Hazelnuts, the edible nuts of trees and shrubs in the genus Corylus, are true tree nuts. Known historically as cobnuts or filberts, these nutrient-dense foods have been a part of the human diet for millennia. The nut is consumed worldwide in various forms, from a raw snack to a paste used in modern confectionery and chocolate spreads. The expanding global demand for these flavorful kernels has led to the establishment of vast commercial orchards, primarily focused on the European species.
The Ideal Growing Environment
Commercial hazelnut production requires a specific set of environmental conditions, primarily thriving in temperate climates characterized by distinct seasonal shifts. A necessary period of winter cold is required for the trees to properly enter dormancy, a process known as chilling hours, which typically requires exposure to temperatures between 32°F and 45°F for 800 to 1,600 hours, depending on the cultivar.
While winter cold is necessary, the trees are highly sensitive to extreme temperature fluctuations during the flowering period. Temperatures dropping below approximately 10°F can severely damage the trees, and late spring frosts are a major concern because they can destroy the delicate male catkins and female flowers, significantly reducing the year’s harvest. Ideal summer weather consists of mild conditions, as prolonged temperatures above 86°F can cause stress and negatively impact nut development and yield.
Successful orchards are established on well-drained, loamy soils that maintain consistent moisture without becoming waterlogged. The hazelnut is a wind-pollinated crop, requiring orchards to include different cultivars planted strategically. This ensures that the pollen shed from the male catkins of one variety coincides with the female flower receptivity of the main nut-producing variety. Humid and windy weather during the mid-winter pollination period is therefore beneficial for effective pollen dispersal.
Global Hubs of Commercial Production
The majority of the world’s commercial hazelnuts originate from a few select regions that meet these precise environmental requirements. Turkey is the undisputed global leader in production, often accounting for 70% or more of the total world supply. Turkish hazelnut production is concentrated along the Black Sea coastal region, a strip of land that benefits from moderate temperatures, ample rainfall, and a suitable soil pH, with provinces like Ordu and Giresun being major cultivation centers.
Following Turkey, Italy is the second-largest producer, renowned for its high-quality cultivars, most notably the ‘Tonda Gentile delle Langhe’ from the Piedmont region. This area’s chalky soil and mild climate contribute to the nut’s distinct flavor and texture, highly prized in the confectionery industry. Other significant European production areas include Spain, where most of the output comes from the Catalonia region, particularly the Tarragona province.
In North America, the United States is a notable producer, with the Willamette Valley in Oregon being the source of over 99% of the country’s commercial crop. Additionally, new production hubs are emerging in the Southern Hemisphere, most notably in Chile, which utilizes its inverse seasons to supply the global market year-round, and Azerbaijan, which is rapidly increasing its output.
Major Hazelnut Species and Their Native Regions
The term hazelnut generally refers to the fruit of any species in the genus Corylus, but commercial agriculture primarily uses a single type. Corylus avellana, the Common or European Hazel, is the shrub native to Europe and Western Asia that forms the foundation of nearly all commercial production worldwide. Most popular cultivars, such as ‘Barcelona’ and ‘Tonda di Giffoni,’ are selections or hybrids of this species.
Another related species is Corylus maxima, known as the Filbert or Giant Filbert, which is native to southeastern Europe and southwestern Asia. This species is a parent of many modern hybrid cultivars, identifiable by its nut being almost completely encased by a long, tubular husk. The American Hazelnut, Corylus americana, is a multi-stemmed shrub native to the eastern and central United States and Canada.
The nuts of C. americana are smaller than the European varieties, but the plant is valued for its hardiness and resistance to Eastern Filbert Blight, prompting its use in breeding programs to create new, disease-tolerant commercial hybrids. Finally, Corylus colurna, the Turkish Hazel, is a large, pyramidal tree native to Southeast Europe and Asia Minor. While its nuts are edible, it is primarily used in orchards as a non-suckering rootstock onto which commercial varieties are grafted or as a durable ornamental tree in urban environments.