test annually, as soil fertility changes and fertilizer application rates also change accordingly.
It is important to bear in mind that (a) all nutrition should be targeted correctly, since an incorrect balance can promote vegetation instead of new wood for fruit production; and (b) over-enthusiastic applications of chemical fertilizers result over time in lowered production, nitrate poisoning of the soil, and pollution of groundwater and nearby waterways.
You may also wish to explore organic modes of production, as these operate on different sets of principles and focus on a range of ways other than through the use of chemical fertilizers to build a healthy and productive soil. For information about organic growing, go to the Organics page.
When should olives be harvested?
In New Zealand the variation in climatic conditions mean that harvest times will vary greatly whether the fruit is being processed for oil or table olives. Initially the olive skins are green and as they ripen they change first to a straw colour then port-wine and finally black. The flesh also changes from green in unripe olives to black in over-ripe fruit.
Table olives
Depending on the variety, table olives will be harvested green to straw coloured, when the skins are black and the flesh white or when the skin and flesh are completely black. The olives need to be harvested with care to avoid bruising and ideally, only blemish-free fruit should be processed.
Oil
The recommended time for harvesting is when the fruit is at optimum maturity. This will vary with the climate, the growing conditions and the cultivar, as different cultivars ripen at different times.
Olives do not ripen uniformly on the tree and in the traditional olive-growing regions olives are usually harvested when the skin of most fruit is black and the flesh is violet-coloured half way to the stone. The remaining olives will be either straw or port wine in colour. At this level of maturity, there should be good yields of high-quality oil. In the colder regions where there is risk of early frosts, it may not always be possible to wait for optimum maturity. Olives are sensitive to frost damage and the oil quality will be adversely affected if frosted olives are processed.
Where do I get my olives pressed?
Most regions have pressing companies who contract press for outside growers. Contact the regional chairperson in your region to find out who these people are.
Approximately how many kilograms of olives would be found on an average tree?
There are many factors that determine fruit set on any individual cultivar in any one season. These include the age of the tree; the pruning regime in the grove; presence of disease; and climatic factors, such as the frequency and velocity of wind and rain over the period of fruit set. Some of the established groves are reporting crops of 40-50 kgs. on some trees but they cannot safely predict that they will harvest this quantity from all trees on an annual basis.
How many litres of olive oil could be made from an average mature tree?
It is difficult to state a definitive quantity at this time, not least because different cultivars have the potential to yield different quantities of oil (see next question); fruit set is affected by seasonal variations; greener fruit does not yield as much oil as riper fruit; and rain just before picking also affects the oil yield, as can different pressing practices.
Do some varieties have higher oil content than others?
Yes, there is variation in regard to the percentage of oil from the fruit among the different cultivars. The range is approximately 12-23%.
Is the pit crushed as well?
Yes. Traditionally the entire fruit is crushed.
What is an extra virgin olive oil?
Extra virgin olive oil is obtained from the fruit of the olive tree solely by mechanical means without the addition of chemicals or heat to aid the extraction process. To be classified as extra virgin in New Zealand, olive oil must meet chemical and sensory criteria based on the standards set by the International Olive Council. These are:
Chemical Analysis: The Free Fatty Acid level measured as oleic acid must be less than 0.5% and the Peroxide Value less than 15mEq per kg. The standards for extra virgin olive oil set by the IOC are less than 0.8% FFA and a Peroxide Value of less than 20.
Sensory Analysis: In New Zealand this is undertaken by the Olives New Zealand Sensory Panel. In 'blind' tastings the oils are evaluated for the absence of defects that can arise through poor harvesting and processing, and storage of oil, and the presence of the required desirable attribute, namely fruitiness.
Are there significant health benefits associated with the use of extra virgin olive oil?
Yes, when used as part of a balanced diet, extra virgin olive oil has a number of health benefits. It contains monounsaturated fatty acids and antioxidants that have been shown to play a preventative role in heart disease and some cancers.
How can I be sure that I am purchasing an extra virgin olive oil?
The Olives New Zealand Certification programme provides quality assurance to the consumer and retailer. Only New Zealand extra virgin olive oils displaying the red “OliveMark” can give this assurance. Olives New Zealand follows similar, but tighter guidelines as the International Olive Council in Madrid, the body that controls the standards for olive oil, worldwide. For more information please see Certification on this site.
How should olive oil be stored?
Olive oil is best stored in dark glass bottles or cans in a cool, dark place; the ideal storage temperature is 12° C. Once opened, if it is not used within two or three months, it is best stored in the door of the refrigerator. The oil may become cloudy in the refrigerator but this does not affect it and the oil will clear when brought to room temperature.
What is the shelf life of olive oil?
Unopened bottles or cans of extra virgin olive oil should, if stored in a cool, dark place, keep for between 18 months and 2 years. However, as with all oils, extra virgin olive oil will lose flavour and become rancid over time, so to enjoy it at its best, ideally use it within one year of its pressing date.
Is there a source I can go to for events and other information?
A key source is the Best Practices for Olive Growing in New Zealand. Information on the topic areas covered in this manual is on the home page. You may also wish to contact the chairperson in the region where you have or are considering buying land for a grove.
Who are the chairpersons in the various regions?
To contact a Regional Chairperson email info@olivenz.org.nz
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