Why the humble hazel tree was once considered the Swiss Army knife of nature

Nature · Published 30 September 2026 Swipe more like this →

In short: From ancient Celtic myths of wisdom-granting salmon to the modern naming of ballistic missiles, the hazel genus has left an indelible mark on human culture. Beyond its legendary status, this resilient plant supports diverse ecosystems and provides versatile materials that have shaped human history for thousands of years.

Hazels, belonging to the genus Corylus, are deciduous plants native to the temperate Northern Hemisphere. While typically classified within the birch family, Betulaceae, some botanists argue for a separate family, Corylaceae. These plants exhibit remarkable diversity, ranging from suckering shrubs to towering trees that can reach 35 metres in height. Their reproductive strategy is equally distinct; they produce monoecious flowers very early in spring, with male catkins releasing vast quantities of pollen—up to 4933 grains per square metre—which often triggers seasonal allergies.

The genus is famously versatile, earning the nickname the Swiss Army knife of plants. Historically, hazel wood was coppiced on a seven-year cycle to provide durable materials for wattle fencing, baskets, and coracle boat frames. Beyond utility, the hazel holds a deep place in folklore. Celtic tradition tells of nine sacred hazel trees surrounding a pool, where salmon consumed fallen nuts to gain wisdom, a quality eventually passed to the legendary hero Fionn Mac Cumhail. In the Brothers Grimm tales, hazel branches were imbued with protective powers against snakes, while a planted branch served as a site for granting wishes in Cinderella.

Ecologically, the hazel is a cornerstone species. It maintains mutualistic relationships with at least 21 species of fungi and supports specialized insects, such as the aphid Myzocallis coryli and various moths. Its nuts are a vital food source for wildlife, including dormice and red squirrels. Despite its long history—with fossils dating back to the Cretaceous—the exact number of species remains a subject of scientific debate, with estimates varying between 14 and 20 depending on whether one consults the World Flora Online or the Flora of China. Today, the genus remains economically significant, particularly for its edible nuts and its role as an ornamental garden plant.

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