Olives (Olea europea)How well established is this crop?
This crop is relatively new. It has been grown commercially for approximately 10 years. Commercial returns, current growers and some level of regional based research may be available to help those new to this industry.Background
Olives are an internationally traded commodity that has been creating a lot of interest in Central Otago in the past 5-10 years. They are traditionally grown in Mediterranean countries such as Italy, Spain, Greece and Tunisia which between them account for 80% of world fruit production and 85% of world oil production.
Statistics have shown that consumption has been increasing about 1% per annum for olives and 1.5% for olive oil over the past 25 years. This is being driven by the perceived health benefits of Mediterranean style eating habits.
The interest in a New Zealand industry is being driven by high prices being achieved for oil from some of the earliest plantings. This is up to $65/L for oil and compares to retail prices for imported oil at about $10/L. Table olives are too difficult to mature in Otago's climate.
Olives can be susceptible to a range of climatic issues as they grow through a season. In spring late frosts can damage growing tips and frosts in December can affect flowering. Warm summers are needed to grow the fruit. In autumn early frosts can damage fruit before harvest which occurs in late May or even into June. Most varieties need at least 900 growing degree days during the season to ripen the fruit.Winter Chilling and Frosts
Tree damage can occur if temperatures drop much below -8°C, but this does depend on variety.Rainfall and Irrigation
American research has shown that olives require at least 1000mm of water from irrigation and rainfall combined to produce maximum yields.
Most growers use under-tree mini-sprinklers for irrigation. Use 1 mini-sprinkler between 2 trees.
Even though Olives grow into large trees, they still benefit from some wind protection, especially when they are young. It reduces the chance of bruising on the fruit and reduces the drying effects of wind over the summer period.
Most blocks rely on natural tree shelters. A good rule of thumb when designing shelter is to multiply the final height of the shelter by 10. Use that measurement as the distance you position your shelters apart. For example, when using shelter trees that are 6m high you will need shelters 6m x 10 = every 60m.
Olives will grow in most soil types as long as they are well drained. Steep slopes should be avoided if you plan on using any form of machinery such as mechanical harvesters. Friable free draining soils with good organic matter are best for this crop.Fertility
Olives require reasonable levels of soil fertility. Regular soil and foliage tests will quickly identify a deficiency and this can be easily corrected with the addition of fertiliser. Companies such as Hills Laboratories and Ravensdown have a datasheet with the recommended soil and leaf nutrient levels for this crop. See the ‘Contacts’ section at the end of this datasheet.Weed Control
Weed control in olive blocks tends to be quite straightforward. When young trees are planted, plastic spray-guards are put around the trunks. This prevents rabbit damage and allows herbicides to be sprayed right up to the tree. Weeds growing up inside these guards are removed by hand. As the trees mature the bark on the trunk hardens and herbicides can be sprayed on them with no damage to the tree.Varieties
A range of olive varieties are available to the new grower. All of these have been imported and more are coming. Talk to local growers before deciding which varieties to plant. Some of the common varieties at the present time include:
- Leccino – upright growing with good oil content.
- Frantoio – partially self fertile, drooping habit.
- Pendalino – Pollinator for Leccino up to 10% of a planting.
- Picual – Survives most frosts but not fruiting well at this time.
Olives tend to be relatively free of pests and diseases with the exception of root rot diseases on wetter soils. Growing on the right soil type will get around this problem. In Central Otago there is good potential to grow olives and produce oil that is organically certified.Layout
Most olive plantations are relatively small at present but they have all allowed for tractor access between rows. This means spacing rows 4.5 -5.0m apart with in the row spacing of about 4m. Final tree height is anywhere from 4-7m.General Management
Ground preparation is the key to start an olive plantation. Irrigation installation and any drainage work is done before planting. Trees are delivered from the specialist nursery in pots.
Tree rows are usually ripped with a deep blade to free up the soil. Holes are dug and the trees planted and staked, with a spray guard added to the base.
Weed control using herbicides, mowing, spraying and irrigation are needed from this time. Some pruning and tree shaping is also done, generally in the spring. The idea behind this is to open the tree up to light and air movement.
If growing on a small scale hand harvesting of the fruit is recommended. If being done on a larger scale harvest machinery is used. This usually consists of either a whole tree shaker or a limb shaker. Fruit needs to be processed as soon as possible after harvest to reduce the risk of oil oxidation and fermentation.
Table olives are treated by pickling. Recipes for this vary. Oil is extracted by crushing the olives. Extra virgin, virgin and ordinary virgin oil is made by crushing the olives with pressure only. The plant solids left after the extraction process is known as ‘pomace’. This can be further treated with solvents, to extract even more oil.
Because most blocks of olives are relatively small in New Zealand, only limited amounts of machinery is needed. Most growers have a tractor to mow grass and tow a herbicide tank for weed spraying. Harvesting means having labour, buckets, rakes for collecting olives etc. Bins for the fruit and a method of getting these to the crushing plant may require a tractor or truck. Very few growers have their own press due to the cost. They tend to be operated by cooperatives.Returns
It is very hard to put a number on the returns due to the inflated prices currently being received for New Zealand oil. Planting now means you are unlikely to get these returns when trees mature.
When mature in Years 8-10, you could expect to pick 20-30kg of fruit per tree. This equates to 2-L of oil after pressing. A hectare block could hold 300 trees depending on layout and shelterbelts.
If you are thinking of growing olives, contact the Central Otago Olive Growers Association through the New Zeland Tree Crops Association www.treecrops.org.nz
For fertility information contact
Hills Laboratories 07 8582000
Ravensdown Direct 0800 100 123