Mushroom cultivation relies on the basic principle of introducing an organism to a food source. Mushrooms and other fungi digest organic material and draw that nutrition to a reproductive structure that we call a “mushroom,” a fruiting body that’s the reproductive part of a fungus. The fungal mycelium secretes enzymes to break down the nutritious matter it encounters.
To cultivate mushrooms at home, you can start with a mushroom, mushroom spores, or spawn (a culture of the fungus, typically on grain or sawdust). Spawn can be purchased, and it’s a great option for beginners. And for the advanced mycophile, there are multiple ways to make spawn at home, starting with a piece of mushroom or with spores.
Mushroom Cultivation on Household Compost
You may have a compost pile at home, where grass clippings, fall leaves, and garden scraps go. Why not employ mushrooms to help break it down? Agaricus species will work if the matter is well-composted already. If it’s not broken down, try wine cap mushrooms or blewit mushrooms. You can start with pieces from freshly collected mushrooms (the trimmed ends of stalks) or with spawn.
To prepare the site, just rake back a layer of compost. Add your spawn, and cover it with compost.
Water the soil to help keep moisture levels up and to help speed up the spawn run. The mushrooms will fruit in late fall, or even winter in warmer climates. If one type of mushroom fails to work, don’t give up; just try another species to find the one that works best on your compost.
Growing Blewits on Composted Leaves
Blewits grow naturally on leaf litter on the forest floor. They’re typically a fall mushroom, fruiting late in the year. Starting a bed of blewits in leaf litter is an easy way to get great edible mushrooms after much of the mushroom season is over. They can appear by the hundreds at times, and they’re a favorite of experienced mushroom hunters. If you have a pile of leaves from last year at your disposal, you have a great substrate for blewit cultivation.
For fall inoculation, start with trimmed stalk ends from freshly collected mushrooms; just place them in your leaf pile. At other times of the year, spawn can be purchased and works well. For summer inoculation, find an area in the shade to start the bed.
Rake away debris to expose the soil surface. A heavy watering at this point will give you a nice source of humidity as the mycelium develops. Using leaf litter from last fall, cover the prepared area to a thickness of about 2 inches. Blewits are aggressive, and sterilizing the substrate isn’t necessary. Any leaves will work, but if you’re going to use pine needles, mix them with the leaves of other trees. Add blewit spawn to the leaf litter. Stir it around, breaking up all the chunks. Cover the spawn layer with another layer of leaves, and then give the bed a good watering. Don’t oversoak it and drown the mycelium, but give it enough water for the leaves to stick together.
You can cover the bed with a sheet of clear or white plastic for a couple of months to help get the colony going, but it’s not absolutely necessary. Black plastic can cause the bed to overheat and potentially kill the mycelium, so avoid it. If you do cover the bed with plastic, peel it back and water about once per week. Blewits appear in large troops in fall, and they grow quickly.
Inoculation of Straw
To inoculate straw, you can use one of two basic methods. The first is used when the straw is isolated in its own environment, and the second involves direct soil contact. Oyster mushrooms and blewits don’t require soil contact, so they grow well in containers or plastic sleeves. But some other mushrooms, such as wine caps, require contact with soil to grow. These mushrooms are typically grown outdoors or in a greenhouse.
Growing Oysters and Blewits on Straw in a Container
Using straw for a substrate on which to grow mushrooms can be fast and effective. Colonization is far quicker with straw than it is with other substrates, and it may produce mushrooms as soon as two weeks after inoculation. It’s a cost-effective way to obtain high yields from limited material. The mushrooms will be cleaner than they would be if they were grown on wood, and they’ll require little preparation after harvest.
Many different types of containers work for the cultivation of oyster mushrooms on straw. The purpose of the container is to hold the straw together while offering openings for oxygen to reach the mycelium. Plastic bags work well for this, but any container can be used to grow oyster mushrooms. You can drill into a plastic pail to allow oxygen to reach the sides of the straw pack and encourage mushrooms to begin fruiting. You can pierce a flower pot in the same fashion, creating a decorative oyster-growing container to hang in or near a garden. You can find bales of straw at most garden or farm supply stores.
To prepare the straw for the cultivation of mushrooms, run it through a leaf shredder to increase its surface area and make it easier to handle. This isn’t a necessary step, but it does make packing the containers a bit easier. It also gives the mycelium an advantage by putting more straw in contact with the spawn. In lieu of a leaf shredder, home growers also use weed whackers or push mowers to shred up straw nicely. Plan ahead: If you also intend to cultivate from straw in contact with soil, shred in that location, and it will make for less cleanup.
Whole or chopped straw must be pasteurized to eliminate contaminating microbes. Most hobbyists will have great success with cold pasteurization. Soak the straw in water for 3 to 5 days. Drain the straw for 24 hours to prevent excessive water in the containers. Once the straw is drained, you’ll be ready to inoculate.
Wash your hands thoroughly before handling the spawn and straw substrate. Any spores or bacteria present on your hands could colonize the straw and outrun the oyster mushroom mycelium. Use trimmed pieces of oyster mushrooms or purchased spawn. Trimmed pieces of store-bought oyster mushrooms will work if they’re fresh. Purchased spawn will likely work much better, as you can use lots of it (the higher the inoculation rate, the faster the mycelium will colonize the substrate, and the faster you’ll see mushroom production). Plus, it comes sterile from the factory. If you’re using spawn, sprinkle it in an even layer over the top of the straw. After each application of spawn, roll and fold the straw by sliding your hands underneath it, palms up. Then, lift your hands up and turn your palms down, folding the straw over on itself. When the spawn has all been mixed in evenly, the prepared substrate will be ready for containers.
Sterile plastic sleeves are the recommended containers for oyster production, but, as previously mentioned, any container with holes drilled into it can work. If you use a container instead of a sterile plastic sleeve, wash and dry it before you pierce holes into it.
Start with a thin layer of prepared substrate on the bottom of the container. Pack it in, making sure to fill any corners of the container. The idea is to eliminate all air from the inside of the vessel to promote fruiting at the locations you created. If you’re using plastic sleeves, pack both corners of each sleeve first, as tightly as possible. It can be difficult to get a solid mass at the bottom of the bags. Adding small amounts to start with will make this easier. Fill the container as much as possible.
You’ll need to add a lid to close a solid container, or use a layer of aluminum foil and a rubber band as a clamp. The mushrooms will fruit from the holes you pierced when you prepared the container. If you’re using plastic sleeves, close them with cable ties, and tighten them as much as possible. Use a knife to slice fruiting holes into the plastic sleeve. Make an opening about every 6 inches around all sides of the sleeve. These are the escape holes for the mushrooms to fruit.
Over the following few weeks, the oyster mushroom mycelium will incubate. It requires a humid environment and at least some light. For the more colorful strains of oyster mushrooms, more light should be allowed. This will improve the color of the mature mushrooms. Humidity and temperature affect incubation times. A room that’s 85 percent humidity is ideal for production.
The colonization will take anywhere from 2 to 10 weeks. You’ll start to see the straw change color in just a couple of weeks. This is the mycelium colonizing the straw. Young mushrooms will start to form at the fruiting vents soon after complete colonization. These “pins” will develop quickly into mature mushrooms.
Oyster pins will only take a day or two to grow to maturity, and they should be harvested immediately. If left on the container, they’ll rapidly begin to rot. This can put the container at risk for contamination and affect future fruitings.
Oysters are easy to harvest. Simply grab the mushroom by the base and twist it off. There will be straw debris connected to the base; it can be trimmed with a knife or picked off with your fingers. The entire oyster mushroom is tender and edible, so don’t trim off more than necessary.
Growing Wine Caps on Straw on the Ground
Wine caps (Stropharia rugosoannulata) are a great mushroom to grow on the ground, with little chance for failure. They’re a large, flavorful mushroom that will tolerate the high temperatures of summer. The process is relatively simple and can produce mushrooms quickly.
Place a wine cap bed in an area that’s shaded for at least most of the day. Prolonged periods of direct sunlight will overheat or dry the bed and damage the fungus, possibly killing it. Water the ground thoroughly before you start. Remove any green matter so all the debris in the bed is dead. A great method is to simply rake a compost pile to the side, exposing the bare ground beneath it, and start your bed there. Leaving twigs and dead leaves is acceptable, as the wine cap mycelium will colonize that as well, and use it for additional nutrition. Never substitute hay for straw. Hay composts far too quickly, and you won’t get any mushroom production.
Because you’re not going to be packing the straw into small containers, it’s not necessary to shred it. Start by soaking it for 3 to 5 days. This can be done in a large container. Fill the container with water so all the straw is covered. Then, add weight to the straw to ensure all of it is submerged. Remove the straw from its container and let the excess water drain off for a few minutes. It’s not necessary to drain the straw completely.
Shake the straw onto the bed so it’s rather fluffy when it piles up. The first layer should end up being about 4 inches thick and as even as possible. Break apart any large clumps to ensure the most exposed surface area possible.
The next step is to add an even layer of spawn to the first layer of straw. Grain or sawdust spawn can be purchased for this purpose. Spread it as evenly as possible, and break up any clumps that fall into the straw. The more finely the sawdust is sprinkled, the more contact between spawn and substrate will occur. This will ensure a fast spawn run and thorough colonization.
The bed will then be ready for the second layer of straw. Remove another batch of straw from the water and let it drain for a few minutes. Shake the straw as you did in the first layer, and spread it evenly over the entire bed to a depth of about 2 inches. Remember to break up any large clumps of straw to keep the substrate as even as possible. This will ensure a cosmetically appealing bed and keep the spawn run efficient through the entire bed. Use the back of a rake to tamp the layers together. This will increase contact between the spawn and the straw and provide a better rate of colonization. Any spawn that doesn’t contact straw will eventually die, and this will slow down colonization. You may choose to repeat with another layer of spawn and a final layer of straw on top. When inoculation is complete, give the bed a good watering.
After the last dressing of water is applied, the bed will be ready for its cover. Place a clear plastic sheet cut to size over the entire bed, and weigh it down around the edges. This will prevent evaporation of the water you applied in the last step. Don’t use black plastic, as it may overheat and kill the fungus within the bubble. Leave this plastic in place for four weeks.
Inspect the bed at least once per week to ensure it’s staying wet. If the bed seems to be drying out, add 2 gallons of water. Adding too much may drown the mycelium. You should see droplets of water on the inside of the plastic bubble.
At the end of the four-week incubation period, remove the plastic sheet and water the bed. Peel back the straw in different places around the bed to check for spawn run, which will be a white, stringy mat with a sweet smell. Replace the straw as close as you can to where it was. If there’s no spawn run, or if it appears to be weak, replace the plastic for another week or two, and continue the watering regimen. The mushrooms should start fruiting 3 to 5 weeks after you remove the plastic sheet. The first mushrooms will appear around the outer edge of the bed, but there will be others hiding in the deeper straw. They can be difficult to find. Look for irregular bulges in the straw.
Once you master growing a few mushrooms, you can expand your operation for more variety, or work on perfecting your setup for more fruits with less work. The mycological world is yours to explore.
Britt Bunyard and Tavis Lynch are mycologists with decades of experience studying, foraging, and growing mushrooms. Bunyard is the founder, publisher, and editor-in-chief of the journal Fungi, and Lynch is the author of Mushroom Cultivation. Excerpted from The Beginner’s Guide to Mushrooms (Quarry Books).
Additional Resources
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