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Growing Olives

Taken from 'The Olive Handbook' (published by Salsi Pty Ltd), this section contains information about growing olives - from choosing a site, to planting, pruning and picking!

The following should be taken into account when selecting a site for an olive grove.

  • Soil type and drainage - waterlogging kills olive trees.
  • Availability of nutrients in soil.
  • Soil acidity, olives grow best in soils with a pH of 7.0-8.0.
  • Rock will impede infrastructure development such as irrigation trenches.
  • Climate - olives like cool winters and hot summers.
  • Winter frost is necessary for most varieties.
  • Rainfall.

A soil survey is recommended to determine the suitability of the soil for olive production, and possible remedial action.

A soil survey, soil analysis and report from a professional consultant will cost approximately $2500. The survey/analysis should determine:

  • Soil structure and drainage.
  • Soil pH or acidity.
  • Soil fertility.
  • Readily Available Water (RAW).
  • Presence of residual chemicals which may affect future organic registration.
  • Presence of nematodes and fungal spores which affect olives.

The grove design must:

Provide maximum sunlight exposure of the planned number of trees during all stages of growth and at maturity.

Allow for efficient equipment operation.

Tree density

Opinion varies on optimal tree density, depending on variety, soil fertility and grove management. Denser plantings are adopted to give higher yields per hectare from younger trees.

The following should be considered when choosing varieties for the olive grove.

  • Availability.
  • Whether the aim is to produce oil or pickling/preserved olives, or both.
  • Demand for the final product.
  • Compatibility with the soil type.
  • Growth rate.
  • Yield.
  • Is the variety predisposed to alternate bearing.

The following should be considered when purchasing olive trees:

  • Purchase trees from reputable nurseries with good quality control.
  • Trees are generally available at 12 months and 18 months, costing approximately $5 and $10 on site respectively.
  • Smaller trees cost less to transport but are more susceptible to setbacks once planted.
  • Ask the nursery whether the mother stock has been verified as the true variety.
  • Request information on the diseases experienced in the nursery.
  • Orders can be placed year round, but generally orders are placed in January/February for delivery for spring planting in September.
  • A deposit of 10% to 20% is generally paid on order, refunds of the deposit less an administration fee can generally be negotiated.

Olives can be planted in irrigated olive groves year round if winter temperatures do not fall below -5 degrees Celsius. However, planting in Australia is generally done in spring.

  • Complete site preparation.
  • Plant windbreak crop to protect young trees, do not shade grove.
  • Mark out tree positions.
  • Dig hole approx 35cm deep x 20cm wide, do not glaze sides.
  • Fill hole with water.
  • Remove plastic plant bag or pot.
  • Tease out bottom 3cm of roots.

A mature orchard in a 500mm rainfall area will need at least 5 megalitres of good irrigation water per hectare.

Applying one mm of water on to one hectare uses 10 kilolitres of irrigation water.

Important factors affecting irrigation are:

Olives are grown in a variety of soils and conditions. Therefore customised management of tree nutrition is required.

The four tools for optimal nutrient management are:

  • Observation of trees and environmental conditions.
  • Soil and water analysis.
  • Leaf analysis.
  • Recording.

Observation

Visual symptoms should be used as an aid to interpreting soil and leaf analyses:

There are as many opinions on pruning as there are methods. The information provided below is should be used as a guideline only and research should be conducted into the benefits of the various methods of pruning, and pruning requirements for different types of harvesting. Overpruning is common amongst inexperienced grove managers.

First 12-18 months

  • When tree is 300mm to 600mm remove branches which start to grow below 300mm.
  • Branches which grow above 300mm and challenge the leader should be cut in half to slow their growth.
  • Replace slow growing or damaged leaders with a strong fast growing branch.
  • When the tree is between 900mm and 1.2m, remove branches growing from the trunk between 300mm and 600mm.
  • When the tree is 2m, cut in half (head) any branches growing between 600mm and 900mm.
  • Depending on variety, land preparation and climate, development from 300mm to a 2m tree with a 1.2 metre straight trunk required for mechanical harvesting should take from 18 months to 2 years.

  • Changes affecting fruit set start in preceding summer.
  • Sufficient water during preceding summer assists the change from vegetative buds into flower buds.
  • Stress from water shortage, pests, diseases and nutrient deficiency can severely affect fruit development and yield.
  • Flowering usually occurs in September and October, depending on variety and conditions.
  • July and August are critical for ensuring tree is in peak condition.
  • Dry-land trees can have as many as 52% sterile flowers, compared to suitably irrigated trees with 7-8%.

A general list of pests and diseases of the olive tree is provided. They are not all prevalent in all regions.

Nematodes

  • Several species of root lesion, citrus and root knot nematode can attack olive roots.
  • Nematode attack generally results in reduced vigour and possible stunting of trees.
  • Root knot nematodes cause the formation of galls or knots on the roots.
  • Testing soil samples from the proposed grove site for nematodes is recommended.
  • If root lesion, root knot or citrus nematodes are present, fumigation before planting will reduce the incidence of attack.
  • Nematodes cannot be completely eradicated over a large area and populations will rebuild.
  • Trees with healthy root systems have a better chance of resisting nematode attack.

  • Olives for pickling are usually hand-harvested to reduce damage to the fruit through bruising.
  • Olives for oil are generally mechanically harvested.
  • The method chosen is also strongly influenced by the size of the grove.

Timing

There are six major influences on the timing of harvest:

  1. Whether the fruit is destined for oil production or pickling.
  2. The ripeness of the fruit.
  3. The requirements and availability of a processor.
  4. The availability of labour or a mechanical harvester.

  • Avoid damage which might promotes rapid oxidation and degradation.
  • Equipment required includes:
    • A plastic hand rake (approx $15) or fruit stripper (approx $20).
    • A nylon ground net (approx $50)
    • Fruit storage containers (approx $5 each)
    • Ladder
  • Fruit is dislodged, using a cupped, gloved hand or the rake, into the net doing as little damage to the tree as possible.

Pre-requisites for mechanical harvesting are correct tree spacing (no closer than 8mx5m) and correct pruning. Indicative costs are $3-$5 per tree.

  • Mechanical harvesters can be attached to tractors or are complete units.
  • They can be purchased, hired or contracted.
  • Some machines catch fruit, others dislodge it into a net.
  • Harvesting rates vary from 1-2 trees per minute.
  • Terrain, slope and ground cover affect the speed of harvest, the flatter the faster.
  • Vase shaped pruning is preferred to monoconical to avoid bruising.