The hazelnut, commonly known as the filbert, is the edible nut produced by trees of the Corylus genus, belonging to the birch family Betulaceae. The species most widely cultivated is Corylus avellana, native to Europe and Western Asia. Hazelnuts have been cultivated for thousands of years, with major contemporary production concentrated in Turkey, the world’s largest producer, and in regions of the United States like Oregon.
Establishing the Orchard
Successful hazelnut cultivation begins with selecting a site that meets specific environmental needs for the tree to thrive. Hazelnuts prefer a temperate climate characterized by mild winters and summers that are not excessively hot. The trees require a substantial chilling period, typically around 1,200 hours between 5°C and 7°C, to ensure reliable flowering and yield.
The ideal soil is a deep, well-drained loam, with a slightly acidic to neutral pH between 6.0 and 7.0. Heavy clay or very sandy soils should be avoided, as the fibrous root system of the hazelnut tree draws moisture primarily from the upper soil layer. Planting stock, whether bare-root or containerized, is typically placed in the autumn or late winter.
For commercial orchards, trees are spaced to accommodate machinery and allow for sufficient sunlight, commonly around 15 to 20 feet between trees and 20 to 30 feet between rows. A critical step is incorporating pollinizer varieties, as hazelnut trees are self-incompatible despite having both male and female flowers. Pollen is transferred by wind, so compatible varieties must be planted nearby, ideally no more than 50 feet away, to ensure female flowers are receptive when male catkins shed pollen. Growers often use two or three different pollinizer varieties to ensure pollen availability throughout the entire flowering period, which extends from late November to early March.
Maintenance and Maturation
The years following planting are focused on training the young tree to establish a strong, productive structure. Hazelnut trees naturally grow as multi-stemmed shrubs, but commercial orchards often train them into a single-trunk tree, typically using a modified central leader system, to facilitate mechanization and orchard management. This structural pruning, performed during the dormant season, aims to develop three to five strong scaffold branches evenly spaced around the trunk.
Ongoing maintenance involves managing the tree’s health, including removing suckers that grow from the roots or base of the trunk. Once established, maintenance pruning focuses on removing dead or diseased wood and making thinning cuts to allow light and air to penetrate the canopy, which helps reduce disease and stimulates new fruiting wood. Proper irrigation is especially important during the first few years and in dry summer periods, as the trees require consistent moisture for optimal growth.
Hazelnut trees typically begin to produce a harvestable yield between three and five years after planting. It can take an additional two to five years for the trees to reach their full commercial bearing potential, usually between six and ten years. Consistent fertilization based on soil testing helps provide the necessary nutrients, particularly potassium, which is important for nut development.
Harvesting and Post-Harvest Preparation
The harvest season for hazelnuts generally occurs in late summer or early fall, typically from late August to October, once the nuts have fully matured. A primary indicator of readiness is when the nuts naturally drop from the tree to the ground. Commercial orchards use mechanical harvesting methods, which involve sweeping or vacuuming the fallen nuts from the cleared orchard floor.
The first step after collection is to clean the nuts immediately to remove debris such as soil, stones, leaves, and empty shells. Specialized cleaning equipment uses air flow and rotary sieves to separate the nuts from lighter and heavier foreign materials. Prompt cleaning is important to prevent the nuts from absorbing moisture and developing mold.
The most critical post-harvest step is drying, essential for ensuring the nuts can be stored long-term. Hazelnuts must be dried to a specific moisture level to inhibit mold growth and rancidity. The target moisture content for in-shell hazelnuts is typically 7 to 10% (4 to 6% for the kernel), and drying is achieved by spreading the nuts in a single layer or using specialized commercial dryers.