The smoke effect: Napa winemakers battle with the legacy of wildfire

Six months on from the California wildfires that struck Napa Valley’s vineyards, we look at the lasting impact on the region's winemaking – and especially the insidious problem of "smoke effect"

Words by Adam Lechmere

The Butts Fire in Pope Valley over shadows the vineyards and winerys of Californias Napa Valley
Californian wineries are still reeling from the devastation of the 2020 wildfires

A recent headline in the San Francisco Chronicle was stark: “California braces for extreme 2021 wildfire season”. Low winter rainfall has left a tinder-dry chaparral on the ground, among other indicators that the area can expect to see more intense fires this year – and potentially occurring even earlier in the season.

No one is more aware of the dangers than the wine producers of Sonoma and Napa, who are still reeling from the devastation of the wildfires around harvest time in 2017 and 2020. Almost all have come to the same sobering realisation: “wildfire season” is here to stay – and is expanding.

“There’s no longer the assumption that it’s going to be in October,” Dan Petroski of Larkmead winery in Napa told cluboenologique.com. “Fire season starts in April – and it goes on to December. The non-fire season is now January and February.”

While fire experts are relatively agreed on the strategies to control fires and limit damage – even down to banning highly flammable bark mulch in suburban gardens – there is far less agreement on how to deal with one of the most enduring legacies of the fires: the effect of smoke on grapes.

Wildfire on California coast - Sonoma County by ocean with view above marine layer.
Wildfires in Sonoma (pictured) and Napa are expected to be even more intense in 2021, potentially striking even earlier in the season

Indeed, winemakers can’t even agree on what the phenomenon should be called, and how it should be presented to wine consumers. Some – like Cathy Corison of Corison winery in Rutherford – prefer a less-loaded term than “smoke taint”: “We’re not using the words [smoke taint]. We’re calling it “smoke effect”, because it’s going to be a characteristic of the vintage.”

The problem goes deeper than simple nomenclature. The question of how smoke can affect a grape is straightforward: burning wood produces free volatile phenols (organic chemical compounds) which are absorbed by a grape’s skin. They then bind to grape sugars to produce glycosides. These glycosides can break apart during fermentation and barrel ageing and release the volatile phenols, which in this instance have smoky flavours. Glycosides can also – intriguingly – remain “bound” until they get into the mouth, at which point they turn “free” – and taste of smoke.

Crucially, it’s not only wildfires that create glycosides: a barrel that has been toasted releases the same phenols – except they’re tightly controlled and give attractive toasty oak flavours rather than a wet ashtray stink, which is one of the hallmarks of badly smoke-tainted wine.

California wildfires near a vineyard
Burning wood produces free volatile phenols which are absorbed by a grape’s skin and can alter the taste of the wine

To make things more complex, glycosides aren’t the only “smoke taint precursors” as they’re called. There may be dozens more that have not yet been identified. “To be honest, the more I read, the more I realise we don’t understand it very well,” Napa consultant Andy Erickson says. “We don’t even know if we’re measuring the right compounds. In Australia they are measuring a limited number of compounds and we’re not even sure that these are the right ones.”

Erickson, who has consulted for some of the most renowned vineyards in Napa, including Screaming Eagle, Harlan Estate, Staglin and Dalla Valle, also notes that certain red grapes – Petite Syrah, Cabernet Franc and Syrah, for example – naturally accumulate smoky aromas. “I used to put ‘smoky’ as a positive in my tasting notes. Now I think, ‘That’s not going to work’.”

Lab analysis can detect glycosides (from fires, from toasted barrels) far more efficiently than even an expert wine palate. “Chemical analysis reveals levels of taint or effect that you can’t smell or taste. But you look at the numbers, and you have what would be called a problem wine,” Erickson said.

Even if lab tests come back negative, the fact that glycosides can become free during barrel ageing is another headache for winemakers. At St Supéry in Rutherford, CEO Emma Swain told cluboenologique.com, they made no red wine in 2020 – the entire crop of its 500 acre (202ha) Dollarhide Estate Ranch in north-eastern Napa was lost. “We did roughly 150 individual bucket fermentations – we sent them to the lab and the analysis showed smoke taint. Even if we couldn’t taste it, there’s a chance it might show up later and we couldn’t risk that.”

‘California winemakers are anxious that every wildfire vintage is not seen as a “tainted” vintage’

The idea that a wine fault may be undetectable at first and then show up after years of ageing is not new (Burgundians are still working out exactly what causes premature oxidation in white wines). But California winemakers are anxious that every wildfire vintage is not seen as a “tainted” vintage – and in particular that smoke does not somehow come to be accepted as a part of terroir. “To say that smoke effect is going to be part of our winemaking? That’s a terrible argument,” Petroski says. “We are selling a luxury product.”

There’s no doubt that 2020, like 2017, will forever carry a “tainted” reputation. “We might as well get straight to the point. Is all of 2017 in Napa Valley smoke-tainted or not?” Antonio Galloni asked in a June 2018 Vinous article (before stressing the nuances of the situation and that he had tasted many wines with huge potential).

The 2020 vintage is more complicated in that the wine country fires started in mid-August, weeks earlier than the fires of 2017, which struck in October when some 80 per cent of grapes had been harvested. In 2020, unharvested grapes were enveloped in a blanket of smoke. It turned night into day, viticulturalist Phil Coturri, who manages some 600 acres of vineyard across the Sonoma and Napa Valleys, said. “On September 9th, the sun never came out. My chickens didn’t leave the coop because they thought it was still night.”

Californian oaks at the Meadowood resort, where much of the property was destroyed. Now, “the branches are pushing innumerable green shoots – it’s a sign of resurgence,” said managing director David Pearson

How such apocalyptic conditions affect vines – and wines – might not be fully understood, but winemakers stress that perspective is needed, and that while chemical analysis is a vital tool, the evidence of one’s senses should be as valuable. Erickson reckons 80 to 90% of wines that come back from the lab are in “the grey area” where there is a number associated with the wine, yet you can’t pick up any fault. “No-one has ever shown me a wine that has turned smoky after two years in barrel.”

Of the few critics who have seen the wines, Alder Yarrow of the website Vinography said he had seen “no evidence of taint” in the samples he had tasted.

There are so many unknowns in this situation but what is certain is that 2020 has been existentially painful for the wine community. To lose a crop, the result of a year of dedicated, often gruelling work, as Phil Coturri said, “it puts a hole in your heart.”