The hazelnut, also known as a cobnut or filbert, is a popular edible nut used in confectionery and snacks. It originates from a specific type of plant widely cultivated across the globe.
The Hazelnut’s Source: Defining the Corylus Genus
The hazelnut originates from the Corylus genus, a group of deciduous shrubs and small trees belonging to the Betulaceae, or birch family. These plants are generally multi-stemmed shrubs or small trees native to the temperate regions of the Northern Hemisphere. The genus Corylus includes about 15 species, all of which produce an edible nut.
The common term “hazelnut” generally refers to the nut from Corylus avellana, the most widely cultivated species globally. The name “filbert,” often used interchangeably, can sometimes refer specifically to nuts from Corylus maxima. The key difference between the two is the leafy involucre, or husk: it fully encloses the nut in C. maxima but only partially covers the nut in C. avellana. These nuts are botanically fruits, but are classified as nuts in common culinary use.
Identifying Features and Major Varieties
The hazelnut plant is characterized by its simple, rounded leaves that have a distinct double-serrated margin. The leaves are deciduous and turn vibrant shades of yellow or red in the autumn. Hazelnut plants are monoecious, meaning they bear separate male and female flowers on the same plant, which bloom very early in the spring before the leaves emerge.
The male flowers are conspicuous, hanging as pale yellow catkins that are 5 to 12 centimeters long. The female flowers are much smaller, appearing as tiny, bright red styles barely protruding from a bud.
The two main species of commercial relevance are the European Hazel (C. avellana) and the American Hazel (C. americana). C. avellana is the source of many large-nut cultivars, such as ‘Barcelona,’ which produces a large, round nut with a thick, hard shell. The American Hazel, C. americana, is typically a smaller shrub with nuts that tend to be smaller and have thicker shells than their European counterparts.
Commercial Production and Harvesting
The majority of the world’s commercial hazelnut supply comes from the European Hazel (C. avellana). Turkey is the leading global producer, accounting for over half of the world’s total production, with Italy being a distant second. In the United States, production is concentrated primarily in the Willamette Valley of Oregon, where the climate supports the large-scale cultivation of high-yielding cultivars.
Hazelnut plants prefer full sun and well-drained soil, and they require cross-pollination, meaning orchards must include different compatible cultivars. A plant begins to bear nuts around four years of age but does not reach full commercial productivity until about seven years. The nuts mature and naturally drop from the tree over a period of several weeks in the late summer and early autumn.
Commercial harvesting is mostly mechanized, relying on the nuts to fall to the ground when ripe. The ground beneath the shrubs is kept clear, and specialized machinery, including sweepers and vacuums, collects the nuts from the orchard floor. Prompt collection is important as nuts left on the ground for too long can develop defects, such as moldy kernels.