Botanical characteristics of the olive tree

The olive tree (Olea europaea) is an evergreen plant, which means that if the environmental conditions are favorable, it can live over 100 years.

The trunk of the olive tree has a gray bark that flakes off with time. Its wood is hard, resistant and fragrant, often used for fine furniture. The plant can develop nodules in the lower part of the trunk and on the branches, caused by natural factors but not by diseases.

Image : olive tree-source: Pxhere (n.d)

Its leaves are narrow, grayish-green in color and resist the dry climate well. In spring, it produces small white flowers, while its fruit, the olive, is a drupe that changes color from green to purplish as it ripens.

Olives can be smaller (2-3 grams) if used for oil, or larger (4-5 grams) if intended for table consumption. The pulp is rich in oil (25-30%) and the seed is protected by a hard, rough shell. Some varieties may have stones without embryos, reducing the commercial value of the fruit.

Climate and soil requirements

The olive tree thrives in Mediterranean climates, which are characterized by mild winters and hot, dry summers. The ideal average annual temperature for cultivation is between 15°C and 20°C. The plant can tolerate high temperatures of up to 40°C without damage, but it suffers when temperatures drop below -7°C, beyond which serious damage can occur to trees. The resistance of the olive tree to cold also depends on factors such as the duration of frost, the presence of cold winds, humidity, and the health of the plant. To ensure good production, the tree also needs a minimum number of hours of cold in winter, which varies according to the cultivar. For this reason, the olive tree cannot be successfully cultivated in tropical climates, where such conditions are not met.

The olive tree grows best in well-drained, lime-rich or clayey soils, with a pH between 5 and 8.5. To adjust the pH, you can use limescale to increase it or sulfur to lower it. Soil rich in organic matter improves plant growth.

For example, in Italy, Basilicata is part of the Central Mediterranean meteorological region and is included among the annual isotherms 16°-17°C. It has a typically Mediterranean climate, characterized by hot summers and rainfall concentrated in winter.

It is essential to avoid waterlogging, choosing soils with good drainage and limiting the areas where pools of water form, as excessive humidity can compromise the health of the roots.

Varieties of olive trees

There are many varieties of olive trees, each with different characteristics that affect the flavor and quality of the oil. Some of the best known are:

• Arbequina (Spain) – Produces a sweet, light and fruity oil.
• Frantoio (Italy) – Famous for its balanced oil with herbal notes.
• Koroneiki (Greece) – Generates a very aromatic and resistant oil over time.
• Picual (Spain) – Intense and robust oil, with a slight almond aftertaste.

Each variety is suitable for different climates and growing methods, and the choice depends on the end use of the oil and the soil conditions. For example, in Italy, there are over 538 varieties of olive trees, which produce olives mainly intended for the production of oil. Most oil olives are not suitable for direct consumption, but some varieties can also be enjoyed at the table, taking the name of table or table olives. The different varieties of olive trees are called cultivars, a term that derives from the Latin varietas culta, or "cultivated variety". Each cultivar produces olives with unique characteristics, influencing the flavor and quality of the oil. Other large olive oil producers, such as Spain and Greece, do not have a diversity of cultivars comparable to that of Italy.

Image : Distribution of the World Genetic Heritage of Cultivated Olive Trees by Country- source: Assoprol. (2020)

Sustainable olive cultivation and harvesting practices

To cultivate the olive tree, in addition to choosing well-drained soil, it is essential to carry out periodic treatments and proper pruning of the plant. Treating the olive tree in medium and large-scale farms is a demanding task that requires a well-defined intervention plan throughout the year. Treatments begin in March with white oil to combat scale insects, followed by copper at the end of April to prevent diseases such as peacock eye, rogna, and carles. During pre-flowering, boron is applied to promote pollination and counteract the presence of the olive moth, while at the end of flowering, preventive treatments for peacock eye and rogna are repeated. In summer, action is taken against the olive fruit fly, a pest that can significantly damage both the quality and quantity of the crop. Post-harvest treatments have two main objectives: protecting the olive tree from potential bacterial attacks with copper, which has bactericidal properties, and strengthening the tissues to better withstand the winter. Additionally, copper helps the plant resist low temperatures. This substance is compatible with organic farming, provided it is used within allowed limits. Pruning is one of the most delicate and technical operations for the olive tree, essential for keeping the plant healthy and productive. The goal is to balance the size of the canopy with the trunk, ensuring that the plant maximizes sunlight to nourish the fruits. Incorrect pruning can reduce oil yield and cause the growth of unnecessary branches, while a well-executed intervention guarantees good production. It requires experience and in-depth knowledge of the soil, variety, and geographical area.

Sustainable olive growing involves:

• Reduction of the use of pesticides and chemical fertilizers:

One of the first steps towards agricultural sustainability is the reduction of the use of pesticides and chemical fertilizers. These products, especially if used excessively, can contaminate groundwater and deplete soil biodiversity. Natural alternatives, such as compost and biofertilizers that allow the soil to be enriched without negative side effects, and the adoption of targeted phytosanitary treatments limited to periods of need to reduce their environmental impact, while still keeping crops protected, are certainly preferable. Reducing the use of pesticides and chemical fertilizers is a goal of the European Union (EU) to make agriculture more sustainable. The EU has committed to reducing the use of chemical pesticides by 50% by 2030.

• Drip irrigation to optimize water consumption:

Water is a precious resource, and efficient irrigation systems are essential for sustainable agriculture. Techniques such as drip irrigation minimize water waste and allow plants to be nourished constantly. Rainwater harvesting can also be a simple and beneficial solution, especially in areas at risk of drought. These methods, combined with mulching practices that reduce evaporation, ensure responsible use of water resources.

• Adoption of precision agriculture:

Thanks to technology, precision agriculture is an increasingly accessible solution: sensors, drones and monitoring systems make it possible to analyze soil conditions, moisture levels and plant growth in real time, to intervene only when necessary. This strategy helps to reduce the waste of resources and optimize each phase of the production cycle, with a reduced environmental impact.

• Supporting biodiversity:

Biodiversity is essential for maintaining an ecological balance and reducing the negative impact of agriculture on the environment. Creating ecological corridors and refuge areas for insects and useful animals, such as pollinators and natural predators, helps keep pests under control without the need for direct human intervention. In addition, the introduction of native plants improves soil quality and contributes to the preservation of a healthier environment.