Olives for Extra Virgin Olive Oil and Pickling
Olives and the resulting extra virgin olive oil are our main focus.
Below is a little information on the olive varieties we have and on growing olives for those that are interested.
Photos from our 2009 picking can be seen here
What is "Extra Virgin Olive Oil"?
First the bad news - there is no legal definition of olive oil standards in New Zealand, so the supermarkets can and do sell what they will marked "extra virgin olive oil". Further, the names are misleading.
The IOC (International Olive Council), a northern hemisphere dominated organisation, sets the international rules, but we don't have any enforcement in New Zealand.
Within New Zealand, Olives New Zealand has a tighter version of the IOC standard, but it is voluntary and assessment costs are significant for a small grower. Products that have applied for and meet this standard will bear a small red sticker to that effect.
In order of qualtiy, starting with the best, olive oils are mostly graded as follows:
- Extra Virgin Olive Oil - leaving aside the issue of what is an "extra virgin", this is supposed to be the best oil. The IOC and Olives New Zealand lay down specific chemical and taste panel criteria for this grade. Don't expect that supermarket oil to meet them. New Zealand oil, including our own, usually meets these criteria easily.
- Virgin Olive Oil - Not typically seen in New Zealand, this is first (virgin) pressing oil that doesn't make the "extra" grade.
- Pure - Pure? - yeah right. Well I guess it is all olive oil, but don't ask how they got it! Avoid - leftovers, second pressing, heat and chemical extraction territory.
- Pomace - Last and least. Pomace is the sludge left over after pressing. But with a little bit of heat and maybe a few chemicals we can get the last bit of oil out.......avoid, avoid, avoid!
Olive Trees on our Grove
The Wairarapa region of New Zealand is on average a cool climate for growing olives. While summers are typically dry, yearly rainfall is, for olives, quite high.
These factors have influenced our olive tree choice. We grow many of the popular varieties found in the Wairarapa:
Frantoio
Our dominant Tuscan variety. Grows well, crops well and consistently. Medium or slightly below medium size olives, not the easiest to pick. Is prone to Peacock Spot (a fungal disease mainly of the leaves) and occasionally the tree can be hurt by a bacterial disease commonly called "Bacterial Blast".
Leccino
Our second Tuscan variety. Very strong grower so needs more pruning. Medium sized olive.
Pendolino
We have a few of these primarily as a pollinator for the Tuscan trees. As you might guess from the name, has a tendency to droopy branches. Medium or slightly below medium size olives.
Barnea
An Israeli cultivar developed from the Kalamata variety. Originally believed to be the best tree for both here and some other parts of New Zealand, many were planted, and it is the most populous tree on our grove. However, very strong foliar growth, erratic crops - at least when young, and a tendency to let people know when conditions are not perfect (e.g. turning a yellowish hue when diseased or lacking trace elements) has seen many groves pull them out and replace, mostly with Frantoio. We believe this to be short sighted, cropping appears to become more consistent with age, and although they let you know when conditions are not perfect, they are no more prone to disease than other varieties, plus they have a large, easy to harvest olive. The biggest downside is the strong vertical plant growth, requiring regular pruning. The olive oil they produce is typically mild with a slight banana taste, and makes an excellent base for blending. The fruit is large and pointy, like the Kalamata.
Manzanilo
A Spanish pickling olive tree we have dispersed in small numbers among the Barnea as a pollinator. In contrast to the Barnea they are more bushy, and their olives are large and nearly spherical.
Picual
A Spanish variety. Small trees, comparatively low growth, and consistent heavy cropping make this a rewarding tree. Allegedly copes better with wetter soil conditions than other olives. Prone to Peacock Spot so should be pruned for good air circulation. Medium sized fruit.
Other Varieties
For pickling, which we do as a support product rather than our main product extra virgin olive oil, we have a very small number of Kalamata and South Australian Verdale. Both produce large olives.
Other varieties we don't grow that are common in the Wairarapa include the Greek Koreneiki which produces a great oil but has small, difficult to harvest olives, and Picholene, now used as an alternative pollinator for Barnea.
Olive Growing
Looking After Your Olive Trees
There are routine tasks that must be performed on an olive grove. They include:
- Pruning. Every tree should ideally be pruned every year. See below.
- Nutrition. New Zealand soils typically are short in some trace elements, with Boron being of most significance to olives. We have soil sample and leaf samples analysed every second year to track Boron and some other trace elements and use foliar sprays to compensate for the deficiencies.
- Harvesting around the end of May into June. Actual timing varies year-to-year depending on how the olives have ripened.
- Irrigation. Olives are well adjusted to surviving dry conditions but if you want good harvests in a dry year then a little extra water at the correct times is a must. We use drippers under each tree so as not to waste water.
Olive Pruning
Pruning has the following objectives:
- to keep branches from drooping to the ground (skirt pruning) where disease infection can occur
- keeping the height manageable (for spraying and manual harvesting)
- prevent the trees becoming dense bushes which would lead to retaining moisture and so promote disease.
- opening up the middle of the tree to light to promote a more uniform crop and ripenning.
- to counter any tendency to biennial (two yearly) cropping
Always prune in dry weather, regardless of the time of year. Rain can potentially infect new, open cuts.
There are many views on when to prune, so remember - no one is right! And often for smaller groves with no full time workers it comes down to whether there is even enough time in the year to prune all the trees.
Summer pruning is favoured by some as the normally driest time of the year. This suppresses bacteria and fungi. Winter pruning is favoured by others as the cold of winter supresses bacteria and fungal growth.
From a crop point of view pruning after harvest in winter will have the least direct impact on flowering and fruit. If you prune in summer you will be directly pruning some of your crop.
For the home gardener with one or two trees, you can prune when you like - just do it when it is dry.
We like to use an anti-fungal sealer on any large cuts. While many people don't bother with this, we see as being like using an antiseptic on a cut finger. If you cut your finger and take no special care, you will probably be OK, but if you put antiseptic on the cut, that "probably" becomes almost certainly.
If you use a sealer, the most important place for it is around the edges of the cut, where the tree's growing layer is.
To counter any tendency to biennial cropping the theory is that how hard you prune will affect how the tree responds. If you had a poor crop, so expect a big crop next year, then prune more severely. This should cause the trees to respond by putting more energy into branch and foliage growth next season. Conversely, if you had a big crop, prune light so the trees are not so encouraged to branch and foliage growth.
Olive Pests
Leaf Roller caterpillars were significant when the trees were first planted, but we have never needed to spray. As the trees get larger, the number of caterpillars per tree does not seem to grow bigger and the damage caused becomes insignificant.
Birds such as Starlings and Thrushes eat or attempt to eat a fairly consistent amount of olives every year. This can be alarming early on when crops are small and are nearly destroyed by the birds. As the crops increase over the years, the percentage lost to the birds decreases to the point where it is not usually a major problem.
Beyond that, hares damaging the trunks to mark territory, and rabbits digging around the trunk are the only other pests of significance.
Frosts are a problem around harvest time, with smaller young trees the most vulnerable. If the olives get badly frozen, cell damage occurs and the olives can become unuseable. Larger trees tend to provide their own frost shelter and are less affected. Keeping the inter-row grass mown short is one thing that will reduce frost severity.
Olive Diseases
The best way to handle diseases is to avoid them. Good grove management by way of pruning, disinfecting pruning equipment during pruning, and good plant nutrition all help. We have only seen two diseases on our grove, Peacock Spot, a fungal disease common throughout New Zealand, and Bacterial Blast, a bacterial disease that we beleive has affected us through the stone fruit trees that were once grown on parts of our grove.
Peacock Spot is the most common olive problem throughout New Zealand, although less so in the Wairarapa region than some more humid areas. It appears as black sooty spots on the leaves that grow in size to become a sooty ring. The tree reacts to a severe attack by dropping affected leaves.
Peacock Spot flourishes in warm and wet conditions. Preventative action is pruning to thin out the foliage to allow better air circulation, minimising humidity within the tree. Severe attacks can be treated with copper based sprays.
Leaf severely infected with Peacock Spot
Bacterial Blast is caused by a bacteria, Pseudomonas syringae pv. syringae. In general, olives are not much affected by it, but it has been more common in the Wairarapa than elsewhere. Fortunately the effects tend to occur more with young trees, and in our case we have only ever seen it in plots where stone fruits were once grown. Copper based sprays can be used to control it.
Trees with Bacterial Blast turn a yellowish hue, and some leaf-tip die-off may occur. If severe, the tree may also loose foliage.
Perhaps not too obvious from this photo, this Bacterial Blast affected tree has a more yellow tinge than the trees around it, and is much less vigorous.