Like Leamington has for the past century, Tracy Tucker and her family have relied on H.J. Heinz Co.

The dark-haired 29-year-old moved to Leamington, "the Tomato Capital of Canada", a town that grew and thrived over more than 100 years of tomato farming – to work at the Heinz factory after both of her parents got full-time positions. Her uncle left high school to start working at the plant 30 years ago. And her brother-in-law was just recently hired.

Ms. Tucker bought a new SUV six months ago, a new house three months ago and is seven months pregnant, but now is months away from being laid off – along with 739 other full-time workers, 200 seasonal workers and most of her family and friends. She said the small Ontario town is destined to die.

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"I'm glad I didn't paint the baby's room," Ms. Tucker says. "Everybody I've talked to is leaving town."

Ms. Tucker and her family have not wasted any time: Her parents listed their new house last night – one among many of the panicked locals calling real estate agents to sell houses – and Ms. Tucker plans to do the same thing, as well as returning her car. She still hasn't told her 10-year-old daughter, but she plans to move to B.C., where she thinks her fiancé's asphalt business will thrive, instead of struggling for business in a declining small town. Her sister, Sarah Crawford, who plans to move to Saskatoon, feels bitterly about the now worthless pension documents her husband was given earlier in the week – which hinted at a future here. "Bastards," she mutters. Their parents will move back to Newfoundland, where the family is from, because they can't yet retire and can't see a future in Leamington that isn't tied to tomatoes.

Because in Leamington, tomatoes were everything: They were jobs at the plant for workers and lucrative plants in the field for farmers; they required labels from local factories and gave shipping contracts to local trucking companies; they were a way of life and a sense of identity and they sustained the town as many other small towns died. And now that Heinz is leaving, there is no reason to grow tomatoes any more and that is a truly heartbreaking idea in Leamington. The town has a vibrant downtown and a greenhouse industry that doesn't feed into Heinz, but folks aren't kidding themselves that this week hasn't been brutal for the community.

In 1909, Henry John Heinz selected Leamington, with its fertile soil, transportation links and the most southerly climate Canada can muster, as the place for a tomato processing plant to make his famous ketchup. Local farmers got $25-million worth of contracts to grow tomatoes each year and that money trickled down through suppliers and workers to provide middle-class livelihoods for thousands of people over the years. The firm's engineers built the giant metal-and-fibreglass tomato that acts as a town tourist booth, and Heinz also sponsors the annual Tomato Festival in August, as well as the Ketchup to Art Show, where some artists paint with ketchup.

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Leamington's farmers have had tomatoes in their soil and in their blood for more than a century, but they've always known the factory could close. Tomatoes are harvested ripe and don't travel well, so if there's no processing plant, there's no tomato growing. Farmers will now likely grow other crops.

Ron Janzen, who now runs a John Deere dealership, is a third-generation tomato farmer who remembers "the old guys" talking about bringing tomatoes to the Heinz plant with a horse and buggy. He said in the mid-1980s, some Heinz executives were threatening to close the plant if they didn't get more tomatoes for less money. His father, Mr. Janzen recalls, then brought up his son's frequent ridealongs on the tractor and retorted: "Weren't you listening? They've been threatening to close the plant since the 1950s!" Mr. Janzen said his business might take a small hit but his reach goes well beyond local tomato farmers.

Walter Brown, who has grown tomatoes for Heinz for 47 years, like his father before him, has a barn full of tomato-specific equipment that he doubts he can sell – given the region's 46 growers are also likely to sell their equipment all at the same time. And he has a tomato field that is already fertilized and bedded at a cost of $25,000 that will not receive any tomatoes. He says that, around the time NAFTA was negotiated, Heinz asked Leamington farmers to get globally competitive by bringing up yields, which required them spending millions on better machinery and irrigation that are not required for other crops.

"Everybody's going to suffer," Mr. Brown said. "Tomatoes over the years have paid a lot of bills."

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But more than a hundred years after the plant opened in Leamington, in a time of global capital flows and North America's disappearing middle-class jobs, Heinz's new owners are a Brazilian private equity firm called 3G Capital and Berkshire Hathaway's Warren Buffet.

Dennis Jackson prefers the past. He's a Heinz memorabilia collector who started working at Heinz in quality control on Dec. 17, 1964. Shortly after retiring in 2000, he lost his wife to cancer and the company offered him a job running Heinz's gift shop. His old uniform is now on a mannequin in the permanent Heinz collection at the Leamington Arts Centre, which sells a T-shirt that says "I put ketchup on my ketchup" along with a book commemorating Heinz's centennial in the town.

"It's a new era and this is an old place," Mr. Jackson said, standing in front of the factory and the 1949 pickup he had refurbished with Heinz logos, which he drives in the Tomato Festival parade he now thinks might be too depressing to hold this year. "It's been nothing but the best company in the world to work for. [The closing is] because of the new, modern ways of making money."

The Heinz executive who told Mr. Jackson and managers the plant was closing did so with tears in his eyes, Mr. Jackson said. And some people maintain that Heinz – a distinction is made between the historic company and the new owners – cannot be the target of the community's anger. "We're heartbroken by this. I'm not going to say we're not upset," says mayor John Patterson. "But if you look back, over 104 years, and you see how many families have grown up around this … I find it difficult, if not impossible, to be angry. We've had a good run."

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But it is not as if Leamington, which has struggled through nearby Windsor's travails in the auto industry's restructuring, is a stranger to industrial decline. Scott Graham moved here as a 13-year-old because his dad came for an auto-industry job. He's watched the region struggle through the recession and seen and other factories close. "It's like this area is being punched in the face when everything was recovering," said Mr. Graham, who co-owns a Century 21 office that he says has received panicked calls for listings in the wake of Heinz's Thursday announcement. He, like the mayor, thinks things will be okay.

But there is still a lot of pain, anger and disbelief in Leamington, despite the memories, which makes the mood feel sort of like a communal divorce. Employees said the meeting with unionized staff got heated, with tossed chairs and a lot of swearing. There is particular hatred for Mr. Buffett, the most easily understood of the new owners. "If he shows up here in Leamington, he just might get shot," one man said, trembling at Jose's, a local bar and grill. "That's not how you do business." Employees said they got one-week of pay for every year. One younger employee quit on the spot and spent the day handing out résumés. Many were up all night and called in sick on Friday and everyone talks of leaving.

The town has some industries that don't rely on Heinz. Two Highline Mushroom facilities in Leamington employ about 700 people. The community also forms the largest concentration of greenhouses in Canada, possibly North America, growing fresh produce all year that goes to grocery stores, not processing plants.

Maria Harms, who works in the greenhouse industry and picked tomatoes as a young girl, was sipping a glass of red wine on the evening of the closing announcement at Jose's, a local bar and grill. "It's going to affect businesses like this," she says. "People will be going out less. They'll be watching their dollar." As she's about to leave, she receives a text from a friend in the auto industry who's been laid off. "Does Heinz affect greenhouse at all?" it reads. She shrugs and then she laughs.