When Nan McEvoy fell in love with Tuscan-style olive oil, she decided to make it in her own backyard. It became McEvoy Ranch.

According to company lore, after reading the book “The Feast of the Olive,” she contacted Italy’s Maurizio Castelli, an international expert in olive oil production. He helped her plot out the 550-acre ranch she owned on the edge of Petaluma, picking the perfect spots to plant her trees.

“They were the original crop planted by Mrs. McEvoy when she first bought the property,” said Samantha Dorsey, who worked her way up from tending McEvoy’s olive grove to serving as general manager of the sprawling estate.

Today, McEvoy Ranch is home to 14,000 olive trees. Harvest started last week, meaning crews are busy shaking the green fruit from the trees using a motorized device that jiggles the branches without breaking them. The olives are collected up and quickly pressed into rich virgin olive oil.

“We start at morning light and pick a full day then we mill the fruit each night,” Dorsey said. “Extra virgin is the highest quality olive oil you can make. It has to be 100 percent olives. It also has to pass lab tests and a taste test.”

On average, McEvoy collects 120 tons of olives during its few weeks of harvest season, which when pressed equals more than 5,000 gallons of oil. This year, the crop is smaller than average, due to late-season cold weather last year that stunted the amount of fruit a tree could produce.

“A lot of producers across the state are seeing much lower tonnage,” Dorsey said. “But, here’s the interesting thing that happened. Our oil yield is actually quite high.”

Dorsey explained that because the trees were less crowded with fruit this year, the olives had more room to grow and are much more plump and packed with oil. That means McEvoy expects to get an average harvest of olive oil despite the small crop.

“It’s been a saving grace for us on what would be a light year,” she said.

Olives are not affected by the smoky air that has permeated Petaluma in recent weeks. The oil sits in vacuoles, which are like pockets within the folds of the fruit’s flesh. The thick skin of the olive protects the inner oil from outside environmental influences like smoke.

“Olives are significantly more resistant to smoke taint than grapes,” Dorsey confirmed.

New this year, McEvoy is milling some olives with mint and others with rosemary to produce a deeply herbaceous flavor. The new products will join the company’s tried and true favorites, lemon and jalapeno.