Creating an environment to facilitate mushroom growth is vital
So you want to grow mushrooms? Awesome. We’re proud of you and want to help you create and magnify your impact of a local circular economy. To start with, you’ll need a few essential elements to create an environment for your mushrooms to thrive and do what they do best. Once your environment is created, simply follow the steps below and watch nature thrive.
Start with the contents of your growing medium
Spawn is usually sawdust with mushroom mycelium mixed in. Mushroom mycelium is mushroom spore that has started to root. Although it is possible to start with spore, it is tricky and best left to the professionals, so buying spawn from a home gardening supply store or using spawn in a mushroom growing kit is a better option for beginners. A version called plug spawn is specifically designed for use with newly fallen hardwood. All spawn should be used within a short period of time or refrigerated until use.
Substrate is organic matter that serves as food for the spawn. In nature, mushrooms grow naturally in soil, manure, decaying leaves, and downed tress. Substrate can be made from any organic materials containing carbohydrate and nitrogen. Typical substrate materials include cardboard, coffee grounds, wood chips, straw, and compost. Although at Circular Farm, we use organic soybean hulls and sawdust which is a byproduct of the logging industry.
Mushrooms require warm temperatures during the colonization phase, and cooler temperatures once fruiting begins. Commercial operations have rooms with temperature control, but a warm room or heating pad can be used for home mushroom farming.
Some moisture must be present throughout the mushroom production process. Commercial operations have rooms with humidity control, but misting with a spray bottle can be sufficient for growing mushrooms on a small scale.
Some ventilation is required to help dispel the carbon dioxide given off by the growing mycelium. In a home environment, a fan can be used to keep air moving as long as there is no direct draft.
Now you are ready to grow!
From compost to harvest, follow each step below
1. Create Mushroom Substrate
A mushroom substrate is a material that mushroom mycelium can grow. The substrate provides mushrooms with the nutrients, moisture and energy they need to grow and fruit. Using substrate to grow mushrooms is the equivalent of using soil to grow plants. It’s where the mushrooms will get all of their nutrients while growing.
Common materials used are sawdust, wheat germ, soy bean hulls, cotton seed hulls, coffee grounds and cardboard. At Circular Farm our substrate is most often made up of sawdust (oak or pine) and organic soy bean hulls. To prepare the substrate these are mixed with water and pasteurized.
Just like different plants require soil with different properties, different mushrooms prefer different types of substrates. It’s important to match your mushrooms with the correct substrate to have the best chance of success with growing mushrooms. Click here to download our free PDF detailing which substrates that different species prefer.
After substrate is properly mixed and saturated it can be placed in a variety of containers. For commercial growers, it’s most common to pack substrate into large clear plastic bags. Home growers sometimes use mason jars.
2. Pasteurize or sterilize the substrate
Once that is ready, the substrate needs to be sterilized or pasteurized. This kills off any competing mold or bacteria and gives the desired species of mushroom the best chance at taking hold. Pasteurizing and sterilizing can be executed with a variety of techniques, most of which use hot water and steam. Sterilizing, which requires temperatures above boiling is often done using a pressure cooker. Pasteurizing which requires a much lower temperate is often done using a metal barrel modified with a heating element.
3. Innoculate the substrate with mycelium
Although not necessary, inoculating is generally done under sterile conditions to minimize the chances of mold or other fungi species from competing with the mushrooms you’re trying to grow. At Circular Farm we use a laminar flow hood (link to an example?) with a HEPA air filter. A low tech option that home growers use with great success is a still air box (link with example?/ PDF with instructions on how to make?).
During inoculation spawn (any substance that already has mycelium growing on it which you can use to speed up your mushroom growing process) is mixed into the substrate. Although home mushroom growers can create their own spawn, the process is technical, and most increase their success by purchasing spawn from commercial sources.
4. Colonization or Incubation
During this period, the substrate should be stored in a dark space (bright light inhibits colonization) for 2-5 weeks while the spawn colonizes the substrate with mycelium. White patches of mycelium gradually appear, develop, and grow. Mycelium is always white, so any other color indicates that the substrate is contaminated and must be discarded. The temperature should be tailored to the species being grown, typically 60°F and 75°F.
Once the substrate has fully colonized the mycelium will have formed a thick mat and the substrate will be fully white (for most species). At this point it is ready to fruit and produce mushrooms. To initiate growing the substrate is moved to a room with humidity over 90% and temperature at 55°F to 80° F.
When the mushrooms first appear, they are called pins. Over the next few days, the pin grow larger and develops a stem. The top of the pin separates from the stem, and becomes a mushroom cap. The cap gradually opens, becoming a cup and finally a flat. When the cap starts to invert and the edges become wavy, the gills under the cap are mature and ready to dispel spores.
Each flush of mushrooms lasts 3-5 days, after which mushroom growth is dormant for a few days. Harvesting can continue for several weeks or even months if the conditions are ideal. Once all mushroom growth has stopped, the growing medium cannot be reused because all of its nutrients have become food for the mushrooms. It can be composted, and the cycle begins once more.
Mushrooms can be picked at the cap, cup, or flat stage. Harvesting mushrooms is labor intensive, as each must be stabilized around the stalk with one hand while the stalk is gently twisted off of the base. This is done to prevent the mycelium that is still developing mushrooms from being disturbed. Once harvested, mushrooms are used immediately, refrigerated, packaged for distribution, or dried for future use. The mushrooms can also be pickled for longer shelf life.