To Amy Hobbs Harris, a dozen jars of strawberry preserves are worth $391 – the amount she estimates she’ll save in a year by canning the fruit herself.

Not that she normally would spend that much on jam. But the savings add up once she factors in other uses – giving them away as gifts, for example, or stirring the preserves into plain yogurt instead of buying pricier flavored cups.

Harris, 33, of Tipp City, Ohio, started canning for the first time last summer, putting her a bit ahead of a trend seen around the country: As food prices rise and the economy declines, more people are turning to home canning.

“I started canning to save money,” said Harris. “I really love the self-sufficiency of it, that I know where the produce started and what the process is.”

Harris, a literature professor who chronicles her efforts to pay off her credit card debt on her blog, “My Daily Dollars,” considers canning a frugal way to enjoy high-quality ingredients. Though she has a garden, most of what Harris cans comes from her local farmers market.

“Especially in the winter, when I go down in the basement to get the jars, it’s a nice feeling,” she said. “So many things are unknown with the way food is produced that it feels really good to keep control of it.”

The trend is reflected in the sales of the popular Ball canning jars and supplies, said Chris Scherzinger, vice president of marketing for Jarden Home Brands, maker of Ball products. Retail sales of Ball canning products have increased nearly 30 percent this year, and sales of the company’s plastic freezing containers have doubled over last year, according to market data from Information Resources Inc.

“It fits with what we’ve seen historically from the 1970s and even before then: When people tighten their belts, they focus a little bit less on convenience items and convenience foods and focus a little bit more on staying home and making their own, whether you’re talking about food or fun,” Scherzinger said.

Louise Johnson of Auburn, Maine, grew up tending her parents’ garden and has planted her own for several years. But she didn’t start canning her produce until this summer, when she no longer could stomach the thought of paying higher prices for food packed with preservatives.

“The straw that broke the camel’s back was the economy,” said Johnson, a 33-year-old mother of three boys. “But the underlying reason is healthier food – we’re tired of food that has tons of sodium, preservatives and all the nasty stuff they put in food that you don’t have to be eating.”

Alice Mullen of the University of New Hampshire Cooperative Extension said the canning demonstrations she offers at farmers markets around the state have begun attracting larger crowds. In Florida, the Citrus County Canning Center has seen a steady increase in customers this year, said manager Cindy DeVries.

Customers bring their own produce and jars to the center, which has been open since 1935, and can use the kitchen’s community stoves and sinks.

“What I hear is the words ‘the economy,’ and ‘We’ve started growing a garden because we don’t know what’s going to happen to the economy in the future,'” she said.

Kathy Savoie, who has been teaching canning classes through the University of Maine Cooperative Extension for 12 years, said she usually offers four to eight workshops in a typical summer. This year, she has 25 scheduled through the fall. She anticipated the demand back in the spring, when she heard from a huge number of people starting gardens for the first time.

“This year has been a real surge,” said Savoie, who attributes the explosion in interest to three factors: the economy, retiring baby boomers seeking a simpler life and people who want to extend their access to local food.

Paula Stotts, who runs a small farm with her husband in Mechanic Falls, Maine, began getting calls in February from customers interested in buying their produce through a community-supported agriculture program.

“If I had 1,000 acres, I don’t think I would have been able to accommodate all the phone calls I had,” she said. “And the next question I was frequently being asked was, ‘Do you teach canning?'”

She didn’t, but she arranged for a cooperative extension educator to offer a class in the area and has another planned for later this summer.

Johnson, who was one of 12 participants in the first class, came away impressed and determined to can the 14 different fruits and vegetables she has planted this year.

Cramming everything from tomatoes to zucchini into glass jars is part of her family’s overall plan to insulate themselves against economic uncertainty, Johnson said. They’ve also cut down on driving and are installing a wood stove.