Few things more starkly divide the winemaking world than the philosophy surrounding how fermentation takes place. This is both a literal and philosophical separation. As the single most important chemical change in the context of winemaking (the conversion of the fruit’s sugars to alcohol) it might be said that the method of fermentation is among the most significant ways that the winemaker can shape the final wine.

In my 13 years of visiting wineries, meeting with winemakers and talking with them about their craft, few ideas are held more strongly than a winemaker’s point of view on native (using yeasts found on the grapes and in the winery environment) versus inoculated (using commercially developed yeasts) fermentation.

With an acknowledgement that this issue is far from black and white, here’s how the thinking usually breaks down:

Those who use them believe that native (also known as “spontaneous,” “wild,” or “indigenous”) fermentations yield better wine that is more terroir driven. The argument being that by using the yeasts that naturally coat the berries in the vineyard to ferment the wine, the wine is more truly expressing its place and circumstances of origin. Some people also philosophically object to the idea of adding anything external to their wine, especially eschewing the idea of using a laboratory-raised product in their wine. While there are plenty of cultured commercial yeasts that are neutral (and, in fact, are strains propagated from strains gathered in the wild), natural fermentation proponents in particular object to yeasts that have been selected in the lab to produce specific aromatic effects.

On the other hand, those who prefer commercial yeasts often describe the risks of native yeast fermentations as myriad. Stuck fermentations and weird aromas are the two primary outcomes that such producers are looking to avoid. But many people simply don’t like what they see as inconsistent results from native yeasts. Leaving aside the massive producers for whom the use of commercial yeasts seems all but a requirement for delivering an utterly consistent product to market in huge quantities, proponents of commercial yeasts largely seem focused on what they see as a combination of quality assurance and risk mitigation. To some small producers, the loss of part or all of their vintage due to problematic fermentation might spell financial disaster, and that is a risk that some are understandably unwilling to take.

At the end of the day, the choice of one versus the other is a truly philosophical one — a decision that each winemaker must make based on what they believe is best for their craft and circumstance.

I personally count myself in the camp of people who prefer wines made from native yeast fermentation. And when I say “prefer” that should be understood first as a philosophical preference, not unlike preferring Chinese food without MSG, organic juice instead of standard juice, or raw sugar instead of bleached sugar. I’m not saying that I can tell from tasting whether a wine was fermented with native yeasts versus commercial yeasts, or that natively fermented wines always taste better than commercially fermented wines. I’m also not making a categorical value judgment about wines that are fermented naturally versus those made with commercial yeasts. If you want dogma, you’re not going to get it from me.

But all things being equal, I think a natively fermented wine represents a more artisan-made product, and is a truer expression of what wine really means — that is the translation of a particular place and a particular season into something we can enjoy as food. I have great respect for those winemakers who take it upon themselves to bear the risks of letting their wines be guided from fruit to alcohol using only what circumstance offers in the way of microbiological aids.

Perhaps not surprisingly then, in the course of my visits with winemakers I always make sure to ask them about their philosophy with regards to fermentations. But last week I got an answer to the question “native or inoculated” I had never heard before from a young man named Dom Maxwell, the winemaker for Greystone Vineyards in New Zealand’s Waipara Valley, in the North Canterbury wine region of that country’s south island.

“We ferment in the vineyard,” he said with a smile.

I proceeded to clarify my assumption that he meant they practiced a process known as pied de cuve in which winemakers will often pick grapes and mash them into a small bucket during harvest. This small container, due to its size and lack of temperature control, will usually start fermenting rather quickly. Then once the winemaker has a bin or tank full of grapes ready to go in the winery, this small bucket of bubbling fermenting juice and berries is added to the big tank as a way of kick-starting the fermentation process.

“No,” said Maxwell. “We actually made this wine entirely in the vineyard.”

That’s right, instead of bringing the grapes into the winery, Maxwell and his team brought the winery into the vines.

Here’s how Maxwell described the evolution of his thinking about the process when given the opportunity to speak about it at the Pinot Noir NZ 2017 Conference.

“It’s a privilege to share my story about how we express place and time with vineyard fermentation.

Pinot’s ability to express site through flavor and texture is what excites me about wine. Site is one thing that can’t be replicated. At Greystone, we’re on a mission to express this in a pure form. When I first tarted making wine, I chatted a lot with experienced winemakers, and there was always a sense that wild fermentations made a lot of sense in terms of expressing complexity.

And then I started making wine myself. Wild fermentations were always fascinating. Some years they were vigorous and foamy, and other times subdued. We were working in a contract facility with grapes from lots of different sources and I couldn’t help thinking about effects other batches of fruit were having on ours, and ours on theirs. After the first few years working with Greystone, we moved all our winemaking to a different winery. The wild fermentations there were different again. They had more savory attributes. We wanted to know why this was happening. We were very happy wild ferments, but it didn’t take long for us to begin searching deeper for a sense of authentic Pinot.

First, we stripped out everything we could. We removed all additive and scaled back the oak influence, with the hope of revealing more of the vineyard. But there was something burning a bit deeper, and so I focused back on fermentation. Fermentation serves as the foundation that is built upon, and microbial life in the fermentation is critical.

Basically, I wanted to know if my wild ferments were truly indigenous and what, if any, was the effect of moving fruit away from its point of origin to ferment. In order to figure this out, we needed to remove the influence of the winery building to have the fruit more truly reflect the patch of earth it was grown on. I decided we needed to ferment the fruit right where it grew. Right amongst the vines.

We were operating organically already, with an increased awareness of and sensitivity to microbial complexity, so we thought there was no reason it couldn’t work.

At Greystone there are several mezo climates amongst our vineyards. We assumed this would mean yeast variations between blocks. Wind, proximity to other properties all vary depending on the location. Do yeasts migrate, we wondered? Are they dependent on wind, birds? I wanted to have the differences that yeasts might bring to the process fully expressed. Certainly initially, there were skeptics, but we plowed on.

We kept it simple to start. 4 years ago we placed our first fermenter in the rows where the grapes to fill it came from. We put a clean fermenter on a wooden palette. We filled it by bucket and put hand plunger out there. We filled it up and we just waited for ferment to start. It started so slow, we thought it was going to be a Spring ferment. It ended up naturally getting a 12 day cold soak. Fermentation started slowly, it was cool and the fermenter was at a higher elevation in our vineyards. And with this we started to witness the first positive influence of our experiment. With the fermenter out in the elements it was quite sensitive to the outside temperature. The night lets the heat from the fermentation dissipate, and moderates what might be warmer temperatures of the day. We loved this aspect of this experiment because it makes the fermentation in tune with the vintage weather, and makes the wine that much more reflective of the vintage.

Just by way of comparison the 2016 vineyard fermentation was 2 days long because of the heat during vintage. Again, we’re reflecting the season.

We think these vineyard fermentations provide a detailed window for the wine drinker into terroir. In the winery environment fermentations are more uniform. It pretty much goes the same way. In the vineyard it’s the opposite. They’re dynamic. We leave the lid off.

For our first trial we ran a winery fermentation, picked at the same time. We fermented them side-by-side, so to speak. But they were very different. We ran tests on the resulting wines. The wine fermented in the vineyard was .5% lower in alcohol. We think this is likely due to some evaporation. But every year our vineyard ferments reliably come in lower in alcohol. There’s also an earthier nature to the wine. It has more layers. In some years it’s darker. Some years it’s lighter. Seasonal differences are amplified in vineyard differences.

We were excited about this process. Tasting the wine it really is a new level of expression for us. We had no preconceived ideas — but we did want to taste differences. We wanted to hear the vineyard. For us it’s not about obtaining a specific profile. Apart from the enjoyment of drinking it, Pinot brings people together in the quirks of each vintage. Aiming towards authenticity is powerful.

Vineyard fermentations also have helped connect the vineyard workers with the winery in a new way, and vice versa. Cellar workers get into the vines, which they don’t often do, and the vineyard people are seeing the product of their work. That connection is palpable. It brings together harmony and balance. We see it in the wine.

We’ve noticed plenty of differences between vineyard ferments and winery ferments, and so far have had no problems. It feels like the right direction in our search for expressive Pinot. It started as a way to express our site through vineyard yeasts, but ultimately it has given us more respect for our place.”

I had a chance to taste the two latest versions of Greystone’s Pinot Noir side by side, to see what the differences were between the wine fermented in the vineyard, and the one made in the winery.

Here are my notes:

2015 Greystone Pinot Noir, Waipara, North Canterbury, New Zealand
Medium garnet in color, this wine smells of cherry and raspberry fruit with a hint of brown sugar. In the mouth, relatively pure raspberry and cherry fruit has a hint of vanilla along with its dried herbs and flowers. Faint, suede-like tannins and excellent acidity make this a pretty, nicely poised package. 14% alcohol. Score: between 8.5 and 9

2015 Greystone “Vineyard Fermented” Pinot Noir, Waipara, North Canterbury, New Zealand
Medium garnet in the glass, this wine smells of more savory raspberry and raspberry leaf flavors. In the mouth, beautifully textured flavors of raspberry and herbs have a more velvety tannic structure and great acidity. Notes of herbs and dried flowers linger in the finish. This wine was picked and then fermented directly in the vineyard in a tank out among the vines. Overall this offers a more savory character than the same wine fermented in the vineyard. 13.5% alcohol. Score: around 9.