California’s Central Valley produces an extraordinary range of crops, from almonds and walnuts to tomatoes, cotton, grapes, citrus, and alfalfa. Stretching roughly 450 miles from Redding in the north to Bakersfield in the south, the valley is one of the most productive agricultural regions on Earth. Perennial crops alone now account for roughly 60 percent of its planted area and around 80 percent of its annual revenue, a share that has grown dramatically in recent decades.1Environmental Research Letters. Water shortage risks from perennial crop expansion in California’s Central Valley Understanding what grows here, and why, means looking at tree nuts, fruits, vegetables, field crops, and the environmental pressures reshaping the region’s agriculture.
Tree Nuts Dominate the Landscape
If you fly over the Central Valley in summer, the most visible feature is row after row of orchard canopy. Almonds are the single largest crop by acreage and value, concentrated heavily in the San Joaquin Valley’s western and southern portions. Pistachios have expanded rapidly since the 1990s, thriving in the hot, dry summers of Kern, Tulare, and Madera counties. Walnuts round out the top three tree nuts, with significant production in the Sacramento Valley, where the University of California Cooperative Extension supports growers with cultivar selection, rootstock research, and integrated management strategies for pests like navel orangeworm and codling moth.2UC Cooperative Extension / Sacramento Valley Orchard Source. Walnuts
The shift toward tree nuts has reshaped Central Valley agriculture in ways that go well beyond field boundaries. Perennial crop acreage has nearly tripled in recent decades, meaning vast tracts of land that once rotated between annual crops like cotton or wheat are now committed to orchards that take years to mature and require water every year, drought or not.1Environmental Research Letters. Water shortage risks from perennial crop expansion in California’s Central Valley This inflexibility has significant implications for water planning, which we will return to later in the article.
Stone Fruits, Citrus, and Table Grapes
The San Joaquin Valley is the country’s leading producer of several stone fruits, including peaches, nectarines, and plums. Cherries tend to ripen in the cooler early season, while peaches and nectarines follow through the hotter months. Citrus orchards, particularly navel and Valencia oranges, cluster in Tulare and Fresno counties, where warm days and mild winters suit the trees. The region around Exeter and Ivanhoe has long been a center for citrus research, including pest-control work on citrus red mite that dates back decades.3Oxford Academic. Citrus Red Mite Pesticide Efficacy Tests in the San Joaquin Valley, 1983
Table grapes and wine grapes are another major piece of the valley’s fruit economy. The warm climate of the southern San Joaquin Valley is ideal for table grape varieties that need long, hot growing seasons, while wine grapes occupy cooler microclimates in the northern valley and foothill appellations. Raisin production, centered around Fresno, also relies on the valley’s reliably dry autumn weather for sun-drying the fruit.
Vegetables and Processing Crops
California supplies a large share of the nation’s canned and processed tomatoes, and most of that production takes place in the Central Valley. Processing tomato fields spread across the Sacramento and northern San Joaquin valleys, where summer heat helps concentrate sugars in the fruit before mechanical harvest. Researchers have explored techniques like grafting to improve processing tomato yields under Central Valley conditions, reflecting ongoing efforts to push productivity higher even in established crops.4Acta Horticulturae. Evaluation of grafting for processing tomato production in California’s Central Valley
Beyond tomatoes, the valley produces substantial quantities of garlic, onions, sweet potatoes, peppers, melons, and carrots. Small-scale farming communities, including Hmong growers in the Fresno area, contribute specialty vegetables to local and regional markets. A survey of small-scale Hmong farmers found that while many used practical pest management tactics like crop rotation, about three-quarters were not familiar with integrated pest management as a formal concept, highlighting the diversity of farming knowledge across the valley’s grower communities.5Journal of Integrated Pest Management. Pesticide Knowledge, Attitudes, and Practices Among Small-Scale Hmong Farmers in the San Joaquin Valley of California
Cotton, Alfalfa, and Other Field Crops
Cotton was once king in the southern San Joaquin Valley. Although acreage has declined sharply since its peak in the 1980s and 1990s, the region still grows both Upland and American Pima cotton. Research on planting windows and irrigation timing has shown that early planting is necessary for optimum yield, with the best results coming from planting early and allowing a second fruiting cycle to develop before terminating irrigation.6Journal of Production Agriculture. Planting and Irrigation Termination Timing Effects on the Yield of Upland and Pima Cotton Pima cotton, valued for its extra-long staple fiber, commands higher prices but is more sensitive to planting and irrigation decisions. Much of the acreage that once grew cotton has since been converted to almond and pistachio orchards, driven by higher returns per acre-foot of water.
Alfalfa is one of the valley’s most important forage crops, feeding the state’s dairy herds, which are themselves concentrated in the Central Valley. Because alfalfa is a perennial that uses large volumes of water relative to its market value, it has been a flashpoint in drought debates. During the severe 2011 to 2017 drought, statewide alfalfa production did decline, but the picture was uneven: acreage persisted and even increased in specific areas of the state, suggesting that local water access and dairy demand kept some growers planting even as others pulled back.7Europe PMC. Changes to California alfalfa production and perceptions during the 2011-2017 drought Rice, grown in flooded paddies in the Sacramento Valley, and corn silage for dairy feed round out the valley’s major field crops.
Why Winter Chill Matters
One thing that many people do not realize about the Central Valley is how much its fruit and nut production depends on cold winter nights. Many deciduous trees need a certain accumulation of cool hours during dormancy to flower properly in spring. Without enough “winter chill,” fruit quantity and quality suffer.8Communications Earth & Environment. Seasonal climate forecasts show skill in predicting winter chill for specialty crops in California This is not an abstract concern. Modeling work looking at trends from the mid-20th century through the end of the 21st century has projected that climatic conditions in California could eventually fail to support some of the main tree crops currently grown there. That research concluded the tree crop industry will likely need to develop adaptation measures such as low-chill varieties and dormancy-breaking chemicals, and that for some crops, production might no longer be possible in its current locations.9PubMed Central. Climatic changes lead to declining winter chill for fruit and nut trees in California during 1950-2099
Almonds and pistachios generally need fewer chill hours than crops like cherries or apples, which is one reason the nut industry has been better positioned to expand in the warming valley. But even almond varieties have chill requirements, and a string of unusually warm winters can reduce bloom quality and yields. For growers deciding what to plant today on a thirty-year time horizon, chill projections are becoming as important as soil quality and water rights.
Water, Salinity, and the Sustainability Question
Almost every crop in the Central Valley depends on irrigation. The valley floor receives little rainfall during the growing season, and summer temperatures routinely exceed 100°F. Water comes from a combination of surface deliveries, primarily from the federal Central Valley Project and the State Water Project, and groundwater pumping. The balance between these two sources has been a source of tension for decades, and nowhere in the United States are the interrelated challenges of limited fresh water, high water tables, poor drainage, and soil salinization more apparent than in the San Joaquin Valley.10PubMed Central. Sustainability of irrigated agriculture in the San Joaquin Valley, California
Salinity is a particular problem on the valley’s west side. Selenium and other salts naturally present in the soil accumulate when irrigation water evaporates or percolates through shallow clay layers. Without adequate drainage, salt builds up in the root zone, eventually making land unproductive. Thousands of acres on the west side have already been retired from farming because of salt damage, and more are at risk.
California’s Sustainable Groundwater Management Act, known as SGMA, adds another layer of pressure. The law requires local agencies to bring groundwater basins into balance, which means restricting pumping in overdrafted areas. Surveys of stakeholders have found that secure water supplies such as groundwater recharge and less water-intensive agriculture are the top priorities for adapting, but most respondents prefer the current land-use patterns to major alternatives.11PubMed. From fallow ground to common ground: Perspectives on future land uses in the San Joaquin valley under sustainable groundwater management In practical terms, SGMA is likely to take several hundred thousand acres of irrigated farmland out of production over the next couple of decades, with the biggest impacts in the southern San Joaquin Valley where groundwater overdraft has been most severe.
Pest Pressures Across a Diverse Crop Mix
Growing so many different crops in close proximity creates a complicated pest landscape. Spotted wing drosophila, an invasive fruit fly, illustrates the challenge. Research in the San Joaquin Valley tracked the fly’s seasonal movement through a sequence of ripening fruits: it emerged from both intact and damaged cherries during the cooler early season, stayed at low densities through the hot summer months, then resurged in fall. During that fall period, the fly did not cause damage to intact peaches, nectarines, plums, pears, grapes, pomegranates, apples, persimmons, or citrus, but it did emerge from damaged fruits of those crops.12PubMed Central. Temporal Dynamics of Host Use by Drosophila suzukii in California’s San Joaquin Valley: Implications for Area-Wide Pest Management That finding matters for growers because it means damaged or unharvested fruit left in the field can serve as a reservoir, sustaining pest populations that move from one crop to the next as the season progresses.
Navel orangeworm is the most economically damaging insect pest of almonds, pistachios, and walnuts, and its management drives much of the pest-control calendar for nut growers. Orchard sanitation, which means removing unharvested “mummy” nuts from trees and the ground before the new growing season, is the foundation of orangeworm control. Codling moth remains a major concern in walnut orchards as well.2UC Cooperative Extension / Sacramento Valley Orchard Source. Walnuts The diversity of crops means that pest management in the Central Valley is never a single-species problem; it is a landscape-level puzzle where what happens in one orchard or field affects what shows up in the next.
The Labor That Makes It Work
The Central Valley’s crop diversity creates an almost year-round demand for hand labor. Pruning in winter gives way to thinning stone fruit in spring, picking cherries and peaches in summer, harvesting grapes and tomatoes in late summer, and processing nuts through fall. This staggered schedule is one reason the region has long depended on a large agricultural workforce, much of it seasonal. Research on California farmworkers has documented that undocumented workers play a critical role in preventing labor shortages and stabilizing food prices, while facing disproportionately high food insecurity themselves and hazardous working conditions.13Discoveries in Agriculture and Food Sciences. Essential but Excluded: Undocumented Farmworkers and the Structural Foundations of Food Security in California
Mechanization has reshaped some parts of the harvest. Almonds are shaken from trees and swept from the ground by machines, and processing tomatoes are picked by mechanical harvesters that can clear a field in hours. But many crops resist full mechanization. Table grapes, tree fruit, and specialty vegetables still require careful hand picking to avoid bruising. Labor availability and cost have become significant factors in growers’ crop choices: some have shifted toward crops that can be mechanically harvested precisely because finding enough seasonal workers has become harder.
How Acreage Has Shifted Over Time
The Central Valley of the 1970s and 1980s looked quite different from today. Cotton, grain sorghum, and sugar beets occupied large swaths of the southern valley. Dairy operations were scattered but growing. Tree nuts existed but were a modest share of total acreage. The transformation since then has been dramatic. Perennial crop acreage has nearly tripled, driven by strong global demand for almonds and pistachios and by the higher revenue these crops generate per acre compared to field crops.1Environmental Research Letters. Water shortage risks from perennial crop expansion in California’s Central Valley
This shift has trade-offs. Orchards lock in water demand for twenty to thirty years, because a grower cannot simply fallow a mature almond orchard during a dry year without losing the trees and the decade of investment they represent. Annual crops like cotton or tomatoes offer more flexibility: if water is scarce, a grower can leave a field unplanted and try again next year. The conversion of flexible annual cropland to inflexible perennial orchards has made the valley’s aggregate water demand more rigid, which amplifies the pain during drought years.
At the same time, some formerly irrigated land is going in the opposite direction entirely. SGMA-driven pumping restrictions are expected to push portions of the western and southern San Joaquin Valley out of irrigated production. The question of what happens to that land, whether it becomes dryland farming, solar installations, habitat restoration, or simply lies fallow, is one of the biggest agricultural policy questions in the state right now.11PubMed. From fallow ground to common ground: Perspectives on future land uses in the San Joaquin valley under sustainable groundwater management
Dairy and Livestock’s Quiet Dominance
It is easy to focus on the crops you can see in the field, but by revenue, dairy is consistently the top agricultural commodity in the Central Valley and often in the entire state. Tulare, Merced, Kings, and Stanislaus counties are among the nation’s highest-producing dairy regions. Most of the valley’s alfalfa, corn silage, and other forage crops exist to feed these herds. The dairy industry ties together crop production and livestock in a way that makes pure crop-acreage statistics somewhat misleading: a huge share of what the valley grows never reaches a grocery store shelf because it goes straight into a cow.
This linkage also explains why alfalfa persisted in parts of the valley even during severe drought. Local dairy operations need feed, and transporting hay long distances is expensive. Growers near dairies had a ready market willing to pay enough to justify the water costs, while growers in areas without nearby dairies were more likely to cut back.7Europe PMC. Changes to California alfalfa production and perceptions during the 2011-2017 drought The geography of dairy, in other words, shapes the geography of field crops in ways that pure economics alone would not predict.
Emerging and Niche Crops
Beyond the headline commodities, the Central Valley supports a growing array of niche and emerging crops. Pomegranates have expanded considerably in the southern valley, benefiting from the same hot, dry conditions that suit pistachios. Olives for oil production, once a minor crop, have boomed with the rise of “super-high-density” hedgerow plantings that allow mechanical harvest. Mandarins, particularly easy-peel varieties, have taken over acreage that once grew navel oranges, reflecting shifting consumer preferences.
Fig orchards persist around Madera and Fresno, supplying both dried-fig and fresh markets. Date palms grow in the extreme southern valley and neighboring Coachella Valley. Blueberry cultivation under protective structures has appeared in the San Joaquin Valley, a crop that would have been considered impossible there a generation ago. These niche crops rarely rival almonds or dairy in total value, but they add resilience and diversity to the valley’s agricultural economy, and they represent the constant experimentation that has characterized Central Valley farming since its earliest days of large-scale irrigation.