Debbie Karton couldn't believe her good luck.

"Look!" she said. "French carrots! You can't find them in the supermarket!"

Karton was shopping earlier this summer at the Avalos Farm vegetable stand at the Tuesday afternoon Berkeley farmers market on Derby Street. She held a bunch of slightly misshapen Chanterelle carrots, one of the sweetest varieties.

"They don't look as perfect as the carrots at the supermarket, but they taste a lot better," she said.

They're also a lot fresher.

"I harvested them this morning," said owner Efrem Avalos, who runs the stand with his 11-year-old son, Marco. "The carrots you see in the store take days to get from the field to the shelf."

Every Tuesday, Avalos and Marco make the two-hour drive from their family farm in Hollister to sell their produce in Berkeley.

"It's worth it because the people here appreciate fresh, organic food," he said. "I don't know if we could stay in business if we didn't have the farmers market."

The farmers come from Sonoma County to the north, Davis and Vacaville to the east, and Santa Cruz, Watsonville and Hollister to the south. But a few come from as far as Riverside County in Southern California.

There are three farmers markets every week: Tuesday afternoon in South Berkeley; Thursday afternoon on upper Shattuck; and Saturday morning and early afternoon in the downtown area on Center Street. Each has its own personality.

"They all reflect their own neighborhoods," said Kirk Lumpkin, special events and promotions coordinator for the Berkeley Ecology Center, which operates the farmers markets.

"The Tuesday shoppers are most focused on the shopping. They're there to get their food, and that's what they're about. The Thursday market is in the Gourmet Ghetto, and it's definitely our whitest clientele. The Saturday market has the highest energy, with musicians, masseurs and political tables. People come for the social interaction as much as the food."

All three markets feature farm-fresh produce and organically based prepared foods. The Ecology Center charges vendors rent on a two-tiered basis. The farmers pay a flat rate; the prepared food vendors pay a flat rate plus a percentage of the gross.

"We don't want the prepared foods to be taking away from the farmers," said Lumpkin. "It's a delicate balance. If you look closely, you'll notice an invisible line separating the farmers from the prepared food stands."

About 80 percent of the produce is certified organic. The rest, while awaiting certification, is labeled "pesticide free."

This commitment to natural foods means not everything will be available year round. But the customers have come to accept that.

"I had an obsession with green beans last summer that was hard to let go of — at first," said yoga instructor Naushon Kabat-Zinn. "Then in the fall I moved on to nettles, then greens, and now I'm looking forward to whatever comes next."

The Berkeley farmers markets are celebrating their 20th anniversary with a yearlong series of events.

The next celebration takes place Aug. 25, when the Saturday market presents "Jazzy Tomatoes," a joint project with the Downtown Jazz Festival.

While mandolin player Mike Marshall and Brazilian pianist Jovino Santos Neto perform a live concert, the farmers market will offer tomato dishes prepared by Venus Restaurant.

The culmination of the yearlong party will be a gala dinner Nov. 3 featuring Chez Panisse owner Alice Waters, a longtime customer, and University of California, Berkeley, journalism professor Michael Pollan, author of "The Ominivore's Dilemma."

Waters provided the seed money to help get the Saturday market going. And when Pollan was asked at a recent forum how people could help both the environment and the local economy, he replied, "There's a farmers market on Derby Street tomorrow."

Waters shops at the farmers markets for both her personal use and her restaurant. Ditto for several other high-end eateries, including Lalime's, Olivetto, Ecolo and the Zuni Cafe. 

Although the farmers markets are officially celebrating their 20th anniversary, there actually has been a farmers market in Berkeley for even longer.

The first, located in West Berkeley, was founded in 1981 and lasted four years.

In 1987 the Ecology Center opened its first farmers market, the Tuesday market on Derby Street. Three years later, the Saturday market opened on Center Street, followed by the Thursday market on upper Shattuck in 2003.

In 1992 the Saturday market inaugurated its annual Holiday Crafts Fair, which is still going strong 15 years later.

Befitting their commitment to healthier food, the markets banned produce fumigated with methyl bromide in 1996 and genetically modified produce in 2002.

That same year, the Ecology Center signed a deal with the Berkeley Unified School District to open "farmers markets salad bars," featuring fresh fruits and vegetables, at three elementary schools.

In 2002 the farmers markets broke their longstanding "dead animal barrier" when Fresh Catch began selling locally caught salmon and crab.

Whatever changes the farmers markets go through in the future, they will continue to be a place where Berkeleyans meet and eat.

"People long for something besides convenience," said Lumpkin. "Since before history began, there's a long tradition of people coming together to buy or sell food. People can be a part of that community, whether they know the history or not."