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Growing Olive Trees

Cultivating olive trees is a time-honored tradition in Italy, making it the world's leading producer of high-quality olives. Discover the essentials of olive tree care and the process of establishing a new olive grove in this comprehensive guide.

by BioGrow

Olive cultivation is one of the cornerstones of Italian agriculture. Olive groves have a millennial history, and their legacy has made Italy the world’s top producer of olives in terms of quality. These trees are perfect for organic cultivation and have managed to withstand the intensification of agriculture in recent decades. Today, agricultural techniques have evolved and become more refined compared to the past, but the connection to traditional farming remains strong.

In this article, we aim to provide an overview of all aspects to consider when cultivating an olive tree, especially when establishing a new olive grove.
At Cultivazione Biologica, we hold olive farming in high regard. In the following text, you will find numerous technical insights into various aspects of this important crop, which we invite you to explore.

The Olive Tree

Millennial olive trees
The olive tree (Olea europaea) belongs to the botanical family Oleaceae. It is typically cultivated in the Mediterranean, and its origins date back to ancient times.
One of the distinctive features of this tree is its remarkable longevity. In our southern regions, it is common to find millennial olive groves that bear witness to the history of our territory.
Botanically, the olive tree is an evergreen species with continuous vegetative activity, slowing down only briefly.

  • It reaches varying sizes depending on the variety. The largest specimens can exceed 20 meters in height, although modern olive cultivation tends to favor smaller-sized varieties.
  • The trunk has a characteristic twisted appearance, exuding an image of strength and longevity at first glance.
  • The bark is gray and, as it ages, becomes marked by noticeable cracks.
  • Olive wood is one of the hardest and most precious types of wood in nature.
  • The root system is not deep, rarely exceeding 1 meter in depth. However, it is extensive, with roots that can extend beyond the tree’s canopy.
  • In its natural state, the growth habit is bushy/shrub-like due to its strong tendency to produce basal shoots.

Olive Leaves

Olive leaves
Not everyone knows that olive leaves contain valuable elements beneficial to our health. They are elliptical in shape, have a leathery texture, and an entire margin. Additionally, they feature short petioles and are arranged oppositely on branches, with dark green color on the upper side and silver-white on the lower side. These leaves are renewed periodically; under good cultivation conditions, an olive tree regenerates them every two years.

Olive Flowers

Olive flowers are hermaphroditic, small, and white in color. They are clustered in inflorescences (initially called panicles), which appear in the leaf axils of one-year-old branches. Panicle initiation begins in mid-March, while the actual flowering occurs from early May to early June. Olive pollination is anemophilous, meaning it is carried out by the wind. Most cultivated olive varieties are self-sterile, meaning they require cross-pollination.

Olive Buds

The olive tree bears axillary or apical buds, which, after the vegetative rest, differentiate into:

  • Flower (fruit) buds;
  • Wood buds;
  • Mixed buds.

Olive Fruits

Olive trees are cultivated primarily for their fruit: olives. These are drupes, generally spherical or ovoid in shape, with varying weights and dimensions depending on the variety. Olives consist of pulp (containing oil) and a hard, woody pit.
The drupes ripen definitively and sequentially in the autumn. This is when the olive harvest takes place. Details of this process and the specific equipment used can be found in our related articles, which we recommend reading.

Phenological Phases of the Olive Tree

For those engaged in olive cultivation, it is essential to know and recognize the various phenological stages that the plant goes through. Exact timing can vary from region to region, taking into account different seasonal climate patterns.
In summary, these are the phenological stages of the olive tree:

  • Vegetative rest-winter buds (December-January);
  • Swollen buds, open buds, differentiation, leaf development, shoot growth (vegetative resumption in February);
  • Appearance of flower clusters, swelling of flower buds, corolla differentiation (panicle initiation from mid-March);
  • Initial flowering 5% (early May);
  • Flowering 50% (mid-May);
  • Initial fruit set (late May-June);
  • Post-set fruit growth (from mid-June);
  • Pit hardening (July);
  • Fruit growth (August-September);
  • Onset of ripening (late September);
  • Ripening (from October to December);
  • Full ripening/black olives (November-December).

How Long Does an Olive Tree Live?

As mentioned, olive trees have a long life span, and this is an important consideration for those starting a professional olive cultivation or wishing to establish an olive grove. Due to this longevity, there are distinct age phases of the tree.
First, there is the training phase, following planting, which typically lasts four years. Next is the juvenile phase, with increasing production until the tree reaches eight years of age. From the eighth year until around fifty years, the tree is in the maturity phase, with stable and high yields. After sixty years, the tree enters a slow aging phase.

How to Cultivate Olive Trees

In organic olive cultivation, especially when deciding to establish a new olive grove, it is essential to consider the climatic preferences of the olive tree. You must choose an environment that best meets the crop’s needs. By making this fundamental choice, maximizing the positive relationship between the plant and the environment, there will be less need for intervention by the olive grower. These interventions primarily include fertilization, irrigation, and biological pest control. The olive tree is typically grown in the Mediterranean region. It is a thermophilic species, adapted to warm and temperate environments. It is heliophilic, meaning it requires sunlight and benefits from sunny exposure.

What Is the Right Climate for Olive Cultivation?

In our country, the most important limiting factor for starting a new olive cultivation is winter minimum temperatures. When temperatures drop below -7 °C, the plants begin to suffer damage. With frost and temperatures below -13 °C, the above-ground part of the plant is significantly compromised. Other harmful conditions for olive cultivation include late frosts, which damage the flower buds, and early autumn frosts, which spoil the fruit during ripening and complete maturation. Persistent rains are unfavorable during flowering and can reduce fruit set. There are generally no significant problems with temperatures up to 40/42 °C. The issue is more related to heat associated with drought, which can lead to premature fruit desiccation.

Does Wind Affect Olive Cultivation?

Regarding winds, light ventilation is favorable for anthesis, meaning the transport of pollen during pollination. Therefore, for olive cultivation, it is undoubtedly a positive factor. In already arid areas, the presence of persistent winds accentuates the problem of drought. This facilitates water evaporation from the soil and increases plant transpiration.
In areas too close to the coast, the wind can carry an excess of salt, which can lead to cytotoxicity. Therefore, in these unfavorable areas, it would be advisable to plant windbreaks alongside the olive trees. To do this, it’s recommended to use species suitable for the cultivation area. Lastly, olive trees do not tolerate environments that are too humid, for example, where there are frequent fogs. High humidity promotes fungal diseases and parasite infestations.

What Is the Ideal Soil for Olive Cultivation?

Cultivating olive trees is possible in a wide range of soil types. The olive tree shows great adaptability and can grow and produce even in soils with limited organic matter content. The best results are obtained when olive cultivation occurs on medium-textured soils, such as loamy-sand, loamy-silt, clay-silt, or loamy-clayey soils. The ideal pH should ideally range between 6.8 and 7,5. These types of soils provide a good balance in terms of aeration, permeability, and water absorption. Heavy and waterlogged soils should be avoided, as they lead to water stagnation. It’s important to conduct a thorough soil analysis before deciding to establish a new olive grove. Soil analyses also provide an opportunity to check for the presence of nematodes in your field.
In such cases, intervention may be necessary, and the establishment of the new olive grove may need to be postponed. Another crucial piece of information from soil analysis is the organic matter content. In organic olive cultivation, where no synthetic mineral fertilizers are used, it’s essential to have the topsoil as fertile as possible. This is where the root system develops. Finally, crop rotation should be considered. In the case of olive cultivation, it’s advisable to avoid soils that previously supported intensive crops. We are talking about solanaceous plants (tomatoes, eggplants etc.) or cucurbits (zucchini, pumpkin, cucumber etc). These crops often bring fungal diseases of the root system with them, such as Verticillium wilt.

What Olive Varieties to Cultivate?

Olive of the "Bella di Cerignola" variety

Olive of the “Bella di Cerignola” variety

The world olive germplasm comprises approximately 2,629 varieties. The Italian olive germplasm includes 631 cultivars. Therefore, to initiate olive cultivation using organic methods, significant attention must be paid to the choice of variety.

The decision of which variety to plant must address multiple needs, including:

  • Productivity
  • Resistance to diseases and pests
  • Cross-pollination
  • Mechanization of harvesting
  • Quality of obtainable oil

Anyone deciding to invest in this essential and demanding cultivar undoubtedly aims for excellent production yields. For instance, there are varieties that ensure high yields but may have lower polyphenol content, resulting in lower-quality oil. Conversely, some varieties are less susceptible to fungal diseases and pests but yield less.

Olive Varieties to Cultivate Organically

The advice we offer for choosing the variety for establishing a new organic olive grove is to consult a skilled agronomist. It is crucial that they know how to work with organic olive groves, as decisions of such economic impact should always be supported by adequate consultations. Beginning olive cultivation in a natural manner is not a minor undertaking.

In organic farming, in summary, it is crucial to evaluate the variety’s sensitivity to diseases. This is especially important since synthetic chemicals cannot be used in organic farming. Therefore, it is advisable to lean towards hardier cultivars. Additionally, you should consider whether you want to cultivate single-variety or multi-variety olive groves.

Single-Variety Olive Groves

At an agronomic level, even when cultivating single-variety olive groves, it is necessary to plan for pollinator plants (approximately 10-15% of the total). This serves to ensure cross-pollination. Even self-fertile cultivars benefit from the presence of other varieties and cross-pollination.

Multi-Variety Olive Groves

Another agronomic principle is that when cultivating olives of different varieties (multi-variety olive groves), these varieties should not have significantly different ripening times. For example, it is not advisable to mix table olives (early-maturing and requiring different treatments) with oil olives (typically later-maturing). Making this mistake exposes the olives to multiple generations of pests. In this regard, in organic farming, it is best to prefer varieties with small drupes and early ripening, as they suffer fewer damages from pests.

How to Prune Olive Trees

Olive tree cultivated with a vase shape

Olive tree cultivated with a vase shape

Olivo coltivato a vaso
The choice of the olive tree training system is of fundamental importance for the correct future management of the olive grove. The training system is established at the beginning of olive cultivation, during the initial pruning operations.
Here, we instead focus on the advantages and disadvantages of the most common olive tree training systems in organic farming. This choice, in this case as well, must address various needs, such as:

  • Rapid growth and early entry into production of the olive grove.
  • Canopy aeration
  • Consistent and high production
  • Facilitation of cultural operations such as harvesting and pruning.

Olive Tree Trained as a Polyconic Vase

In organic olive farming, the polyconic vase training system is one of the most common. It has the advantage of providing excellent canopy illumination and aeration, creating unfavorable conditions for pest and pathogen attacks. However, this training system is not suitable for mechanical pruning.

Olive Tree Trained as a Monocone Vase

A variation of the polyconic vase is the monocone training system. A tree trained in this manner has the advantage of being easily shaped with training pruning. Furthermore, the form is perfect for mechanical harvesting with a trunk shaker. It is better suited to mechanical pruning than other forms. However, it has a significant disadvantage in terms of vegetative growth. During the tree’s growth phase, particularly with vigorous varieties, excessive vegetative growth occurs both upward and sideways. This forces the olive grower to make drastic cuts, which can disrupt the vegetative-productive balance.

Olive Tree Trained as a Globe

The globe training system has the advantage of early production. Additionally, the woody parts of the plants are more protected from excessive sun exposure. However, the disadvantage is that the inner parts of the canopy are too shaded, making it more challenging to access the tree’s interior for pest control treatments. The same applies to harvesting, which becomes more difficult.

Spacing in Olive Grove Planting

Cultivation of a modern olive grove

Cultivation of a modern olive grove

The Spacing of a New Olive Grove

Planting an olive grove requires careful consideration of the spacing between olive trees and between rows. Typically, the field is mentally divided into squares or rectangles, and the exact planting distance depends on several factors, including:

  • Vigor of the olive variety.
  • Training system.
  • Soil and climatic conditions.

The goal is to prevent the crowns of the trees from touching each other once they are mature. When crowns touch, there are several risks, including:

  • Excessive shading.
  • Increased susceptibility to pests and pathogens.
  • Difficulty in pruning and harvesting.

Usually, it is advisable to choose wider spacings to avoid these issues while optimizing space, yields, and management costs. The recommended minimum and maximum spacing limits for an organic olive grove are as follows:

  • Rectangular spacing: 5m x 6m – 7m x 8m (338-178 trees/ha).
  • Square spacing: 6m x 6m – 7m x 8m (278-204 trees/ha).

The wider spacings are recommended for vigorous cultivars and those trained with open forms, such as the vase system.

Orientation of Olive Rows

The orientation of rows should also be considered when deciding to grow olives. Ideally, rows should run north to south to ensure uniform sunlight exposure.

How to Establish a New Olive Grove

Soil Preparation

Soil preparation is a crucial step in olive cultivation. Unlike annual crops, olive trees are long-lived, so the soil should provide an ideal environment for centuries of growth. Several steps are involved:

Clearing

If the land previously had other tree species (wild or cultivated), it’s necessary to carefully remove any remnants, especially large roots and stumps. This is essential to prevent competition and infestations and to avoid potential pathogens carried by old residues. You may need a small excavator for root removal or use a shredder to leave organic matter on the soil if no large roots are present.

Surface Leveling

If the soil surface is uneven, it should be leveled before planting the new olive grove. This can be done using a ripper. Multiple passes, reaching depths of 80-100 cm and crossing the work pattern, facilitate future machinery movement. Steeply sloping terrain presents additional challenges.

Excess Water Drainage

In flat areas where waterlogging is a concern, ensure the soil is free from excess water at least 50-60 cm deep (loamy soil). This can be achieved through trenching or installing drains. In hilly terrain, prevent water erosion by creating ditches to divert waterflow safely downstream.

Fertilization
Base Fertilization

Based on soil analysis, determine the amount of organic matter present and decide on necessary amendments. In organic olive cultivation, two types of organic matter are commonly used: cattle manure from organic farms or domestic/industrial compost (following specific regulations). Larger spaces may face practical limitations in adding external organic matter, so cover crops (green manure) are an alternative. When using cover crops for base fertilization, it’s advisable to mow and incorporate them into the soil when they are rich in fiber, increasing stable humus content.

Periodic Fertilization

Olive groves typically require periodic fertilization, usually annually or at wider intervals. Legume cover crops are an excellent choice for periodic fertilization. When fertilizing annually, pay attention to superficial incorporation of organic matter (cover crop or manure).

Plowing

After surface preparation with the ripper and base fertilization, plowing is performed. This plowing should not be too deep (30-40 cm) since the soil has already been worked with the ripper. Only when dealing with highly compacted soils or soils with significantly different texture profiles, where remixing can improve soil conditions for olive cultivation, is traditional deep plowing (70-80 cm) considered.

When to Establish a New Olive Grove

The planting of young olive trees can be done during two different periods; in very hot regions, the best time is in autumn or early winter, avoiding the coldest periods. In these areas, you can also plant in early spring, but in this case, emergency irrigation must be ensured if there is a period of drought after planting. In relatively colder climates, it’s best to plant olives in the spring after the risk of frost has passed. The same applies to emergency irrigation. To correctly plant the trees, follow the general rules we have previously discussed.

Choosing Nursery Material for Olive Cultivation

To start olive cultivation, you need to acquire the right plants. It is advisable to look for plants that are at least 1-2 years old, already grafted, and grown in suitable containers. The nursery must guarantee the young olive plants both from a phytosanitary and clonal perspective.

When and How to Irrigate an Olive Grove?

Irrigation of the olive grove should be carried out when rainfall is insufficient to ensure a successful crop.
Determining precisely when to irrigate is not an easy task, especially given the effects of climate change in recent years, which no longer allow for certain predictions or reliance on historical precipitation data. However, the periods when the olive tree is most sensitive to water stress are:

  • Pre-flowering, flowering, and fruit set (usually rainy periods).
  • Fruit growth (from fruit set to the beginning of pit hardening, usually dry periods).

During these phases, water should be applied only as needed, avoiding excesses that can be more harmful than drought.

The Best Irrigation Systems

The most efficient irrigation systems in olive cultivation are drip irrigation and micro-sprinkler irrigation. These systems prevent water wastage because the plants can absorb it entirely. Additionally, micro-irrigation helps prevent weed growth and the development of pathogens. It is essential to avoid overhead sprinkler irrigation.

Managing the Soil in an Olive Grove

In olive cultivation, you have three options for managing the soil in your grove: ground cover, tillage, and cover crops.

Ground Cover

The ground cover technique can present challenges in areas where water availability (natural and artificial) is limited. This is because it creates competition between the grass and olive cultivation. Therefore, in regions with low precipitation (between 400 and 600 mm/year) and no access to irrigation, it’s advisable to choose tillage instead. Ground cover can be beneficial where water is abundant and on sloping terrain to prevent erosion. In any case, it’s best to implement ground cover after the olive trees are three years old to avoid nutritional competition during the delicate growth phase.

Tillage

Properly conducted tillage ensures good rainwater infiltration into the olive grove soil and significantly reduces water losses due to weeds. However, it results in a significant loss of organic matter through mineralization and exacerbates soil erosion. Typically, one tillage operation is carried out after harvesting to clean the field and bury the organic matter from foliage or added during the fertilization cycle. In spring or summer, a maximum of two light tillage operations, to a depth of 10 cm, can be performed.

Cover Crops

Cover cropping is a technique that falls between ground cover and tillage. Instead of simple tillage after harvesting, an herbaceous species (legumes, grasses, brassicas, etc.) is sown at the end of the harvest season. This vegetation is then mowed and incorporated into the soil in the spring.

Protecting Olive Trees from Pests

Biological pest and disease management in olive cultivation is a broad topic that requires in-depth discussion. Here, we will list the most common problems in olive grove management, dividing them into two lists: insects and diseases (fungi, viruses, and bacteria).

Insects Affecting Olive Cultivation

The insects that commonly affect olive cultivation include:

  • Olive fruit fly
  • Black scale
  • Olive moth
  • Black mealybug
  • Spined soldier bug
  • Yellow scale
  • Green shield bug
  • Olive bark beetle
  • Olive fruit midge
  • Olive leaf weevil
  • Olive twig borer
  • Large olive scale
  • Olive psyllid
  • Olive lace bug
  • Olive fly
  • Olive tree weevil

Diseases Affecting Olive Cultivation

Diseases affecting olive groves can be fungal, bacterial, or viral.

Fungal Diseases
  • Peacock spot
  • Olive leaf spot
  • Olive leaf scorch
  • Verticillium wilt
  • Fruit rot
  • Eutypiosis
  • Canker
  • Olive knot
  • Basal rot
  • Collar rot
  • Copper spot
  • Fibrous root rot
  • Woolly pod rot
  • Sooty mold
  • Olive powdery mildew
  • Parasitic broomrape
Bacterial Diseases
Viral Diseases
  • Olive Latent Ringspot Virus (OLRSV)
  • Olive Latent Virus-2 (OLV-2)
  • Olive Leaf Yellowing associated Virus (OLYaV)
  • Olive Latent Virus-1 (OLV-1)
  • Cucumber Mosaic Virus (CMV)
  • Cherry Leaf Roll Virus (CLRV)
  • Strawberry Latent Ringspot Virus (SLRSV)
  • Tobacco Necrosis Virus (TNV)
  • Arabis Mosaic Virus (ArMV)

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