American white oak—aka Quercus alba—is an integral part of whiskey today. This stately tree is used for the vast majority of both bourbon and rye casks, lending important vanilla and spice notes to the spirit. After being used to age these whiskeys, the barrels continue to spread the influence of American oak around the world, lending their properties to scotch, rum, tequila, and other spirits as well as wine and beer.
The ubiquity of Quercus alba casks is partly due to the vast number of trees available to cooperages. Huge stands of the mighty oaks stretch from Minnesota south to East Texas, all across the South, and up to New England. American oak grows in snowy plains, sun-soaked swamps, and ancient mountain forests. The wood from these trees is often treated as a single material without any differences or variation. But with such a diverse array of growing conditions, distillers must ask: Is all American oak created equal?
Oak is undeniably important to whiskey, and this is especially true for American whiskeys such as bourbon and rye, which require new, unused barrels. Virgin wood can have much more impact than a used barrel, and the oak is responsible for much of whiskey’s flavor. The federal rules that define bourbon and rye say they must use “charred new oak containers,” but they don’t specify that the oak must be American—yet virtually all these barrels are made from Quercus alba.
All oak commonly used to make whiskey contains myriad compounds including eugenol, which imparts a clove flavor; oak lactones, which provide coconut notes; and dozens of organic acids, tannins, and other compounds responsible for a variety of flavors. Oak species is the best indicator of how these compounds will present in the wood. For instance, unlike its European counterparts Quercus petraea and Quercus robur, American white oak has much higher levels of vanillin, a phenolic aldehyde responsible for—you guessed it—the flavor of vanilla.
While the differences among oak species are well established, there is less clarity about how much the oak varies depending on growing conditions. Andrew Wiehebrink, director of spirits research and innovation at Independent Stave Company, says he doesn’t “see much difference in overall flavor profile from oak grown in different countries, let alone different states.” He goes on to explain, “From my experience, the density of the tree varies, which changes flavor delivery but not flavor.” While it may seem contradictory to say that flavor doesn’t change with environment but flavor delivery does, Wiehebrink is speaking here of the density of compounds in the wood.
Delivery, he says, refers to “the sequence in which the flavor components will come in. The ratios will slightly change, but depending on where the tree grows and how fast or slow it develops, the change in density can also change how easily the whiskey can move in and out of the wood. Again, these aren’t huge differences when compared to the differences you get from toasting, for example, but they are measurable in a lab and maybe, to some extent, by olfactory tests.”
Essentially, all American white oak trees contain the same kinds of compounds—vanillin, eugenol, lactones, etc.—but the amounts of these compounds in each tree can vary greatly, influenced by growing conditions. Those conditions can include everything from average temperatures to soil quality to tree density, encompassing any other factor that affects how a tree grows.
Location, Location, Location
Despite a lack of hard research that compares Quercus alba grown in different regions of the United States, many American whiskey producers are convinced the variation is noticeable and important to their spirit’s character. Phil Steger, founder of Brother Justus Whiskey Company in Minneapolis, says he believes the Minnesota oak his distillery uses is crucial to their single malt.
“The oak is really exceptional because, as you can imagine, a white oak tree that grows in Missouri is living in a very different world from a white oak tree that’s living its entire life in northern Minnesota,” he says. Minnesota provides “much longer, colder, darker winters and much shorter and more exuberant summers, and that has a material impact on the grain of the wood, the density of the wood, and the chemical content to the wood, especially its vanilla and tannin concentration, so it does taste different.”
Many coopers agree with that general assessment of regional variation. “Wood grown in hotter, wetter, and flatter environments tends to be faster-growing,” says Brett Wolfington, COO of WV Great Barrel Company in Caldwell, West Virginia.
WV Great Barrel sources lumber from multiple states. “The wood tends to have fewer defects like knots in many cases, but it has wider growth rings,” Wolfington says. Those growth rings provide much of the flavor impact, so more of them in a stave generally translates to a heavier concentration of compounds that give flavor to whiskey. “The wood that we get from around our mills in West Virginia generally tends to be very tight-grained and has more growth rings per square inch. For example, from some of the Tennessee trees, we’ll see nine or 10 growth rings per inch. From our West Virginia wood, it might be as high as 14 to 15 growth rings per inch. And so, there is a difference there in terms of the amount of extractives that are available to be pulled into the whiskey from the wood.”
Iron City Distilling in Pittsburgh taps into the regional specificity provided by WV Great Barrel Company. “They flag as much of the Pennsylvania oak for us as possible,” says Matt Strickland, head distiller at Iron City. “So, to my knowledge, all of our oak comes from [Pennsylvania].” Strickland says he believes using wood from closer to home “will have an impact,” but he acknowledges that the difference between this and oak from nearby West Virginia may be “subtle.”
Going and Growing Local
But if the impact of local oak is subtle, is it worth worrying about at all? Many producers believe it is. After all, it takes a variety of production choices—many seemingly small or subtle—to add up to a distinctive house profile.
At Iron City, for example, Strickland says the oak is “one more piece of the puzzle for us.” Using local oak also fits with Iron City’s goal of keeping everything close to home—the same reason they use Pennsylvania grain as much as possible. “I really do adhere to the whole, you know, local-economy, circular-economy thinking, " Strickland goes on to explain. “So, we try to keep that money in the local community as much as we can.”
Down in Union, Missouri, Nobletons Distilling House takes that local economy mindset a step further. “We actually grow all of our raw ingredients,” says Nobletons head distiller Demetrius Cain. This includes all the grain, such as the heirloom wheat, corn, and barley that Cain personally farms in Missouri and surrounding states. And it extends to much of the wood used for the distillery’s barrels. “We actually grow the wood for about 20 percent of our barrels,” Cain says. “We have it cut into staves at the local mill, air-dried for five years, and then we turn that into our specialty casks.”
Missouri isn’t the only state where distillers are using a hyper-localized approach to sourcing wood. “We also have a couple of customers [who] will ship us their wood,” says Kayla Whited, sales and marketing specialist at WV Great Barrel. The cooperage can then turn that oak into barrels with the source of the wood engraved on the head.
For distillers without their own stand of trees, there are still options for obtaining local oak. While many large cooperages won’t provide state-specific oak—Wiehebrink of Independent Stave Company says they “generally cannot accommodate these requests [because of] the nature of [their] manufacturing process”—plenty of new and smaller cooperages are able to oblige the request.
This can happen by default when a distillery buys barrels from a local cooperage that gets all its wood from local forests for pragmatic, logistical reasons. “I’m willing to bet a lot of people are doing it, and they just don’t realize it,” says Iron City’s Strickland about distilleries located in oak-growing regions.
There are also cooperages such as WV Great Barrel, bringing in lumber from various states but willing to accommodate state-specific requests. “Most of it comes from West Virginia, but we get some from Pennsylvania,” Wolfington says. “We get some from Virginia, North Carolina, Tennessee, Kentucky, and even Ohio.” Even if a distillery isn’t in one of those states, it might make sense to seek out oak from a specific place in hopes of using the unique growing conditions of those regions.
In addition, for those outside of areas where American white oak grows, there are still plenty of great options for finding interesting barrels that fit with the profile of their spirits. “The cooperage industry has expanded, and there are more players in the industry now than there ever have been,” Wolfington says. There is “more commitment to innovation. There’s more willingness on the part of the cooperage to do those kinds of interesting projects with customers.” Gone are the days when distillers had to accept “standard bourbon barrels” as their only option. Today, producers can carefully select how they will use oak as another piece of their spirits’ puzzle.