SAN FRANCISCO (AP) – Prince Charles and his wife, Camilla, took their royal tour of the United States to northern California on Saturday, examining local produce at a market and lunching with locals at an organic farm near San Francisco.

The prince and Duchess of Cornwall will spend more than three days in the region, as the trip shifts from the power centers of New York and Washington to more rural areas, and issues close to the prince’s heart ­ organic agriculture and sustainable food production.

Following a stop at the farmer’s market in the Marin County town of Point Reyes, the couple will visit Bolinas, a small coastal community about 30 miles north of San Francisco, where they planned to lunch at Star Route Farms run by organic pioneer Warren Weber.

They also planned to visit a Berkeley school organic garden sponsored by chef Alice Waters.

The prince is a firm supporter of environmental causes and runs an organic farm on his Highgrove estate in England. He also has a multimillion-dollar line of organic foods, Duchy Originals, whose profits go to charity.

“We’re excited because it takes our message into the world,” said Helge Hellberg, executive director of the farming association Marin Organic. “It’s not just royalty or a celebrity coming, it’s somebody who stands for what we are doing.”

In a recent interview, the prince urged support for small-scale farmers, saying he feared agribusiness would end up “completely industrializing the landscape.”

Charles and Camilla flew to San Francisco late Friday after a brief stop in New Orleans. There they saw a neighborhood obliterated by Hurricane Katrina.

Standing atop a patched 20-foot levee in the impoverished Lower Ninth Ward, they shook their heads in disbelief at the destruction: splintered homes, chunks of concrete, overturned cars. The couple also met residents and rescue workers.