HAZEL: CHARACTERISTICS, TAXONOMY, HABITAT, USES - BIOLOGY - 2024

The hazel (Corylus avellana) is a deciduous tree species statured belonging to the family Betulaceae. Known as Cordovan hazelnut, hazelnut, male hazelnut, hazelnut, common hazelnut, European hazelnut, avillano, cascaruto, gambote, gargoyle or nochizo, it is a native plant of Europe and Asia.

Its name "Corylus" derives from the Greek word "korys", which means hood, in relation to the coating of the shell of the fruit or hazelnut. The specific adjective "hazelnut" comes from "avellanus-a-um" in allusion to the town of Avella Vecchia, near Naples in Italy.

Hazel (Corylus avellana). Source: pixabay.com

It is a 3-10 m tall deciduous shrub or tree with rough bark and an irregular, compact and spreading crown. The root system is shallow, knotty and branched, with numerous suckers that are born at the base of the main stem.

The heart-shaped leaves with serrated margins are light green on the upper side and tomentose on the underside. Hazel is a monoecious species with male flowers in yellowish cylindrical catkins and female flowers grouped in small axillary shoots.

The fruit is a cinnamon-colored cup-shaped achene called involucre, inside which is the seed. When the fruit ripens, after eight months, the involucre dries and opens, leaving the hazelnut free.

At a commercial level, the main demand for hazelnuts comes from the food industry, followed by direct consumption, both with specific quality requirements. Indeed, agronomic management and agroclimatic characteristics affect the nutritional and sensory properties of hazelnuts, consequently, their quality and stability.

General characteristics

Appearance

Hazel is a low-growing deciduous tree or shrub 3-8 m high, reaching 15 m under certain environmental conditions. It usually branches widely from the base to form an extended, dense and irregular crown.

In the young branches, the bark is reddish-brown, smooth and with abundant lenticels, slightly pubescent at the level of the leaf shoots. As the bark matures, it fissures deeply and turns grayish-brown, the rigid and compact wood is very flexible.

Leaves

The large, simple, alternate, deciduous leaves are rounded in shape, 6-12 cm long and wide. The margins are lobed or doubly serrated, the base is heart-shaped and the apex is apiculate or tipped.

The petiole is short and tomentose, with elongated stipules, obtuse, deciduous and green. Slightly pubescent along the upper surface and lower back, with obvious veins and numerous pili.

Hazelnut leaves (Corylus avellana). Source: Willow

flowers

Flowering occurs at the end of winter or early spring, even before the appearance of the first leaves. Hazel is a monoecious species with unisexual flowers, with separate male and female structures, but on the same plant foot.

The male flowers are arranged in long hanging catkins 6-12 cm in length, compact, cylindrical and with yellowish tones. The very small female ones, with reddish stigmas and partially hidden between the buds, once fertilized will give rise to the fruits or hazelnuts.

Fruit

The fruit is a dry and indehiscent 2 cm walnut, globular and ovoid in shape with a pericarp that is woody and reddish-brown in color. Generally, the fruits are grouped into infrutescences of 2-5 units that ripen at 7-8 months when they open and release the hazelnuts.

The hazelnut is a nucula covered by a fine fibrous outer shell, which surrounds a smooth layer that contains the seed inside. The fleshy and fatty cotyledon hazelnut is an edible product with a pleasant taste.

Male inflorescences of hazelnut (Corylus avellana). Source: pixabay.com

Taxonomy

- Kingdom: Plantae

- Division: Magnoliophyta

- Class: Magnoliopsida

- Order: Fagales

- Family: Betulaceae

- Genus: Corylus

- Species: Corylus avellana L.

Synonymy

- Corylus avellana subsp. memorabilis (Sennen) Sennen

- Corylus memorabilis Sennen

- C. mirabilis Sennen

- C. sylvestris Salisb.

Varieties

- Corylus avellana racemosa: trees with numerous leaves and long, sloping branches. The fruits are arranged in clusters, the hazelnuts are orbicular, robust and slightly striated. They are commonly known as San Cono, San Juan, Santa María de Jesús or San Nicolás.

- Corylus avellana glandulosa: the plant has an arboreal development, hazelnuts are small, thick and coniform fruits. The cover is rustic, firm and persistent, compressed at the base and the apex sunken. They are known as common hazel, Spanish hazel, baccilara, cannellina, ghiannusa, nepulli, and piattiddara.

- Corylus avellana maxima: tall tree-like plant with numerous branches and particular leaves. The fruit is rounded, robust, medium and resistant to the skin. They are commonly known as England hazelnut, striated hazelnut, Badarau Bertosa, cerro, San Elmo, San Giorgio, pigra or rizzo.

Tender unfruits of hazelnut (Corylus avellana). Source: pixabay.com

Habitat and distribution

Corylus avellana is a temperate climate species, native to Europe and Asia, currently it has a large area of ​​distribution. It is a plant adapted to hot climates, with high relative humidity and good aeration, conditions that favor the development of hazelnuts.

Its geographical distribution is located from Siberia in North Asia and Russia, to Germany, Austria, France, Italy and Spain. Its natural habitat is located in the undergrowth of fir trees and is located in various environments, from hillsides, meadows, crags or meadows.

The northern limit is located under the 63rd parallel, North Africa to the south and the Caucasus to the east. The optimum temperature is around 12-16 ºC, it tolerates well the cold winter temperatures down to -8 ºC, but it does not support summer droughts.

In the Iberian Peninsula it is located from sea level to 1,900 meters above sea level, being more abundant in the northern region. Towards the south, its presence is limited to protected lands, such as riverbanks and banks of streams, streams or streams.

It grows on fertile and deep soils, calcareous or siliceous in nature, pH between 5.5-7.8, slightly clayey, but well drained. It is a very sensitive species to the absence of humidity, which increases in sandy and calcareous soils.

Hazelnut grows in ravines, ravines or valleys in isolation or in association with other species, forming stands or small forests. It develops on various types of soil, as long as it is not very sandy or of low fertility, requiring constant humidity.

Hazelnuts Source: pixabay.com

Uses, properties and benefits

Properties

Hazelnut is a food with a high nutritional level, it contains vitamin E, thiamine (vitamin B ₁), pyridoxine (vitamin B ₆) and folic acid (vitamin B ₉). Also, minerals such as calcium, copper, iron, magnesium, manganese, and potassium; its calcium content is higher than certain nuts, with the exception of almonds.

Of its total weight, 13-15% corresponds to proteins, 7-8% to fibers and 60% to fats. The fat content is distributed in monounsaturated or oleic fats (55%), polyunsaturated like omega 6 linoleic acid (15%), other polyunsaturated (25%) and saturated (5%).

Benefits

The presence of various secondary metabolites provide beneficial antioxidant properties to prevent cancer and stabilize blood pressure. In addition, it contributes to the proper functioning of the immune and nervous systems, normalizing the level of cholesterol and triglycerides in the blood.

On the other hand, its regular consumption contributes to the health of the skin and eyes, the production of red blood cells and the hormonal system. It also improves the digestive system, prevents constipation and anemia, and provides benefits to the cardiovascular system.

Applications

It is grown mainly for the production of edible fruits due to its high nutritional value, being consumed as a dried fruit and used in confectionery. An oil is extracted from the seeds that is used to make food, cosmetic products and lubricants.

Hazelnut wood is light, dense and manageable, being used in marquetry and cabinetmaking to make pieces such as handles, handles or sieves. The branches and strips of wood are so flexible that they are used in basketry and cooperage, as well as the production of charcoal.

This species is also used as an ornamental and in the reforestation of eroded environments. In the same way as a protector of horticultural crops or fruit trees, creating living barriers or windbreaks.

Hazel female flowers (Corylus avellana). Source: Algirdas

Culture

Requirements

In agronomic management of a commercial hazelnut plantation, it requires low maintenance as long as it is grown on the right soil. This species effectively develops on loamy clay soils, loose, limestone or siliceous in nature, pH (6-7.5), fertile and well drained.

It grows on flat terrain up to altitude levels between 1,600-1,900 meters above sea level, in full sun exposure or under the forest canopy. Some varieties have adapted to living in the shade provided it has abundant humus, in acidic or alkaline pH soils and high levels of contamination.

Hazelnut cultivation requires attention to aspects related to the conditioning of the land that favors the development of the plantation. In this case, elimination of obstacles, leveling the ground, mechanization (plow and harrow) and design of structures that favor drainage.

Floors

This species requires deep soils (40-50 cm), with a loam-clay, clay-silty, silt-clayey or sandy-silty soils, with less than 65% silt. Porous soils are recommended, which favor aeration and moisture retention, as well as pH levels between 6 to 7.5.

Weather

The hazelnut is a species very tolerant to weather conditions, resists extreme cold during winter and summer droughts. However, the best production is obtained in moist, deep, well-drained soils and in full sun exposure.

During winter, the optimum annual average temperature is between 12-16 ºC, being very resistant to cold. In flowering, the female inflorescences tolerate up to -10 ºC and the male ones -16 ºC during development and -7 ºC when flowering.

During the summer, the daytime temperature should fluctuate between 23-27 ºC and at night between 16-18 ºC. Variations above 35 ºC together with low humidity can cause foliage wilting.

In relation to humidity contributions, hazelnut is a crop that does not require irrigation in locations with rainfall greater than 800 mm per year. During the summer, in areas with very long dry periods, the crop requires occasional watering.

Relative humidity values ​​between 70-80% favor the development of the crop during the vegetative period. Indeed, low levels of relative humidity influence the growth of the plant and the appearance of physiological damage to the leaves.

On the contrary, during pollination it is desirable that the relative humidity is low. In hazelnut pollination is anemophilic and requires a dry environment that favors the dissemination of pollen.

Driving

Once the cultivation is established, the plants require different pruning for formation, maintenance, fruiting or health. During the first years it is necessary to carry out training and maintenance pruning to clarify the crown and balance its development.

In adult plants in full production, it is recommended, every 3-5 years, to remove shoots, damaged, diseased, weak or extremely growing branches. As well as the suckers that grow from the base and tend to reduce the productivity and quality of the fruits.

Hazel in its natural habitat. Source: MPF

Plagues and diseases

Pests

The most common pests are aphids or aphids that affect the shoots or buds especially during the spring. Some species, such as Mysus persicae, lodge under the underside of the leaves and on the tender shoots.

The otiorrinco (Otiorhynchus cribricollis) is a beetle that causes foliar damage, although it is the larva that causes the greatest economic damage. On the other hand, the larva of the balanino (Curculio mucum) causes serious damage to the seeds, which are its main food source.

Hazel bugs (Gonocerus acuteangulatus or Palomena prasina) are common in the fruits. The bites cause the abortion or emptying of the fruit and the "enchinchado" drastically reducing the quality of the hazelnuts.

Diseases

Among the diseases, tearing disease (Cytospora corylicola) is one of the most serious, causing damage to the branches. This disease has an incubation time of 4-5 years, which ends with the breaking and death of the infected branches.

The disease called gloesporiosis of hazelnut (Gloesporium corylii) acts on the inflorescences, the tissues become necrotic, considerably reducing the production of pollen. This phytopathogenic fungus has the ability to remain active in the soil, infecting the new inflorescences the next year.

Finally, powdery mildew (Phyllartinia corylea) is an ectoparasitic fungus that affects foliage in dry temperate climates with low atmospheric humidity. The disease is characterized by the voluminous grayish-white pustules that cover the leaves, in severe cases they cause the fall of the fruits.

References

1. Corylus avellana. (2019). Wikipedia, The Free Encyclopedia. Recovered at: es.wikipedia.org
2. Corylus avellana (2018) Argentine National Pest Surveillance and Monitoring System. Recovered at: sinavimo.gov.ar
3. The Hazelnut Cultivation (2018) © Copyright Infoagro Systems, SL Recovered in: infoagro.com
4. Ellena, M. (2009). European hazel. Technical aspects in cultivation. INIA, Tierra Adentro. January-February, (83), 26-28.
5. Enescu, CM, Houston Durrant, T., de Rigo, D., & Caudullo, G. (2016). Corylus avellana in Europe: distribution, habitat, usage and threats. European Atlas of Forest Tree Species. Publ. Off. EU, Luxembourg, pp. e015486.
6. Polanco Zambrano, DA (2017) Common hazel (Corylus avellana). Nature ParadaisSphynx. Recovered in: Naturaleza.paradais-sphynx.com
7. Sánchez de Lorenzo-Cáceres, JM (2014) Corylus avellana L. Ornamental Flora of Spain. Recovered in: arbolesornamentales.es
8. Sarmiento, L. (2019) Characteristics and flowering of the hazelnut tree. Recovered in: jardineriaon.com