Cultivating solutions

Boulder Mushroom uses fungi as a tool for healing people and saving soil—and that shouldn’t sound so radical, they say

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Zach Hedstrom unzips the door of a climate-controlled grow tent—one of several lined up inside Boulder Mushroom, a fungi farm in north Boulder. Within the tent, shelf over shelf of fruiting blue oyster mushrooms are exploding out of substrate blocks like bouquets. Pale fluorescent light reflects off the saucer-shaped gray-blue caps. 

Hedstrom picks one of the blocks up and tilts it, showing off the fungi’s mesmerizing gills.  

“We’ve got different ways of growing these,” he explains. “Some of the chefs like the big wide caps, some of them like a little more stem. It just depends on what they’re doing with them.”

Zach Hedstrom shows off bags of substrate growing oyster mushrooms at his myco-farm in north Boulder. Photo courtesy Boulder Mushroom.

Hedstrom is Boulder’s mycological mad scientist. He forages locally, collecting fungi in nature, cataloging and cloning their wild genes in his laboratory and selectively breeding some of the highest quality culinary and medicinal mushrooms commercially available on the Front Range. His business, Boulder Mushroom, produces golden oyster mushrooms, blue oysters, phoenix oysters, Italian oysters, pink oysters, lion’s mane and royal trumpet mushrooms among other strains. He works with chefs like Chris Clauss of Leaf Vegetarian, who uses anywhere from 20 to 50 pounds of his mushrooms a week. Boulder Mushroom also sells medicinal mushroom tinctures, mushroom home-grow kits and mushroom spawn via its website. 

But that’s all just the top layer of Hedstrom’s master plan for Boulder Mushroom—the duff of his deep vision for this business, if you will. 

While the fruits of Boulder Mushroom’s labor come most obviously in the form of mushrooms sold to local chefs and restaurants, the real power behind this myco-farm lies in fungi’s powerful role as a remediator (or fixer) in nature. Not only do these fungi taste fantastic, but they recycle carbon and foster healthy, living soils; they help plants exchange nutrients, can prevent soil erosion in forests, and even mitigate wildfires. 

“I created this business partially as a culinary mushroom business, and partly as a soil remediation business from the start,” Hedstrom says. “It’s [also] restoration for people, because a lot of mushrooms are medicinal. And we all know organic, locally sourced food is healing for people. Then we kind of take that one step further and look at how [fungi] can heal the environment.”

In another room at Boulder Mushroom, Hedstrom opens a small fridge filled with agar petri dishes, each one labeled and neatly stacked. This is one part of his mushroom tissue collection, an archive of nearly every wild mushroom he’s found while foraging, cataloging their genes in a myological library for Boulder County. He selects an agar dish and holds it up to the light. 

“This strain right here, this is an oyster mushroom [I labeled] ‘Longmont XL,’” Hedstrom says. He’d collected the sample (of Pleurotus pulmonarius) from Longmont’s Ollin Farms in 2021 as part of a Boulder County Sustainable Agriculture grant-funded project—“Fungal inoculation of on-farm biomass for carbon-negative farming best practices”—which started last May. Mark Guttridge, owner of Ollin Farms, was the perfect partner for this trial; he was a recipient of the 2020 Boulder County Sustainable Agriculture Fund and had already been experimenting on his regenerative farm with inoculating compost using Boulder Mushroom’s spent substrate blocks (the leftover material after a mushroom flush) and mixing it into his soil. 

“We’re using the [fungal compost] for a lot of plum trees, chokecherries, gooseberries, currants and elderberries,” Guttridge says. “These perennial ecosystems actually really benefit from having a fungal dominated compost.”

Golden oyster mushrooms are prolific growers which can be used in a wide variety of culinary applications, like stir-fries. Photo courtesy Boulder Mushroom.

For the experiment: Four beds of wood-chips were built on Ollin Farms and three were inoculated with different local strains of edible wood-decay mushrooms; the fourth bed was left uninoculated as a control group. Boulder Mushroom monitored the compost for 12 months before collecting samples and sending them to a lab to be analyzed for nutrient availability and biological makeup. The goal was two-pronged: first, to demonstrate how fast fungi can turn 100% carbon waste (i.e., wood chips) into viable compost; and, second, to reveal exactly which strains work best as remediators in Boulder County.

One day, shortly before Boulder Mushroom and Ollin Farms began the experiment, Hedstrom answered a call from Guttridge. He’d found a troop of wild Colorado oyster mushrooms growing naturally on his farm—and Hedstrom leapt into action. The mushroom archivist sped up to Longmont and started harvesting. 

“[Mark] got all the mushrooms he wanted to eat, and I just took the stems and we cloned them. I got that strain isolated, grew it out, and it ended up being really vigorous [so] we used that in the trial,” Hedstrom says. The other piles in the experiment were inoculated with other locally sourced native strains Hedstrom had collected around the Front Range. But the Ollin Farms strain, eventually named Longmont XL, swept them all away.

“That [wild] strain ended up having the highest fungal content of all of the [wood chip] beds,” Hedstrom says. “It made a perfect full circle.”

The trial, perhaps predictably, was an outstanding success. All of the wood-chip beds that had been inoculated showed visible signs of decay: they were moist and clumping up, dark in color and could be broken between one’s fingers. Full of healthy mycelium, they smelled like earth and were generally well on their way to becoming soil. The control pile, by contrast, looked almost completely unchanged.  

“It’s all about carbon cycling and the way that ecosystems work and the fact that fungi are a substantially important part of building soil. … We can take the concepts of nature and speed that [decomposition] process up a lot by purposefully putting material onto the ground and inoculating it with native microorganisms,” Hedstrom says. “Here we are in 2022, and we’re talking about [how] one of the biggest threats to humanity is agricultural soil going fallow.”

The results of Boulder Mushroom’s experiment on Ollin Farms, testing the power of fungi to decompose on-farm woody waste (the control group is pictured at bottom). Photo courtesy Boulder Mushroom.

Fungi can and should be used as an agricultural tool, Hedstrom argues—a tool devised by nature, perfected by one billion years of evolution, popping up to play an essential role in the natural cycle of life, death, decomposition, rebirth—a tool that’s been largely forgotten, or at least left behind, by modern industrial agriculture. 

Using fungi, “wood, eggplant stalks, sunflower stalks, and [other woody waste]” turn back into soil within a year, Guttridge says. “Whereas in traditional composting, just leaving it [piled up] by the creek or something, it would take years to really break it down. By utilizing fungi we can really turn that waste stream back into soil most quickly.”

Besides fungal compost boosting the soil’s health at Ollin Farms, Guttridge says fungi are being employed elsewhere, too: He’s incorporated mushrooms into areas on the farm with windbreaks and along the edges of fields where it’s harder to irrigate, because, as he explains, mycelium will literally hold the soil together by locking in moisture and enmeshing it in its stringy root-like network of mycelium. 

Which brings Hedstrom to his second environmental goal for Boulder Mushroom (and a particularly pertinent topic for Boulder County at the moment): Fire remediation and prevention.

“There’s actually already data out there that has verified that inoculated wood chips hold double the amount of moisture [as non-inoculated wood chips],” Hedstrom says. “It’s like a sponge. So you can think about it that way: You’re creating a sponge on the forest floor that’s also helping to remediate the watershed.”

He describes two different types of water flow in nature: channel-flow and sheet-flow. Channel flow is the kind of water flow that creates erosion as water carves out gullies and ravines. By contrast, sheet flow is when the soil is cohesively held together by roots, moisture, microorganisms and, of course, mycelium. In sheet flow, water moves through the ground in a plane (like a sheet) through the earth, dispersing across a much wider area and creating a much healthier soil ecosystem.

“That’s what you want in a watershed—[sheet flow] holds more surface moisture. It’s capturing rainwater with nature,” Hedstrom says. “With channel flow, basically when water hits the ground, it can’t infiltrate, there’s nowhere for it to go, and then it just goes away. When that happens those ecosystems dry up.”

And then, he adds, they become vulnerable to massive, uncontrollable wildfires. Something with which Boulder County is becoming all too familiar. 

“The concept with [modern] wildfire mitigation is to go into the forest and thin trees,” he says. It’s supposed to mimic small, naturally occurring burns that clear out dense areas of growth, making room for new growth and returning nutrients from burned debris back into the soil. 

However, instead of cycling the carbon back into the soil, forest crews thinning an area out remove the underbrush, overgrowth and excess timber from the system entirely. 

“What do they do with that [woody waste]? They kind of don’t know what to do with it,” Hedstrom says. “They’ll chip it up and they’ll haul it down to the landfill, or they’ll haul it down and do a community mulch pick-up or something.”

More commonly, however, he says foresters will stack the wood into “slash piles” and leave it to cure for two to three years before eventually burning it.

“Then, that carbon is going up into the atmosphere instead of going into the soil,” Hedstrom points out—it’s moving in the wrong direction. 

Pink oyster mushrooms from Boulder Mushroom. Photo courtesy Boulder Mushroom.

Instead, he proposes chipping the thinned timber and brush, spreading it across the forest floor from which it was cleared and inoculating it with fungi (just like at Ollin Farms), creating a layer of healthy duff (partially decayed organic matter on the forest floor) above the topsoil. That fungi will then propagate deeper into the ground, cultivating a healthy micro-biological ecosystem, absorbing and retaining more water, thus promoting sheet-flow and mitigating the risk of future wildfires.

Hedstrom is putting this process to work in Boulder County via a partnership with Eco-Cycle and Boulder Watershed Collective. Up near Gold Hill, not far from where the Lefthand Canyon fire scorched 460 acres in 2021, a small part of the burn-area will be dedicated to testing this myco-mitigation plan. 

“The Boulder Watershed [Collective] is pretty forward-thinking, and they’re already doing fire mitigation,” Hedstrom says. “So they are going to work with us and we are basically taking wood chips and instead of hauling them away, we’re putting them down on the ground and inoculating them with the fungi.”

Boulder Mushroom is specifically brewing tanks of liquid fungi inoculant for these kinds of large-scale inoculation projects. In this case, Hedstrom says he’ll load a 300-pound tank of inoculant into his truck and drive it up to the area. But thinking about scaling-up the work, he says, you could spray the inoculant from a helicopter, essentially spore-dusting a large area very easily and very quickly. 

Hedstrom says he’s already been talking with Boulder County about doing some soil remediation work within the Marshall Fire burn area as well. 

Taken as a whole, Boulder Mushroom is more than your average mushroom farm. This is a mycological tech company as well as an artisanal, culinary and medicinal mushroom cultivator, helmed by a fungi virtuoso. Hedstrom is linking human health and environmental remediation through organic food. His mushrooms are being served all across Boulder County: sauteed on toast, smoked with spices, or as the centerpiece of Leaf Vegetarian’s risotto entree—marinated, grilled and drizzled with a reduced mushroom consummate stock, “kind of like a mushroom demi gloss,” Chef Clauss describes. 

To wrap all of these things into a single business might sound like enough—but Boulder Mushroom is really just getting started turning our waste and wastelands back into valuable materials and healthy ecoscapes.   

“We’re taking [organic waste] that would otherwise go to the trash, [we’re] growing a high-quality medicinal food off of it. And then when it’s done, 100% of that material, which is now dominated by fungi, goes to local regenerative farms to build soil,” Hedstrom says. “We can take the concepts of nature and mimic them. … This shouldn’t be as novel or as radical as it sounds.” 

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CORRECTION: The original version of this article stated that Boulder Mushroom’s work at Gold Hill was “fire remediation,” when in fact it is “mitigation” and the location is not directly in the burn area, but adjacent to it.

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