Walnuts are a globally popular food crop, and the United States is a significant producer, with commercial operations concentrated in specific regions that offer ideal growing conditions. The geography of walnut production across the US is split between the large-scale commercial cultivation of the English walnut and the more widely distributed presence of the native Black walnut. The distinct environmental needs of each species largely dictate their respective ranges.
The Commercial Heart English Walnut Production
The vast majority of walnuts sold in the United States, and a significant portion of the global trade, are the English or Persian walnut (Juglans regia). This species is not native to the US but was introduced by Spanish missionaries in the 1700s, and it dominates the commercial market. Over 99% of the nation’s commercial English walnut production is centered in California.
The prime growing area is California’s Central Valley, which includes the San Joaquin and Sacramento Valleys. This region offers a Mediterranean-like climate with hot, dry summers and cool, wet winters that the trees thrive in. The deep, fertile soils and extensive irrigation resources provide the optimal conditions for high-yield orchards. Smaller commercial production of English walnuts can be found in specific valleys in Oregon where the climate is similarly moderated.
The commercial operations focus on the nut itself, which has a thin shell and a mild flavor favored by consumers. The scale of this production is immense, involving thousands of growers and hundreds of thousands of acres dedicated to the crop.
Native Species The Range of Black Walnuts
The native American species, the Black Walnut (Juglans nigra), has a far more expansive, though less commercially intense, range across the US. It is widely distributed across the Eastern, Midwestern, and Southern US, extending from Vermont to Florida and west to Minnesota and Texas. These trees typically grow as scattered individuals or in small clusters within mixed hardwood forests.
The Black Walnut is a valuable timber species. Its nuts are often wild-harvested or grown on a smaller, specialized scale for their distinct, strong, and earthy flavor. The nut meat is challenging to extract due to a thick, hard shell, which contributes to its different market compared to the English walnut. The trees prefer rich, moist, well-drained soils, often thriving in bottomlands and along riparian zones throughout the central and eastern states.
Key Environmental Needs for US Walnuts
The geography of walnut growth is determined by the trees’ environmental requirements, primarily the need for a specific winter dormancy period. Both English and Black walnuts require “chilling hours,” or time spent at temperatures below 45°F, to properly break dormancy and produce fruit. The temperate climate of California’s Central Valley provides a reliable chill period without the deep freezes that could damage the trees.
Both species require deep, well-drained, and fertile soil to accommodate their extensive root systems. Commercial English walnut orchards rely heavily on supplemental irrigation, as the trees are not drought-hardy, to achieve maximum yields in the drier western climate. In contrast, the native Black Walnut is more tolerant of a broader range of temperatures and soil types. This tolerance explains its widespread presence across the naturally humid eastern half of the country.