Cousins to marijuana: Hop plants also have compounds that give them their characteristic smell. Thinkstock

There are four main ingredients in beer: water, malt, yeast, and hops. Each component plays an important role, but chances are you like beer because of hops. Hops lend beers their characteristic bitterness, and they also impart distinct floral, fruity, and resinous aromas and flavors that make individual beers unique.

But for all the hop-heavy beers we throw back here in IPA- and pale ale–obsessed Seattle, most of us actually know very little about hops. To peek into the world of hops is to learn about cultish devotion, competitive sourcing, and intricate recipes. Brewers use rapturous, almost poetic language when talking about hop varieties and their flavor profiles.

In the Yakima Valley of Eastern Washington, which produces more than 75 percent of the country's hops, seemingly endless fields of hop vines grow as high as 18 feet. Every year, starting in mid-August, workers harvest the female flower of the hop vine, called the cone. Underneath the cone's tightly layered leaflike structures are lupulin glands, which contain the two main chemical compounds used to make beer: alpha acids and essential oils.

Alpha acids have an antiseptic nature that prohibits the growth of unwanted bacteria while simultaneously promoting the growth of yeast (the fungus that allows beer to ferment and have alcohol content). But their main purpose is to give beer its unique bitter flavor. The IBU (international bittering units) measurement that's often listed after a beer's alcohol-by-volume percentage measures the concentration of alpha acids.

The first step in beermaking is to combine water and malt to form a liquid called wort, which holds bready, sweet, caramel flavors, as well as the sugar that will eventually become alcohol. Then hops are added, and as they cook, the hops' alpha acids are converted into bitter iso-alpha acids, which balance out the wort's sweetness.

"When we add hops to the boil—and we use different varieties and different quantities at different times during the boil—they end up giving us different results," says Reid Spencer, head brewer at Georgetown Brewing Company.

Hops added early to a boil provide a bittering effect, explains Spencer. "But hops added later in the boil, after the boil, or in the fermenter at room temp or when the liquid is cold—those all contribute very specific flavors and aromas.

"When you see something referred to as a 'dry-hopped' or 'late-hopped,' it's an indication that the brewer intentionally used whatever variety of hops specifically for its flavoring and aroma characteristics."

Hop plants are cousins to marijuana plants. They come from the same family, Cannabinaceae, and both have compounds that give them their characteristic smell, which can range from dank and skunky to citrusy and floral.

Some hop varieties, like well-known workhorse Cascade, have been around since the 1970s, while relative newcomers like Mosaic developed more recently and have rabid followers.

Georgetown Brewing uses Cascade the most. Spencer praises the popular variety for its citrus, pine, and mild floral flavors. "It's not super aggressive," he says, "just mellow and really pleasant."

Centennial hops have strawberry and guava scents, while Amarillo evokes peach and melon, says Spencer. Simcoe contains a "wide spectrum" of smells, including pine, skunk, and Juicy Fruit gum.

With so many different hop varieties, craft brewers have entered a new level of experimentation and exploration. Brewing beer "has kind of become more art than science, and you're using your palate to guide decisions," says Justin Gerardy, owner of the Central District's Standard Brewing. When Gerardy first began making beer, he wasn't necessarily aware of how complex the flavor universe of hops was. But, he says, "that's part of what attracted me to it—the depths. And it's one of the reasons beer is blowing up right now."

Gerardy prefers a more melony, citrusy IPA, so he's a big fan of Galaxy hops, an Australian variety that he says has notes of pineapple and mango. "Citra," says Gerardy, "is obviously awesome, too, and then there's Mosaic, which some describe as cat pissy, piney, and blueberry—it's really unique."

Both Citra, which was released into the market in 2007 and is known for its aggressive citrus flavors, and Mosaic, which was released in 2012, are what Gerardy calls "glamour hops"—strong hops that have, in a relatively short amount of time, become favorites among beer drinkers. But with high demand comes high prices and hop shortages.

"Everybody is trying to develop something unique and make a name for themselves," says Spencer. "And the market seems to want hops. [Hops] are an advertising technique so the consumer expects to get those flavor profiles from those hops."

But that doesn't mean those beers will always taste the same.

"Terroir matters," says Gerardy. "You can have the same hops grown in Europe or over here—hops with the same DNA—but the quality of soil and water make the flavors dramatically different."

Because of Washington State's drought, hop quality and flavor may vary significantly. These variations force brewers to adapt and be creative, which leads to new beers.

"For a quality brewer, being perfectly consistent isn't necessarily your biggest priority," says Gerardy. "I don't think people understand how much the beers they love actually fluctuate."

For Spencer, that means understanding each hop's flavor profile. "Some of our IPAs will use up to five different hops, so as we transition from one crop to another—if the Cascade, Amarillo, or Centennial are a little different—we adjust," he says.

To that end, Spencer has started traveling to Eastern Washington to meet with hop farmers. "We need to be out in the fields, smelling the hops when they're on the vines, so we know which crops are going to give us the product that we want," he says.

Spencer says the timing of the hop harvest matters, too. If a cone is harvested before it's ripe, it yields less alpha acids, that all-important bittering component. Its flavors also may not be fully developed.

"When a Cascade gets to its magic stage, it's really piney and fruity. But if it's left on the vine too long, it starts to enter the onion-garlic spectrum," he says, scrunching up his nose.

Bigger breweries are able to contract hops, meaning they commit to purchasing a certain amount of hops in bulk, which allows them to pick the hops they want. Smaller breweries, on the other hand, rely on scrap hops. It doesn't necessarily mean the quality is lower, but it does mean there may be more variation.

Standard Brewing, which uses scrap hops, is in the midst of a significant expansion. With that jump means the ability to contract hops—not that the beer depends on that.

"Hops are just part of the story," Gerardy says. He believes the next frontiers in the local craft-brewing scene will be barrelfermenting, barrelaging, and developing new and entirely local yeast strains.

"Hopefully, the Seattle beer-drinking crowd will begin to understand what's going on and keep digging for a more complex understanding of it." recommended

This article has been updated since its original publication.

This article appeared in the fall 2015 issue of The Sauce.