The walnut you buy at the grocery store, the Persian (or English) walnut, originated in the mountain ranges of Central Asia. Its natural range stretches from the Balkans and Turkey through Iran and the Caucasus, across the Himalayas, and into western China. But the story goes much deeper than one species and one region. The walnut family itself dates back over 100 million years, and different walnut species evolved independently on separate continents.
Central Asia: The Walnut’s Homeland
The Persian walnut (the species grown commercially worldwide) grows wild across a vast arc of mountainous terrain. Natural populations exist in northern Iran, the southern Caspian coast, Turkey’s Anatolian plateau, the Caucasus region of Georgia, the western Himalayas of Pakistan and Kashmir, and as far east as China’s Xinjiang province. Genetic studies have pinpointed the area around the Qinghai-Tibet Plateau, southwestern China, and the Himalayas as the core center of genetic diversity for the species, suggesting this region played a central role in its early evolution.
After the last Ice Age, roughly 20,000 years ago, walnut populations became fragmented and isolated. The Tien Shan and Himalaya mountain ranges blocked gene flow between populations, and the gradual drying of Central Asia’s interior during the following millennia pushed walnut stands into scattered, favorable pockets. This isolation created distinct genetic clusters across Eurasia: three centered in Asia and one in Europe, where small populations managed to survive in the Balkans and parts of southern and western Europe.
The World’s Largest Wild Walnut Forest
One of the most striking remnants of this ancient range sits in the Chatkal mountains of southern Kyrgyzstan, near a village called Arslanbob. This is the world’s largest natural walnut forest, covering about 74,000 acres today. That’s a fraction of the estimated 1.5 million acres the forest once spanned, when wild walnut, apple, pistachio, plum, almond, and pear trees blanketed the surrounding valleys. Some of the deepest sections contain trees that are 500 years old, and locals prize their nuts for a distinctly superior flavor.
A Family Far Older Than the Persian Walnut
The broader walnut family has roots that go back to the age of dinosaurs. Fossil evidence places the family’s origin in the Late to Middle Cretaceous period, roughly 105 million years ago, in the warm “boreotropical” regions that then covered North America and Europe. The fossil record for the walnut family is unusually rich, spanning 60 million years from the Paleocene to the Pleistocene, with many fossils found well outside the family’s modern range, particularly across Europe and at high northern latitudes. Over tens of millions of years, different branches of the family spread and diversified across the Northern Hemisphere, eventually giving rise to the distinct species we know today.
North America Has Its Own Native Walnuts
The Persian walnut isn’t the only walnut species with deep roots. The black walnut is native to the central and eastern United States and evolved there independently. Its natural range runs from Vermont and Massachusetts west through New York to southern Ontario and Michigan, south through Minnesota and Nebraska to central Texas, and east to Georgia and northwestern Florida. Black walnuts thrive as scattered individual trees or small groups, growing best in well-drained bottomlands in the Appalachians and the Midwest. In Kansas, along its western fringe, black walnut is common enough to make up half or more of the tree cover in some stands. It produces a distinctly stronger-flavored nut with a much harder shell than its Persian cousin.
How Walnuts Spread Around the World
Humans have been eating walnuts for a very long time. Evidence of walnut consumption in Persia dates to around 7,000 BCE. From there, trade networks carried walnuts westward. The Silk Road was a major conduit, and genetic analysis of walnut populations across Central Asia confirms that human activity, not just natural dispersal, shaped the species’ spread. Archaeological findings of walnut use along trade routes align with the genetic distribution patterns researchers see today.
The ancient Greeks and Romans played a key role in establishing walnuts across Europe. The Romans cultivated them extensively and spread them into Gaul (modern France) and other parts of Western and Northern Europe. In fact, the Latin name for the walnut was “nux Gallica,” literally “Gaulish nut,” reflecting its association with that region. Genetic evidence suggests that while some walnut populations survived the Ice Age in pockets of southern Europe, the widespread cultivation across the continent was largely a human achievement.
Why They’re Called “Walnuts”
The English word “walnut” itself reveals how the nut traveled. It comes from the Old English “walhnutu,” which literally means “foreign nut.” The first element, “wealh,” meant “foreign” or “from Roman lands” (the same root that gives us “Welsh”). Germanic peoples coined the name because the walnut was introduced to them from Gaul and Italy, and they needed to distinguish it from the hazelnut, which was native to their region. So every time you say “walnut,” you’re using a word that essentially means “the nut that came from somewhere else.”
Walnuts in California
The Persian walnut reached the Americas through Spanish colonization. Franciscan missionaries introduced it to California around 1770, and the first commercial orchard was planted in San Diego County in 1843. California’s climate turned out to be ideal for walnut cultivation, and the state eventually became one of the world’s largest producers. The variety commonly sold as “English walnuts” in the United States are Persian walnuts, a name that stuck because English merchant ships were the primary vessels transporting them to North American ports in the early trade.