The box of organic salad greens, radishes and broccoli that Marge Amberson picks up each week from East Henderson Farm has revolutionized her diet and shopping habits. She tried the crop share last year, then re-upped for another season.

"The flavor is very fresh; the food is not trucked halfway across the country. There's still dirt on it sometimes," she said. Her family is eating more healthful meals, and she loves to visit the farm near her home in Henderson, Minn.

Amberson is riding a trend that's rapidly gaining momentum. Over the past decade, the number of Twin Cities-area residents getting their food through community-supported agriculture (CSA) has nearly tripled, to more than 11,000 people. Twenty years ago, there were two CSA farms. This year there are 81, according to the Land Stewardship Project, which publishes a directory.

"In the last three or four years, there's been an explosion in new CSAs," said Laurie Haugen-Eitzman. She and her husband, David, have operated Big Woods Farm in Nerstrand, Minn., for 19 growing seasons.

To join a CSA, a consumer pays a farmer for a weekly share of the crops, usually $300 to $600 per growing season. The concept started in Europe and Japan, then took root in the United States as a fringe movement in the 1980s.

"In the early days, we had to educate everybody about everything: the importance of buying local food, what you could expect to get, local food as a concept," said Verna Kragnes, a founding farmer at Philadelphia Community Farm in Osceola, Wis., which is in its 22nd season. "Now it's practically a household word."

With obesity, heart disease and diabetes now national epidemics, the potential for CSAs to improve diets and ultimately health has caught the attention of health professionals. HealthPartners, an insurance and health care provider, is studying the impact of CSAs on eating habits. Early results suggest that most people who sign up for CSAs eat more vegetables and a greater variety of them, said Nancy Sherwood, senior research investigator.

Variety can be a mixed blessing for many CSA members. Some weeks the boxes can be heavy on veggies unfamiliar to many tables, such as kohlrabi, garlic scapes and bok choy. "Farmers started to realize they had to provide recipes and take input on what to raise," said Brian DeVore, staff member at the Land Stewardship Project.

But being introduced to new vegetables is part of what many consumers like about CSAs.

"We've learned to eat things we never would have tried," said Judy Goebel of Richfield, a member of Philadelphia Community Farm for more than 15 years. "Like arugula. The first few times, I wasn't so sure. Now I'm crazy about the stuff."

Amberson said she tried kale for the first time last year after finding it in her CSA box. "It's a great way to introduce new vegetables into our lives," she said. Her household is eating healthier since joining a CSA, in part because "I hate to waste anything. Last year, we'd have two or three vegetable servings at dinner when normally we'd have one."

As the CSA movement matures, some farmers are experimenting with different models, such as Gardens of Eagan's new prepaid CSA card. Instead of picking up boxes of that week's harvest packed by the farmer, members pay $50 for a card that they can redeem for $55 worth of vegetables of their choice from the farm's booths at two farmers markets.

"Fifteen years ago, we were hearing the same things you hear now -- that you get things you don't like or don't know what to do with," said farm manager Linda Halley. "If you split a share, you have the complications of splitting. It's a responsibility you have to do every week, even if you go on vacation."

The card was appealing to first-time CSA member Julie McGill of Bloomington. "This is a good option for our family," she said. "We're not always in town on weekends, and I don't like throwing food away."

While the early CSA farms were located in rural areas, most of their members were located in trend-setting urban neighborhoods. Now CSA participation appears to be spreading not only to the suburbs and but also to outstate Minnesota.

"Originally, it was a city thing," DeVore said. "The conventional wisdom was that there wasn't demand in Rochester or St. Cloud. Now more CSAs are finding their markets closer to home. Some are not even bothering to deliver to the Twin Cities."

Meanwhile, in the urban core, more CSA members are getting crops grown right in their neighborhoods, with some farmers operating on vacant lots, underused land and even parking lots.

"On the supply side, there's been a growth of farmers," DeVore said. "The hard-core group has started mentoring beginning farmers, and those interns are now striking out on their own."

For Josh Reinitz, who grew up on a dairy farm and worked at a downtown desk job before moving back to what was left of that family farm several years ago, CSA farming is a new way of supporting an old agricultural model: small-scale sustainable farming.

On the plus side, it allows his family to enjoy "an ideal lifestyle. We work hard, but it's wholesome, valuable work," he said. "I like the diversity of growing a lot of different crops." The downside is 12-hour workdays, six days a week, during peak season. "It's a lifestyle, not a job," he said. "I have found a passion for it."

CSA farming is complex, said Haugen-Eitzman. "You have to have enough food for your members every week."

Those members share not only the farmers' crops but also the risk. "If a hailstorm wipes out everything, there might not be much for a couple weeks," she said.

But DeVore said the surge of CSA farmers has provided some insurance in case of crop failures.

"Now, if one farmer gets his tomatoes hailed out, another farmer who lucked out can help."

Kim Palmer • 612-673-4784