PINE RIVER -- Mushrooms are one of those mysterious natural wonders that can appear seemingly overnight -- much like Rob Prekker and Rachel Ingberg’s small business.

What began as an off-handed remark during a brainstorming session in February has -- just months later -- come to fruition as Strictly Mushrooms, a rapidly expanding culinary mushroom growing operation based in the couple’s Pine River home. They knew they’d found an unexplored niche among lakes area food businesses within moments of seeking their first restaurant customers.

“All we did was introduce ourselves, and you always bring a sample. We’d open up that sample: ‘Yep, I’ll take them,’” Prekker said. “They’d say, ‘You can’t get them up here, there’s nowhere to get them.’”

Fresh shiitakes and oyster mushrooms of the king, blue and yellow varieties grown by Prekker and Ingberg have appeared on plates at 3 Cheers Hospitality restaurants Prairie Bay, Iron Range Eatery and Dock 77, along with Sage on Laurel, Bar Harbor, Black Bear Lodge & Saloon and Maucieri’s Italian Bistro. Prairie Bay executive chef Jenna Brower Von Siebolds chose the company’s mushrooms as one of her three signature ingredients during this year’s Minced cooking competition hosted by Sprout in Little Falls. So sought after are the ingredients by local chefs, the couple is pushing themselves to the limits to meet demand, they said.

This included a July move from Brainerd to a Pine River home better suited for the operation, complete with nearly a month of late nights and early mornings to convert a ramshackle shed into a laboratory and preparation area and a portion of their basement into a fruiting room.

“My plan is by October or November, I want to be doing 100 pounds a week,” Prekker said. “That allows you to join certain programs and organizations. Those help you get more connections and into a bit of the wholesale side of it.”

Living the dream

Strictly Mushrooms has its beginnings as a strong desire on Prekker’s part to once again become his own boss. He has a history of offbeat small businesses, including breeding worms while producing organic gardening soil and logging firewood seven days a week. Both of these previous businesses fell victim to circumstances outside his control, he said -- the worms and soil to the Great Recession, the firewood to a particularly warm winter when fireplaces remained dormant as a home heating alternative.

But this winter had Prekker, 36, dreaming again. He and Ingberg, also 36, first considered becoming organic catnip farmers, even going so far as to acquire equipment. Midstream in the planning process, Ingberg made a half-serious suggestion: What about mushrooms? It was a comment that prompted Prekker to conduct intensive research for days and left him with just one question himself: Why not mushrooms?

Much of the equipment in which they’d already invested translated to mushroom production, and soon they’d “knocked up” their first bags of substrate -- mushroom farmer slang for introducing mushroom spawn to a growing medium. Weeks later, they would taste their first homegrown king oysters.

Ingberg didn’t even like to eat mushrooms at the time.

“Now I love them, I actually want them in things,” she said. “He’s a large advocate of making sure you try things multiple times before you say you don’t like it. So he cooked me mushrooms and that was that. He knows how to make them.”

Ingberg posted the mushrooms for sale on Facebook Marketplace and the response was swift.

“The next day it was sold out with four people waiting,” Prekker said. “Two weekends later, we got another flush and we had 10 pounds. Literally the next day they were gone.”

From spawn to ‘shroom

It’s surprising to learn Prekker and Ingberg are new to the mushroom cultivation world, given the ease with which they explain and seemingly execute the process. They appear to have moved quickly through beginner growing pains into streamlined production, a tour of their operation on a late July evening indicated.

The path from spawn to ‘shroom begins in a steam bath. Bagged blocks of substrate -- which can be any material in which fungus will grow -- are sanitized in 55-gallon drums Prekker rigged to serve as large pressure cookers inside the converted shed. Sanitizing is important, they explained, because any mold growth will smother potential mushrooms by growing at a faster rate.

Once the bags are steamed and cooled, they head to the lab for inoculation. The couple’s lab is an area of the shed they’ve sectioned off with plastic walls and a zippered entrance. Inside, positive pressure is created with an air conditioner that pumps in outside air through a HEPA filter, blocking out almost 100 percent of particles larger than .3 microns. This provides a second defense against the introduction of mold. Then, millet spiked with mushroom spawn is added to the substrate in specially designed bags featuring a small breathe patch allowing the exchange of carbon dioxide. The bags are tightly sealed and placed on shelves, where they’ll sit for weeks to months, depending on the variety.

Dozens of these bagged blocks in various states of growth lined the couple’s shed, tendrils of white mycelium snaking through the substrate. Mycelium is the root part of the fungus, while the eventual mushrooms are the fruit of the organism. Prekker knows the bags are ready to move to the basement when a popcorn texture appears on the surface. Unlike plants and more like humans, fungus exhales carbon dioxide and breathes in oxygen.

“It’s trying to grow, but there’s not enough oxygen,” he said. “I’ll cut that bag open and move it to the fruiting room, where it gets a boost of oxygen and a temperature change.”

Down in the basement, another airtight area the couple built with thick plastic walls contains the final product in process. Walking through the door of the fruiting room is akin to emerging from an air-conditioned room to the outdoors on a humid Minnesota summer day; a wall of water-infused air marks a significant atmospheric change. Metal shelves hold the blocks, now sporting pins -- essentially, mushroom sprouts -- or full-on stems and caps of colorful mushrooms. A PVC pipe with small holes runs across the ceiling, and with the flip of a switch it emits a mist that helps maintain 95 percent humidity in the space.

Once a block produces a harvestable amount of mushrooms, it’s still not spent. Prekker and Ingberg simply flip the block over and wait for a second flush, or growth of mushrooms. This typically produces about half the weight of mushrooms as the first go-around, but is worth skipping the first several steps for more of the good stuff.

Working in this airtight space with actively growing mushrooms means wearing facemasks, protecting the respiratory system from prolonged exposure to the constant output of spores from maturing mushrooms. The room requires regular disinfecting, once again in an effort to stave off mold growth and contamination.

To the uninitiated, the process might seem meticulous and cumbersome. But, Prekker and Ingberg emphasized, it doesn’t have to be this complicated or large scale. Inoculated blocks, logs and other growing mediums can be purchased and grown into mushrooms by the consumer in humidified plastic containers or even just on the kitchen counter.

“You can literally spend $16 plus shipping on the block, and all you really need is a (small) tote,” Prekker said. “You can put a grocery bag over the top of it and spray water twice a day and you could grow a pound or two of mushrooms.”

Or instead, let Prekker and Ingberg do the work and enjoy the fruits of their labor, either at an area restaurant or by purchasing direct from them.

For the love of fungi

Proselytizing about mushrooms seems to come second nature to Prekker and Ingberg now. The taste, appearance, health benefits and beauty of their harvest -- all of it rolls off their tongues like true mushroom junkies. The king oysters, which occupy the most real estate, are in particular the apple of Prekker’s eye.

“The flavor is excellent, it’s a mild mushroom flavor. The mushrooms at the store don’t have flavors. It’s like nothing,” he said. “They’re large. They’re so meaty that vegans will use them as a substitute for scallops. … You can cook them for hours and they have a texture to them. They hold up well in the fridge. They are the perfect mushroom, especially for restaurants.”

The couple is in the process of expanding their offerings, including a batch of chestnut mushrooms that were beginning to pin in the fruiting room in July and plans to produce morels and almond mushrooms in a greenhouse next spring and summer. Almonds, which appear much the same as the button mushrooms found in produce aisles, are anything but ordinary, according to Prekker. Beyond their enviable flavor, benefits to the immune system in humans and animals from the mushroom have led to its use in a surprising way -- as a cattle feed supplement in Europe, intended to reduce antibiotic use.

For now, Prekker continues to work three 10-hour days a week and Ingberg works as a nurse for Essentia Health. But Prekker hopes to soon be a stay-at-home mushroom dad. With a major expansion and upgrade out of the way, the focus is on increasing production and maintaining that output. Selling direct to consumers at farmers markets is a possible next step, along with introducing more area restaurants to their fungi gold mine.

“It’s really been a nonstop expansion since April or so. It’s a few more dollars we put into it coming here, that’s for damn sure,” Prekker said. “Once you get that big chunk of upgrade, it’s just make sure you keep maintaining it at a low budget. Then you start rolling out mushrooms.”

For your info

• Business: Strictly Mushrooms.

• City: Pine River.

• Number of employees: Two -- founders Rob Prekker and Rachel Ingberg.

• Did you know? Before becoming a mushroom farmer, Prekker ran businesses including breeding red worms and nightcrawlers, developing organic garden soil and compost and logging firewood.

1/8: Rachel Ingberg holds a mushroom grow bag, in which a culture of mushrooms takes root. Kelly Humphrey / Brainerd Dispatch

2/8: Rachel Ingberg holds a mushroom grow bag, in which a culture of mushrooms takes root as Rob Prekker explains the process. Kelly Humphrey / Brainerd Dispatch

3/8: Rachel Inberg picks up a bag of blue oyster mushrooms growing in the climate controlled room in the basement. Kelly Humphrey / Brainerd Dispatch

4/8: Strictly Mushrooms grows yellow and blue oysters in a climate controlled room in the basement. Kelly Humphrey / Brainerd Dispatch

5/8: Rachel Ingberg and Rob Prekker, Strictly Mushroom business, are surrounded by a variety of the mushrooms they grow and sell to area restaurants. Kelly Humphrey / Brainerd Dispatch

6/8: Rob Prekker talks about the yellow and blue oyster mushrooms, several of a variety of mushrooms growing in the basement. Kelly Humphrey / Brainerd Dispatch

7/8: Rachel Inberg picks up a bag of blue oyster mushrooms growing in the climate controlled room in the basement. Kelly Humphrey / Brainerd Dispatch

8/8: Rob Prekker and Rachel Ingberg grow mushrooms in the converted shed on their property. Their mushrooms have appeared on plates at a number of notable area restaurants. Kelly Humphrey / Brainerd Dispatch