With snow still visible on the Mayacmas mountains, the chardonnay vines at Balletto Vineyards west of Santa Rosa are stirring to life.

Little green buds about the size of Q-Tips are poking forth from thick brown vines now awakening from hibernation.

"This week it will happen. It will pop all over the county," said Nick Frey, spokesman for Sonoma County's grape growers. "There won't be much rest between now and harvest."

Temperatures are expected to top 80 degrees this week, shaking the winter slumber out of the county's 56,000 acres of grape vines.

"It's the start of another year," said Jeff Carlton, vineyard manager at Dutton Ranch. "We've been waiting."

Weeks of cold, wet weather that blanketed mountain ranges with snow and dumped near-record rain in March on the valley floors stalled the season by about two weeks.

"Now you can just see a very tiny bit of green," said Mike Rowan, owner of Wine Creek Vineyard in Dry Creek. "The vines are getting ready to push."

Growers call this annual kickoff "bud break," which refers to the process in which a verdant little shoot emerges from the dry, brown bark and within a few days begins to unfurl its bundle of tightly-packed leaves.

"You're just seeing the first leaves on the chardonnay vines. They're peeling off now," Carlton said. "Drivers will be able to see them from the road in about a week and a half."

The county's economy is inextricably connected to the growth cycle now underway. The vines bear the weight of the county's roughly $2.5-billion wine industry, according to the Sonoma County Winegrape Commission. That represents about 12 percent of the county's total gross domestic product.

Right now, the first visible signs of growth are emerging in early-developing varietals, said Rhonda Smith, viticulture adviser with the UC Cooperative Extension in Sonoma County.

Chardonnay is often the first to begin bud break, and cabernet sauvignon is often the last, she said. But all of the vines have been slowly stirring back to life for some time now even though nothing was perceptible to the eye, she said.

Vine growth will move rapidly now. Within a week or two, tiny clusters destined to become flowers will begin to appear, said Frey, president of the Sonoma County Winegrape Commission. This is the first visible sign of the fertilization process that results in grapes.

Throughout April the shoots will grow and elongate, and by May those little clusters of flowers will begin to open. At that point, the crucial pollination process will begin.

Grape vines are self-pollinating, meaning bees or other insects are not required to fertilize the vine's many eggs. The vine does that all itself, and those fertilized eggs, called embryos, are destined to become grapes.

The fertilization process usually takes place throughout May and into June. Wet, cold weather can easily disrupt the vine's reproductive cycle and growers often find themselves on edge.

"I can make myself overly anxious," Rowan said. "But the fact is, it's really not until the end of June that anyone can put an estimate on what the crop will be."

The vine embryos begin to transform into grapes, which first show up as clusters of tiny green balls smaller than BB pellets located under the thickening canopies.