By Babette Wils
Since 2009, I have been fascinated by growing mushrooms and always looking for a low-tech, low-input way to grow them. Throughout the years, I tried growing mushrooms with pasteurized cardboard, coffee grounds, and old newspapers. I tried NYT bags, woodchips in the yard, tree stumps, and logs. I even tried mushroom kits — all with zero or mediocre success. However, I did become an expert at growing green mold! It was embarrassing - I genuinely have minimal innate mushroom-growing talent. Yet, I grow them today as a profitable little side-bar business on our farm — this is part of the story of how we learned.
After my many failures in 2021, I decided I needed a more rigorous, systematic approach, one where I would try multiple experiments side by side but not break the bank. In the years since 2009, mushrooms have become very popular, and by 2021, the internet was exploding with YouTube videos and written guides with hundreds of different variations on growing mushrooms. I enrolled in YouTube University and spent weeks looking at all of it - taking notes, comparing, and deciding which techniques I would try. I took over a room in our house as a laboratory to try different growing methods and learn which would work for me.
Through my research, I realized that growing mushrooms also requires understanding what makes them so challenging to grow. Why is it so easy to grow green mold when growing mushrooms? Because they are related — they are both forms of fungi. They both like to grow in the same moist environments and on the same food. The mold tends to be aggressive. You must be clever to create conditions conducive to fungi (mold and mushrooms) that allow mushrooms to get ahead.
Nature does this with overwhelming numbers. A single mature mushroom releases a gazillion spores. These float around until a few million find a good spot. There, they germinate and start to grow mycelium. If nobody eats them and nothing else bad happens, when they are ready, and the conditions are right, another mushroom grows, and the cycle starts again. Success is rare, but the process is simple.
Since humans like to control the success rate, things are complicated. Most modern human mushroom production looks like this: In a sterile lab, a person in a hazmat suit collects mushroom spores from a mushroom. They are cautious to avoid getting mold into the spores. The spores are grown out in a petri dish in the lab. The petri dish concoction is injected into sterile syringes. Be careful: mold can get into the syringe. The liquid mycelium is then injected into a bag with a water-saturated nitrogen-rich grain, like millet, sterilized by heat. Mold must not get in anywhere during the injection or the grain. If all goes well, the spores colonize the grain with mycelium – thin white strands that smell earthy. Once the bag is colonized (a colonized bag is called spawn), the grower distributes the spawn into about ten more bags with sterilized grain. For this, a hazmat suit is unnecessary, but a spore-free space is created using a laminar flow hood or a still air box. This second generation colonizes the bags. You can expand for multiple generations, each time in new sterilized grain bags, but the spawn gets weaker (therefore less likely to fruit) with each expansion. To get mushrooms (the fruits of the fungus), you need to put spawn into a cellulose-rich substrate like a log, newspaper, straw, or sawdust pellets, again being sterile or at least very clean. Finally, to produce mushrooms, you must provide the mycelium with the exact environmental conditions it likes.
Step 1 - Expanding Mushroom Grain Spawn
Building a sterile lab room was expensive and seemed complicated, so I purchased spawn bags. However, as I was learning, there would be many failures, which would require a fair number of spawn bags. Grain spawn bags are expensive ($30 a pop). By expanding them, I could make many grain spawn bags out of one. I wanted to do this step in an easy, low-tech, low-input way.
For the most straightforward grain expansion approach, I purchased a 16-quart pressure cooker ($150), millet and rye (about $100), single-use, virgin plastic grow bags specifically for mushrooms ($50) and grain spawn bags; I wanted to work with Reishi, Shiitake, Chestnut, Pioppino, King Oyster, and Blue Oyster ($181). To save money and virgin materials, instead of buying an expensive laminar flow hood, I re-used some plastic to jerry-rig a still air box (a two cubic foot transparent container with holes for your arms, inside which you can create a clean environment).
In principle, expanding spawn bags is simple: hydrate and sterilize the grain and add spawn to the grain, but it has to be done just right. That said, mushroom aficionados (e.g., North Spore, FreshCap, GroCycle, Midnight Mushroom) have developed variations on the right process. First, they use a variety of grains: millet, rye, oats, birdseed - I tried millet, rye, and 50:50 of each. Then, they use different grain hydration methods to get it just right: too wet or too dry weakens the mycelial growth. Three variations for hydration are: simmer for 30 minutes then drain; soak for 24 hours then drain, or mix the correct ratio of grain and water from the get-go - I tried all three. Third, hydrated grains need to be sterilized. Everyone agrees if you make 5 lb bags, sterilize them in a pressure cooker at 15 PSI for about 2.5 hours. There is varying advice on how to keep the bags from melting in the cooker. A cooker full of grain bags can quickly get hot spots that melt bags. I learned through multiple melting episodes that the simplest solution is not to overfill and put in enough water (about 2” depth) to maintain even temperature throughout the cooker.
Once I had cooled sterile bags, the next step was to transfer some of my purchased grain spawn into each bag. For this, I needed a clean environment in front of a laminar hood or a still air chamber. I used an air chamber. I put everything inside - the spawn bag, sterilized grain bags, alcohol, scissors, and something to close the bags. I put my hands through the special holes in the still air chamber and sprayed the inside down with alcohol, including my hands, the bags, and your scissors. I cut open my purchased spawn bag and one sterilized grain bag and dropped 1/6 of the spawn into the grain bag without touching the grain. I resprayed my hands and closed the bag quickly, avoiding touching the inside. I sealed my bags with mushroom clamps (you can also use an electric sealer). Then did the next bag, etc. It was all a bit nerve-wracking! However, I made approximately six new spawn bags from each purchased bag.
Then, I put them on a shelf and wait for the mycelium to colonize the bags. Mycelial growth starts within a few days; it's very exciting! Amazingly, the results of even my first experiment in spawn expansion were good, with two notable exceptions. All of the Pioppino and Shiitake bags succumbed to green or black mold. The Pioppinos are a mystery, but the Shiitake bags succumbed because I closed the bags outside the still air box. Mushrooms are fussy! Of the Oyster, Chestnut, and Reishi, only two of the bags were colonized successfully. The three-grain mixes and the three hydration methods all performed similarly, although it looked like some of the recipe hydration bags had excess moisture on the bottom where there was no colonization. The hydration matters. I also noted later that the millet grain seemed to produce larger harvests.
Step 2 - Four Low Investment Methods for Growing Mushrooms
I had Black Oyster, Blue Oyster, Chestnut, and Reishi bags to work with. Now, how to grow mushrooms? Having so many online instructions for just about any mushroom was wonderful! I decided on three growing methods. One was in single-use bags, as on most mushroom-growing farms. The second was in a monotube, and the third was in 5-gallon buckets. Each of these steps involved purchasing additional material, but none of it broke the bank.
To grow mushrooms in bags, you first make sterilized bags of growing substrate. Hardwood pellets are commonly recommended, hydrated at 6 cups of pellets to 5 cups of water. They are sterilized in the pressure cooker at 15 PSI for 2.5 hours. Then, the bags are put into the still air box with the spawn bag, alcohol, mushroom bag clamps, and scissors, and you do the same thing as expanding your grain spawn bags. This works! I tried it with Reishi, making seven bags. The mushrooms started pinning on all the bags a few days later; I sprayed them regularly with a half-gallon garden pump sprayer and got a bounty of cool-looking Reishi! Amazing!
Once you get the hang of making bags in the cooker and keeping things clean in the still-air box, the process is versatile and straightforward. In the summers of 2022 and 2023, we grew almost all of our mushrooms - Oyster, Shiitake, Reishi, and Lion’s Mane - in this way. I found biodegradable bags online to make plastic use more aligned with my ethics. We built our own grow closet to regulate moisture and reduce the need for spraying automatically. It worked pretty well. But, I didn’t like growing mushrooms this way - sterilizing the bags is energy-intensive, and I didn’t find a way to compost the biodegradable bags. Eventually, I pivoted away from the bags again.
Growing Mushrooms in Reusable Monotubs
Next, I tried monotubs. These work for upright-growing mushrooms like Chestnut and King Oyster. The monotub advertises itself as a “care-free self-regulating tool to grow mushrooms.” It is a rectangular growing container with strategically placed holes, usually 22” wide, 15” deep, and 12” tall, like a grow tray and dome that people use to start vegetable seeds or sprouts on steroids. It self-regulates the air and moisture content through the holes covered with tape or discs to let the right amount of air and moisture through. You cover the holes with paper tape during the colonization phase, when the mycelium loves lots of carbon dioxide, and then cover with air-permeable micropore tape during the oxygen-loving fruiting phase. They are pricey - I purchased eight for $265 in 2021.
To inoculate substrate in a monotub, work quickly in a clean space to minimize contamination. In an enormous bowl, hydrate a mix of pellets following an online recipe (there are multiple). You can vary the substrate (I find newspaper pellets work best) and include a nitrogen-rich additive like alfalfa or soy pellets for more and faster fruiting. Spray your monotub with alcohol. Spray your hands with alcohol. Open your bag of spawn with alcohol-sprayed scissors. Spray the monotub again. Put in a layer of the hydrated pellets, a layer of spawn, and then layer pellets, spawn, and pellets. Close the monotub. Cover the holes in the monotub with masking tape or little purchased discs. Done. There is no sterilizing or pasteurizing - fantastic!
It takes 4-6 weeks for the substrate to get nicely colonized with mycelium, which you can tell when the substrate is more or less all-white. At that point, to initiate fruiting, replace the masking tape with permeable micropore tape to start airflow and increase oxygen in the tub while still regulating contamination. So easy, right? That’s why we pay big(ger) bucks for monotubs.
Some sources say to cover the colonized substrate with a layer of coco coir or peat moss once you initiate fruiting. I tried this, but it led to contamination. So did using hardwood pellets and adding lime to raise the Ph. I only had success with un-cased newspaper pellets with one additive. The soy pellet additive led to higher harvests than alfalfa. When it was successful, we harvested pounds of nice-looking King Oyster and Chestnut mushrooms. The downside is that the monotubs are unreliable: green mold appears in about 30 percent of the tubs. Still, they are a simple way to grow Chestnut and King Oyster, so I use them sometimes and may improve my technique over time.
Growing Mushrooms in 5-gallon Buckets
The third method I used for growing mushrooms is the one I love most: reusable 5-gallon buckets. Buckets are suitable for shelf mushrooms that colonize aggressively – oyster mushrooms (except for the upright oysters like King). Buckets are inexpensive and ubiquitous, and you can even use ones you already have that leak. To prepare the bucket, drill ¼” holes in a diamond pattern, each about 4 inches apart and some small drainage holes in the bottom. Clean it well.
I used straw during my experiments in 2021 for the growing substrate and still do today. Following online directions, I filled a pillowcase with 5 gallons of cut straw, put the bag in a large pot, and poured boiling water over it. The next day, I drained the straw and layered it in the prepared 5-gallon buckets with about 1/3 of a grain spawn bag. I put the buckets in a shady place. I passed them many times daily with a spray bottle next to them. When little mushroom pins appeared, I could easily spray the buckets multiple times daily without interrupting my workflow. It worked! I had oyster mushrooms reliably sprouting out of buckets.
I did experiments using newspaper pellets – since they worked so nicely in the monotubs – but this did not work in the buckets. I later found a more straightforward pasteurization method for the straw: soak it for 24 hours in cold water with enough hydrated lime to raise the pH to 13 (Note: use lime for stucco work, not gardening lime).
I hope that these stories of ways we managed to have some success growing mushrooms with few inputs are helpful to those wanting to grow mushrooms on a small, simple scale. Mushrooms can be tricky and have rules different from those of plants and animals, but they are a rewarding and fun food to grow!
Babette Wils (she/her) owns and runs Big Foot Food Forest, a diversified permaculture farm in Montague, MA and can be reached at bigfootfoodforest@gmail.com
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