Walnuts originated in the mountain ranges of Central Asia, with the western Himalayas likely serving as the core region of their genetic diversity. From there, they spread across a vast arc stretching from western China through present-day Tajikistan, Uzbekistan, and the Caucasus region of Georgia and Turkey. The walnuts most people eat today, often called English walnuts or Persian walnuts, trace back to these wild populations. But North America has its own native walnut species with a completely separate history.
The Wild Roots of the Persian Walnut
After the last Ice Age, wild walnut trees survived in scattered, nearly isolated stands across Asia, from the Xinjiang province of western China through Central Asia to the Caucasus. Over thousands of years, major geographic barriers shaped these populations into distinct groups. The Tien Shan and Himalaya mountain ranges blocked gene flow between populations, and the gradual drying of Central Asia during the current geological epoch further fragmented walnut habitats into isolated pockets.
Genetic research has pinpointed three regions with especially high walnut diversity. The first and most important is south-central Asia: Tibet, the Kashmir and western Himalaya corridor (particularly Pakistan’s Hunza and Gilgit valleys), the northern Pamir ridges of Tajikistan, and the Tien Shan foothills of Uzbekistan. A 2024 study in population genetics confirmed that the western Himalayas are likely the core region of common walnut genetic diversity, making it the closest thing to a single “birthplace” for the species. The second hotspot sits in the Caucasus, spanning Georgia and northeastern Turkey. The third, more surprisingly, is in the Balkans, including parts of Greece, Romania, and Moldova, suggesting walnuts established themselves in southeastern Europe far earlier than once thought.
How Walnuts Reached the Rest of the World
People have been eating walnuts for a very long time. Archaeological evidence places walnut consumption in Persia as far back as 7,000 BCE, where the nuts were valued both as food and for religious purposes. From Persia, walnuts traveled along the Silk Road, the network of trade routes connecting Central Asia to the Mediterranean and East Asia. Genetic studies suggest that the patterns of walnut distribution across Asia owe more to human activity, specifically trade and deliberate planting, than to natural seed dispersal.
The Romans are credited with bringing the Persian walnut into northern Europe, planting trees as they expanded their empire. This is where the confusing name “English walnut” comes from. The species has nothing to do with England. English merchants simply became the primary traders shipping these nuts to their colonies and trading partners, and the name stuck in American English to distinguish the imported variety from native North American species. In much of the world, the same nut is still called the Persian walnut, which is far more accurate.
North America’s Own Walnut: The Black Walnut
While Persian walnuts were spreading along ancient trade routes, a completely different walnut species was thriving in North America. The black walnut is native to the central and eastern United States, with a range stretching from Vermont and Massachusetts west through New York to southern Ontario, down through the Midwest to eastern South Dakota and Nebraska, and south to central Texas and northwestern Florida.
Unlike the Persian walnut, which was cultivated and spread by people, the black walnut grew wild as scattered individual trees or in small clusters throughout mixed hardwood forests. It rarely formed pure stands. The tree thrived in well-drained river bottoms and coves, particularly in the Appalachians and the Midwest. Near the western edge of its range in Kansas and beyond, it was often confined to floodplains, growing alongside elm, hackberry, and ash. Black walnuts have a stronger, earthier flavor than Persian walnuts and an extremely hard shell, which is one reason the milder, easier-to-crack Persian walnut dominates grocery stores.
Where Walnuts Grow Today
China is by far the world’s largest walnut producer, accounting for roughly 59% of global production with about 1.55 million metric tons in the 2024/2025 season. The United States comes in second at 21%, producing around 547,000 metric tons, almost entirely from California’s Central Valley. Chile (6%), the European Union (5%), and Ukraine (4%) round out the top five.
This modern map of production looks nothing like the walnut’s original range. Both the Persian walnut and the pecan (a relative in the same botanical family) are now cultivated well outside their native habitats, including in South America, northern and southern Africa, Australia, and New Zealand. The Xinjiang region of China, once home to wild walnut populations, remains important, though genetic research suggests that most of Xinjiang’s current walnut populations were introduced by humans rather than descending directly from ancient wild trees. One notable exception is the Gongliu Wild Walnut Valley in Xinjiang, which harbors genetically distinct wild populations that conservation scientists consider a priority for protection.
The walnut’s journey from isolated mountain valleys in Central Asia to farms on six continents is one of the longest stories in agricultural history, shaped as much by ancient traders and Roman soldiers as by the trees’ own biology.