Tomatoes in the Delta, Part 1 of 2

Major Crop Expanded with Mechanical Harvesting

Canning tomatoes vine ripened and ready for harvest. Photo: Rich Turner

Tomatoes have been grown in the Sacramento-San Joaquin Delta region since the Gold Rush and the region continues to be a significant producer of fresh market tomatoes. In recent decades, however, the amount of tomatoes grown for the fresh market has been small compared to the tonnage grown for processing or canning—canned as peeled or diced tomatoes or as paste and ultimately used in products including sauces, ketchup, salsa, and juice. Two Delta counties, San Joaquin and Yolo, have consistently been among the leading producers of canning tomatoes. 

Tomatoes for canning became a major crop in the region in the 1930s and 1940s, when several tomato processing plants were built. An important factor in this trend was a 1934 increase in the U.S. tariff on imported canned tomatoes. Tillie Lewis’s Flotill Corporation of Stockton bought a bankrupt cooperative cannery and began canning tomatoes in 1935, as did the Aaron Hershel Cannery. A few years later, the Thornton Cannery started up. The Heinz Company built its largest tomato processing plant in Tracy, on the south edge of the Delta, in 1946—Heinz had been making its famous tomato ketchup since 1876 in Sharpsburg, Pennsylvania. A year after the Heinz plant in Tracy, Campbell Soup Company established a plant in Sacramento (between Yolo and San Joaquin counties) and in 1956 Hunt Foods built a tomato processing plant in Davis (Yolo county). There were several other canneries in the heartland and big processers located outside the region—such as Del Monte and Libby, McNeil and Libby—consolidated truckloads in local fields and transported the fresh tomatoes to their canneries.

Back-breaking labor prior to mechanical harvesting in the San Joaquin Valley. Photo: Sherman Indian Museum circa 1940.

The University of California, Davis (UC-Davis) played a key role in developing the first commercial mechanical tomato harvester and in breeding machine-harvestable tomato varieties that revolutionized the growing and canning of tomatoes in the 1950s and 1960s. 

Growing the Heat-loving Fruit…er, Vegetable 

Tomatoes are descended from a wild ancestor from the Andes Mountains of Peru and Ecuador, first domesticated by Native peoples in what is now southern Mexico more than 2,500 years ago. Spanish invaders in the 1500s changed the Aztec word tomatl to the word still used in Spanish: tomate

Field trial of separation unit in at UC Davis, 1952. Photo: UC Davis Special Collections

Some historians believe that Spanish conquistador Cortés first brought tomatoes to Europe in 1521; others think that the Genoese we know as Christopher Columbus may have brought them there in 1493. Tomatoes were clearly mentioned in Italian literature by 1544.

Technically, the tomato is a fruit, but it is considered a vegetable for most culinary purposes. In 1877, U.S. tariff laws on vegetables raised the classification of the tomato as a legal issue; the U.S. Supreme Court settled the question in 1893 by declaring the tomato a vegetable, based on popular definition.

Because tomatoes require a long, warm growing season and are sensitive to frost, they have traditionally been grown in the “sun belt” states of the U.S., especially Florida and California. For good plant growth, fruit set, and fruit development, tomatoes need daily air temperatures between 77 and 95°F, and with adequate soil moisture can tolerate temperatures over 100°F. Tomato development and fruit quality are significantly reduced when night temperatures fall below 50°F. The climate in most of the Delta region is ideal for growing tomatoes. 

Tomatoes can be directly planted as seed or seedling plants can be transplanted, which is increasingly preferred. Transplants are mechanically planted in early March through June. Sandy soils are best for the earliest plantings because they are more quickly workable after the winter rains and they warm sooner in the spring. Otherwise, heavier loams and clay soils are more productive than sandy soils. The older soils on the periphery of the Delta, between the sandy alluvial fans of the modern rivers, are thus preferred tomato-growing acreage.

In 1940, when San Joaquin county first became the number one county in the nation in canning tomato production, an acre of cropland planted to tomatoes yielded about ten tons. In 1960, the yield had increased to seventeen tons of tomatoes per acre. And in 1980 it was up to twenty-four tons per acre—nearly a 250 per cent production increase in forty years.  

The College Farm at Davisville and the Legacy of UC-Davis

UC College Farm at Davisville, 1908. Photo: UC Davis Special Collections.

The University of California (UC) College Farm at Davisville, which became UC-Davis, played a major role in developing many crops and particularly in the mechanization of tomato harvesting.

A College of Agriculture was required by the law that created the University of California in 1868. The first building on the Berkeley campus, South Hall, was built to house the ag program. About thirty years later, UC established a permanent program that put farm advisors in the field, working directly with California farmers. That outreach function was furthered in 1906 with the establishment of a College Farm at Davisville (in Yolo county, west of Sacramento).

George W. Pierce, Jr., a UC alumnus who lobbied for the university to choose Davisville for the College Farm, said with wonderful hyperbole:

The College of Agriculture is more necessary to the state than the school of medicine, law or theology. If we lived a more natural life in the fresh air, we could get along without medicine. If we had no lawyers, we might get along with justice. If we had no theology, we could get along with religion. But we could not live at all without an adequate supply of food, and for that we are dependent upon an intelligent system of agriculture. (David Vaught, After the Gold Rush: Tarnished Dreams in the Sacramento Valley, 2007)

A Federal law in 1914 mandated a new outreach effort called the Cooperative Extension, which combined university extension and state agents, and that program began in California in 1915.

In 1921, growers’ cooperatives forced a kind of ag education master plan through the California Legislature that broadened the research and training mission and made Davis the northern branch of an expanded UC agriculture program. 

Plant breeding became an important mission of the UC College of Agriculture. The Davis campus became a center for scientific hybridization and Davis agronomists initiated the California Approved Seed Plan in 1934, in cooperation with the State Department of Agriculture and the Farm Bureau. The farm mechanics program at Davis also started in the 1920s and gained prominence in the 1930s. 

After World War II, California poured more money than any other state into its College of Agriculture and its Cooperative Extension Service. UC-Davis was given full independent university status in 1959 and several departments were moved from the Berkeley campus to Davis.

UC-Davis developed close working relationships with growers and food processors, as evidenced by many cooperative research programs and field trials. Botanists and agricultural engineers at UC-Davis working closely with local growers and canners was critical to developments in many agricultural commodities, especially the successful machine-harvesting of canning tomatoes.

The University of California’s role as an integral part of the industry was crucial. The University provided practically all the scientific research capability, including the new tomatoes that were the necessary prerequisites to success of the [mechanical harvester]. It was the focal point through which all segments could interact… Finally, the University was involved in all phases of the development and diffusion of the harvester system and the necessary associated cultural practices. (Alain de Janvry, et al., The Political Economy of Technological Change: Mechanization of Tomato Harvesting in California, 1983)

Harvesting Canning Tomatoes (video courtesy of Bowles Farming Co.)

Prior to 1960, the manual harvesting of tomatoes was done by local workers, migrant laborers who moved throughout California harvesting crops, and by Mexican workers brought in during World War II. Because individual tomatoes ripened at different times, it was usually necessary for pickers to make three to six passes through the tomato vines during each harvest season. Stooping to pick the tomatoes and carrying lug boxes full of tomatoes was backbreaking labor.  

Labor shortages during World War II (1939-1945) stimulated research into the mechanical harvesting of tomatoes. In 1951, a Federal law created the second, post-War bracero program that allowed laborers from Mexico to temporarily visit the United States to harvest crops. By the time that bracero program ended in 1965, the machine harvesting of canning tomatoes had become widespread. 

UC Davis botanist G.C. “Jack” Hanna with prototype harvester, 1958. Photo: UC Davis Special Collections.

Blackwelder Manufacturing Company of Rio Vista, in the heart of the Delta, built the first commercial mechanical tomato harvester in 1960, dubbed the “UC-Blackwelder.” (informative 3 minute video) The next year, UC-Davis botanist G.C. “Jack” Hanna introduced a new tomato variety that dominated the canning tomato industry into the 1970s and would become the “parent” to many later important varieties. The UC Cooperative Extension, tomato growers, and tomato canners cooperated through the 1960s to do field trials to determine the best growing and handling practices for the machine-harvested varieties of tomatoes. 

The mechanical tomato harvester was quickly adopted by growers because it lowered tomato harvesting costs by half. A big part of the savings was because the harvesters made only one pass through the field—the tomatoes had been bred to ripen all at one time. The Lodi News-Sentinel said that the machines would “help in the transition from braceros to domestic labor in California canning tomato fields.” 

By 1970, virtually all the canning tomatoes in California were harvested with mechanical harvesters. This rapid changeover was all-the-more impressive given the numerous changes it required in planting densities, cultivation, fertilization, irrigation, transportation, handling, processing, and marketing. 

Modern mechanical harvesting of canning tomatoes. Photo: Bowles Farming Co.

Since the advent of mechanical harvesting, tomatoes grown for processing have been picked ripe and red (in contrast to most fresh market tomatoes that are picked green) and processed or canned within six hours of being picked. 


Part two of this article will provide more-detailed stories about the cooperative efforts—coordinated by UC-Davis—to perfect a machine to harvest tomatoes and the huge effort to breed tomato varieties that could accommodate mechanical picking. While you are waiting for part two, visit the San Joaquin County Historical Museum  in Micke Grove Regional Park (south of Lodi) to see an early UC-Blackwelder tomato harvester in the 9,000 square foot “Innovations in Agriculture” exhibition.

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