Mushroom Lab on the Farm | Notes from American Farmers’ Markets
Author’s Note
I.
“Silage is green,” she explained. “It still has the seeds on it; sometimes the seeds haven’t even sprouted yet—basically, it’s tender. Once it matures and the grain is harvested, what’s left is straw. Cattle and horses won’t eat this; it’s too old and has no nutrition, but we can turn it into mushrooms. Strictly speaking, what we use here is wheat straw, which we buy from elsewhere.”
“People actually sell this?”
“They do. Besides mushroom growers, cattle farmers buy it to bed their barns. We have a grass cutter; once the straw arrives, Xiao Tang chops it up. He fills a large oil drum with water, lights a fire underneath to bring it to the boil, and boils the straw for an hour to kill off any mould or other fungal colonies. That way, our own mushrooms can grow properly.”
“Oh, and then you scoop the straw out and put it on this table?”
“That’s right. Xiao Tang built this table to suit his own height, so it’s a bit too high for me. Making the mushroom blocks is just like making sausages: you fit a large plastic bag over one end and turn on a fan at the other. You spread the straw in the middle, mix in the spawn, stir it by hand, and then pack it into the bag into a long cylinder—like a big sausage. Those are the oyster mushroom blocks you see hanging in this room.”
We stepped into the damp, cool mushroom house, where nearly a hundred oyster mushroom columns hung like boxing punch-bags. I couldn’t resist giving one a light punch, but the bag of straw didn’t budge an inch; when I tried to lift it with both hands, it felt immensely heavy.
“This bag must weigh over ninety pounds; it’s not just straw in here, there’s a lot of water too. Mushrooms grow on water, which is why they grow so quickly—they can spring up overnight. Once they’ve absorbed the water, it’s like pumping up a tyre; they snap upright with tremendous force. These slits in the plastic, however, were made by us beforehand, not pushed open by the mushrooms themselves, as they need air to breathe. Most people don’t use bags this large for oyster mushrooms, but Xiao Tang insisted on making them this heavy; he hung every single one of them up by hand.”
Among the burly farmers of the market, Xiao Tang had the air of a frail scholar; I hadn’t expected him to be so strong, nor had I realised that growing mushrooms was such strenuous labour. He is in his early fifties, but looks remarkably young; his wife, Xiao Wen, is even more quiet and elegant, the slight wrinkles at the corners of her eyes unable to mask an eternal schoolgirl quality. When I first visited this little market over a decade ago, I was immediately drawn to their mushrooms. At the time, their daughter was only eleven or twelve, occasionally helping at the stall like a tomboy; she is now a secondary school teacher, yet Xiao Tang and his wife seem hardly changed in appearance over the years.
Seeing me secretly punching the oyster mushroom columns again, Xiao Wen laughed. “Our two children have done Taekwondo since they were small; they use these things for practice. After a flush of mushrooms, the bag becomes much lighter as the water is depleted. They produce three or four flushes in total before they’re spent, and we then take the remaining straw to the vegetable garden to use as mulch. However, the plastic bags can’t be reused or recycled—they have to be thrown away. There’s really no way around that.”
Initially, a nurse friend I met at a small market gave me three grains; in three months, they had grown into a cluster of over a dozen. The nurse’s grains came from an Eastern European lady, but where did the lady’s grains come from? Long ago, in the North Caucasus mountains, every household had its own ancestral Kefir grains, held as sacredly as ancestral tablets and never given to outsiders. For two hundred years, between the Black Sea and the Caspian Sea, the Turkic peoples endured successive reshufflings of empires, and their near-divine Kefir grains spread across the world amidst the turmoil. Now, Kefir can be bought in ordinary American supermarkets; it tastes no different from regular yoghurt, lacking both the alcoholic notes and the tartness, mostly flavoured with artificial essences and, in any case, loaded with sugar.
II.
A stream winds through the valley, surrounded by dense forest. By the water’s edge stand two mushroom houses converted from old cowsheds, a low-slung cold store resembling a small village shrine, and a home for four. Outside the front door is a vegetable garden; a few steps from the back door, sheltered by the shade of the trees, stands a separate small wooden cabin—Xiao Wen’s laboratory, which, naturally, had been built for her by Xiao Tang.
“On this plate is potato dextrose agar. This layer of white threads on the agar is the mycelium; mushrooms grow from the mycelium specifically to disperse spores, much like apples grow on an apple tree. See that yellow line in the middle? That’s a boundary line. On this side, we have Lion’s Mane mycelium, and on that side, Oyster mushroom mycelium. They’re fighting; they’ve fought until this boundary formed—basically saying, ‘you stay out of my way, and I’ll stay out of yours’. It’s caused by a chemical they secrete. Why grow two types of mycelium on one agar plate? No, it’s not just to watch them fight. Normally, I don’t do this. But since I’ve just made a fresh batch of liquid culture, I wanted to test the purity to see if anything other than the inoculated mycelium starts growing.”
“It works like this: once the mycelium grows on the agar, I put it into a liquid culture to ferment further, and then I inoculate it into grain. I usually use naked oats, sometimes millet, but millet isn’t a local crop here, so I don’t use it often—I can never quite get the proportions right. The grain has to be sterilised first. I pour a little bit of liquid culture into a bag and let it grow until every single grain is covered in mycelium. That’s the spawn. Finally, I take them over to the growing room, mix them with straw, and make oyster mushroom blocks.”
“Where does the mycelium on the agar come from? From the mushroom itself, not from spores. I sometimes collect spores for fun, just to see what grows. But if you want to grow mushrooms to make a living, you can’t afford to gamble with spores. That’s sexual reproduction—it’s like having children; you never know what they’ll turn out like, right? Mushrooms are even more mysterious than that. We need a high success rate, so it has to be asexual reproduction—yes, exactly, cloning. How do you clone them? You just carve out a small piece from the inside of a mushroom, place it on agar, and it becomes mycelium again. It’s like an apple turning back into a tree, isn’t it? All the white button mushrooms sold in US supermarkets for years have been cloned from a single individual; they have identical genes. And some you might think are different varieties—like the large, dark-capped Portobello or the fancy-sounding Crimini—they’re actually all just white button mushrooms, just slightly mutated or harvested at different stages of growth.”
“So it’s a cycle: mycelium grows mushrooms, and mushrooms become mycelium. Agar, liquid culture, grain—these are all just ways to scale it up. One of these palm-sized agar plates is enough to keep us selling mushrooms for six months. A tiny bit of mycelium in a small bottle of liquid culture can inoculate 15 bags of grain. Sometimes, after too many cycles, the mycelium loses its vigour—it gets ‘old’, so to speak. What do you do then? You have to find someone else, go to another lab and get new mycelium. I keep some ‘young’ mycelium in my fridge, but the shelf life is limited. The only truly foolproof way is to freeze the active mycelium; it can stay frozen indefinitely and comes back to life once thawed. But you need liquid nitrogen for that, and I don’t have any.”
III.
In the latter half of the nineteenth century, Pasteur and Koch developed germ theory, proving that many infectious diseases did not arise spontaneously or come from the air, but were spread by infinitesimal bacteria. Almost simultaneously, the German physician Heinrich De Bary discovered that fungi were the source of many plant diseases, and he described the process by which fungal colonies in soil or decaying wood grow into mushrooms. De Bary’s students developed the technique of eliminating other microbes on agar plates to “culture” a specific type of mushroom; Xiao Wen could be considered a direct intellectual descendant of this lineage.
Of course, being able to grow mushrooms is not the same as understanding them. As Xiao Wen noted, these organisms are far too mysterious. The appearance of the same fungus can vary wildly depending on the environment, and their methods of reproduction are incredibly diverse. Until 2013, it was common for a single fungus to carry two or more Latin names. Before the advent of gene sequencing, mycologists accumulated deep-seated animosities over arguments as to whether colonies with different appearances belonged to the same species.
As for the endless cycle of collaboration and warfare between fungi and plants, or fungi and bacteria—and the unfathomable number of human lives lost or saved in the process—the figures are staggering. Even something as simple as my kefir grains is a symbiotic community of bacteria and yeast (fungi); the bacteria provide the acidity, while the yeast provide the alcohol. But which specific bacteria and yeast are involved? Every batch is different. I have no idea which ancient sheepskin bag my particular strain was passed down from.
The US Department of Agriculture published its first dietary guidelines in 1916, and in 1995, it turned those written instructions into a visual aid, introducing the Food Pyramid. Mushrooms had no place in it. In a US agricultural system that venerated wheat and beef, mushrooms were practically a joke as a food source. They lacked all three major nutrients—carbohydrates, proteins, and fats—making it almost impossible to feel full on them. The reason is simple: as reproductive organs, mushrooms cannot absorb nutrients themselves; they rely on mycelium for supply. Mycelium are microbes that feed on decaying wood and stone; to cultivate a large mushroom from this is no small feat. Energy must be budgeted strictly, and where possible, shortcuts are taken. If they grew as solid as a potato, the system simply could not support them.
The latest version of the pyramid tucks mushrooms away in the footnotes, classifying them as “other vegetables”. This pyramid is not just for public education; it involves vested interests. Federal government-funded food programmes, such as public school lunches, must follow the USDA’s dietary guidelines. After years of struggle, the mushroom world has finally made it into the footnotes, which is cause for celebration, even if the classification is rather frustrating. Mushrooms are not vegetables—it bears repeating—they are not plants at all and cannot produce their own sugar through photosynthesis.
Despite their humble status as a footnote, the US mushroom industry had already industrialised on a massive scale by the twentieth century; the number of farms decreased while the output of individual farms grew. The “white mushrooms” Xiao Wen mentioned were the only kind of fresh mushrooms I ate during my first ten years in the US. Known scientifically as *Agaricus bisporus*, they are called button mushrooms in supermarkets. Because they are native to Europe and North America, they are also translated into Chinese as “Western mushrooms”. They have no particularly distinctive flavour, yet they aren’t unpleasant; like KFC or McDonald’s, they offer no surprises but never disappoint, always hitting the expected mark. After all, their genetics are identical. Specifically, almost all *Agaricus bisporus* supplied through North American commercial channels for forty years originated from a single “super spore” discovered in 1980 by Gerda Fritsche, a Dutch researcher at the Max Planck Institute for Breeding Research—naturally high-yielding, disease-resistant, and consistent in taste.
IV.
“You’ve never had oyster or shiitake mushrooms?”
“Never even heard of them.”
“Then how did you come across the idea of growing them later on?”
“Read about it in a book, and there were people in the market asking for them—especially Asian restaurants, they wanted to buy them.”
Thus, the market possesses its own inherent genetic diversity; like sterilized grain left out for a while, all sorts of things eventually sprout back up. Of course, new demands do not simply emerge from nowhere. The ‘theory of spontaneous generation’ has long been replaced by ‘germ theory’; this nascent diversity stems from invisible bonds—social mobility, new residents bringing new cultures, and new paths leading to new trading partners.
“Have you ever seen a mushroom called a stinkhorn?” I asked Xiao Wen.
“Hmm, that thing, yeah… I actually have. Gosh, the look of it… and especially that smell. Have you smelled it? I’d suggest you experience it at least once in your life…”
I had only seen them in books. Their appearance is indeed rather awkward, looking much like some kind of human organ sprouting from the ground. I’d heard the scent is equally potent—the kind that could knock you flat on your back—and that they are highly toxic.
“You know, I’ve eaten those since I was a child.”
“How is that possible?”
“Right? I only found out recently myself! When we were kids, we ate them dried; I didn’t realise that’s what kind of mushroom it was! Actually, the stench and the toxins are only in the cap. If you remove that part, the stem is edible. You can find them in Chinese supermarkets.”
“Do they taste good?”
“I wouldn’t say they have much of a taste of their own. We put them in soup where they absorb the oil and the savoury umami of the meat. The texture is quite interesting too, like a sponge; I loved that chewy feeling when I was little. But they seem quite expensive over here, so I haven’t made them in ages. They probably like growing alongside bamboo; we call them bamboo fungus.”
“Do you also eat a mushroom called wood ear?”
“Yes, yes. I’ve eaten it, but I’ve never actually seen it. Have you seen wood ear growing on a tree?”
“We have them in our woods. I’ve seen them, but I’ve never eaten them, haha! We call it Judas’s Ear.”
“I’ve heard that name. Where does it come from?”
“Because this mushroom likes to grow on elder trees. It’s said that after Judas betrayed Jesus, he hanged himself from an elder tree. I’m not sure if the Bible actually says that, but that’s what I’ve heard.”
“To be honest, I used to be unsure if wood ear was even a mushroom. It looks nothing like a typical one.”
“It’s a very primitive type of fungus, a bit like the coelacanth—a living fossil. You see, most mushrooms hold up a cap like an umbrella to shield themselves from the sun and rain, releasing their spores underneath. Wood ear is much more basic; it has no cover or protection and just releases its spores directly from the surface.”
“I see. There’s also a white mushroom similar to wood ear that we use for desserts. Have you seen it?”
“No, I haven’t. Is it sweet?”
“It’s not sweet itself, but once it’s cooked down, it gets a gelatinous texture. It’s quite delicious with a bit of sugar.”
“We have a mushroom too, called a candy cap. It’s used for desserts; it’s not sweet itself, but it’s very fragrant. They aren’t common around here, but you find more of them in California. After you eat it, even your sweat smells like the mushroom.”
“Good heavens. Oh, right—I heard that some tribes in Siberia used to eat a poisonous mushroom, similar to drinking or smoking something strong. It was very precious, not everyone got a share, so if they couldn’t get any, they’d drink the urine of someone who had eaten the mushrooms to get high in the same way.”
“Oh, well, that’s one way to do it, hahaha! You have to be careful with poisonous mushrooms; they can be truly terrifying.”
“Yes. The most terrifying thing I’ve heard of was an inky cap growing out of an artificial heart valve.”
“Err, let’s talk about something else…”
There is no end to the stories of mushrooms; in truth, Xiao Tang and Xiao Wen have stories of their own. While their lives may not be as eccentric as the fungi they grow, they have built a family, run a farm like a craft workshop, preserved a stretch of wild woodland, and raised two children to live life on their own terms. To have survived and thrived amidst a sea of industrial mushroom factories, living so contentedly for all these years, is surely anything but a dull experience.
Foodthink Author
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Editor: Tianle