Hazelnut: origin, value and characteristics
El hazel (Corylus avellana L.) is a deciduous shrub or tree that stands out among the nut crops with the longest history and projection. Native to the region between Iran, Iraq and Turkey, its hardiness and adaptability have allowed it to spread throughout Europe, being common to find it on hills, slopes, roads and stream banks. The nutritional value of its fruits, hazelnuts, making it a crop of both commercial and ornamental interest, thanks to its hardiness and multiple uses. Hazelnuts have been with humans since prehistoric times, long before other crops such as olives and grapes.
In many countries, and especially in areas of southern Europe, hazel has been used on marginal and steeply sloping land, contributing to soil protection and allowing for a alternative source of income in areas where other fruit trees hardly thrive.
Climatic conditions and optimal temperatures for hazelnuts
Hazelnuts adapt to different climates, although it is important to consider the characteristics of each variety. Requires temperate average annual temperatures, situated between 12 and 16°C, and can withstand winter lows close to -8°C. The essential requirement is to achieve at least 700 hours of cold below 7°C to ensure proper budding and flowering.
La sensitivity to high temperatures It is particularly noticeable in the shade above 30°C, which can cause stress in summer and affect both fruit development and overall yield. Hazelnut trees prefer cool, well-ventilated environments with a certain degree of humidity.
To optimize pollination, it is recommended soft, dry winds in the months of January and February. On the other hand, autumn storms They can harm the harvest by causing landslides and waterlogging. Fruit development is especially active from May to June, while the grain develops mainly in July and August, times when a lack of water can limit production.
The hazel tree is tolerant of frost in flowering when the cold is constant, but is susceptible to late frosts in spring which can reduce the number of buds and affect sprouting. Therefore, it is preferable to plant in areas with no risk of severe frost at this time.
Characteristics of the ideal soil for planting hazelnuts
The hazel tree is known for its rusticity and a certain capacity to adapt to different types of soil, although for optimal performance it prefers fertile, loose soils with a depth greater than 50 cm. The ideal pH range is between 5,5 and 7,5, although it can tolerate values up to 8, avoiding the active limestone content exceeding 8% to prevent iron chlorosis.
It is not recommended to plant hazel trees in excessively sandy soils., as they don't retain enough moisture and nutrients, nor do they thrive in clay soils where waterlogging and lack of oxygen can be problematic and limit their growth. Poorly drained, excessively heavy, or shallow soils are also unsuitable.
To facilitate both plant development and harvesting, the soils must be little stony and well leveled, with slopes of less than 10%. It's also important to ensure good drainage to avoid root asphyxiation and fungal diseases.
In garden spaces, hazel trees can thrive in moderately compacted soil, as this helps support the tree as it matures. However, if the soil is poor, it is advisable to incorporate organic matter before planting.
Water needs and irrigation management
The hazel tree is very sensitive to drought; in dry and calcareous soils, or if it suffers from a water shortage, it is common for the fruits to fall prematurely, reducing the annual production. The greatest water needs are concentrated from May to July, coinciding with fertilization, floral induction and fruit growth.
In regions with a Mediterranean climate or areas with low rainfall, it is advisable to use irrigated crops or in drylands that receive at least 600 mm of annual rainfall. Irrigation should be frequent but not flooding, and should be adapted to the soil texture and weather. A good strategy is to check soil moisture before each irrigation.
In garden conditions, watering every three or four days may be sufficient, avoiding wetting the foliage to reduce the risk of disease. In light soils, watering should be shorter and more frequent, while in heavier soils, watering can be spaced out but should be abundant.
Hazelnut pollination and compatibility
Hazelnut is a monoecious, wind-pollinated species; its male and female flowers develop on the same tree, but most varieties are self-incompatible, so it is necessary to have at least two different and compatible cultivars in the plantation to achieve effective pollination and good fruit production.
During the flowering (January-February)Gentle, dry winds help disperse pollen better, while prolonged fog or excessive humidity can hydrate pollen and limit fertilization, negatively affecting yield.
The groups of varieties They must be selected based on their flowering coincidence and genetic compatibility, which is crucial in commercial plantations.
Location and space needed to plant hazelnut trees
It is essential to select a spacious location, in full sun or semi-shade, where the hazelnut tree can grow unrestricted. Depending on the variety and the growing purpose (shrub or tree), it can reach 3 to 10 meters in height and easily expand in width, developing new basal shoots. This expansive tendency makes it ideal for both row production and ornamental use and for separating spaces in gardens.
In commercial plantations, single-trunk training is preferred to facilitate mechanized harvesting and pruning. In gardens, a bushier growth can be achieved, which contributes to creating hedges, shaded areas, and habitats for biodiversity.
Interestingly, in certain regions, hazelnut trees are used as hosts for truffle cultivation, taking advantage of the symbiosis between their roots and these prized fungi.
Soil preparation, fertilization and planting of hazelnut fruit
Before sowing the fruit or planting a hazel tree, it is advisable to carry out a deep soil preparation, removing stones and root debris and correcting any drainage problems. A few days or weeks before planting, it's a good idea to enrich the soil with well-rotted organic fertilizer, mature manure, or compost to provide nutrients and improve soil structure.
- Deepening and tilling: Dig a hole about 40-50 cm deep into the ground and level the area to facilitate root development.
- Selection of seeds/fruits: If you choose to sow hazelnuts directly, use ripe, fresh, and healthy fruits. It's recommended to soak them in warm water for 48 hours and then stratify them for a few weeks in cold, damp sand to improve germination.
- Plantation: It is planted once the favorable period has begun, in 30 x 30 cm holes, burying the seeds at a depth of 3 to 4 cm. If seedlings or young specimens are planted, the roots will spread well and should be covered with firm but loose soil around the neck.
Essential care after planting: watering, pruning and maintenance
During the first few months and up to the first year, it is essential to keep the soil moist but never waterlogged. mulching Organic mulch around the base helps retain moisture and limits weed growth.
Regarding pruning, there are three main types that are applied depending on the stage of the hazel tree:
- Formation pruning: It is done in the first years to establish the basic structure of the tree or shrub.
- Fruiting pruning: It stimulates flower and fruit production by removing old or poorly positioned branches; pruning twice per season is sufficient.
- Maintenance pruning: It involves removing dry, diseased, or damaged branches, as well as clearing the interior to improve ventilation and light intake.
It is advisable to prune during periods of dormant vegetation, preferably in winter, when the tree is dormant.
Diseases, pests and prevention
Hazelnuts can be attacked by various pests and diseases. The most common problems include:
- Bacteriosis and anthracnose: Diseases caused by bacteria and fungi can be prevented with good aeration, avoiding waterlogging, and applying specific treatments when necessary.
- Worms and caterpillars: They can damage leaves and fruits, so they should be controlled through regular inspections and, if necessary, with biological insecticides.
- Mites and aphids: They affect sap and growth. They are managed by monitoring for pest emergence and using appropriate ecological or phytosanitary methods.
Uses, benefits and interesting facts about hazelnuts
In addition to its nutritional valueHazelnuts are famous for their sweet flavor, their richness in healthy oils, and antioxidants such as flavonoids and oleic acid. Hazelnuts are eaten raw or roasted and are used in baking, as an ingredient in chocolates, creams, and oils. Hazelnut oil, highly prized, is used in both gastronomy and cosmetics for its nourishing and emollient properties.
The hazel's strong, lightweight wood is used to make walking sticks, basketry, charcoal, and utensils. In gardening, its expansive growth is often used to form hedges, separate areas, and create cool, shaded spaces.
In commercial plantations, hazelnut can be grown as a shrub or as a single tree, especially if grafted onto non-sprouting rootstocks, which facilitates maintenance and mechanical harvesting.
A relevant curiosity is its use as a symbiotic tree for truffle production, since its roots can associate with mycorrhizal fungi, generating another product of high economic value.
Planting, caring for, and harvesting hazelnuts requires following a series of agronomic recommendations to ensure good production and quality harvests year after year. By following these simple tips and constantly monitoring the plant's condition, it is possible to enjoy both the ornamental and nutritional value of hazelnuts, even in less favorable soils or small home gardens.