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

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What Are Mushroom Growing Bags?

Mushroom growing bags—also called mushroom cultivation bags or mushroom grow bags—are special, heat-resistant plastic containers. They are made to help you grow mushrooms well. They are usually made from polypropylene or polyethylene. These bags are built to handle high heat when you sterilize them with pressure cooking or autoclaving. What makes them different is that they have tiny filter patches. These patches let air in and out cleanly, and they keep bad germs out. Our mushroom grow bags are designed with high-quality filters for maximum airflow and contamination resistance, giving you the best chance at strong, healthy harvests.

Mushroom growing bags come in different sizes, shapes, and filter setups. What you need will depend on how you grow. Many have a gusseted shape. This means they expand to hold more and stand up better when filled. Most mushroom growing bags are made to hold 0.5 kg to 2 kg. But bags for commercial use can be even bigger.

There are two types of grow bags:

1. 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.

2. 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.

Why Use Mushroom Grow Bags?

Mushroom growing bags have many benefits over other growing containers like glass jars, monotubs, or plastic bins. If you grow mushrooms for fun or run a small farm, their benefits make growing much easier.

Cost-Effectiveness

Compared to hard plastic containers or jars, mushroom grow bags are very cheap. You can buy them in bulk for much less per bag. This makes them cheap for any size of grower. For example, 100 standard gusseted bags may cost less than $50. Buying the same amount in glass jars could easily cost more than $200.

Faster Colonization

Because they have a wider surface and good air exchange through filter patches, grow bags help mycelium grow faster. A 2016 study (Andrade, 2016) found that mushroom grow bags sped up colonization times by 20–30% compared to glass jars. Faster growth not only makes your growing cycle shorter. It also means less time for things to get contaminated.

Lower Contamination Risk

One of the best things about these bags is their very good filter patches. These filters, from 0.2 to 5.0 microns, let sterile air in and stop dangerous molds, bacteria, or outside spores from getting inside. This greatly lowers the need for always watching or stepping in, which is a big help for new growers.

Space Efficiency

They are flexible and can be flattened, which makes bags very good for small spaces. When sealed and growing mycelium, you can stack them side-by-side or hang them from shelves. This lets you use them vertically, which makes grow bags perfect for city growers, those growing in closets, or anyone with little space.

Scalable Operations

If you grow five bags in your basement or 500 bags in a warehouse, mushroom grow bags can be used for growing more and more. Their same size and sterile nature make them perfect for organized ways of growing used in commercial farming.

Types of Mushroom Growing Bags: How to Choose the Right Bag

Different growing stages and mushroom types need different kinds of grow bags. Here's a closer look at what you can find:

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:

1. Easy: All-in-one bags require minimal prep, the substrate is pre-mixed and inoculated, saves time and effort.

2. Beginner friendly: These bags are great for mushroom growing beginners, they simplify the process and reduce the risk of contamination.

3. Consistent results: The pre-mixed and sterilized substrate ensures consistent growing conditions, higher chance of harvest.

4. Variety: All-in-one bags available for many mushroom varieties, oyster, shiitake, lion’s mane and more.

How to Use All-in-One Grow Bags:

1. Follow Instructions: Read and follow the manufacturer’s instructions for best results.

2. Keep Conditions Right: Keep the recommended temperature, humidity and fresh air exchange for the mushroom variety you’re growing.

3. Watch for Contamination: Check the bags regularly for signs of contamination, discoloration, bad smell or unwanted mold growth.

4. Harvest Promptly: Harvest mushrooms as soon as they’re mature to prevent over maturity and contamination.

5. 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.

Unicorn-Style Bags

These high-quality bags are a top choice when growing mushrooms for sale. They are known for their strength and always getting good results. Both dedicated home growers and businesses often choose them. Original Unicorn Bags come in many models like 3T and 14A. Each has different filter types and thicknesses made for specific uses.

Injection Port Bags

These bags have a self-healing rubber or silicone port. This lets you inject sterile liquid culture into the growing mix without opening the bag. This is very helpful when you use spore syringes or mycelium cultures you bought. And it greatly lowers the chance of contamination.

Gusseted vs. Flat Bags

• Gusseted Bags expand at the sides and bottom. They can stand upright on shelves and hold more growing mix.
• Flat Bags do not stand up on their own. They are better for the first steps of adding mycelium or for small projects.

Grain Spawn Bags

These are smaller, thicker bags. You use them to grow mycelium on sterilized grains like rye, millet, or sorghum. Their main job is to grow strong, healthy mycelium. This mycelium will then be used to add mycelium to larger fruiting mixes.

Preparing and Inoculating Grain Spawn Bags

Preparing grain spawn bags involve:

1. Hydrating the Grain: The dry grain is soaked in water for a specific time to absorb moisture and become fully hydrated.

2. 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.

3. 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.

4. 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:

1. 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.

2. 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.

3. 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.

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:

1. 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.

2. 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.

3. 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.

4. Seal the Injection Port: After inoculation cover the injection port with micropore tape or a self healing injection port cover to prevent contamination.

5. 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:

1. Temperature: Most mushroom species grow between 70°F to 80°F (21°C to 27°C). Consistent temperature is key to good growth.

2. 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.

3. 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.

4. Light: Most mushroom species prefer low light or dark during colonization phase. Direct light can cause premature fruiting or other issues.

Fruiting Substrate Bags

These are larger than spawn bags. You use them when the mushrooms are growing fruits. These bags often hold sawdust, straw, or growing mixes with added nutrients like soy hulls.

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.

How to Use Mushroom Grow Bags Correctly

Follow these best ways to do things to get the best results:

1. Substrate Preparation
   Sterilize your substrate well using a pressure cooker or autoclave. Common growing mixes include sawdust, hardwood with added nutrients, straw, or grain with mycelium already growing.

2. Bag Filling
   Let the sterilized growing mix cool. Then fill the bags using clean tools to stop contamination.

3. Sealing the Bags
   Seal with an impulse sealer or twist ties. Make sure to leave the filter patch clear.

4. Inoculation
   Use clean methods in a still-air box or under a laminar flow hood. If you use a liquid culture, inject it through the port if there is one.

5. Colonization Phase
   Store bags in a dark, humid space between 65–75°F (18–24°C). And check often to see if mycelium is growing.

6. Fruiting Phase
   Once fully covered with mycelium, move the bags to a fruiting chamber. This chamber should have the right humidity (80–90%), indirect light, and good airflow.

Can You Reuse Mushroom Grow Bags?

Technically, yes, but it’s usually not a good idea because of the risk of contamination. Once a grow bag has been used and punctured or folded, it is hard to sterilize it to get rid of all germs. According to a 2017 study by Chang & Miles, if you reuse mushroom growing bags without stronger sterilization methods like gamma irradiation, the contamination rate can go up by as much as 50%.

When Can You Reuse?

If your bag is still whole and shows no signs of contamination:

• Wash it well in soapy water and rinse it well.
• Sterilize it using a pressure cooker (this is best) or an industrial autoclave.

Heavy-duty bags may last for one more cycle. But they are rarely reliable after that.

Ways to Repurpose Spent Bags

Growers who care about the environment often use old bags for other things:

• You can compost the used growing mix for garden beds.
• You can reuse parts of the bag as clear covers for young plants.
• You can use leftover plastic for arts and crafts or small greenhouse projects.

Always check with your local waste place to see if PP #5 plastic can be recycled.

What to Look for When Choosing Mushroom Grow Bags

Not all mushroom grow bags are the same. Here are important things to look for:

Filter Patch Size

Choose the right size for the stage:

• 0.2 Micron – For the fruiting stage, for better control over contamination.
• 0.5 Micron – Works with grain spawn.
• 5.0 Micron – Best when you need a lot of air moving fast.

Plastic Composition & Thickness

• Material: Polypropylene (best) or Polyethylene.
• Thickness: At least 2.0–3.0 mils for enough strength.

Sealing Method Compatibility

Depending on your operation:

• Impulse Sealer: Gives an airtight seal that cannot be easily opened.
• Twist Ties: Quick and reusable for temporary use.
• Clip Seals: Look like zip ties. They are good if you need to seal many bags.

Volume Capacity

• Small (0.5–1.0 kg) – Good for small test batches or special kinds of mushrooms.
• Medium (1.5–2.0 kg) – Standard size for typical indoor grows.
• Large (3.0+ kg) – For big industrial uses or big starter bags for big harvests.

Mushroom Growing Bags vs. Other Cultivation Containers

Here’s how mushroom grow bags compare to other setups:

Mushroom grow bags offer good efficiency, can be used for growing more, and help control contamination. This makes them a good choice for most growers.

Alternatives to Using Mushroom Growing Bags

Can’t or don’t want to use bags? Try these:

• Mason Jars: Great for small PF Tek grows.
• Plastic Storage Tubs (Monotubs): Best for large fruiting projects.
• Buckets with Holes: Cheap for oyster grows.
• Reusable Hard Plastic Containers: Better for the environment. But you might need to add ways to move air in and out.
• Hydroponic Racks: Very good for growing vertically. But they are better for experienced growers.

Each method has good and bad points. But few are as easy to use or as cheap as mushroom grow bags.

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.

Other Issues and Solutions

Besides contamination and moisture problems there are other issues that can occur when growing mushrooms with spawn bags:

• Slow colonization: If the spawn is taking too long to colonize the substrate it could be due to wrong temperatures, lack of air exchange or a weak or contaminated spawn. Check your conditions and consider using a more aggressive spawn strain.

• No pinning/fruiting: If the fully colonized substrate doesn’t produce mushroom pins or fruits it may be due to wrong fruiting conditions (temperature, humidity, light etc.), no casing layer or other environmental factors. Adjust your fruiting parameters accordingly.

• Mushroom mutations or deformities: While not a problem per se some mutations or deformities in mushroom shape or size can occur due to genetic factors, environmental conditions or contaminants. As long as the mushrooms look healthy they should be edible.

Monitoring your spawn bags and being aware of potential issues is key to successful mushroom growing. If you have problems or questions don’t hesitate to ask experienced growers or consult mushroom growing resources.

Are Mushroom Growing Bags the Best Option?

Yes—especially for small, indoor, and new mushroom growers. Mushroom grow bags offer a good mix of low cost, good efficiency, and the ability to grow more. They are faster and cleaner than jars. They also give you more control than buckets, and they take up less space than monotubs. Whether you are just trying it out or growing for sale, good quality mushroom growing bags will give you the best chance to do well.

💡 Pro Tip: For highly-rated grow bags that are good and not too costly, check out Zombie Mushrooms’ chosen selection. They are made for all kinds of growers.

Citations

• Andrade, R. (2016). Comparative study of mycelial colonization in different containers for indoor mushroom cultivation. Journal of Agricultural Technology.
• Chang, S. T., & Miles, P. G. (2017). Mushrooms: Cultivation, Nutritional Value, Medicinal Effect, and Environmental Impact. CRC Press.
• Lee, M. H., Choi, J. W., & Kim, H. G. (2019). Efficiency of sterile cultivation methods for gourmet mushrooms in filter-equipped grow bags. Mycobiology, 47(2), 159–165. https://doi.org/10.1080/12298093.2019.1605650
• USDA National Agricultural Statistics Service. (2020). Mushrooms Annual Summary. https://www.nass.usda.gov/Publications/Todays_Reports/reports/mush0920.pdf