A hazel tree is a deciduous plant belonging to the genus Corylus, typically found in the temperate regions of the Northern Hemisphere. These versatile plants grow as large, multi-stemmed shrubs or small trees, valued both for landscaping and for their edible fruit. The fruit of the hazel is the hazelnut, a source of quality oil and a staple in confectionery. The genus is classified within the birch family, Betulaceae, and contains numerous species that contribute to forest ecosystems and commercial agriculture globally.
Identifying Features and Species
Hazel trees are readily identifiable by their distinctive foliage and flowering structures which appear early in the year. The leaves are broad and rounded, featuring a softly hairy surface and a doubly serrated margin. The bark is generally smooth and gray-brown on younger stems, sometimes developing a slightly peeling texture as the plant matures.
The hazel tree is monoecious, producing separate male and female flowers on the same plant. The male flowers are conspicuous, forming long, pale yellow, pendulous catkins that often emerge in late winter before the leaves. The female flowers are much smaller, appearing as tiny, bud-like structures with distinctive bright red styles protruding from the bud scales.
The common European hazel, Corylus avellana, is frequently cultivated and typically grows as a multi-stemmed shrub. In contrast, the American hazel, Corylus americana, is a smaller shrub native to eastern North America, producing nuts that are generally smaller than their European counterparts. Other species, such as the Turkish hazel, Corylus colurna, grow into much larger, single-trunk trees, valued primarily for their ornamental qualities and urban tolerance.
Habitat and Growing Requirements
Hazel trees thrive across temperate environments, commonly found along woodland edges, in hedgerows, and in scrubland areas. They tolerate various soil types but perform best in fertile soil that maintains moisture while possessing good drainage. Waterlogged conditions should be avoided, as the relatively shallow roots often stay within one meter of the soil surface.
For optimal growth and nut production, hazels require a position that receives full sun to partial shade. They are cold-hardy, but commercial nut yields can be negatively affected by extremely low temperatures, especially those below -10°C, which can damage the early-flowering catkins. Cultivation often involves selecting a sheltered position to protect the plants from harsh, persistent winds that can slow growth and reduce productivity.
The Harvest: Hazelnuts
The hazelnut develops from the fertilized female flower over seven to eight months. Each nut is enclosed either partially or fully by a leafy, cup-like structure called an involucre, or husk. The nut itself is a hard-shelled fruit containing the edible seed, which is released from the husk when it ripens and falls to the ground in late summer or autumn.
The commercial significance of the hazelnut is substantial, with Turkey being the world’s largest producer. Hazelnuts are a nutrient-dense food, providing approximately 628 kilocalories per 100 grams, composed of about 61% fat, 15% protein, and 17% carbohydrates. The fat content is predominantly monounsaturated fat, primarily oleic acid.
In a one-ounce serving, hazelnuts are an excellent source of micronutrients, including vitamin E, manganese, and copper, and a good source of thiamin, magnesium, dietary fiber, and folate. This rich profile makes them a popular ingredient in the food industry. The nuts are a primary component in products like praline, chocolate truffles, and hazelnut cocoa spreads, and are used in several ways:
- Consumed as a snack.
- Pressed into a flavorful oil for cooking.
- Used extensively in baking.
- Used extensively in confectionery.