Mushroom Grow Bags: Mycelium to Mushroom, The Complete Guide to Growin

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What are Spawn Bags?

Spawn bags are bags specifically designed for growing many types of mushrooms. They are self contained growing environments for mushroom enthusiasts and commercial growers to grow their own crops of delicious and nutritious fungi.

Grow bags are made of a breathable, microporous material that allows for gas exchange while maintaining the desired humidity inside the bag. They are pre-filled with a pasteurized or sterilized growing medium, such as a mix of grains, sawdust or other substrates that provide the nutrients for the mycelium to grow. Grain, being a high nutrient medium, is particularly effective for rapid mycelial expansion, though it requires careful handling to avoid contamination.

There are two types of grow bags:

All-in-One Grow Bags: These bags have a fully prepared growing medium, often a mix of different substrates like straw, sawdust and supplemented grains. All-in-one bags are inoculated with mushroom spawn and once fully colonized can be opened and put in fruiting conditions to produce mushrooms.
Grain Spawn Bags: These bags are filled with a grain based substrate, such as rye, wheat or millet. Grain spawn bags are inoculated with mushroom spawn or liquid culture and once fully colonized the colonized grain can be used as a spawn to inoculate larger bulk substrates or fruiting containers.

Growing with grow bags has many benefits:

Convenience: Grow bags are ready to use, self contained growing environment, no need for extensive setup or special equipment.
Reduced Contamination Risk: The closed nature of the grow bags minimizes the risk of contamination from airborne spores or other external sources, a more controlled environment for mushroom growth.
Space Efficient: Grow bags have a small footprint, perfect for small scale or urban mushroom growing where space is limited.
Easy to Handle: Grow bags are lightweight and portable, easy to transport and manage the growing process.
Versatile: Many mushroom species can be grown in grow bags, from oyster and shiitake to more exotic or medicinal species.
Cost Effective: Grow bags are cheap and can be reused multiple times, great for both hobbyists and commercial growers.

Grow bags have made mushroom growing accessible and convenient for many, for individuals and small scale operations.

How to Choose the Right Mushroom Grow Bag

When choosing the right mushroom grow bag there are several things to consider to ensure a successful grow. The type of mushroom you are growing, the growing medium and your budget are all key factors that will determine the right grow bag for you.

Considerations

Type of Mushroom: Different mushroom species grow in different environments and require different substrates. Oyster mushrooms prefer high nitrogen substrate like straw or sawdust, shiitake mushrooms grow best on supplemented sawdust or wood logs. Knowing the specific requirements of the mushroom you want to grow is crucial in choosing the right grow bag.

Growing Medium: Mushroom grow bags can be filled with many different growing media, grains (rye, wheat, millet), sawdust, straw or a mix of these substrates. Wheat bran can be mixed with other substrates to enhance mycelial growth. The growing medium you choose should provide the nutrients for the mushroom you are growing and maintain the right moisture and air exchange.

Bag Size and Volume: Grow bags come in different sizes from small for home growers to large commercial bags. The size and volume of the bag you choose should be based on how much mushrooms you want to produce and the space you have for growing.

Popular Options for Different Mushroom Species

Oyster Mushrooms: Straw based grow bags or sawdust based bags.
Shiitake Mushrooms: Supplemented sawdust bags or wood log bags.
Button Mushrooms: Compost based grow bags or manure based substrates.
Lion's Mane Mushrooms: Supplemented sawdust bags or grain based bags.

Premium vs Budget Grow Bags

Premium mushroom grow bags may cost more but they offer better quality and features that will help your grow. These bags are made from higher quality materials that provide better air exchange, moisture retention and resistance to contamination.

Budget friendly grow bags are more affordable but lack some of the features of premium bags. But with proper care and attention to the grow process, budget friendly bags can still produce a good mushroom harvest.

In the end, the choice between premium and budget friendly grow bags will depend on your experience level, budget and the scale of your mushroom cultivation.

Preparing the Substrate

Preparing the substrate is a crucial step in mushroom cultivation, as it provides the foundation for mushroom mycelium to grow and thrive. Common substrates for mushroom cultivation include straw, wood chips, and grain bags, each offering unique benefits depending on the mushroom species being grown.

To prepare the substrate, it must be pasteurized or sterilized to eliminate any contaminants or pests that could hinder mycelial growth. This process involves heating the substrate to a high temperature, typically around 160°F (71°C), for several hours. Pasteurization can be done using a variety of methods, such as steaming, boiling, or using a pressure cooker.

Once the substrate is pasteurized, it is essential to let it cool down to room temperature before inoculating it with mushroom spores or plug spawn. This step ensures that the substrate remains free from contaminants and provides a suitable environment for the mushroom mycelium to colonize. By carefully preparing the substrate, you create an optimal growing medium that supports healthy and vigorous mycelial growth, setting the stage for a successful mushroom harvest.

Preparing the Spawn Bag

Inoculation Process

Inoculation is a critical step in mushroom growing with spawn bags. It involves introducing the mushroom spawn or liquid culture into the sterile substrate inside the bag. Here’s how it’s done:

Prepare the Spawn Bag: Make sure the spawn bag is sealed and intact. Wipe down the self healing injection port with an alcohol wipe to sterilize the area.
Load the Syringe: Using a sterile technique, draw the desired amount of mushroom spawn or liquid culture into a syringe. For grain spawn bags 3-5 cc of spawn per pound of grain is typical.
Inject the Spawn: Carefully insert the syringe needle through the self healing injection port and inject the spawn or liquid culture into the bag. Don’t introduce any contaminants during this process.
Seal the Injection Port: After inoculation cover the injection port with micropore tape or a self healing injection port cover to prevent contamination.
Shake or Mix the Bag: Gently shake or massage the bag to distribute the spawn evenly throughout the substrate. This step is important for even colonization.

Incubation Requirements

Proper incubation conditions are important for successful colonization of the spawn bag. The requirements may vary depending on the mushroom species but generally:

Temperature: Most mushroom species grow between 70°F to 80°F (21°C to 27°C). Consistent temperature is key to good growth.
Humidity: Mushroom spawn bags need a humid environment to prevent the substrate from drying out. Keeping the substrate in a plastic bag helps maintain moisture levels during incubation, which is crucial for mycelial growth.
Air Exchange: While the spawn bag should be sealed to prevent contamination, some air exchange is needed for gas exchange and colonization. This can be done through micropore filters or self healing injection ports.
Light: Most mushroom species prefer low light or dark during colonization phase. Direct light can cause premature fruiting or other issues.

Signs of Mushroom Mycelium Colonization

As the mushroom spawn colonizes the substrate inside the bag you’ll see several visual signs of growth. The spawn run is a critical phase in the colonization process, where the mycelium spreads throughout the substrate:

Mycelium Growth: The most obvious sign of colonization is the white, fuzzy mycelium growing throughout the substrate. This mycelium will spread and consolidate inside the bag.
Substrate Consolidation: As the mycelium colonizes the substrate it will start to bind the grains or substrate together forming a solid, consolidated mass inside the bag.
Metabolite Odor: Many mushroom species produce a distinct earthy smell as they colonize the substrate. This metabolite odor is a good sign the colonization is on track.
Time Frame: The time for full colonization can vary depending on the mushroom species, spawn rate and incubation conditions. It can take anywhere from 10 days to several weeks for full colonization.

By watching for these signs and providing the right incubation conditions you’ll have a successful colonization and be ready for the fruiting stage.

Mycelium Development

Mycelium development is the process by which mushroom mycelium grows and colonizes the substrate, transforming it into a nutrient-rich environment for mushroom production. This phase is critical for the success of your mushroom growing efforts, as it lays the groundwork for the eventual fruiting of mushrooms.

During mycelium development, the mycelium will break down the substrate and produce enzymes and other compounds that support mushroom growth. This process typically takes several days to several weeks, depending on the mushroom species and environmental conditions. To promote rapid mycelial expansion, it is essential to maintain a consistent temperature, typically between 55-60°F (13-15°C), and humidity levels between 70-90%.

Fresh air exchange is also crucial during this phase, as it helps to prevent the buildup of carbon dioxide and ensures the mycelium receives the oxygen it needs for healthy growth. Adequate moisture is another key factor, as it keeps the substrate from drying out and supports mycelial activity. By providing the right conditions for mycelium development, you create a robust foundation for your mushrooms to grow, leading to a bountiful and healthy harvest.

All-in-One Mushroom Grow Bags

All-in-one mushroom grow bags are a easy and self contained way to grow mushrooms. These bags have a pre-mixed and sterilized growing substrate, usually a combination of hardwood fuel pellets, soybean hulls and vermiculite. The substrate is pre-inoculated with live mushroom spawn, no need to inoculate separately.

Benefits of All-in-One Grow Bags:

Easy: All-in-one bags require minimal prep, the substrate is pre-mixed and inoculated, saves time and effort.
Beginner friendly: These bags are great for mushroom growing beginners, they simplify the process and reduce the risk of contamination.
Consistent results: The pre-mixed and sterilized substrate ensures consistent growing conditions, higher chance of harvest.
Variety: All-in-one bags available for many mushroom varieties, oyster, shiitake, lion’s mane and more.

Drawbacks of All-in-One Grow Bags:

Limited flexibility: The pre-mixed substrate can’t be easily modified, not ideal for experienced growers who want to experiment with different substrates.
More expensive: All-in-one bags are more expensive than buying separate components for traditional mushroom growing methods.
Single use: Most all-in-one bags are designed for one flush of mushrooms and can’t be reused for subsequent grows.

All-in-One Grow Bags:

Follow Instructions: Read and follow the manufacturer’s instructions for best results.
Keep Conditions Right: Keep the recommended temperature, humidity and fresh air exchange for the mushroom variety you’re growing.
Watch for Contamination: Check the bags regularly for signs of contamination, discoloration, bad smell or unwanted mold growth.
Harvest Promptly: Harvest mushrooms as soon as they’re mature to prevent over maturity and contamination.
Dispose Properly: After the last flush, dispose the spent bags properly to prevent contamination spread.

All-in-one mushroom grow bags are easy and beginner friendly but experienced growers may prefer more customizable traditional methods.

Grain Spawn Bags for Mushroom Growing

Grain spawn bags are a part of the mushroom growing process, they are the initial vessel for inoculating and colonizing the grain substrate with mushroom mycelium. These bags are filled with a specific type of grain, rye, wheat or millet which provides the nutrients for the mushroom mycelium to grow.

Grains for Spawn

Rye grain is one of the most used grains for mushroom spawn because of its high nutritional content and can support heavy mycelial growth. The shelf life of different grains used for spawn can vary, with some grains like rye and wheat offering better longevity compared to others. Wheat grain is another popular choice because it’s available and affordable. Millet, sorghum and even brown rice can also be used depending on the mushroom variety and personal preference.

Preparing and Inoculating Grain Spawn Bags

Preparing grain spawn bags involve:

Hydrating the Grain: The dry grain is soaked in water for a specific time to absorb moisture and become fully hydrated.
Sterilization: The hydrated grain is then loaded into the spawn bags which are made of polypropylene or other breathable materials. The bags are then sterilized using a pressure cooker or autoclave to kill any potential contaminants or competing microorganisms.
Inoculation: Once the sterilized grain bags have cooled, they are inoculated with the mushroom spawn or liquid culture. This can be done by injecting the spawn through the self-healing injection port or by opening the bag under sterile conditions.
Incubation: The inoculated grain spawn bags are then placed in a controlled environment with the right temperature and humidity to promote mycelial growth. During this incubation period, the mycelium will colonize the grain substrate, a white fluffy growth will cover the entire bag.

Preparing and inoculating grain spawn bags is a critical part of the mushroom growing process as it sets the stage for a successful and abundant mushroom harvest. By following the right techniques and using quality grain and spawn, growers can increase the chances of a healthy and productive mushroom crop.

Casing and Fruiting Mushrooms from Spawn Bags

Casing is an important step in the mushroom growing process when using spawn bags. It involves adding a layer of moistened substrate, usually a mix of peat moss, vermiculite and calcium carbonate over the fully colonized spawn bag. This casing layer serves:

Moisture Control: The casing regulates the humidity required for mushroom fruiting. As the mycelium colonizes the casing layer it will draw moisture from it and create the right microclimate for primordia (mushroom pin heads) formation.
Microbial Balance: The casing layer introduces a diverse population of beneficial microorganisms that will prevent the growth of unwanted molds and bacteria that could contaminate the mushroom crop.
Structural Support: The casing provides a structure for the mushrooms to grow and emerge through, for proper stem and cap formation.

To make the casing layer, mix the casing ingredients (peat moss, vermiculite and calcium carbonate) in the right ratio and pasteurize the mixture to kill any potential contaminants. Once cooled, the casing can be applied gently over the colonized spawn bag, a smooth and even layer about 1-2 inches thick.

After casing, the next step is to induce fruiting by introducing specific environmental triggers such as lowering the temperature, increasing fresh air exchange and adjusting light. This “shocking” process will tell the mycelium it’s time to produce mushrooms.

In a week or two you should see the first primordia forming in the casing layer. As the mushrooms grow, make sure to maintain the right humidity and provide fresh air exchange to prevent CO2 buildup.

Once the mushrooms are the desired size you can start harvesting by twisting and pulling them from the base. Be careful not to damage the surrounding mushrooms or the casing layer during the harvesting process.

With the right casing and fruiting techniques your mushroom grow bags can produce multiple flushes of mushrooms over several weeks or months, it’s a great and sustainable way to grow many mushroom species.

Troubleshooting

Contamination

Contamination is the biggest threat to a successful mushroom growing with spawn bags. Contaminants like mold, bacteria and other fungi can quickly overgrow and ruin your mushroom crop. Make sure to follow sterile procedures when handling spawn bags to prevent contamination.

Some signs of contamination are discoloration, bad odors and fuzzy mold growth. If you see any of these, discard the contaminated bags immediately to prevent spreading to other bags or your growing area.

To prevent contamination, work in a clean and sanitized environment and use sterile techniques when inoculating or handling spawn bags. Pasteurize or sterilize all grains, substrates and equipment before use. Don’t open spawn bags in areas with high air circulation or potential contaminants.

Moisture and Humidity Issues

Proper moisture and humidity is crucial for mushroom growing in spawn bags. Too much moisture can cause bacterial contamination and too little can stunt growth and prevent fruiting.

If your spawn bags look too dry you can add a small amount of sterile water or humidity by misting the bags or placing them in a humid environment. Be careful not to overdo it as excess moisture can cause other problems.

On the other hand if your bags look too wet or soggy you may need to increase air exchange or use a desiccant to absorb excess moisture. Proper air flow and gas exchange is crucial to prevent stagnant and too humid conditions in the bags.

Mushroom Grow Bags: Mycelium to Mushroom, The Complete Guide to Growing

What are Spawn Bags?