Barley, hops, water and yeast. And wild sage and dandelion greens, yarrow and golden currants. Oh, and rabbit brush. These are some of the ingredients that were used by seventeen Colorado breweries as part of this year's Beers Made by Walking.

The festival, today at the Wynkoop Brewing Company, is one of the most unusual events that takes place during Great American Beer Festival week in Denver. All of the beers were made using some plant that the brewers discovered on a local walk.

See also: The Great American Beer Festival 2013: Do this, not that

"I had two criteria driving my beer," says Scott Witsoe of Wit's End Brewing, who created Killer Rabbit, a beer made with rabbit brush and rabbit brush honey. "I wanted to use a plant that is indigenous to Colorado, and I wanted to find something that grows on the South Platte bike path, which is just about a quarter of a mile away."

Since Witsoe doesn't know what wild plants are edible, though, he enlisted the help of a local herbalist named Joan Zinn, who showed him the rabbit brush.

"It's medium height with flowers at the end. It is incredibly fragrant and reminded me of chamomile, with honey notes," Witsoe says. "It's really aromatic."

The resulting beer is a blond ale that comes off more like a saison and has some funky notes from local rabbit-brush honey, which Witsoe also added. It will join sixteen other beers at the festival tonight, including those from Crooked Stave, Our Mutual Friend/Cerebral Brewing, Fate, Mountain Sun, Elevation and Wynkoop (see the full list of beers and ingredients on the next page.)

Created several years ago by Colorado Springs beer blogger, homebrewer and professor Eric Steen, Beers Made by Walking started small, but took on a life of its own in 2013 as Steen moved to Portland and created a second chapter there.

"I have a fascination with environmental education and being outdoors," Steen says, adding that it took him a couple of years to start inviting breweries on his walks. "Beer gets us to slow down and be with friends. Walking is also something that does that. Slowing down is at the heart of what I like to do in the world."

At first, Steen organized all the walks, but as more breweries heard about the idea, they began organizing their own trips, either to the mountains or natural areas nearby, or simply around the urban environments in Denver or Boulder. The Wynkoop, for instance, is making a beer with blue gummy bears that is based on the Big Blue Bear.

"These people are making some of the most interesting craft products available, so getting out into nature embeds a level of environmental respect into what they are making," Steen says. "This allows them to get into nature and have it still be work."

Beers Made by Walking takes place from 5 to 8 p.m. tonight at the Wynkoop. Tickets, $30, are available in advance at ticketalternative.com or at the door -- if it isn't sold out.

Turn the page to see the list of beers: Boulder Beer / Spirit Guide / Stout brewed with Chokecherry, Dandelion, Milk Thistle, and Echinacea. 7% ABV.

Crooked Stave / Colorado Wild Sage / Vielle Barrel-Aged Saison with fresh cuttings of Colorado Wild Sage. 4.2% ABV

Elevation / Last Run / A bright, citrusy, hoppy blonde ale brewed with a hand-made extract composed of wild red currants. 5% ABV.

Fate / WILD Flower Honey Wheat / Classic American Wheat brewed with honey, Summit hops, and Brettanomyces.

Grimm Brothers / Kinder Beer / Bohemian-Style Pilsner blended with wild raspberries picked while hiking near near Mt Bierdstadt.

Mountain Sun Pub / Achilles Field / A Saison that highlights the earthy flavors and aromas of Yarrow, which grows all over Denver. 5.6% ABV.

New Belgium / Mint Mild / A take on the English Mild Style, using mint to provide subtle herbal balance to its malty backbone. 4.5% ABV

Our Mutual Friend and Cerebral / Urban Flora / Saison brewed with fresh Denver dandelion greens and hand-toasted sunflower seeds. 6.9% BV.

Paradox / Wild Chokecherry Sour / Created using a Sour Mash technique, the tartness of the wild chokecherries is balanced with locally sourced honey and wild hops. 7.5% ABV.

Phantom Canyon / Electric Eye / A 50/50 blend of two Saisons, aged for one year. One Saison is our previous BMBW offering brewed with three-leaf sumac and rose hips. The other, contains hibiscus flowers, galangal, lemon and orange zest.

Pikes Peak / Currantly in Colorado / Imperial Brown Porter brewed with Golden Currants, based on a hike near the Palmer Lake Reservoir. 6.5% ABV.

Strange / Noah's D'Ark / A Belgian Dark brewed with wild hops and prickly pear cactus fruit harvested along Clear Creek and Bear Creek, after the floods. 6.5% ABV.

Three Barrel / TBA

Twisted Pine / Flatirons Vista Wit / A light, crisp Witbier brewed with White Nectarines, inspired by fruit discovered on the Flatirons Vista Trail in Boulder.

Wit's End / Killer Rabbit / A blonde Belgian ale made with Rabbit Brush form the South Platte River trail in Denver, with local Rabbit Brush Honey. 6.5% ABV.

Wynkoop / Blau Bär / A lager infused with raspberries, thyme and blue gummy bears. Inspired by the large blue bear in front of the convention center in Denver. 4.2% ABV.

Yak & Yeti / Needles! / Colonial-style spruce beer, with Colorado blue-spruce tips, aged on cedar. The beer was inspired by a hike near Buffalo Bill's Grave in Golden, CO. 7.9% ABV.

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