Wild walnut trees grow across a broad swath of the eastern and central United States, from New England to the Great Plains and south into Texas and Georgia, while commercially farmed walnuts are overwhelmingly a California crop. The US is home to multiple walnut species, each with its own geography, and the answer to where you’ll find them depends on which walnut you mean. Black walnut, the most widespread native species, shows up in forests, backyards, and city parks across roughly two-thirds of the country, while the English walnut most people buy at the grocery store comes from irrigated orchards in the Central Valley.
Black Walnut Across the Eastern Half
Black walnut (Juglans nigra) is the walnut tree most Americans encounter without realizing it. It does not form dense stands the way oaks or maples do. Instead, it grows as scattered individual trees or in small groups throughout central and eastern forests. According to USDA silvicultural data, its natural range stretches from western Vermont and Massachusetts west through New York to southern Ontario, across to central Michigan, southern Minnesota, eastern South Dakota, and into northeastern Nebraska. Going south, it reaches western Oklahoma, central Texas, and then curves east through to northwestern Florida and Georgia, though it largely skips the Mississippi River floodplain and Delta region.1USDA Forest Service. Black Walnut
That range is enormous, but black walnut is choosy within it. The best specimens, the tall straight-trunked trees prized for veneer-quality lumber, grow on deep, well-drained bottomland soils in the Appalachians and the Midwest. Coves, stream terraces, and fertile valleys produce the fastest growth. On dry ridgetops or heavy clay, the trees survive but stay small and gnarled. Missouri stands out as a stronghold: a spatial analysis of land suitability found roughly 16,000 square kilometers of Missouri land suitable for black walnut, far exceeding the suitable area identified for other tree crops like pecan and Chinese chestnut in the same region.2Wiley Online Library. Significant opportunities for tree crop expansion on marginal lands in the Midwest, USA States like Indiana, Ohio, Illinois, Iowa, and Kansas also fall within the heart of its range, and driving through rural areas there in autumn you’ll often spot the telltale green-husked nuts littering roadsides.
English Walnuts and the California Orchard Belt
When Americans think of eating walnuts, they are almost always thinking of the English walnut (Juglans regia), a species native to Central Asia that was brought to California by Spanish missionaries in the late 1700s. Today, California dominates US walnut production by a wide margin. The state’s Central Valley, with its Mediterranean climate of hot dry summers and mild winters, turned out to be nearly ideal for the crop. Most commercial acreage is concentrated in the Sacramento and San Joaquin valleys, with San Joaquin, Stanislaus, Tulare, and Butte counties among the heaviest producers.
English walnuts are also grown on a much smaller scale in Oregon’s Willamette Valley, where the climate is cooler and wetter but still workable for certain cultivars. A handful of growers in other western states experiment with them, but outside California and Oregon, English walnut orchards are rare. The tree needs a specific combination of winter chill hours, warm summers, well-drained soil, and reliable irrigation that few other US regions can deliver at commercial scale. If you see a walnut tree growing wild east of the Rockies, it is almost certainly a black walnut or one of its relatives, not an English walnut.
Butternut in the Northeast
A third US walnut species gets far less attention but matters ecologically: butternut (Juglans cinerea), sometimes called white walnut. Butternut’s range overlaps with black walnut’s northern and eastern portions but extends farther into New England and the upper Midwest. It favors stream banks, moist slopes, and mixed hardwood forests from southern Quebec down through the Appalachians. Surveys in the northeastern US have confirmed its continued presence, though often in declining numbers.3Canadian Journal of Forest Research. Butternut (Juglans cinerea) health, hybridization, and recruitment in the northeastern United States
Butternut is in serious trouble. A fungal canker disease first reported in southwestern Wisconsin in 1967 has since spread across virtually the entire range. Since the 1980s, the number of butternut trees and butternut volume have dropped by about 58% and 44% respectively across the US range, pushing the species toward local extinction in some areas.4PubMed Central. Regional patterns of declining butternut (Juglans cinerea L.) suggest site characteristics for restoration More recent research describes the species as having been “decimated” by the disease, and field trials are now testing whether certain hybrid crosses with Japanese walnut show better resistance.5Canadian Journal of Forest Research. Susceptibility to butternut canker disease in field trials is influenced by disease level and hybridization If you find a butternut in the wild today, there is a good chance it shows signs of canker damage. Smaller trees in riparian habitats tend to carry the most cankers.3Canadian Journal of Forest Research. Butternut (Juglans cinerea) health, hybridization, and recruitment in the northeastern United States
Thousand Cankers Disease and the Western Walnut Problem
Black walnut faces its own disease crisis, and the geography of the threat is counterintuitive. The biggest mortality events have not occurred in the species’ native heartland but in the western US, where black walnut was widely planted as an ornamental and shade tree outside its natural range. Since 2001, widespread die-offs of black walnut have been reported along Colorado’s Front Range. The culprit is a combination of the walnut twig beetle and a fungus it carries, which together cause what researchers named “Thousand Cankers Disease” because mortality results from an enormous number of small bark cankers that eventually coalesce and girdle branches and trunks.6Plant Health Progress. Black Walnut Mortality in Colorado Caused by the Walnut Twig Beetle and Thousand Cankers Disease
The disease has since been confirmed in symptomatic black walnut trees in California, Idaho, Oregon, Washington, New Mexico, and Utah, causing extensive and intensifying mortality across the western US.7Plant Health Progress. Thousand Cankers Disease is Widespread in Black Walnut in the Western United States The fear among forest pathologists is that the beetle-fungus complex could be introduced into the eastern native range, where black walnut has enormous economic and ecological value. Several eastern states enacted quarantines on walnut wood movement in response. It has been detected east of the Mississippi in a few locations, including Tennessee, but so far the catastrophic die-offs seen in Colorado and the Pacific Northwest have not materialized in the core native range. Urban tree inventories in cities like Knoxville, Tennessee, track hundreds of black walnut specimens in parks and along streets, though the actual number of trees in unmanaged areas is likely much larger.8Journal of Forestry. Status and Impact of Walnut Twig Beetle in Urban Forest, Orchard, and Native Forest Ecosystems
Walnut Trees in Cities and Backyards
People sometimes think of walnut trees as forest species, but they thrive in urban and suburban settings too. Black walnut is a common large-diameter tree in Midwestern cities. An inventory of Springfield, Missouri’s urban canopy, for example, found that black walnut was one of the most common large trees in the city alongside silver maple and hackberry.9Northern Research Station, U.S. Department of Agriculture, Forest Service. Springfield, Missouri’s urban forest, 2018 Similar patterns hold across the Midwest and mid-Atlantic. Older neighborhoods in cities like Indianapolis, Cincinnati, Louisville, and St. Louis often have mature black walnuts towering over lawns and lining streets.
For homeowners, these trees are a mixed blessing. They provide excellent shade and produce beautiful, dark-grained wood that can be worth thousands of dollars when milled into lumber. But they also drop heavy nuts by the hundreds, stain driveways and sidewalks with their green-black husks, and have a chemical defense system that makes gardening underneath them a headache.
The Juglone Effect on Surrounding Plants
Black walnut trees produce juglone, a chemical compound that is toxic to many common garden plants. Tomatoes, peppers, azaleas, blueberries, and some apple rootstocks are among the sensitive species that wilt or die when planted within the root zone of a walnut tree. The compound is present in roots, leaves, husks, and bark, and it leaches into the surrounding soil. Research has shown that juglone concentrations in the soil decline with both depth and distance from the trunk, so the effect is strongest close to the tree and near the surface.10PubMed. Juglone concentration in soil beneath black walnut interplanted with nitrogen-fixing species
This does not mean nothing will grow near a walnut tree. Plenty of plants are juglone-tolerant, including many native woodland species that evolved alongside walnut. Hostas, daylilies, ferns, black raspberries, beans, squash, and most grasses grow fine. The practical rule for landscaping around walnut trees is to avoid known sensitive species within about 50 to 60 feet of the trunk, roughly where the root system extends. Raised beds filled with imported soil can also create enough of a buffer for sensitive vegetables.
Agroforestry and Walnut Plantations
Black walnut is not just a wild tree. It has been deliberately planted across the Midwest for decades in agroforestry systems that combine tree and crop production. Missouri has been a leader in this approach since at least the 1960s. A program initiated there in 1965 establishes black walnut on wide spacing with row crops like wheat, sorghum, and soybeans grown between the trees for the first 10 to 12 years, followed by cool-season forage grasses once the canopy closes. Economic analyses of these systems show the highest returns come from combining nut and timber production within the same agroforestry regime.11The Forestry Chronicle. Black Walnut (Juglans nigra L.) Agroforestry – Its Design and Potential as a Land-use Alternative
More recently, researchers have measured carbon storage in black walnut alley cropping sites across Missouri and Arkansas, destructively harvesting trees to quantify above- and below-ground biomass.12Agroforestry Systems. Carbon and nitrogen accumulation within four black walnut alley cropping sites across Missouri and Arkansas, USA These systems are gaining interest not only for their nut and timber income but also for their potential role in carbon sequestration on agricultural land. Grafted cultivars selected for heavy nut production are typically planted rather than wild seedlings, and some Midwestern landowners manage walnut plantations as a long-term investment, since the trees take decades to reach harvestable timber size but the wood commands premium prices.
How Squirrels Shape Where Walnuts Grow
Walnut trees owe a significant part of their distribution to squirrels. Black walnuts are heavy, round nuts that don’t blow far from the parent tree on their own. The species depends on animals, especially gray squirrels, to move its seeds to new germination sites. Gray squirrels scatter-hoard nuts, burying individual nuts across a wide area and inevitably forgetting some of them. Those forgotten caches become new trees. Red squirrels, by contrast, tend to pile nuts into centralized larder hoards, which concentrates the seeds and makes germination less likely.
Field observations in the central hardwoods region found that gray squirrels were significantly more likely to scatter-hoard walnuts and acorns, while red squirrels tended to hoard items in larders or trees. The researchers concluded that red squirrels cannot fully compensate for the loss of gray squirrels as seed dispersers in agricultural landscapes where gray squirrel habitat has been fragmented.13Canadian Journal of Zoology. Food-hoarding behavior of gray squirrels and North American red squirrels in the central hardwoods region: implications for forest regeneration In other words, the distribution of walnut trees in any given area is partly a product of which squirrel species live there and how much forest corridor remains for them to operate in.
Indigenous Peoples and the Spread of Nut Trees
Human activity has shaped walnut distribution for far longer than European settlement. Research on the legacy of Native American land management has found that the distribution of certain nut and fruit trees in the southeastern US correlates with the locations of former indigenous settlements. A study examining honey locust, another tree with edible pods, found that its presence and abundance in parts of Appalachia was strongly associated with proximity to former Cherokee settlements, with tree abundance declining as distance from those sites increased.14PLoS ONE. Ghosts of Cultivation Past – Native American Dispersal Legacy Persists in Tree Distribution
While that particular study focused on honey locust rather than walnut, the principle extends to other nut-bearing trees that indigenous peoples valued and likely transported. Black walnut, butternut, and hickory were all food sources for various Native American groups, and their disproportionate presence near archaeological sites in parts of the Ohio Valley and southern Appalachians likely reflects centuries of deliberate or semi-deliberate cultivation. When you come across a big black walnut tree growing in an unexpected spot, the explanation may trace back to human hands working the landscape long before modern agriculture arrived.
How Climate Change May Shift Walnut Ranges
The map of where walnut trees grow in the US is not fixed. Climate projections suggest that suitable habitat for many eastern hardwood species, including black walnut, will shift northward over the coming decades. Models combining US and Canadian forest inventory data predict that habitat losses will occur primarily along the southern edges of species’ ranges while gains appear along northern range limits, especially under higher-emission scenarios.15Diversity and Distributions. Combining US and Canadian forest inventories to assess habitat suitability and migration potential of 25 tree species under climate change
For black walnut, that could mean reduced suitability in parts of Texas, Oklahoma, and the deep South where summers are already pushing the tree’s heat tolerance, while new habitat opens up in Minnesota, Wisconsin, and southern Canada. The catch is that trees cannot migrate quickly. The same modeling work found that only a small portion of newly suitable habitat is likely to be naturally colonized by the end of this century, even under optimistic assumptions about tree migration rates.15Diversity and Distributions. Combining US and Canadian forest inventories to assess habitat suitability and migration potential of 25 tree species under climate change Seeds travel short distances on their own, and their squirrel couriers don’t relocate entire populations hundreds of miles north over a few generations. The result could be a prolonged mismatch: the climate where walnuts currently grow becomes less favorable, but the trees haven’t yet established in the places that are becoming newly suitable. Human-assisted planting, including the kind of agroforestry programs already running in Missouri and Arkansas, may end up being the most effective way to help the species keep up with shifting conditions.
For English walnuts in California, the picture is different but no less uncertain. Rising temperatures and increasingly unreliable water supplies in the Central Valley are putting pressure on all irrigated tree crops. Some growers have already shifted acreage north within the valley, and interest in walnut cultivation in the Pacific Northwest has grown. Whether English walnut production stays concentrated in California or gradually disperses will depend less on biology than on water policy and economics in the decades ahead.