What: Sisters Fresh Hop Festival

When: Noon-8 p.m. Saturday

Where: Village Green Park, Sisters

Cost: $5 for the pint glass, $1 per token (good for a 4-ounce sample)

Contact: sistersfreshhopfest.com

Don’t blink, or you’ll miss one of the most fleeting times of the year for beer — fresh hop season. The annual hop harvest begins roughly around the end of August and can last through the beginning of October. This key beer ingredient is harvested, kilned (or dried), packaged, and distributed for breweries to use throughout the year.

We live in one of the most beer-savvy regions of the country, so likely you are already familiar with the spicy green herb. Hops add bittering balance to beer’s sweet malts, as well as microbial stability for preservation. They can add intensely floral, fruity, zesty character to the finished beer, as any IPA lover will tell you. Perhaps you grow them in your own backyard; if you do, you know that right now is when they need to be picked and dried.

Or not: What if you added the freshly picked cones into a beer you were brewing, straight from the vine? You end up with a beer classified as “fresh hop” (or sometimes “wet hop”), with the undried flowers contributing a different, green and pungent character to the finished brew.

“The minute a hop cone is picked off of the bine it begins to degrade, like any other piece of produce,” said Miles Wilhelm of Terrebonne’s Smith Rock Hop Farm. “So the sooner you can get those cones into the boil or hopback of a brew, the fresher and possible more distinct that beer will taste.”

This is why fresh-hop beer season is such a fleeting, ephemeral time of year. With such a relatively narrow window during which the harvest occurs, this truly is the only time of the year these beers are available.

As it happens, the Pacific Northwest grows more hops than anywhere else in the world — over 50,000 acres between Washington, Oregon and Idaho. Most breweries in the region are located within a few hours’ drive of a hop farm. The brewery starts a batch of beer while a brewer drives to the farm, picks up a load of freshly picked hops, and drives back just in time to add them to the beer.

At least half of Central Oregon’s breweries produced fresh hop beers this year, and you’ll be able to taste many of them at the seventh annual Sisters Fresh Hop Festival Saturday. Taking place from noon to 8 p.m. at Village Green Park, the event is a terrific showcase for the harvest beers, featuring 24 different breweries pouring their creations.

Among them, Bend’s newest brewery, Immersion Brewing, will be pouring its High Desert Terroir, a pale ale brewed with 100 pounds of fresh Centennial hops from Smith Rock Hop Farm. Immersion’s head brewer, Josh Cosci, coordinated with Smith Rock’s Wilhelm to plan the brew day. Volunteers picked the hops at the field in Terrebonne, and they were at the brewery within an hour of being harvested.

“It was so aromatic, it was immediately permeating the room,” Cosci said. “The restaurant was full of people, just packed, and it was so aromatic with hops, it was brilliant.”

Immersion is the only brewery to use fresh Smith Rock hops in a brew.

“The locality of it really hit home for me, and I started to get really inspired,” said Cosci. He acquired the malt for the beer from Mecca Grade Estate Malt in Madras, and said the finished result has a subtle, citrusy grapefruit character, entirely brewed with local ingredients.

Cosci got his start in the brewing industry at Three Creeks Brewing in Sisters, and in 2010 was part of the team at Three Creeks that first brewed Cone Lick’r Fresh Hop Ale and started the Sisters Fresh Hop Festival. Both the beer and the festival have returned each year since.

“We decided to go big or go home this year,” said Zach Beckwith, Three Creeks’ head brewer, “and brewed 60 barrels worth of Cone Lick’r at our production plant using 900 pounds of fresh Centennial (hops) from BC Farms in Woodburn and bottled 500 cases of 22-ounce bottles.”

You will be able to sample Cone Lick’r and Three Creeks’ other fresh hop beer, Hop Wrangler, at the Fresh Hop Festival alongside Immersion’s High Desert Terroir and the verdant harvest brews of 22 other breweries.

Don’t miss this opportunity to sample the freshest beers this side of the hop fields.

—Jon Abernathy is a local beer blogger and brew aficionado. His column appears in GO! every other week.