The royal walnut tree has been traveling the Silk Road for two millennia.

Nature · Published 3 October 2026 Swipe more like this →

In short: Known as the Persian or English walnut, Juglans regia is a botanical globetrotter. While its native range spans from the Balkans to the Himalayas, humans have carried this regal tree across continents for thousands of years, turning a wild mountain species into a global agricultural staple.

The name Juglans regia carries a sense of ancient prestige, derived from the Latin terms for Jupiter and royalty. This deciduous tree, which can reach heights of 25 meters, is native to a vast region stretching from northeastern Türkiye through the Caucasus and into the western Himalayas. Its natural distribution is difficult to map precisely because the tree has been a companion to human migration and trade for ages.

Central Asia serves as a critical center of genetic diversity for the species. Extensive, nearly pure forests of these trees still thrive in Kyrgyzstan at altitudes between 1,000 and 2,000 meters, particularly in the Jalal-Abad Province. While these forests are iconic, some researchers suggest they may be of cultivated origin. Genetic studies reveal that diversity is highest near Sariosiyo in Uzbekistan, pointing toward the complex history of how these trees were moved and selected by ancient civilizations.

The spread of the walnut was accelerated by historical figures like Alexander the Great, who introduced the 'Persian nut' to Macedonia. Romans later distributed lateral-bearing varieties across southern Europe and North Africa. By the time the tree reached China about 2,000 years ago via Silk Road merchants, it had already undergone significant hybridization. Today, the species is cultivated globally, from the temperate zones of the Northern Hemisphere to parts of the Southern Hemisphere, with farmers selecting for larger nuts and thinner shells over centuries of domestication.

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