How to Grow Culinary Mushrooms

I tasked The Bird on Fire staff with describing, discovering, and detailing PVS hobbies. Alyna reminded us we fell into some “interesting” hobbies during quarantine. Luke gave us sage advice on collecting vinyl (Avoid scratches). This summer, Levi took up growing mushrooms . . . in his grandparents’ bathroom. Here is his tale.

Ms. Zachik, Blog Advisor

By Junior Levi Kassinove

I realize that, in writing this, few people will have the time and energy to grow mushrooms. If you do, however, choose to grow culinary mushrooms, know that you will end up growing many more than you know what to do with. It’s a rewarding yet comprehensive process. And, obviously, if you ask me, I’d tell you that it is totally worth it. All the information in this guide comes from my own experience growing pink oyster and lion’s mane mushrooms. 

Part 1: Life Cycle of a Fungus

Before learning how to grow mushrooms, it is necessary to understand the life cycle of the fungus itself due to its drastic differences from the life cycle of a plant. Additionally, note that fungi are neither plants nor animals, but rather their own kingdom. 

The life cycle starts with spores, which are microscopic balls of DNA that are released by the billion from the mushroom’s gills. The spores travel the universe by wind and sometimes an animal’s foot if it had stepped on a mushroom. Eventually, some spores settle on dirt, corpses, feces, basically anything with nutritional value. I’ve seen people grow mushrooms on cardboard. When two spores meet, they form a microscopic white strand between them called a hypha. Over time, the hyphae will branch out and grow in new directions, making connections between new strands. Collectively, these hyphae are called the mycelium. The mycelium is basically the entirety of the fungus. Its most basic functions are to absorb and send nutrients throughout the mycelial network. A good way to think of a fungus is to compare it to an apple tree, where the tree is the mycelium, and the mushrooms are the apples. But some more interesting functions of the mycelium include deciding when it’s time to produce mushrooms, and even communicating (to a degree) with surrounding trees (Science Direct-Fungal Consciousness). According to the University of Illinois, the mycelium’s “network-like design mirrors that of dark matter, neural connections in the brain, and even the human-created Internet.” But this is not a discussion about philosophical questions; this is about growing mushrooms. So, when the conditions are right, the mycelium will produce the fruiting bodies known colloquially as mushrooms. As the mushrooms mature, their caps will open up and release spores. The cycle starts once again. The whole process takes a few months. 

Part 2: Growing at Home

As I said earlier, mushrooms can pretty much grow on anything with nutrients. They don’t need sunlight (although its benefits are debated by the mushroom growing community, more on why later), and they don’t need much water. What they do absolutely need is a sterile environment (nothing will ever be truly sterile, but I will use the word to describe sterility to the degree that matters to us), which is the main difficulty in mushroom cultivation. You might be wondering why that matters if mushrooms can grow just fine in the wild. Well, the mushrooms we see in the wild have stood the test of time and beaten out all other microscopic competition (mold, bacteria, and other mushrooms). There’s a reason why mushrooms produce billions of spores; it’s incredibly rare that a given set of spores survive in the wild. If you attempted to grow mushrooms without using a sterile technique, the mycelium would quickly become overtaken by mold or bacteria. It is by luck that a given set of spores end up beating competition and creating mushrooms in the wild. This means that, in your own home, you have to kill all other competition. So how is that accomplished? 

Mushrooms require a sterile medium to grow in. The easiest option for us homegrowers is precooked, microwavable-ready rice. The exact kind you can buy at any supermarket. Be careful, however, to not buy any rice with a high sodium content (>500mg) or any flavorings. Plain old brown rice is the best way to go. Now, since the area within the ready-rice bag is sterile, you need to somehow transfer the spores into the rice without introducing contaminants. This process is called inoculation. There are multiple ways to accomplish this, but the easiest way is to use an MSS (multi-spore syringe) to pierce the unopened bag and inject the spores. It is a syringe with a solution consisting of water and spores, which can be bought online. The idea is to inject the spores into the bag of rice and squirt the solution, then quickly cover the hole. The needle will come sterilized, but you still need to sterilize the environment surrounding the bag just before you inoculate. It is not overkill to spray the entire room with Lysol spray. You need to be absolutely sure that nothing gets in the bag but spores. If contaminants get in, there is no chance your young and ungerminated spores will be able to fight them off. So spray the room with Lysol; get gloves on; mask up (so you don’t breathe on the bag); and wipe the bag down with alcohol wipes. One of the required materials I did not mention before was medical grade paper tape (name brand is Micropore, found at CVS), which is needed as a means to get oxygen into the bag while simultaneously filtering out contaminants. So once the spores are injected (injecting any more than 1cc of solution will induce bacterial wet rot), quickly cover the hole with the paper tape. This tiny hole, of course, will not provide sufficient oxygen. To provide sufficient oxygen, cut the corner of the bag (1 in. wide, with scissors wiped with alcohol) and cover it completely with paper tape. All of this should be completed within a minute or so, starting from once everything is sterilized. Now, you can leave it alone for a few weeks without touching the bag. The bag needs to stay sealed. The hardest part is truly over now, although this was not my main challenge when growing. I also should stress that you are only minimizing the chances of contamination, and not completely eliminating it. Doing all these steps in a relatively dirty house with pets would likely get you a bag full of mold. 

Part 3: The Waiting Game 

The amount of time it takes for the mycelium to fully colonize the bag is dependent on temperature, genetics (luck if you’re using a Multi-Spore Syringe), and the method of inoculation. The ideal temperature for mycelial growth is 75-77 degrees Fahrenheit. So room temperature will work for most people. Anything colder will slow down the growth, anything higher will increase the probability of contamination and start to cook the mycelium. The colonization process will take about a month. You can tell when it’s 100% colonized when the bag is hard all the way through. Not rock solid, but it should be quite firm. If it is firm in some areas but mushy in others, it still has a ways to go. The genetics are completely random and vary from spore to spore in an MSS (the species is guaranteed of course), but you can also inoculate the rice with a liquid culture syringe or a colonized agar wedge for faster colonization. A liquid culture syringe is a syringe with a solution of already established mycelium as opposed to spores, which saves about a week of waiting. An agar wedge is a wedge cut from an agar plate, which is basically a petri dish filled with nutrients (with mycelium growing in this case). The advantage of an agar wedge over a liquid culture syringe is that it is possible to genetically isolate the fastest and strongest mycelium in an agar plate. Unfortunately that is too advanced for this post; after all, I did recommend growing these things in a bag of ready-rice. 

At one point I grew pink oyster mushrooms in fancy mason jars I bought online specifically designed for growing mushrooms. They contain sterilized rye berries, a self-healing injection port, and a filter. I know I could have gone with the ready-rice method, but this method further reduces the chance of contamination since you don’t need to make your own filter. Anyway, the white stuff you see in the picture to the right is mycelium, and when the jars are fully white, they are ready for the next phase. 

Part 4: Spawning to Bulk

A mere bag of rice will only yield about five mushrooms, so the next step is to expand the mycelium further. Though if you want, the process could end with the rice. Given enough time, the mycelium will just start pumping mushrooms like no tomorrow, and you’ll end up with a bag of deformed little mushroom children. I don’t think they’ll taste good. Moving on, the idea of spawning to bulk is that you can dump the colonized rice in some actual soil to grow out the mycelium in a shoebox. Sterility is not as important now because at this point the mycelium is big enough to deal with its own problems (antibiotic properties). The real issue now is what soil to use. You can either choose to make your own substrate (a real pain), or buy it online. For mushrooms that grow on the ground, your best bet is to go with a coco coir-based substrate. Coco coir is the fibrous husk of the coconut. A condensed brick of coco coir could be found at PetSmart, which is actually ideal for this process because of a reason I’ll explain later. Grounded mushrooms can grow on just coco coir, but a blend of coco coir, vermiculite, gypsum powder, and coffee grounds is optimal. Mushrooms that grow on trees prefer either a sawdust or straw-based blend with the optional addition of the other ingredients from the grounded blend. As long as its base is correct, you can use any combination of the other ingredients. For example, sawdust and coffee grounds work fine. You can either buy all of these ingredients separately at PetSmart and Home Depot, or buy a pre-made substrate online like I did somewhat idiotically (I bought a coir-based substrate even though pink oysters grow on trees, but it ended up working). It’s cheaper, as you can imagine, to just buy the raw ingredients. But there’s a caveat: you need to pasteurize and hydrate the substrate.

 Pasteurizing is basically partially sterilizing something. You pasteurize the substrate because although the mycelium is big and strong, you still don’t want contaminants lurking in that coco coir. Normally it takes two months for the mushroom mycelium to end up producing spores, but mold can start blasting spores within days of its existence. Within the week you will be growing a green box of death instead of delicious mushrooms. But, you don’t want to kill all the microorganisms, as some are beneficial to the process (Science Direct). Hydration on the other hand is a whole different ball game. You need to hydrate the substrate so that it’s not too dry and not too wet. It’s called field-capacity, which in dummy terms means the maximum amount of water that soil can contain without dripping if you hold it up. There is a proper way to calculate field capacity, but I think saturating the substrate and then squeezing the water out is pretty surefire. You can pasteurize and hydrate the substrate in one go if you use boiling water and a bucket, which also expands the brick of coco coir. You can also pasteurize substrate with an oven, but I don’t know why you would do that. Once you have your pasteurized substrate, you can open the bag of rice and dump everything in a shoebox, mixing well. Close the lid on the shoebox and wait for the mycelium to fully colonize the substrate. After it’s fully colonized, it’s mushroom time, baby. Now, herein lies the final challenge. 

Part 5: Fruiting 

The most difficult part of this process for me was the fruiting conditions. I’ll explain why soon, but first it is critical to understand what fruiting conditions are in order to understand how I messed up. Also, at this point the colonized substrate-grain mix is called a cake. Fruiting conditions are the conditions necessary for the mycelium to produce mushrooms. The factors here include temperature, sunlight (you thought I forgot about that), humidity, and fresh air. The only thing you need to do to initiate fruiting conditions is crack the lid open. Now, obviously you need to take other measures to ensure things don’t go awry, but that is pretty much it. Mycelium likes a marked decrease in carbon dioxide levels and an increase in oxygen levels. Why? Because when mycelium is growing underground and has finally reached the surface, exposing it to fresh air, it knows that mushrooms will protrude above the surface. The same concept applies to sunlight. Sunlight is used as an indicator of when it’s time to fruit, because the mycelium will only sense the light of day when it has colonized the surface. Mushrooms can easily grow in the dark, however, much like how mushrooms can grow in the bags of rice. But the presence of sunlight is argued to decrease the time it takes for pinning to occur (mushroom babies forming). This along with many other things is a subject of great debate within the hobbyist mushroom growing community. The optimal temperature is about five degrees Fahrenheit below the colonization temperature in order to “shock” the mycelium into fruiting (cornell.edu). The relative humidity of the air around the cake should be at least 90% (the mycelium will produce humidity). Now back to my grave error. I grew these pink oysters during the wintertime, so it was extremely dry in my home. I took no precautions to ensure the humidity was right, and so the cake ended up completely drying out. It was cracking. And so, in a last ditch effort to save my mushrooms, I completely filled the shoebox with water. I had scoured the internet for what to do when your cake dries out, and submerging it in water was pretty much the only solution. I let it soak for a few hours as advised by the wizards of the internet, and drained the water afterwards. Then I bought a humidifier and put it next to the box. Every day, it is important to mist your cake in order to ensure the same thing doesn’t happen to you. Also, it is important to fan your cake every day with the lid in order to introduce fresh air and move away the stale air. Don’t fan so much that the cake dries out, though. And similarly, don’t mist too much or something will grow on the mycelium. If you’ve got all this down, pins will appear in no time. After I soaked my cake I got mushrooms within two weeks. Once you see pins, fully grown mushrooms will be present within one week. They grow rapidly. Also, when the mycelium stops producing mushrooms, the mushrooms on the cake are called a flush. The crazy thing is that you can have multiple flushes! In order to do this, cut the mushrooms from the cake (pulling can damage the mycelium) and soak the cake in water overnight. The mycelium puts most of its water into the mushrooms, so in order for it to grow more, it needs to be rehydrated. Eventually the mycelium will run out of nutrients, but you can solve that problem by soaking the cake in coffee instead of water. You can pretty much get an infinite amount of mushrooms with one cake, that is, until senescence catches up to it. You can also just take a spore print of the mushroom and scrape the spores into a new bag of rice with the same sterile techniques. 

The possibilities are endless. Now, onto the ways mushrooms will save the world, and after that, recipes! Just kidding, goodbye.