New York Times bestelling author Amy Stewart, a garden writer and horticultural expert, kicked off the 2013-14 Rae Dorough Speaker Series at the Bankhead
New York Times bestelling author Amy Stewart, a garden writer and horticultural expert, kicked off the 2013-14 Rae Dorough Speaker Series at the Bankhead Theater in Livermore, Calif., on Tuesday, Oct. 8, 2013, entertaining the audience with the science and folklore of the plants behind their favorite cocktails. (Livermore Valley Performing Arts Center)

LIVERMORE -- Ever wonder how many kinds of plants go into a traditional Manhattan cocktail?

Writer Amy Stewart did, and after an illuminating experience in a Portland bar, the author spent years researching the flora behind your favorite alcoholic drinks, culminating in her latest book, "The Drunken Botanist."

In town Tuesday for the first talk in this season's Rae Dorough Speaker Series at the Bankhead Theater, the best-selling author regaled listeners with tales of medicinal brews, do-it-yourself liqueur and the science behind the plants we ferment, distill, extract, infuse and guzzle.

A garden writer and naturalist, Stewart -- an ex-Santa Cruz resident who lives in Eureka -- is the author of four New York Times best-sellers about the darker side of the natural world, including "Wicked Bugs," "Wicked Plants" and "Flowers Confidential."

The inspiration for her latest came -- as many great ideas do -- in a bar. She and a companion were imbibing when Stewart remarked on the plants needed to make a bottle of gin; juniper, lavender and sarsaparilla to name a few. Where others saw booze, she envisioned a garden.

"Everything behind the bar was plants in liquid form," Stewart said. "Fortunately, I could still read my handwriting the next day."

Her subsequent research had her globe trotting to wineries, bars and distilleries, provoking countless interviews with botanists, including at UC Davis, where scientists are mapping the genetics of wine varietals.

"It's interesting to take a global perspective," she said. "There are all kinds of plants we don't think about here that are consumed other places."

From corn in bourbon to agave in tequila, plants have a long history in alcoholic spirits, Stewart explained. Since at least the eighth century, humans have been putting them in distilled drinks and soaking herbs in alcohol to preserve their medicinal properties. European explorers searching for dysentery remedies stumbled on the bark of the angostura plant, the namesake for (but no longer an ingredient in) the bitters used in a Manhattan.

The rest of the cocktail, Stewart said, contains well over a dozen plants. Besides the corn, rye, wheat and barley in whiskey, there's a number of various secret herbs and spices in vermouth and bitters -- not to mention the oak in the whiskey barrel.

Stewart's presentation wove through the sometimes sordid folklore behind the "Black Republican" cherry, the makings of the true maraschino cherry (the real stuff is infused with Luxardo liqueur), and once-banned plants like black currant and the Cuban mojito mint.

Livermore's Alden Lane Nursery, which Stewart had connected with for her first book on gardening, served up a nonalcoholic lemon verbena iced tea in the Bankhead's foyer and displayed plants commonly used in liqueurs: sweet potato vine, coriander, fennel.

"It's an interesting approach," said Cyndee Carvalho, the nursery's general manager. "We're hoping it will connect with someone a little younger who hasn't tried gardening yet,"

As the evening concluded in the heart of Livermore's wine country, Stewart said she hoped the audience of about 300 -- including a sizable group of local high school students -- would walk away thinking a little more about what's in all those bottles.

"It's more than just the flavor; it's what's behind it," Stewart said. "It's really about the history of people."

Contact Jeremy Thomas at 925-847-2184. Follow him at Twitter.com/jet_bang.