Tractors still dot the fruit-and-nut themed roads (Plum, Pecan, Apricot) of Canyon County’s Sunny Slope, but these days party-themed limousines and weekend wine tourists are also in evidence.

Their quarry is a cluster of mostly small wineries with an increasingly big reputation.

“We have eight wineries within 10 miles, which is enough for a two-day trip,” said Ron Bitner, who recently opened a small bed-and-breakfast at his hilltop winery overlooking the Snake River south of Caldwell.

Expand your search across Ada County and into Washington and Owyhee counties, and the Treasure Valley boasts more than half of the state’s 43 wineries, a tally that has nearly quadrupled since 2002, when Idaho had 11 wineries.

That’s a fraction of the explosive growth seen earlier in Oregon and, especially, Washington. They rank third and second among all states in number of wineries, eclipsed only by behemoth California. Idaho comes in at No. 22, tied with New Mexico, in Wine Business Monthly’s most recent ranking.

But Idaho has been easing its way up that list in a steady expansion that has continued through the Great Recession, said Moya Shatz, executive director of the Idaho Wine Commission.

“We’re actually doing pretty darn well if you consider how the economy’s doing,” Shatz said. “We get calls every week from people wanting to start a winery or plant a vineyard.

“The growth is manageable, and it seems like people are happy.”

An economic impact study conducted by Boise State University in 2008 found that Idaho’s wine industry contributed about $73 million to the state’s economy and 625 jobs, Shatz said. She doesn’t expect to commission another such study until around 2015, she said, but “I think our numbers have increased.”

PRIME SPOTS FOR WINE GRAPES

At Bitner Vineyards south of Caldwell, an old tractor shed has morphed into a tasting room with an expansive deck to make the most of views that glide across grapevines and other crops to the Snake River, Lizard Butte and beyond.

Bitner bought the hilltop site, which includes a steep south-facing slope, for the view in 1981. He didn’t think the five acres would be suitable for crops.

“I didn’t know what to do with the steep slope,” he said. But Ste. Chapelle’s first winemaker, Bill Broich, was building a home downhill from Bitner and offered an idea.

“He said, ‘This is a world-class site for Chardonnay,’” Bitner recalls. “I said, ‘Cool. What’s Chardonnay?’ ”

Three decades later, Bitner fully appreciates the vineyard virtues of the land he lucked into. An entomologist and international expert on leaf-cutter bees, he immersed himself in a second vocation. He recently completed a term as president of the Winegrape Growers of America.

In 1995, Greg Koenig, among the first in a new wave of Idaho winemakers, approached Bitner to buy some grapes. Soon Bitner was enlisting Koenig to make wines under the Bitner label. Their first vintage, a 1997 Cabernet, won a gold medal in New York in 1998.

“Then we knew we were on to something,” Bitner said.

Bitner’s steep slope protects his grapes from cold and frost, allowing him to keep fruit on the vine late into Idaho’s relatively short growing season. That allows the sugars to develop, he said, producing luscious, fruit-forward wine.

“I honestly wouldn’t trade these spots along the Snake River, including mine, for any in the country,” he said.

GAINING ACCLAIM AND ATTENTION

Idaho wines regularly net honors in regional and national competitions, and the media are increasingly taking notice

“They want something new to write about, and that’s us,” Shatz said.

The October issue of Sunset magazine sports a feature story headlined: “Discover new wine country: In Idaho’s low-key Snake River Valley, the wine is getting seriously good.”

Wine-based tourism also is on the rise, particularly among visitors from Utah, said Martin Fujishin, who runs Fujishin Family Cellars.

“People come up from Salt Lake City, stopping at fruit stands, stopping at the wineries,” Fujishin said.

More Sunny Slope B&Bs are in the planning stages, and several local companies offer winery tours by van or limo.

On a recent sunny Saturday, George Condit of Idaho Wine Tours enjoyed the view on Bitner’s deck while his customers tasted the wine. It was one of five winery stops on a full-day tour that includes lunch at the nearby Orchard House.

Business has doubled since Condit started the company two summers ago, he said, and the clientele varies.

“I’ve had weekends that have been nothing but people from Salt Lake City,” he said. “But I also get wedding parties, people up here for a cardiology conference, plenty of locals.”

Tour van passenger Pamela Bybee of Las Vegas said she was greatly impressed by the Idaho wines she sampled. The small Sunny Slope wineries were new to her — and to the Boise friends she was visiting.

“Before, all I knew about Idaho wine was Ste. Chapelle,” Gary Newman said. That pioneering Canyon County winery, now owned by Ascentia Wine Estates, produces more than three-quarters of all of the wine made in Idaho.

Many Ada County residents seem unaware of the wine-tasting options that are so near, Bitner said.

“I keep telling people, we’re just 32 miles from the (Boise) farmer’s market,” Bitner said.

THE WALLA WALLA FACTOR

Many people associated with the Idaho wine business or wine-themed economic development draw parallels to the early days of winemaking in Walla Walla, Wash.

“Walla Walla has been a great role model for the Treasure Valley,” Fujishin said. “They have shown how you can shape a primarily agricultural community into a wine community with wine tourism and ag tourism combined.”

In the past decade or two, downtown Walla Walla has sprouted dozens of tasting rooms and thousands of wine-loving tourists. The area has about 200 wineries now, “and there’s this great symbiotic relationship between the new wine industry and existing agriculture,” he said.

“It’s unbelievable how that’s grown,” Fujishin said. “I’m quite boggled myself.”

One of Walla Walla’s prime wine business assets is the viticulture program at Walla Walla Community College, which provides research and trains future winemakers.

The Treasure Valley followed that lead, although on a much smaller scale, by opening a similar program at Treasure Valley Community College in Caldwell.

And since the 1990s, the University of Idaho’s Parma research center has hosted one of the Idaho wine grower’s most remarkable assets, Bitner said: Two wine-grape researchers funded by the U.S. Department of Agriculture.

“There are only 28 in the United States, and we have two here,” Bitner said, crediting that coup to the clout of then-U.S. Sen. Larry Craig.

Bitner’s ties to Craig likely helped the cause: Bitner was quarterback of the eight-man Midvale High School football team when Craig played center. Idaho Speaker of the House Lawerence Denney played guard on the same team.

Kristin Rodine: 373-6447