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Olive growing guide

Recommended types:

Starter Fertilization

1. Introduction

Greece:
Over 132 million olive trees are cultivated in the country.
Olive oil and olives are key export products.
Greece is among the world’s largest olive oil producers.

Internationally:
Olive cultivation covers more than 11 million hectares worldwide.
Leading producing countries (2024): Spain, Italy, Greece, Tunisia, Turkey.

  1. Olive Oil:
    Rich in monounsaturated fatty acids and antioxidants.
    Used in cooking, pharmaceuticals, and cosmetics.

    Table Olives:
    Consumed directly or processed into gourmet products.
    Key varieties: Kalamata, Halkidiki, Amfissa.

    By-products:
    Olive pits: Fuel for biomass and energy production.
    Olive pomace: Animal feed and organic fertilizer.
    Cosmetic products: Oils and extracts for hydration and therapeutic use.

  1. Olive Oil Varieties:
    Used for olive oil production.

    • Koroneiki:
      The most widespread variety in Greece (about 60% of production).
      Small-fruited, drought- and wind-resistant.
      Produces high-quality olive oil with a fruity taste and low acidity.

    • Athinolia:
      Medium-sized fruit, late ripening (December to January).
      Produces high-quality oil with mild flavor and low acidity.

    • Manaki (Kothreiki):
      Resistant to colder climates and high altitudes.
      Produces oil with a mild, fruity flavor, suitable for blending.

    • Tsunati (Ladolia):
      Cold-tolerant, mainly cultivated in Crete.
      Produces high-quality oil with low acidity and strong aroma.

    • Koutsourelia (Patrini):
      Very productive and resilient variety.
      Produces oil with balanced flavor and high nutritional value.

    Table Olive Varieties:
    Used for direct consumption as edible olives.

    • Kalamon:
      Internationally recognized for its flavor.

    • Halkidiki:
      Large-fruited, ideal for stuffed olives.

    Dual-purpose Variety:
    Produces both oil and table olives.

    • Megaritiki.

Crete: The largest olive oil producing region.
Peloponnese: Renowned for the Koroneiki variety.
Mytilene: Known for high-quality oil and organic cultivation.
Halkidiki: A key area for table olives.

  • Temperature:
    Optimal growth at 15–25°C.
    Tolerates drought and high temperatures up to 40°C.
    Sensitive to frost (<–7°C) during flowering and early fruit stages.

    Humidity and Rainfall:
    Requires annual rainfall of 400–700 mm.
    Resistant to dry and hot conditions but needs irrigation for high yields.

    Soil:
    Adapts to poor, rocky soils.
    Ideal pH: 6.0–8.5.

Drought Resistance:
Thanks to its deep root system, it survives well in water-deficient conditions.

Perennial Crop:
Long lifespan (over 100 years).

High Economic Yield:
Stable demand for olive products and olive oil.

Environmental Sustainability:
Low-input cultivation with limited water and fertilizer needs.

2. Botanical Characteristics and Physiology of the Olive Tree

Deep and branched for maximum water uptake from deep soil layers.
Lateral roots utilize moisture in surface layers.
Regenerative capacity: Ability to develop new roots after injury or pruning.

Trunk: Twists and spirals with age, forming irregular shapes.
Bark: Smooth texture in young trees, rough and cracked in mature ones.
Shoots: Multiple suckers developing from the base of the trunk.

Evergreen: Lance-shaped, 3–9 cm long and 1–2 cm wide.
Green on the upper surface and silvery underneath to reduce evaporation.
Wax coating on the surface (cuticle): Reduces water loss and increases drought resistance.
Leaf lifespan: 1.5–3 years, with gradual renewal.

Hermaphroditic (perfect) flowers: Contain stamens and pistil for self-pollination.
Sterile flowers (male): Produced in certain varieties.
Inflorescence: Formed in clusters (racemes) at the leaf axils.
Pollination: Mainly wind-driven, but also supported by insects.

Drupe (flesh + pit):
The flesh contains 20–30% oil, with the remainder being water and sugars.
Color: Changes from green to purple or black as it ripens.
Pit: Hard, containing a single seed.
Fruit weight: 1–10 g, depending on the variety.

Radical growth and formation of the basic skeleton.
Limited flowering and fruiting.

Gradual increase in fruit production.
Alternation between high (good) and low (poor) yields due to alternate bearing.

Stable fruit production.
Requires proper pruning and fertilization to maintain yield.

Reduced productivity.
Rejuvenation through deep pruning or grafting.

The deep root system absorbs water from deeper soil layers.
The transpiration reduction mechanism limits water loss.
High tolerance to saline soils (up to 4–8 dS/m).

Tolerance to high temperatures (40–45°C).
Sensitivity to frost (<–7°C), especially during flowering.

Slow growth in the initial stage but steady increase after establishment.
Fruit production depends on the accumulation of thermal units (vernalization).

3. Soil Preparation and Planting

  • Sandy loam and clay loam soils with good drainage.

  • Deep soils with high water-holding capacity.

  • Slightly rocky soils with adequate aeration.
  • Heavy clay soils with poor drainage, which cause root suffocation.

  • Soils with very high salinity (>8 dS/m) require special irrigation management.
    • Optimal pH: 6.0–8.5.

    • Tolerant to slightly acidic (pH 5.5) or alkaline (pH 9.0) soils with proper management.

    Addition of lime (CaCO₃) to correct acidic soils.
  1. Deep Plowing (40–60 cm):

    • Breaks compacted layers and improves aeration.

    • Facilitates root system development.

  2. Land Leveling:

    • Enhances drainage and irrigation efficiency.

    • Reduces erosion on sloped areas.

  3. Incorporation of Organic Matter:

    • Compost or manure (2–5 tons/stremma) to increase organic matter content.

    • Improves moisture retention and supplies essential nutrients.

  4. Base Fertilization:

    • Addition of phosphorus (P) and potassium (K) before planting.

Use of sulfur (S) to balance pH in alkaline soils.

Spring (March–April): For areas with cold winters.

Autumn (October–November): For mild climates to ensure better root establishment.

Cultivation System

Distance Between Trees (m)

Distance Between Rows (m)

Plants/stremma

Traditional

6–7

6–7

18–25

Intensive

4–5

5–6

35–40

Super-Intensive

1.5–2

3–4

120–160

    • Planting Pits: 50 x 50 x 50 cm for young saplings.

    • Add organic material and moisture before planting.

    • Place the plant so that the root ball sits 1–2 cm below soil surface.

    • Firm the soil to ensure stability.

Wild Olive (Olea europaea var. sylvestris):
Resistant to drought and Verticillium wilt.

Clonal Rootstocks:
Selected for high yield and specific growth characteristics.

Wind Protection: Use of support stakes.

Irrigation of Young Trees: Regular watering during the first months (1–2 times per week).

Weed Control: Removal of weeds around the root zone to reduce competition.

Application of Fungicides and Insecticides: Prevent diseases and protect against pests (e.g., olive fruit fly).

4. Fertilization

  1. Foliage and Root Development:

    • Healthy foliage for maximum photosynthetic capacity.

    • Strong root system for efficient nutrient and water uptake.

  2. Flower Formation and Pollination:

    • Ensure adequate flowering and reduced fruit drop.

    • High boron (B) availability to improve pollination success.

  3. Fruit Formation and Oil Quality:

    • Adequate potassium (K) and nitrogen (N) supply for uniform fruit size.

    • Enhance oil synthesis for higher fatty acid content.
  • Moderate Nitrogen (N) Requirements:
     Promotes vegetative growth and flowering.
     Avoid excess, which leads to excessive vegetative growth and reduced fruit quality.

  • High Potassium (K) Requirements:
     Improves drought tolerance and oil synthesis.
     Essential during fruit ripening and oil production.

  • Boron (B) for Pollination:
     Crucial for pollination and fruit set.
     Deficiency results in smaller fruits and reduced yields.

  • Sulfur (S) and Magnesium (Mg):
    Sulfur (S): Important for protein synthesis and foliage development.
    Magnesium (Mg): Regulates photosynthesis and energy transfer.

Growth Stage

Main Nutritional Needs

Key Nutrients

Vegetative Growth and Leaf Expansion

Foliage and root development

Nitrogen (N), Phosphorus (P)

Flowering and Fruit Set

Support for pollination and inflorescence growth

Boron (B), Potassium (K)

Fruit Formation and Pit Hardening

Boost metabolism and oil formation

Potassium (K), Magnesium (Mg), Sulfur (S)

Fruit Ripening and Oil Quality

Enhance oil content and stability

Potassium (K), Calcium (Ca)

  1. Nitrogen (N) Deficiency:

    • Symptoms: Leaf yellowing, reduced shoot growth.

    • Solution: Apply 5–8 kg N/stremma early in spring.

  2. Potassium (K) Deficiency:

    • Symptoms: Leaf scorching, lower oil quality.

    • Solution: Apply 6–10 kg K₂O/stremma before flowering.

  3. Boron (B) Deficiency:

    • Symptoms: Empty fruits, poor pollination.

    • Solution: Foliar spray with 100–150 g/stremma before flowering.

  4. Magnesium (Mg) Deficiency:

    • Symptoms: Interveinal chlorosis.

Solution: Apply 2–3 kg MgO/stremma.

Olive cultivation requires a balanced supply of nutrients to maintain foliage development, ensure pollination, and promote oil synthesis in the fruits.

  • Macronutrients (N, P, K, Mg, Ca, S): Cover the fundamental needs of tree growth.

  • Micronutrients (B, Zn, Fe, Mn, Cu): Play a crucial role in specific processes such as fertility, enzymatic activity, and photosynthesis.
  1. Nitrogen (N):
    Role:
  • Essential for foliage development and photosynthesis.

  • Promotes flower formation and fruiting.

  • Regulates amino acid and protein synthesis.
    Deficiency Symptoms:

  • Chlorosis on older leaves and reduced leaf size.

  • Poor shoot and fruit development.

  • Reduced flower cluster production.
    Application Rates:

  • Base fertilization: 6–10 kg/stremma in autumn or early spring.

  • Top dressing: 3–5 kg/stremma before flowering.

  1. Phosphorus (P):
    Role:
  • Supports root growth and flowering.

  • Contributes to energy transfer (ATP) and fertilization.

  • Enhances stress tolerance.
    Deficiency Symptoms:

  • Weak root growth.

  • Reduced fruiting and delayed ripening.

  • Lower oil content.
    Application Rates:

  • Base fertilization: 3–6 kg/stremma before planting or in autumn.

  • Foliar application: 100–150 g/stremma in cases of deficiencies.

  1. Potassium (K):
    Role:
  • Regulates oil quality and fruit ripening.

  • Increases drought and disease resistance.

  • Promotes sugar transport and fatty acid synthesis.
    Deficiency Symptoms:

  • Leaf margin yellowing.

  • Reduced oil content.

  • Poor fruit development and premature fruit drop.
    Application Rates:

  • Base fertilization: 6–12 kg/stremma before planting or in autumn.

  • Top dressing: 4–6 kg/stremma during flowering and fruit filling.

  1. Magnesium (Mg):
    Role:
  • Key component of chlorophyll and photosynthesis.

  • Improves energy transfer and fatty acid synthesis.
    Deficiency Symptoms:

  • Interveinal chlorosis on older leaves.

  • Reduced growth and oil quality.
    Application Rates:

  • Base fertilization: 2–4 kg/stremma as magnesium sulfate.

  • Foliar application: 150–200 g/stremma at critical stages.

  1. Calcium (Ca):
    Role:
  • Improves cell wall structure.

  • Enhances water and nutrient transport.

  • Promotes fruit firmness.
    Deficiency Symptoms:

  • Fruit cracking and deformities.

  • Poor root development.
    Application Rates:

  • Base fertilization: 5–8 kg/stremma before planting.

Foliar application: 100–150 g/stremma during fruit development.

  1. Boron (B):
    Role: Critical for pollination and fruit formation.
    Deficiency Symptoms: Empty fruits and low fertility.
     Dose: 100–150 g/stremma as a foliar spray before flowering.
  2. Zinc (Zn):
    Role: Enhances photosynthesis and leaf development.
    Deficiency Symptoms: Small leaves and delayed growth.
     Dose: 150–200 g/stremma as a foliar spray during shoot growth.
  3. Iron (Fe):
    Role: Participates in chlorophyll synthesis and electron transport.
    Deficiency Symptoms: Chlorosis on young shoots.
     Dose: 2–4 kg/stremma with chelated forms or foliar applications.

The implementation of a comprehensive fertilization program is essential for optimal growth, fruiting, and the quality of olive oil or table olives. The program must be adjusted according to soil and leaf analysis to meet the actual nutritional needs of the crop at each growth stage.

Objective:

  • Strengthen the root system and prepare the tree for the new growing season.

  • Supply slow-release nutrients for continuous availability.

Nutrient

Rate (kg/stremma)

Application Method

Nitrogen (N)

6–8

Soil incorporation or surface application

Phosphorus (P₂O₅)

4–6

Deep incorporation for root development

Potassium (K₂O)

8–10

Improves drought resistance and oil quality

Magnesium (MgO)

2–4

Apply before vegetative growth to support photosynthesis

Sulfur (S)

3–4

Supports protein synthesis and metabolism



Objective:

  • Support vegetative growth, flowering, and pollination.

  • Enhance fruit set and fatty acid synthesis.

Growth Stage

Nitrogen (N)

Potassium (K₂O)

Phosphorus (P₂O₅)

Special Applications

Early Spring (Vegetative)

3–4 kg

3–4 kg

2–3 kg

Foliar Zn (150–200 g/stremma)

Flowering (May–June)

2–5 kg

3–5 kg

2–3 kg

B (100–150 g/stremma) for pollination

Fruit Set (Summer)

2–4 kg

3–6 kg

2–3 kg

Mg (200–300 g/stremma) for oil quality



Objective:

  • Maintain high oil quality and increase fruit weight.

  • Improve fatty acid content.

Growth Stage

Nitrogen (N)

Potassium (K₂O)

Magnesium (MgO)

Special Applications

Fruit Filling (September)

–

1–2 kg

1–2 kg

Foliar Ca (100–150 g/stremma) for firmness

Fruit Ripening (October)

–

1–2 kg

2–3 kg

S (100–150 g/stremma) for oil stability



  1. Boron (B):

  • Rate: 100–150 g/stremma before flowering.

  • Purpose: Enhances fertility and prevents fruit deformation.

  1. Zinc (Zn):

  • Rate: 150–200 g/stremma during shoot development.

  • Purpose: Improves root development and photosynthesis.

  1. Sulfur (S):

  • Rate: 100–150 g/stremma.

Purpose: Improves oil quality and enhances disease resistance.

Fertigation is highly efficient in irrigated groves because it:

  • Improves nutrient absorption.

  • Reduces fertilizer losses and saves resources.

Fertigation Recommendations:

  • Early Spring: Apply N and P for foliage development.

  • During Flowering: Add K, B, and Zn to support fruit set.

  • During Ripening: Increase K and Mg to boost oil quality.

Micronutrient application in olive cultivation is essential for supporting critical physiological functions, such as pollination, fruit development, and oil quality. Micronutrients can be applied through base fertilization or foliar sprays for rapid absorption, especially during high-demand periods or when deficiencies are detected.

Boron (B):

  1.  Role: Essential for pollination and fruit set; promotes cell wall synthesis and sugar transport.
    Deficiency Symptoms: Hollow fruits, poor fertility, leaf and flower deformities.
    Application:

     

  • Foliar: 100–150 g/stremma before flowering.
  • Soil: 0.5–1 kg/stremma as borate fertilizers.
  1. Zinc (Zn):
     Role: Promotes photosynthesis and auxin synthesis for shoot growth; supports root development and protein production.
    Deficiency Symptoms: Small leaves, stunted shoots, chlorosis of young leaves.
    Application:

     

  • Foliar: 150–200 g/stremma during leaf development.
  • Soil: 1–2 kg/stremma in chelated form (EDTA-Zn).
  1. Iron (Fe):
     Role: Key for chlorophyll synthesis and respiration; improves drought tolerance.
    Deficiency Symptoms: Yellowing of young leaves (chlorosis), reduced photosynthetic activity.
    Application:

     

  • Foliar: 200–300 g/stremma using chelated forms (EDDHA-Fe).
  • Soil: 2–3 kg/stremma before flowering.
  1. Manganese (Mn):
     Role: Regulates photosynthesis and enzymatic activities; promotes cell wall formation.
    Deficiency Symptoms: Chlorosis of young leaves, reduced growth, increased disease sensitivity.
    Application:

     

  • Foliar: 150–200 g/stremma before flowering.
  1. Copper (Cu):
     Role: Strengthens plant defense against diseases; involved in enzyme synthesis and respiration.
    Deficiency Symptoms: Shoot tip dieback, leaf deformation, increased susceptibility to fungal infections.
    Application:

     

    • Foliar: 50–100 g/stremma as copper oxychloride.
  1. Foliar Application Stages:

Growth Stage

Micronutrients & Rates

Objective

Early Vegetative (Spring)

Zn (150 g/stremma), Fe (200 g/stremma)

Leaf and shoot growth, enhanced photosynthesis

Flowering (May–June)

B (100–150 g/stremma), Mn (150 g/stremma)

Support pollination, reduce flower drop

Fruit Formation (Summer)

K (4–5 kg/stremma), Mg (200 g/stremma), Fe (150 g/stremma)

Boost fruit development and oil synthesis

  1. Advantages of Foliar Feeding:
  • Immediate absorption: Nutrients enter directly through the leaves.

  • Deficiency correction: Rapidly addresses nutrient shortages during critical stages.

  • Efficiency: Can be combined with plant protection treatments.

5. Irrigation and Water Management (Summary)

Annual requirement: 300–650 mm/year.

Needs vary depending on soil type and climate.

Flowering (April–May): High water demand to support pollination.

Fruit Development (June–July): Ensures optimal fruit size and oil synthesis.


Fruit Ripening (August–September): Maintains oil content and quality stability.

  • Deep root system enables water uptake from lower soil layers.
  • Reduced water loss due to waxy leaf cuticle.

  • Advantages:

    • Targeted water delivery to the root zone.

    • Minimal evaporation losses.

    • Allows fertigation (fertilizer application through irrigation).

    Disadvantages:

    • High initial installation cost.

    • Requires regular pipe maintenance to prevent salt build-up.

  • Sprinkler or flood irrigation is not recommended for modern olive cultivation.

Goals and Advantages:

  • Combines irrigation and fertilization, reducing costs and losses.

  • Ensures uniform distribution of nutrients in the root zone.

  • Suitable for light soils or areas with high fertilization requirements.

Application Recommendations:

  • Nitrogen (N): During vegetative growth.

  • Potassium (K): During fruit filling and ripening.

  • Boron (B): Before flowering to improve pollination.

  1. Use of Soil Moisture Sensors:

  • Measures soil moisture for timely irrigation planning.

  • Reduces water losses from over-irrigation.

  1. Adjustment to Climate Conditions:

  • Increased irrigation during high temperatures.

  • Reduced watering during cooler periods.

  1. Precision Irrigation:

  • Use of satellite imagery and sensors to analyze soil moisture variability.

  • Focused water application to areas with higher demand.

6. Plant Protection

  1. Olive Fruit Fly (Bactrocera oleae)
    Symptoms: Causes holes in the fruit and damages the pulp, reducing oil quality.
    Control:
  • Biological: Pheromone traps.

  • Chemical: Contact or stomach insecticides.

  • Preventive: Regular monitoring of populations with traps.

  1. Olive Moth (Prays oleae)
    Symptoms: Damage to flowers, fruits, and leaves.
    Control:
  • Biological Products: Use of Bacillus thuringiensis.

  • Chemical Measures: Application of insecticides during fruit formation.

  1. Olive Weevil (Rhynchites cribripennis)
    Symptoms: Holes in leaves and fruits.
    Control:
  • Cultural Practices: Removal of plant residues.

Chemical Control: Sprays with pyrethroid insecticides.

  1. Olive Knot (Pseudomonas savastanoi pv. savastanoi)
    Symptoms: Formation of knots (galls) on branches.
    Control:
  • Preventive Measures: Pruning with clean, disinfected tools.

  • Chemical Measures: Application of copper-based products after pruning.

  1. Verticillium Wilt (Verticillium dahliae)
    Symptoms: Leaf and shoot wilting due to vascular necrosis.
    Control:
  • Cultural Measures: Avoid crop rotation with susceptible plants (e.g., cotton).

  • Biological Methods: Use of resistant rootstocks.

  1. Olive Leaf Spot (Spilocaea oleagina)
    Symptoms: Brown–black spots on leaves, leading to leaf drop.
    Control:
  • Preventive Measures: Pruning for better tree aeration.

  • Chemical Measures: Copper sprays or specific fungicides.

7. Harvest and Storage

  1. Ripening Indicators:
  • Olive Oil Varieties: Fruits change color from green to purple or black.

    • Ideal oil content: 18–30%.

  • Table Olive Varieties: Harvested when fruits reach marketable size and proper texture.

    • Green olives are harvested before full ripening, while black olives are harvested at full maturity.

  1. Harvest Timing for Oil Production:
  • Ideal period: October – December (depending on region).

  • Early Harvest: Higher oil quality but lower yield.

Late Harvest: Higher yield but possible quality deterioration.

  1. Manual Harvesting
    Advantages:
  • Superior fruit quality with minimal damage.

  • Suitable for table olive varieties.
    Disadvantages:

  • High labor cost.

  • Low harvesting speed.

  1. Mechanical Harvesting (Shakers & Harvesting Machines)
    Advantages:
  • High harvesting speed.

  • Ideal for oil varieties and super-intensive orchards.
    Disadvantages:

  • Potential damage to sensitive fruits.

Requires uniform tree shaping.

    1. Immediate Transport to Mill:

    • Olives should be processed within 24–48 hours after harvest.

    • Delays cause fermentation and increased acidity.

    1. Sorting and Cleaning:

    • Removal of foreign materials (leaves, branches) using mechanical sieves.

    Washing of fruits to prevent contamination in oil extraction.

  1. Storage Tanks:
  • Use stainless steel tanks with inert gas (nitrogen) to prevent oxidation.

  • Storage temperature: 15–18°C to maintain quality.

  1. Protection from Oxidation:
  • Keep in dark spaces, away from light and heat.

  • Use small containers for daily consumption.
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