The Mushroom Lab on the Farm: American Farmers’ Market Notes
Author’s Note
I.
“Silage is green, you see. There are still seed heads on it, and sometimes the grain hasn’t even fully formed yet — it’s all still tender. You wait until the crop ripens, harvest the grain, and what’s left is straw. You can’t feed this to horses or cows — they won’t eat it. It’s too old, no nutritional value. But we can turn it into mushrooms. Strictly speaking, this is wheat straw. We buy it from someone else.”
“Someone actually sells that, do they?”
“They do. Apart from us mushroom growers, cattle farmers buy it too — they spread it on the floors of their barns. We’ve got a chaff cutter. Xiaotang chops up the straw, and we fill this big oil drum with water and light a fire underneath to bring it to the boil. You put the straw in and boil it for an hour to kill off all kinds of mould and other organisms, so that only our own mushrooms can grow.”
“Oh, and then the straw gets lifted out and placed on this bench?”
“Right, that’s a bench Xiaotang built to his own height. It’s a bit too high for me. Making substrate blocks is just like making sausages — you fit a large plastic bag over one end, switch on the fan at the other, spread the straw in the middle, mix in the spawn, stir it all through by hand, then pack it into the plastic bag until it’s shaped like a big sausage. And that’s what all those oyster mushroom columns hanging up in this room are.”
We walked into the cool, damp mushroom house, where nearly a hundred oyster mushroom columns hung like punching bags. I couldn’t help giving one a little punch — the bag of straw didn’t budge at all. I scooped it up with both hands: incredibly heavy.
“This bag must weigh over ninety pounds, and it’s not just straw inside — there’s a lot of water too. Mushrooms grow by drinking water, so they grow very fast. They can shoot up overnight. Once they’ve absorbed water, they’re like a tyre with air pumped into it — they spring up all at once, with quite a force. But those slits in the plastic bag are cuts we make beforehand — they don’t push through themselves, because they need air too. Most people growing oyster mushrooms don’t use bags this big, but Xiaotang always has to make them so heavy. And he hung every single one up there himself, bare-handed.”
Xiaotang looks more like a slight, scholarly type among the big, burly farmers at our market. I wouldn’t have guessed he had so much strength, or that growing mushrooms could be such physically demanding work. He’s in his early fifties but looks very young. His wife Xiaowen is even more delicate and refined — not even the faint lines around her eyes can dull her perpetual schoolgirl air. The first time I visited this little market to buy vegetables, over a decade ago, I spotted their mushrooms at once. Back then their daughter was about eleven or twelve and would sometimes help at the stall — a proper little tomboy. She’s a secondary school teacher now, and Xiaotang and his wife have barely changed in all those years.
Xiaowen caught me sneaking another punch at one of the columns and laughed. “Our two children practised taekwondo from a young age — and this is what they’d spar against. After each flush, the bag gets noticeably lighter — the water’s gone. You get three or four flushes in total, and then it’s done. Afterwards we take the leftover straw to the kitchen garden for mulch. But the plastic bags can’t be reused or recycled — just thrown away. There really is no way around that.”
At first, a friend from the market — a nurse — gave me three grains, and within three months they’d already produced a whole colony of a dozen or so new ones. My nurse friend’s grains came from an older lady from Eastern Europe — and where did she get hers? In the old days, in the high Caucasus mountains, every family had its own ancestral kefir grains, as sacred as ancestors’ spirit tablets and never to be handed to outsiders. Over the past two centuries, among the Turkic-speaking peoples between the Black Sea and the Caspian, successive empires reshuffled their lives again and again, and the milk wine grains they revered almost as deities were carried across the world in all that upheaval. Nowadays you can buy kefir in any ordinary American supermarket, but it tastes no different from regular yoghurt — no alcohol, no sourness, mostly flavoured with artificial fruit essences and loaded with sugar, one way or another.
II.
A stream winds through, surrounded by dense woodland on the hillsides. Along the bank sit two mushroom houses converted from old cow sheds, a low cold-storage room like a little earth-shrine, the family home for four. Out the front door is the vegetable garden; out the back door a couple of steps, and beneath the tree shade stands a little detached cabin — Xiaowen’s lab, built, naturally, by Xiaotang.
“This plate is potato dextrose agar. That white layer of threads on top of the agar is mycelium. Mushrooms grow from the mycelium — they are the fruiting body, dedicated to releasing spores, rather like apples growing on an apple tree. Do you see that yellow line in the middle? It’s a boundary. On this side is lion’s mane mycelium; on that side is oyster mushroom mycelium. They’re fighting, and after a while this boundary line appeared. You stay in your territory and I’ll stay in mine — it’s a chemical they secrete.” “Why are you growing two kinds of mycelium on one agar plate?” “No, it’s not just to watch them fight. Normally I wouldn’t do this. I’ve made a fresh batch of fermentation broth, so I wanted to test its purity — to check whether anything grows besides the mycelium I put in.”
“So, once the mycelium has grown on the agar, I transfer it into the fermentation broth to continue fermenting, then inoculate it onto grain. I usually use rye, though some people use millet. But millet isn’t a local crop, so I don’t use it much — I can never quite get the ratios right. The grain has to be sterilised first. You pour in a small amount of fermentation broth and let it keep growing until every grain is covered in mycelium — that’s the spawn. Then you take it over to the mushroom house and mix it through the wheat straw to make the oyster mushroom columns.”
“But where does the mycelium on the agar come from? From the mushroom itself — not from spores, from the actual mushroom. I do collect a few spores for fun, to see what grows. But if you were trying to grow mushrooms from spores and make a living that way, you simply couldn’t afford it. That’s sexual reproduction — like having children, you never know what they’ll look like, right? And mushrooms are even more unpredictable. We need to think about success rates, so we can only use asexual reproduction — yes, that’s cloning. How do you clone? You cut a tiny piece from the inside of a mushroom and put it on agar, and it becomes mycelium again. Yes — it’s like an apple turning back into a tree. Pretty fascinating, isn’t it? Every single white button mushroom sold in American supermarkets over all these years has been cloned from one individual, genetically identical. And those supposedly different kinds — the dark-capped portobello, the crimini that sounds so fancy — they’re all button mushrooms too, just slightly mutated and harvested at different stages of growth.”
“So it’s a cycle: mycelium grows mushrooms, mushrooms turn back into mycelium. The agar, the fermentation broth, the grain — they’re all just helping it multiply. One agar plate the size of my palm can supply enough to sell mushrooms for half a year. You pick a tiny bit of mycelium, put it in a small bottle of fermentation broth, and that can inoculate fifteen bags of grain. Sometimes the cycle runs too many times and the mycelium gets tired — gets old, essentially. Then what do you do? You have to ask other people, other labs, for fresh mycelium. I keep some young mycelium in the fridge, but it doesn’t last long. The real solution is to freeze the vigorous mycelium — it can stay frozen indefinitely. You thaw it and it comes back to life. But you have to freeze it with liquid nitrogen, and I don’t have that.”
III.
In the latter half of the nineteenth century, Pasteur and Koch developed the germ theory, proving that many infectious diseases were not spontaneously generated or carried by the air, but spread by incredibly minute bacteria. Almost simultaneously, the German physician Heinrich de Bary discovered that fungi were the cause of many plant diseases, and described how a colony on a patch of soil or a piece of rotting wood could grow into a mushroom. De Bary’s students developed the technique of wiping out every other microorganism on an agar plate to ‘grow’ a single designated mushroom species; Xiaowen could be called a direct descendant in that lineage.
Of course, being able to grow mushrooms does not mean you understand them. As Xiaowen said, the whole thing is impossibly mysterious. The same fungus looks so different in different environments; its modes of reproduction are so varied. For a single species of fungus to bear more than one Latin name was still the norm before 2013. Before gene sequencing was available, mushroom scientists accumulated no small quantity of blood-feud hatred while arguing over whether colonies of different appearance belonged to the same species.
As for the endless cooperation and warfare between fungi and plants, fungi and bacteria — how many human lives they have claimed, how many they have saved — all are numbers beyond reckoning. Take something as simple as my milk wine grains: they are a symbiotic colony of bacteria and yeast (a fungus). The bacteria produce the sourness; the yeast produces the alcohol. But which species of bacteria and yeast exactly? Each batch is truly different — I have no idea from which sheepskin pouch my particular line was passed down.
The United States Department of Agriculture published its first dietary guidelines in 1916. In 1995 those written guidelines were turned into a diagram and the Food Guide Pyramid was launched — and mushrooms had no place in it. In an American agricultural system that reveres wheat and beef, mushrooms as food are practically a joke: the three great macronutrients — carbohydrates, protein, fat — it has none of them, and eating your fill on mushrooms alone is virtually impossible. The reason is simple. As a reproductive organ, a mushroom cannot draw nutrients for itself; it relies on its mycelium to supply them. And mycelium is a microorganism, gnawing its way through rotting wood and stubborn stone to rear a swollen mushroom — no easy feat. Calories have to be rationed meticulously, and corners cut where possible. If the thing grew as dense and starchy as a potato, the mycelium simply could not afford it.
The latest edition of the Pyramid has tucked mushrooms into a footnote, classified as ‘other vegetables’. The Pyramid is not merely for public education, though — it also carries financial weight, because federally funded food and agriculture programmes, such as public-school lunch, all follow the Department of Agriculture’s dietary guidelines. The mushroom world, after years of lobbying, has finally wriggled into a footnote — something to celebrate, in a way, though the classification is rather galling. Mushrooms are not vegetables — it bears repeating. They are not plants at all, unable to make their own sugars through photosynthesis.
Despite being just a humble footnote, the American mushroom industry completed its industrial consolidation in the twentieth century without any drama — fewer farms, each producing more and more. The little white mushroom Xiaowen mentioned was the only fresh mushroom I had eaten in my first ten years in America. Its formal Chinese name translates as ‘two-spored mushroom’; in the supermarket it is simply called the button mushroom; and because it is native to Europe and North America, Chinese speakers also render it as the ‘Western mushroom’. Nothing remarkable in flavour, but hardly unpleasant — rather like KFC or McDonald’s: no surprise and no disappointment, always landing exactly on the expected value. The genes are identical, after all. Specifically, for the past forty years virtually all the button mushrooms supplied through commercial channels in North America trace back to 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 well-flavoured.
IV.
“Haven’t you ever had oyster mushrooms or shiitake?”
“Haven’t even heard of them.”
“So what made you decide to grow these things?”
“Read about them in books, mostly. And people at the market were asking about them — especially the Asian restaurants, they wanted to buy them.”
So the market also carries within it the seeds of diversity — like a bag of sterilised grain left out for a while: all sorts of things begin to sprout again. Of course, new demand does not appear out of thin air. The theory of “spontaneous generation” has long been superseded by “germ theory”, and the diversity that springs up comes from invisible threads — social mobility, new residents bringing new cultures, new roads finding new trading partners.
“Have you ever seen a mushroom called a stinkhorn?” I asked Xiaowen.
“Well, that thing, you know — hm, hm… I have actually seen one. Oh, the way it looks… and especially the smell — have you ever smelled it? I’d say you ought to smell it at least once in your life…”
I had only ever seen one in books, and indeed its appearance is something of an embarrassment — it bears a striking resemblance to some human organ poking up out of the ground. I have heard the smell is equally overwhelming, the kind that could knock you flat on your back on the spot. And it is highly toxic.
“Did you know? I have been eating this since I was a child.”
“How is that possible?”
“I know — I only just found out! When we were little we always ate them dried. I had no idea it was that sort of mushroom! Actually, the smell and the toxins are only in the cap at the top. You cut that bit off and the rest is perfectly edible. Go to any Chinese supermarket and you’ll see them.”
“Is it nice?”
“I can’t say it has much flavour. We put it in soup — it soaks up oil and the savouriness from the meat, and the texture is rather fun, like a sponge. When I was small I loved the way it felt between my teeth. But here it seems quite expensive, and I haven’t cooked it in ages. It must like to grow alongside bamboo — we call it bamboo fungus.”
“Don’t you also eat a mushroom called wood ear?”
“Yes, yes — I’ve only ever eaten it, never seen it growing. Have you ever seen wood ear growing on a tree?”
“We’ve got some in our woods. I’ve seen it, but never tasted it, ha! We call it Judas’s ear.”
“I’ve heard that name. How does it get that?”
“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 don’t know whether the Bible actually says that — it’s just what I’ve heard.”
“Honestly, I used to be unsure whether wood ear is a mushroom at all. It looks so different from a regular one.”
“It’s a very primitive kind of mushroom — a bit like a lobe-finned fish, a living fossil, in a way. You see, most mushrooms hold up a cap — they use it as a shield against sun and rain, releasing spores from underneath. Wood ear is far more rudimentary — no protection at all. It simply releases its spores straight from the surface.”
“I see. There’s also a white mushroom, rather like wood ear, that we use in desserts. Have you ever seen one?”
“No. Is it sweet?”
“It’s not sweet, but when you cook it down it takes on a sticky, gelatinous texture. Add a little sugar and it’s quite lovely.”
“We also have a mushroom called the candy cap — in Chinese it might be rendered as Lactarius — which we use in desserts. It has no sweetness of its own either, but it’s wonderfully fragrant. Not common round here, but you find more of them in California. After you eat one, even your sweat smells of that mushroom.”
“Goodness! Oh, right — I’ve heard that some tribes in Siberia used to eat a kind of poisonous mushroom, much like drinking or smoking opium. It was very precious — not everyone got a share. If you couldn’t get any, you’d collect a little of the urine from someone who had eaten the mushroom, and that would get you high just the same.”
“Oh well, that’s a method too, ha ha! You do have to be careful with poisonous mushrooms. When mushrooms turn terrifying, they can be truly terrifying.”
“The most horrifying thing I’ve ever heard about is a shaggy ink cap — the kind that drips black ink — growing inside an artificial heart valve.”
“Er, let’s change the subject…”
Stories about mushrooms never run out. In fact, Xiaotang and Xiaowen are themselves people with stories of their own. Their tale may not be as endlessly varied as a mushroom’s, but it amounts to starting a family, running a farm like a little workshop, safeguarding a stretch of woodland left to grow as it pleases, raising two children who live by their own lights, surviving among all those super mushroom factories — and after all these years, seeming to live rather comfortably. Surely that is no dull story.
Foodthink author
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Editor: Tianle