Olive oil has the grape harvester to thank for its status as one of the fastest growing industries in California, growing by 50 percent this year alone.

Without a modified version of the mechanical contraption – it drives over treetops to harvest olives at up to 670 trees an hour – olive oil would still be a boutique industry.

Instead, California olive growers pressed 675,000 gallons of oil from 21,000 acres of land last year, and plantings are expected to grow by 10,000 acres annually through 2020, according to Patricia Darragh, executive director of the California Olive Oil Council.

"It has a place here," said A.G. Kawamura, state secretary of food and agriculture. "Any time we can compete with imports, when we can become domestic producers, that's a good thing because that keeps the dollars in this country."

The world is taking notice of the amount, and the quality, of olive oil made in California. About 300 international experts convene today at the University of California, Davis, for the first of three days of panels and research presentations about extra-virgin olive oil.

California was known mainly for table olives before boutique growers started pressing quality oil in the early 1990s. McEvoy Ranch was one of the first premium producers, and now tends 18,000 Italian varietal trees on 80 organic acres in Petaluma, according to general manager Dick Neilsen. But the McEvoy customer is special, willing to pay $20 for a 375-milliliter bottle (about 13 ounces).

A more accessible product emerged in 1998 when California Olive Ranch developed 483 acres in Oroville. The trees were planted on trellises, similar to grapes, so a modified grape harvester could pluck olives mechanically. It revolutionized production.

Historically, olives were harvested by hand or allowed to ripen so they could be shaken from the trees. While small growers can still get olives to the mill in a time-efficient manner – McEvoy presses most of its olives within eight hours of harvesting – the painstaking process posed a hurdle for mass producers.

Spanish growers, using varietals that adapt easily to the hedge shape, were first to make olive trees fit grape harvesters. The result: up to 670 trees an acre instead of the traditional 150, and the ability to harvest an acre of trees in an hour, said Gregg Kelley, president and chief executive officer of California Olive Ranch.

The company now processes 8,000 acres of olive trees. It gets its olives from tree to mill within 90 minutes and charges less than $10 for a 500-milliliter bottle (about 17 ounces). The amount of time between harvest and pressing is a key component to good olive oil.

"Hand harvesting is really expensive, and it's sometimes hard to find the labor," said Dan Flynn, executive director at the UC Davis Olive Center. "Mechanical harvesting cuts production costs quite a bit and allows California to compete more effectively with imported oil."

In a time of drought, olive trees also are appealing to area farmers because they demand a quarter of the water rice requires, and about half what almond trees need, said Kelley of California Olive Ranch.

Olive oil is relatively new to the American diet. That is changing due to the health benefits of olive oil: It's high in monounsaturated fat, which is believed to help lower bad cholesterol, and contains antioxidants.

Still, an American consumes an average of 750 milliliters, or about four-fifths of a quart, of olive oil a year, compared with the average Greek's 24 liters – about 28 quarts – and about 14 liters (16 quarts) for each Italian and Spaniard, according to Paul Vossen, the farm adviser for the University of California cooperative extension in Sonoma County.

"The U.S. consumes 8 percent of the world's olive oil," Vossen said. "We're the No. 4 consumer just because we're a big country."

More than 99 percent of the olive oil Americans eat is imported, mostly from Italy, although olives processed in that country might have been grown elsewhere.

"The market is there; the market is huge," Vossen said. "The main obstacle is that people don't know that much about olive oil. Most Americans don't know what good olive oil is."

Although it became illegal in California this year to sell olive oil as extra-virgin if it doesn't meet a high standard, there's no enforcement; sometimes bottlers use confusing terms such as "extra light."

The industry is working to teach Americans about labels – how to determine where the olives were grown, how long they were off the tree before pressing, and to mind "use by" dates. Olive oil should be used within six months of opening.

"A good analogy is wine. When you first started drinking wine, you had to educate your palate," Vossen said. "People just need to go out and try and buy and use olive oil over a period of 10 years. It's not going to happen overnight."

Call The Bee's Gina Kim, (916) 321-1228.