Hazelnut (Corylus) — description, cultivation, uses, and varieties

Edible kernel of hazel trees (also called filbert or cobnut). Overview of botany, cultivation, culinary uses, nutrition, major producers, and distinctions between varieties.

Overview

Hazelnuts are the edible kernels produced by species of the hazel genus (Corylus). Commonly called hazelnuts, cobnuts or filberts, these nuts are used fresh, roasted, or processed into pastes, oils and butters. The term "filbert" often denotes a more elongated nut, while "cobnut" is used regionally for certain rounded varieties. In botanical and culinary contexts they are treated as a type of nut.

Botanical characteristics and harvest

Hazel shrubs and small trees produce clusters of hard-shelled kernels enclosed by leafy husks. The plants are typically monoecious: male flowers appear as long catkins that release pollen, and small female flowers develop later on the stems. Nuts ripen on the tree and usually fall from their husks when mature — often several months after pollination. After harvesting, kernels are dried to reduce moisture and prepared for storage or processing.

History, cultivation and major producing regions

Hazelnuts have been cultivated in temperate and Mediterranean climates for many centuries and are associated with traditional agroforestry in parts of Europe and western Asia. Modern commercial production is concentrated where climate and soils suit hazel species: notable producing areas include Greece, Turkey, Italy and the United States, particularly the Pacific Northwest states of Oregon and Washington. Cultivation requires attention to pollination (many varieties are wind-pollinated), spacing, and post-harvest drying to prevent spoilage.

Uses and culinary applications

Hazelnuts have a wide range of culinary uses. Their rich, slightly sweet flavor pairs well with chocolate and they are commonly used in confections, pralines, truffles and baked goods. Hazelnuts are ground into pastes and nut butters, pressed for oil used in cooking and cosmetics, and incorporated into spreads and flavorings. Lower-grade nuts or byproducts may be used as livestock feed or in industrial processing.

Whole or chopped—confectionery, baking, salads
Roasted and blanched—snacking and pastry fillings
Ground into paste—spreads, pralines, and confections
Pressed oil—culinary and cosmetic uses

Nutritional profile, health and safety

Hazelnuts are valued for their nutrient density. They contain appreciable amounts of plant proteins and are high in heart-healthy unsaturated fats, including monounsaturated fatty acids. Hazelnuts also supply dietary fiber, vitamin E and various minerals. As with other tree nuts, hazelnuts can trigger allergic reactions in susceptible individuals. Proper drying and storage are important because improperly stored nuts can develop fungal contamination; processing standards and regulation help reduce such risks in commercial supplies.

Varieties and notable distinctions

Several species and cultivated varieties exist. European hazel (Corylus avellana) is widely grown for commercial production in Europe, while North American species (e.g., Corylus americana) have local importance. Cultivars are selected for nut size, shell strength, flavor and suitability for mechanized harvest. The common naming differences—"filbert" for elongated nuts and "cob" or "cobnut" for rounder varieties—are useful for distinguishing forms but do not imply fundamentally different uses.

In summary, hazelnuts are a versatile, nutrient-rich nut with a long history of cultivation. They play important roles in regional agriculture, global confectionery, and the culinary arts, and are processed into a variety of foods and oils prized for flavor and texture.