At night, a vineyard smells different. Daytime dust is damped down by fog rolling off the ocean. The glare of fluorescent lights makes silhouettes of farmworkers moving swiftly in the shadows. They are harvesting wine grapes.

"It's better at night," said Fermin Manzo, foreman of the crew picking pinot noir grapes for Hartford Family Winery on a crisp, fall night.

At night, temperatures are lower. This benefits grapes and workers.

In the day, grapes that sit in bins under the sun can start to ferment -- not a good thing. Meanwhile, employees run the risk of heat-related illnesses if they try to work a full shift. "They'll pick just maybe four hours, and they'll be tired," Manzo said. "At night you go slower, but you can work longer."

Hartford Family Winery vineyard manager Walt Chavoor likes the fact that crews can go longer and make more money. And he is happier with the results. "I am convinced that one of the most crucial things we can do for wine quality is to bring fruit in cold," he said.

Of course, visibility is the big challenge.

The key is getting enough lights ready and meticulously planning which rows are going to be picked so there is no fumbling around in the dark, said Sonoma County vineyard owner Saralee Kunde, who has switched to doing about two-thirds of harvest at night.

"Everybody wants cold fruit. This way we can satisfy everyone," she said. "And it's so much nicer on the guys. Our crew is much happier picking at night."

Picking at night by machine has been common for some years, said John Miles, an agriculture engineer at the University of California at Davis.

What is new is that smaller, boutique-style wineries that rely on hand picking, which they believe yields higher quality fruit, have been joining the night owls. Miles said a very rough estimate might be as much as 10 percent of the hand-picked harvest is nocturnal.

Night picking will not work everywhere; the ground needs to be relatively flat and the vines trained to grow so the grapes are easily visible.

From a distance, night harvesting lends an eerie glow to quiet fields.

Up close, nature and machine set up dueling symphonies, crickets chirping as the tractors rumble.

Vineyards use different methods, but at Hartford Family Winery the darkness is dispelled by a big metal stand studded with fluorescent tubes that is dragged along the rows by a trailer.

The pickers work with a practiced rhythm, stripping the vines of ripe fruit and tossing full bins of the gleaming black grapes into waiting containers.

Vintner Mike Moone, a fan of night harvesting, likes the concept so much he recently threw a party at his Luna Vineyards in Napa where workers and guests picked pinot grigio grapes as a huge harvest moon sailed above.

Said Moone with a smile, "Nighttime's the right time."

Nighttime in Annapolis, Calif., and pickers cull vines for pinot noir grapes at the Hartford Family Winery vineyard.