A Mushroom Lab on the Farm | Notes from US Farmers’ Markets

I was initially given three grains by a nurse friend I met at a local market. Within three months, they had spawned a brood of over a dozen new grains. My friend received hers from an elderly Eastern European woman. But where did she get them? In days past, across the North Caucasus mountains, every household safeguarded its own heirloom kefir grains, treating them with the same reverence as ancestral tablets and never passing them to outsiders. Over the past two centuries, the Turkic-speaking peoples between the Black and Caspian Seas have weathered the relentless shuffling of empires. Amidst this upheaval, these sacred kefir grains, regarded almost as deities, were scattered to every corner of the globe. Nowadays, you can buy kefir in any standard American supermarket, though it bears little resemblance to the traditional brew. Lacking both its tang and its subtle alcohol notes, it is typically drenched in sugar and masked with artificial fruit flavourings.

II.

“Right from here,” Wen replied, a mix of pride and shyness on her face, “come and see my lab.”

A stream flows through the valley, hemmed in by dense woodland. Lined along its bank are two mushroom houses converted from old cow sheds, a low refrigerated room resembling a small earth-god shrine, their four-person household, and a vegetable garden just outside the front door. A few steps out the back, beneath the tree canopy, stands a detached wooden cabin: Wen’s laboratory, naturally enough, built for her by Tang.

“This petri dish contains potato dextrose agar. The white threads growing on top of the agar are the mycelium. The mushrooms themselves grow from the mycelium specifically to disperse spores, much like apples grow on an apple tree. Do you see that yellow line in the middle? Think of it as a border river. On this side is lion’s mane mycelium, on the other is oyster mushroom mycelium. They’re fighting. After battling it out, they’ve drawn this border line: ‘You keep to your side, and I’ll keep to mine.’ It’s a chemical barrier they secrete. Why grow two different types of mycelium on one agar plate? No, it’s not just so I can watch them fight. I wouldn’t normally do this, but I just brewed up a new batch of liquid culture, and I wanted to test its purity—see if anything other than the inoculated mycelium starts growing.”

“Here’s how it works: once the mycelium has grown on the agar, I transfer it into a liquid culture to keep fermenting, then inoculate it into grain. I usually use rye, though sometimes millet. But millet isn’t a local crop, so I’m not as familiar with it; I always struggle to get the ratios right. The grain needs sterilising first. I pour a small amount of the liquid culture into each bag and let it grow until every kernel is colonised with mycelium. That’s your spawn. Finally, I take it over to the mushroom house, mix it with wheat straw, and press it into oyster mushroom fruiting blocks.”

“Where does the mycelium on the agar come from? From inside the mushroom itself, not the spores. I do collect spores occasionally just to tinker and see what pops up, but if you’re trying to grow mushrooms to make a living, you can’t afford to play around with spores. That’s sexual reproduction—it’s like having children; you never know exactly what you’re going to get. And mushrooms are particularly unpredictable. We need reliability, so we stick to asexual reproduction—yes, cloning. How do you clone? You simply take a small plug from the centre of the mushroom, place it on agar, and it regenerates into mycelium. Think of it as an apple turning back into a tree. Fascinating, right? Every single white button mushroom sold in supermarkets across the US for decades is cloned from one original specimen—genetically identical. And those ‘different’ varieties you might think exist, like the big dark Portobello or the fancy-sounding cremini? They’re all just the same white button mushroom, with minor genetic variations and different stages of maturity.”

“So it’s a continuous cycle: mycelium produces mushrooms, mushrooms regenerate mycelium. The agar, the liquid culture, the grain—they’re all just tools to scale it up. One palm-sized agar plate like this can keep us in mushrooms for half a year. A tiny scrap of mycelium dropped into a small bottle of liquid culture can inoculate fifteen bags of grain. But sometimes, after too many generations, the mycelium loses its vigour—it ages, if you will. What do you do then? You have to source new cultures from another lab. I keep young cultures in my fridge, but their shelf life is limited. The real safeguard is cryopreserving vigorous mycelium; it can stay frozen indefinitely, and revives the moment it thaws. The catch is you need liquid nitrogen for that, and I don’t have any on hand.”

What is there to fault in the analogy of a mushroom as an apple upon a tree, save that its “tree” is invisible? If you have ever foraged in the grass, you will know the stalk snaps off with little effort. But if, like me, you cannot resist the urge to dig deeper, you will find nothing. There are no roots beneath the cap, only soil, leaving you to wonder how the thing holds itself upright. A mushroom is, in truth, the macroscopic reproductive organ of a microorganism. In Robert Hooke’s 1665 engraved atlas *Micrographia*, one illustration captures mould sprouting from a scrap of parchment. The backdrop is stark and desolate, evoking a patch of lunar flora. They are, of course, not plants, and would not be termed “fungi” until much later. The fungal kingdom encompasses several phyla; strictly speaking, only the fruiting bodies of the Basidiomycota qualify as mushrooms. Many, however, find such academic pedantry unnecessary. To them, any fleshy, macroscopic structure that fungi use to disperse spores and that can be seen without a microscope deserves the name mushroom. The mould Hooke depicted belongs to a phylum that never produces mushrooms. Yet these invisible creatures exhibit a peculiar cooperative spirit, one that Chinese makers have long harnessed in the fermentation of tofu.

In the latter half of the nineteenth century, Pasteur and Koch developed germ theory, demonstrating that many infectious diseases do not arise spontaneously or from the air, but are transmitted by microscopic bacteria. Around the same time, the German physician Heinrich Anton de Bary identified fungi as the cause of numerous plant diseases, and described how a mycelial colony in soil or decaying wood develops into a mushroom. De Bary’s students pioneered techniques for sterilising agar plates of other microbes in order to ‘cultivate’ a specified mushroom, and Xiaowen could be considered a direct academic successor to this tradition.

Of course, being able to cultivate mushrooms is not the same as understanding them. As Xiaowen puts it, they are profoundly enigmatic. A single fungal species can look entirely different depending on its environment, and their reproductive strategies are remarkably varied. Prior to 2013, it was standard for a single fungus to be known by more than two Latin names. Before genetic sequencing became available, mycologists had accumulated considerable animosity over debates about whether visually distinct colonies belonged to the same species.

As for the ceaseless cooperation and conflict between fungi and plants, or between fungi and bacteria, and the countless human lives lost or saved in the process, the numbers are beyond calculation. Take something as simple as my kefir grains: they are a symbiotic community of bacteria and yeast (a fungus). The bacteria impart the sourness, the yeast the alcoholic tang. But which specific strains are at play? It varies from household to household. I have no idea which traditional goatskin bag my particular strain was passed down from.

The US Department of Agriculture first published dietary guidelines in 1916, and in 1995 rendered the textual advice into the visual Food Guide Pyramid, which originally made no mention of mushrooms. In an American agricultural system that reveres wheat and beef, mushrooms as a food are virtually a laughingstock. They contain negligible amounts of the three major macronutrients—carbohydrates, protein, and fat—and you would hardly feel full eating them alone. The reasoning is simple: as a reproductive structure, the mushroom itself cannot absorb nutrients and must rely on its mycelial network. That network operates at a microbial level, feeding on decaying wood or hardy bark to fuel a sizeable fruiting body. It is no easy task, so caloric resources must be allocated with extreme precision, taking every shortcut where possible. Were mushrooms to grow as dense and substantial as potatoes, the mycelium simply could not afford the energy cost.

The latest iteration of the pyramid tucks mushrooms into a footnote, categorising them under ‘other vegetables’. The pyramid is not merely a tool for public education; it also carries financial implications, as federally funded food and agriculture programmes—such as public school lunches—must adhere to the USDA’s dietary guidelines. After years of lobbying, the mushroom industry’s inclusion in a footnote is cause for celebration, even if the classification is rather galling. Mushrooms are not vegetables. It bears repeating: they are not plants, and cannot produce their own sugars through photosynthesis.

Despite their footnote status, the American mushroom industry had already unequivocally achieved large-scale commercialisation during the twentieth century, consolidating into fewer farms with ever-increasing yields. The small white mushrooms Xiaowen mentioned were the only fresh variety I consumed during my first ten years in the US. Scientifically known as *Agaricus bisporus*, they are sold in supermarkets as button mushrooms, and translated in Chinese as ‘foreign mushrooms’ owing to their native origins in Europe and North America. They lack any distinctive flavour, yet they are far from unpleasant. Much like KFC or McDonald’s, they offer neither surprise nor disappointment; they consistently hit the mark, largely due to their genetic uniformity. In fact, for forty years, virtually every button mushroom supplied through commercial channels in North America traces its lineage back to a single ‘super spore’ discovered in 1980 by Dutch researcher Gerda Fritsche at the Max Planck Institute of Breeding Research. It naturally exhibited high yields, disease resistance, and a reliably good flavour.

The market seems to carry its own current of standardisation. Ever since Ford worked out how to mass-produce cars on the assembly line, the Ford factory has served as the blueprint for virtually every agricultural and industrial sector in the United States. Take a typical mushroom farm, for instance: you won’t find a gingerbread-house-style laboratory like Little Wen’s. Instead, they buy ready-made strains from breeding companies, run them through assembly lines, and produce a million tonnes of mushrooms from a single small agar plate. Amidst such overwhelmingly abundant monotony, the palate of a middle-class household is as pure as a bag of sterilised grain.

IV.

“What kind of mushrooms did you used to eat when you were kids?” I asked Tang. He scratched his head for a while before replying, “I don’t think I ever ate many mushrooms as a child… Occasionally we’d forage for morels in the woods and take them home to cook, but I can’t really remember much else.”

“Have you never even tried oyster mushrooms or shiitake?”

“Never even heard of them.”

“So how did you end up thinking to grow these things later on?”

“I read about it in books. Plus, people at the market started asking about them, especially those Asian restaurants—they wanted to buy.”

So the market itself carries a genetic code for diversity, much like sterilised grain left out in the elements will eventually sprout all sorts of different things. Of course, new demands don’t just appear out of thin air; the theory of spontaneous generation was long ago replaced by germ theory. This fresh diversity springs from invisible connections—the movement of society, new residents bringing new cultures, new routes finding new trading partners.

“Have you ever seen a mushroom called a stinkhorn?” I asked Wen.

“Hmm, that thing, yeah… I actually have. Good lord, the way it looks… and especially that smell. Have you ever smelt it? I’d recommend giving it one sniff in your lifetime, just for the experience…”

I’ve only seen it in books. It certainly has an unsettling appearance, looking much like some human organ poking out of the soil. I’ve heard the smell is potent enough to knock you off your feet, and it’s said to be highly toxic.

“You know what? I’ve been eating that since I was a kid.”

“No way.”

“Seriously, I only just found out myself! When we were little, we only ever ate it dried, so I had no idea what the actual mushroom looked like! The foul smell and toxins are only in the cap at the top. If you cut that bit off, the rest is perfectly edible. You can see it in Chinese supermarkets.”

“Is it good?”

“It doesn’t have much flavour of its own, but we used to drop it into soups. It soaks up the oil and the savoury taste of the meat. The texture is rather fun, like a sponge, and I loved the way it felt when I chewed it as a child. It seems pretty expensive here, though, so I haven’t made it for ages. It tends to grow near bamboo, I think. We call it bamboo fungus.”

“Do you also eat a mushroom called wood ear?”

“Yep, exactly. I’ve only ever eaten it too, never seen it in its natural state. Have you ever seen wood ear growing on trees?”

“We’ve got them in our woods. I’ve seen them, but never eaten them, haha! We call them Judas’ ears.”

“I’ve heard that name before. Where does it come from?”

“Well, the fungus likes to grow on elder trees. The story goes that after Judas betrayed Jesus, he hanged himself on an elder tree. I’m not sure if the Bible actually says that, but that’s what I was told.”

“To be honest, I used to wonder whether wood ear was actually a mushroom at all. It looks so completely different from the usual kind.”

“It’s a very primitive mushroom, a bit like a coelacanth—practically a living fossil. You see, most mushrooms grow a cap to shield themselves from the sun and rain, releasing their spores underneath. Wood ear is much more rudimentary; it has no cover at all and just releases its spores straight from the surface.”

“I see. There’s also a white, wood-ear-like mushroom we use in desserts. Have you come across it?”

“Never heard of it. Is it sweet?”

“Not naturally sweet, but once it’s boiled down, it gets a thick, gelatinous texture. It’s quite nice with a bit of sugar.”

“We’ve got one over here called the candy cap mushroom (sometimes translated as milk cap). It’s used in desserts too. It’s not sweet itself, but it’s wonderfully aromatic. It’s not common around here, but you’ll find it more often in California. After you eat it, your sweat actually smells like the mushroom.”

“Goodness. Oh, speaking of which, I heard that some tribes in Siberia used to eat a hallucinogenic mushroom. It was like drinking or smoking opium—very precious, not something everyone could get. If you couldn’t find any yourself, you’d just collect the urine of someone who had eaten the mushroom, and that would get you high just the same.”

“Oh, well, that’s one way to do it, haha! You do have to be careful with toxic mushrooms. Fungi can be pretty terrifying when they put their mind to it.”

“Yeah, the creepiest story I’ve heard is about ink cap mushrooms growing out of artificial heart valves.”

“Uh, let’s change the subject…”

There’s no end to mushroom stories, and Tang and Wen are certainly people with their own tales. Nothing as wonderfully varied as fungi, perhaps, but then again, building a family, running a farm that feels more like a craft workshop, protecting a patch of woodland to grow wild, raising two children free to live life on their own terms, finding your footing and surviving alongside a ring of industrial mushroom factories, and seeming to thrive through it all for years—that hardly sounds like a dull chapter.

Foodthink Author

Shang Yi

A long-time regular at the farmers’ market, currently teaching at a university in the Midwestern United States.