It is easy to learn to grow mushrooms, each with its own unique set of steps. These steps can be grouped into four key phases: Inoculation, Colonization, Fruiting, and Harvesting.
Mushroom spores do not contain chlorophyll and therefore rely on substances like sawdust, straw or wood chips for nourishment. Blending the spores with these nutrient sources creates a substance called spawn.
Substrate
Mushroom cultivation is a complex endeavor. It’s a multifaceted, interconnected system with strategies for energy, water and waste management. Mushrooms are at the center of a food web that branches out into nutrient cycling, composting, soil regeneration and regenerative agriculture. Mushroom cultivation is also a crucial part of climate adaptation and sustainability.
To grow mushrooms, you need a substrate that the mycelium can colonize. Suitable materials include straw, sawdust, grain, and other organic matter. A mushroom kit that comes with a pre-spawned substrate is often the most convenient option, or you can prepare your own by using a spore print and spore syringe. The syringe needle should be sterilized by holding it over a flame for several seconds.
After you’ve contaminated your substrate with a spore print or spore syringe, spread it over a layer of compost or potting mix 5-8cm deep. Cover it with damp newspaper and wait several weeks until white, thread-like mycelium is visible. A layer of coarse material such as peat moss or ground limestone can be used as casing. This protects the delicate mycelium and allows rhizomorphs (mushroom initials) to form.
When using this method, it’s important to pasteurize the substrate or sterilize it. Otherwise, any microorganisms that survived the pasteurization process could compete with or contaminate your mushroom project.
Another easy way to grow mushrooms is to use logs. This method works well for most gourmet mushrooms such as lion’s mane and oyster mushrooms that can be grown outdoors, but it can take longer to fruit than other methods. It also requires a lot of time, effort and money to prepare logs for the growing environment. It’s best to choose a log location that is protected from the elements.
Inoculation
When a substrate is inoculated, mushroom mycelium takes up residence by secreting digestive enzymes to break down the lignin, cellulose and hemicellulose of the casing. After fully colonizing the substrate, the mycelium then produces small mushroom ‘pins’ that will eventually mature into mushrooms under the right conditions. These growing conditions are controlled by temperature, humidity, CO2 and airflow and should mimic those found in nature. The ability to maintain these conditions is an ‘art form’ that separates beginner growers from expert cultivators.
Initially, the inoculation method of choice is mushroom spawn (the equivalent of plant seeds) or spores. Spores are microscopic in size and provide the blueprint for new growth. For beginners it is recommended that you use spawn as it is easier to work with than spores.
To get started with this growing method, you can purchase a kit that includes a pre-spawned compost or substrate and a tray for inoculation. This is perhaps the easiest and least complicated way to grow mushrooms at home but it still requires a significant level of involvement from the cultivator.
Alternatively, you can prepare the substrate yourself by mixing together vermiculite and brown rice flour before sterilizing the jars that will contain your spawn. This can be done using a pressure cooker or simply by boiling the jars and substrate in a pot. Once the jars are sterilised, you can add your spores or spawn and inoculate them. Once the inoculation is complete, the jars need to be placed in a dark place where they can remain for several weeks to begin colonisation and pinning. When this is complete, the jars can be moved to a bright location for fruiting.
Colonization
Mushrooms are grown from spores (the fungi equivalent of seeds for plants), which fall to the ground and mix with compatible spores, starting the growth of mycelium. The mycelium spreads and grows until it begins to produce tiny bumps called pins, which eventually grow into full-sized mushrooms if the growing conditions are right. The whole process is much like making sourdough bread, but instead of using flour, the mushroom mycelium uses straw or grain as its substrate. Commercial mushroom farmers purchase mushroom spawn from companies that specialize in it.
Growers use a variety of different materials as their substrates, including straw, wood shavings and composted manure. They choose the material that offers the best balance of cost, labor efficiency and nutrient availability. Straw is popular for its economical and logistical benefits, as it’s often available in compressed 40lb bales that are easy to transport and store. Straw also has the advantage of being able to absorb and retain moisture more effectively than most other materials.
To make the straw casing a suitable growth medium, it’s sterilized by mixing in a mixture of peat, vermiculite and wheat bran that has been colonized by mushroom mycelium. This addition is called casing inoculum, or CI. Adding CI decreases cropping cycle time, increases uniformity of mushroom distribution over the bed and improves mushroom cleanliness. It also minimizes greasiness in the compost that can inhibit mushroom emergence, and improves contaminant control by eliminating pathogens, weed molds and nematodes that interfere with harvesting.
When a bed of CI is added to the straw substrate, the mycelium from the CI colonizes the straw casing, fusing with it as it expands. This fuses the two materials, increasing yields by minimizing the amount of time it takes for the gills to reach the surface and begin producing mushrooms.
Fruiting
Mushrooms are not the easiest crop for beginners to grow, but once you master this technique it can be a rewarding hobby. Indoor mushroom growing is more convenient than outdoor cultivation as mushrooms do not require sunlight, but do need a consistent cool climate. Mushrooms can be grown on a variety of substrates including sawdust, straw and wooden logs. This is a very simple method and there is no need to pasteurize or sterilize the substrate, making this an ideal beginner mushroom growing method.
The mushroom growing process begins when spores land on a suitable substrate, germinate and propagate to become “hyphae.” These mycelial cells secrete digestive enzymes internally to break down their substrate and eventually enlarge to produce fruiting bodies or mushrooms. These mushrooms then sporulate to release their spores back into the environment so that the fungal life cycle can repeat itself.
To cultivate mushrooms, you must first acquire or create a spawn culture. Spores are then re-hydrated using sterile water (or distilled) and mixed with a suited material such as straw or sawdust to form what is called a “mushroom spawn.” This spore syringe is then used to inoculate the bulk substrate with the spawn.
Once the substrate is fully colonized it is misted to trigger fruiting. Once this has happened, you are then ready to start harvesting. During the fruiting phase, you can harvest mushrooms every few days until the crop is complete. The terms flush, break and bloom are all names for a series of 3- to 5-day harvest periods that happen throughout the cropping cycle. If you follow the proper protocol, you can maximize your yield by supplementing the compost with nutrients at casing.
Harvesting
Mushroom cultivation is the art and science of harnessing mycelium, the root-like structure of fungi, to promote the growth of mushroom fruiting bodies. Spores land on a suitable substrate and, if they are compatible with the environment, fuse to form dikaryotic mycelium. As the mycelium grows, it secretes digestive enzymes externally to break down its substrate and to stimulate fruiting. When the mushrooms are ready to mature, they “sporulate” and release spores back into the environment to start another cycle.
Fungi are ancient and non-photosynthetic organisms that belong to a different kingdom from plants and animals. Their life cycles have four key phases: Colonization, Inoculation, Initiation and Fruiting.
For the most part, mushroom growers need to create a completely controlled growing environment. This means keeping everything as clean as possible to keep competing life forms (such as bacteria, nematodes, fungi and molds) out of the way. To achieve this, growers need to make sure they wipe surfaces and tools down with isopropyl alcohol and sterilize all containers before using them.
The first step is to prepare the substrate. This can be done in a number of ways, depending on the growing method and the mushroom species. Some growers use low tech methods like straw, cardboard or logs and others opt for high nutrient materials like sawdust, hardwood fuel pellets and a mix of grain and seed hulls to increase metabolite production.
Once the substrate is prepared, a layer of casing (usually a mixture of peat moss and ground limestone) is applied to the surface. This allows for water to retain moisture and acts as a place where rhizomorphs, or thick string-like structures that form mycelium, grow. These rhizomorphs are what eventually develop into mushroom caps. For most species of mushroom, once they have developed rhizomorphs, they begin to fruit.