The Weird World of Mushroom Farming

Farming, as a profession, is generally a pretty good way to keep yourself humble. You quickly learn, when planting and growing crops, that the crops seem to have a mind of their own, and you are just along for the ride. Seed, water, wait, pray.

Growing mushrooms for commercial harvest doesn’t seem to be much different, despite the fact that it often takes place in climate- controlled rooms that feel more like a science lab than a field. Maybe they’re not praying for rain the same way that dryland wheat farmers do, but the brave souls growing Blue Oyster and Lion's Mane mushrooms know that they’re always at the mercy of the fickle fungi.

“If there’s anything mushrooms hate, it’s an ego,” said Ben Jaffe, owner of MarrowStone Mushooms in Fremont. “As soon as I feel like I’m really good at growing one of these, they just decide to not cooperate at all.”

In Season 12, Washington Grown TV visited two mushroom farms in Washington state to understand how mushrooms are grown and cultivated here. MarrowStone Mushrooms, which Jaffe founded in 2022, is located in the bottom floor of an urban building in Fremont, between a massage parlor and a psychic reader. The entrance looks like an old apartment building, but inside, each room is filled with shelving units stacked with blocks of sawdust, which are in various stages of being colonized by mushroom mycelium.

“We have about 1,500 square feet here, and we put out about 400 pounds of mushrooms a week,” said Jaffe as he showed host Kristi Gorenson around the facility. “So you can really get a lot of production out of a pretty small space. But it is messy – if you don’t like cleaning out that jam jar that’s been in the back of your fridge for six years, you’re not going to like growing mushrooms.” He turned and laughed as Gorenson made a face. “Sometimes it’s a little gross.”

Across the state in Walla Walla, Chesed Farms and owner Sundown Hazen are blazing a very similar trail – only in a small town instead of a big city.

“I’ve had a passion for local food for about 3 decades,” said Hazen. “Being in the Walla Walla Valley, the strong tourism industry means we have great restaurants. So there was a demand for fresh local gourmet mushrooms. It fits within that lifelong purpose and drive, and passion that I’ve had for local foods.”

While the two growers have different settings and different clientele, they have a lot in common. Primarily, both operations are built around the three primary stages of a mushroom’s life cycle. In very simplified terms, growers must introduce the mushroom spawn to an environment, give it time to colonize, and then initiate the “fruiting” process, which is when the recognizable mushroom shapes are produced.

“Lovingly, we like to call this a resort for alien lifeforms that we call fungi,” said Hazen. “We start with preparing their ‘rooms’, and we like to fill their room up with all the right food and water that they like to have.”

This first step in commercial mushroom cultivation is to provide a substrate – essentially a bag filled with water and a nutrient-rich mulch. Sometimes that substrate is made from sawdust or soybean hulls or coffee grounds or a mixture of grains. Into those bags of substrate, the growers introduce a small amount of the mushroom spawn.

“The premise is that I can carve a little wedge (from a petri dish) and flick it into (the bag of substrate) and it will eventually colonize the whole bag,” said Jaffe, gesturing to a shelf full of petri dishes, each containing a different variety of mushroom spawn. “About a week after, you can see all those little spots, little pieces of grain that are colonizing.”

From then, it’s just a matter of waiting and keeping the temperature and humidity consistent.

“Once the bag is fully colonized, it will get taken over to the fruiting room, and we’ll cut a little slit in the bag. Then the mushrooms will pop out of the slit,” said Jaffe. “We keep the humidity in the fruiting room at about 95%. There’s a lot of airflow going in, and a lot of airflow going out. Mushrooms are like us; they breathe in oxygen and breathe out CO2.”

After the mushroom fruit appear on the outside of the blocks, they’re cut away from the substrate and packaged for sale. Both the growers have partnerships with local grocers and regularly participate in local farmers markets. Growing mushrooms is hard work and can be nerve-wracking like any other kind of farming.

“It’s kind of hard to pick a favorite, they’re all like my children,” said Jaffe with a laugh. “And just like my children, some of them are very naughty sometimes.”