John Roncoroni likes to joke that he limits the number of people he pisses off each day to two or three. He says it with a smile, but behind that quip lies decades of experience that have occasionally ruffled a few growers' feathers. He’s one of the most fantastically generous individuals I’ve had the chance to work with—engaged, interested, and always willing to ensure you fully grasp the nuances of weed management. John may not have all the answers, but he’s an expert on a crucial piece of the puzzle. In a world obsessed with what's happening above ground—where talk of heat waves and climate change dominates conversations—John's focus on what’s beneath our feet might just be the key to enduring whatever Mother Nature throws our way.
The Weed Whisperer of Napa Valley
John's reputation precedes him. His work in Napa, backed by 25 years at UC Davis, has earned him the respect of the valley's finest. By the time he arrived in wine country, he felt like he already knew everyone. "It’s all about talking to people," John says, and he certainly excels at it.
He regales me with stories that sound like a who's who of the wine world. There's the 45-minute chat about pond weeds with Warren Winiarski, casual strolls through vineyards with Volker Eisele, and visits to the hallowed grounds of Opus One, Harlan, and Screaming Eagle. But it's clear that John's heart lies with the little guys - those small growers who just need a helping hand and are eager to soak up his sage advice. As he puts it with a grin, "It's just fun."
Now retired and holding the title of University of California Agriculture and Natural Resources Emeritus, John hasn’t slowed down a bit. He’s still teaching local master gardener courses and frequently appears as a speaker at industry events. Our conversation meanders through the intricacies of weeds, weed management, and herbicides—because in this field, these topics are inextricably linked—John’s observed the industry gradually shifting away from herbicides. It's not a sudden change, but rather a slow, steady evolution that John has been anticipating and, in many ways, encouraging for years. Conventional farmers, once perhaps skeptical of alternative methods, are now showing keen interest in John's insights. It's a testament to the growing recognition that sustainable vineyard management is no longer just an idealistic goal but is becoming a necessity, as more wineries are choosing to purchase grapes farmed without the use of Roundup.
Despite being such a crucial aspect of a vineyard, the vineyard floor is often overlooked by the industry. John observes that very few growers have developed true competence in this area. As he explains, "People start in vineyards knowing a lot about grapes, or at least with a good education in grapes, but when it comes to weeds and cover cropping, it's something you have to learn over time. You can't get it in your first or second year—it takes 7 or 8 years to really learn."
The Great Divide: Winemakers vs. Viticulturists
It's no secret there's often a schism between those who make the wine and those who grow the grapes. The vineyard, surprisingly, isn't always the top priority. John shares a story that perfectly illustrates the challenges. Picture this: He's got a great undervine cover crop experiment going at a conventional vineyard looking to go organic. Year one, they're using a broadleaf herbicide, planning to transition to organic over time. John's excited. The growers are excited. It's all going swimmingly.
Cut to year two. John shows up, ready to see how the experiment progressed. Instead, he's greeted with an apologetic, "Sorry, John, your cover crop study is beside the road. It's what people see, and it looks pretty messy, so we're not going to continue it next year."
I can hear the disappointment in John's voice. It's a perfect example of how aesthetics and economics often dictate decisions in an industry so dependent on the whims of nature.
The Economics of Weed Management
As John delves deeper into the industry's challenges, it becomes clear that the wine business is as much about economics as it is about agriculture. "Economic forces push down and insist that you have to perform well every year," John explains, his voice tinged with a mix of understanding and frustration. "They want to produce a great bottle of wine every year, which is why we have drip irrigation—because we seek consistency."
He pauses, then adds with a wry smile, "We have bean counters, a market, and a tightening market, so everything has to be good every year." It's a stark reminder that even in the romantic world of wine, bottom lines matter.
This economic pressure has led to prioritization in vineyard management. John shares his short list of vineyard priorities: powdery mildew at the top, followed by insects, and then weeds. John chuckles as he recalls a grower correcting him, "Actually, fertilizer comes before weeds."
John has spoken at length about alternatives to using Roundup and we won’t get into all of it here, links are shared in the footnote. "For a long time," he says, "the reason so much Roundup was used was that by the time they addressed everything else—cover cropping, pruning, mildew treatments, and maybe insects—there was little budget left for anything but a cheap spray of Roundup."
But there's a silver lining to this story. John leans forward, his voice brightening, "The best thing to come out of all this is that people had to start thinking about weeds again."
The Soil Revolution
Reverence for the soil is the first step in weed management. There has been a shift from the French plow dominating viticulture in the 1980s to today's understanding that less soil disturbance is better.
"My work has shown that moving the soil as little as possible and keeping it covered with plants is beneficial," John says, his eyes lighting up. It's clear this isn't just a job for him—it's a mission.
John has been "watching vineyards for 30 years beat the crap out of their soil to get that tortured grape so they can make delicious wine..." "People talk about fewer microbes under something that has been sprayed with Roundup. Well, is it the Roundup that's causing that, or is it the fact that you've had no plants growing, which would normally slough off roots?" (For those readers that are not soil scientists, the life cycle of roots, growing and dying create food for microbes, aerate the soil, decrease compaction and increase water penetration.)
John's voice takes on a teacher's tone as he explains, "When the roots die, the microbes feed on them. If you keep something bare all the time, you're not going to have microbes because they have nothing to eat!"
The Three-Year Rule
As our conversation winds down, John shares what he sees as the pinnacle of his life's work—his three-year rule for weed control. "I'll consider my career a success if people can balance their weed control and cover cropping on a three-year basis instead of just focusing on one year," he says, emphasizing the importance of a long-term approach. "By keeping plants on the ground, growers might initially produce two tons instead of five or seven," he explains, "but the real payoff comes with time and patience." Achieving production goals while maintaining effective weed control takes a few years, as both vines and cover crops need time to acclimate.
Starting Your Weed Management Journey - Plant Identification
When and how do you begin? John's advice is clear: Start now with plant identification and implement a strategy depending on the type of weed. Without understanding the biology of the weeds in your vineyard, their growth patterns, and the potential dangers they pose to your operation, any intention to control them is futile at best.
When asked what he teaches organic farmers, John's response is vehement: "Plant identification and biology because they need it more than anyone." He offers practical advice: "If you have johnson grass growing on the edge of the field, you should focus on digging it out. If you have groundsel, don't worry about it—the first step is always plant identification."
For growers contemplating the shift from conventional to organic farming, John offers some candid advice: "Ask anyone who has made the transition from conventional to organic. Those first three years are a nightmare; it just takes that long. It's similar to the first three years of planting a vineyard—it requires a lot of work. But hopefully, after that, it starts to get a little easier."
With vineyard-specific plant identification and consideration of production goals and any block-specific issues, selecting the right cover crops is the next step in honing sustainable vineyard floor management. John discusses various types of fescue and ryegrass, emphasizing the importance of understanding both cover crops and their life cycles. His message is clear: know your plants, both the desirable and the unwanted ones.
The Uniqueness of Each Vineyard
John emphasizes that each vineyard site is different. "Designing a weed control program is as critical as creating an effective vineyard spray program," he says. His words carry the weight of decades of experience as he lists the factors to consider: competition for water and nutrient resources, potential hosts for detrimental pests, and even antagonistic benefits to pests.
He doesn't stop there. "Wildfire considerations and even something as minor as tall weeds annoying labor crews picking grapes are all things to take into account.” It's a reminder of how interconnected every aspect of vineyard management truly is.
Case Studies in Weed Management
John's wealth of knowledge comes alive through his experience and studies. "Do you have fluvellin in your vineyard?" he asks. He then recounts an Oakville study he conducted, demonstrating that the sooner you address it, the better. "In the first year, find it and hoe it out, or use a directed spray to eliminate the problem," he advises. "By year three, fluvellin could overtake the vineyard."
He shares another example with equal urgency. "Take perennial pepperweed. If you act quickly and dig out a few plants, you can keep it under control." His voice carries a note of warning, underscoring the importance of early intervention.
Tools of the Trade
If John could give one tool to all vineyards, it would be a mandatory weed identification book. His second choice? An undervine mower for weed control, specifically when used at the right time of the season. However, he cautions, "If you continue to mow—like anything else—you will start favoring certain weeds, particularly perennials or low-growing types."
Always one to advocate for diversity in approach, John adds, "I don't like to do anything all the time. No matter what it is, you'll start choosing which weeds take up residence, and nature will find its way. When you continue to do just one thing, nature will figure it out."
He mentions a close second to the undervine mower: a blade, often referred to as a weed knife. This tool cuts the soil just an inch or so below the surface and does a good job on weeds. Ultimately, he suggests that the best approach may be to use these tools in sequence, allowing for some minor soil disturbance.
In Summary
John Roncoroni advocates for a sustainable, long-term approach to vineyard floor management, emphasizing soil health and weed control over immediate results. By focusing on plant identification and using tools like undervine mowers and weed knives in sequence, he highlights the importance of flexibility and patience to maintain a productive vineyard ecosystem. His message to the wine industry is clear: identify your weeds, adopt a long-term perspective, and remember that viticulture is about nurturing a flourishing ecosystem, not just growing grapes.
His parting words of wisdom? "Now you have to plan out what you're actually going to do."
Resources for Further Learning
For those eager to dive deeper into the world of vineyard floor management, John has recommended some invaluable resources:
UC Davis Weed Gallery John has tirelessly updated this comprehensive resource, making it an essential tool for weed identification in California vineyards.
Podcasts featuring John Roncoroni For more in-depth information on management practices and implementation, check out these podcasts:
Sustainable Winegrowing with the Vineyard Team Listen to John share his expertise on sustainable practices.
The Vineyard Team: Pest Management Dive into specific pest management strategies with John and the Vineyard Team.
These resources offer a wealth of knowledge for both novice and experienced vineyard managers. Whether you're looking to identify a troublesome weed or implement new management practices, these tools will help you on your journey to sustainable vineyard floor management.
Pressure Bomb is your go-to platform to share conversations and join a community built on helping each other. Enjoyed reading? Subscribe now! We’re diving into questions from readers and the industry, straight from the vineyard, cellar, and market!