Growing your own mushrooms at home can be a fun, rewarding experience. The idea may initially seem intimidating, especially if you’re a novice gardener with little to no experience growing mushrooms. But if you take the time to learn the growing process, you may be surprised by how easy and straightforward it actually is.
To grow mushrooms in a grow bag, acquire the spawn of your desired mushroom species, the substrate, and a grow bag. Next, inoculate the mushroom spawn, wait for the mycelium to grow, and trigger the fruiting process. Maintain ideal fruiting conditions and harvest the mushrooms when they’re mature.
The rest of this post will explain how to grow mushrooms in a grow bag in greater detail. Stick around to learn how to produce the perfect mushroom crop.
1. Choose a Mushroom Variety To Grow
We’ll start off simple. The first thing you need to do is to decide which mushroom you’ll be growing. You have many options, each with a different taste, growing time, and care requirements. Some varieties grow in as little as two weeks, while others take months.
Here is a brief overview of some of the more popular varieties of mushrooms commonly grown by hobbyists such as yourself:
- Shiitake. These mushrooms are very popular in east Asian cuisine. If you frequent Chinese or Japanese-style restaurants, you’ve likely already tried them. They’re relatively easy to grow.
- Oyster. Oysters are by far the most commonly grown mushroom type. They’re extremely beginner friendly and can be used in a wide range of recipes.
- Lion’s Mane. Another popular mushroom type, although not commonly grown indoors. They have incredible health benefits and are a great option for anyone into healthy eating.
- Wine Cap. Wine caps are quick-growing mushrooms. You may have an easier time growing them due to their natural resilience.
If you have a particular variety in mind, feel free to go with it. But if you’re just dipping your toes into mushroom growing, I recommend starting with oysters. They’re great all-purpose mushrooms you can’t go wrong with.
2. Purchase or Grow Mushroom Spawn
Next up is sourcing spawns of your preferred mushroom variety. Mushrooms grow from spawns the same way plants grow from saplings.
You can purchase mushroom spawn online inexpensively. It’s worth paying some attention to where you acquire your mushroom spawns. Bad mushroom spawn will set you up for failure, so make sure you buy from a trustworthy source. Also, remember that spawn does not last indefinitely; you’ll have to use it before it expires.
It’s also possible to make your own spawn at home if you have mushroom spores from a previous harvest. Spores are released by mushrooms when they’re fully grown.
Here’s how to grow mushroom spawn using spores:
- Place gelatine in a sealed container, such as a jar or a dish.
- Place mushroom spores in the gelatin using sterile tweezers.
- Poke some holes in the lid to facilitate air exchange.
- After about a week, combine the gelatin with millet seeds; you’ll end up with mushroom spawn.
Tip: If this is your first time growing mushrooms, you might be better off sticking to store-bought spawn because it’s easier to propagate.
3. Acquire Suitable Substrate
With the spawn secured, the next ingredient you’ll need to find is the substrate. The substrate is a wood-based growing medium for mushrooms. It’s like soil for plants.
Certain mushrooms can grow in soil, as they often do in the wild. However, substrate makes for a better, more nutritious growing medium. Garden soil cannot be used as a substitute for wood-based substrate when growing in a grow bag.
As with the mushroom spawn, you need to put some thought into choosing the substrate because this is what your mushrooms will be using as their food source.
Here are some common substrates:
- Wooden chips/Wood shavings. Hardwood is ideal.
- Straw pellets.
- Sawdust.
- Compost.
I recommend sticking to straw pellets since they come pasteurized and ready to use.
Speaking of which, the substrate needs to be clean and contaminant free, so it’s only the mushrooms we plant that grow in it. We don’t want our mushrooms to be contaminated by bacteria or mold; that would make them inedible.
As you become more experienced with mushroom growing, you can mix and match different substrates to get better results. Many expert mushroom growers use blends of straw and sawdust to get the best of both worlds. Some add a secondary substrate, such as vermiculite or coffee grounds.
Straw pellets are best for this recipe, but feel free to use anything wood-based. Believe it or not, mushrooms can even be grown on wet cardboard. This isn’t advisable, though, because cardboard has poor nutritional value, and you won’t get a great yield.
Pasteurizing and Sterilizing Substrate
If you’re using a substrate other than straw or wood pellets, it’s likely yet to be pasteurized. You’ll need to take an extra step to rid the substrate of any microorganisms still inside.
Before we move on, what is the difference between the two processes?
Essentially, pasteurization kills most microorganisms. Sterilization kills all of them.
On paper, sterilization is clearly the better process. However, pasteurized substrate rarely gets contaminated. If it does, it’s usually because of a handling or technique error.
Usually, pasteurization is good enough. It’s unclear whether the extra effort and resources required for sterilization are actually worth it, especially when working on a small scale.
Most substrates can conveniently be pasteurized in a pressure cooker with boiling water and a few hours of wait time. You can read more here.
Here’s a video that shows you 5 ways to pasteurize some common substrates.
4. Get a Proper Grow Bag
You need a proper, high-quality, dedicated grow bag to grow your mushrooms in. Regular old plastic bags won’t work.
Grow bags are specialized polypropylene bags that can withstand high temperatures and pressure. They also have an air filter that allows for ventilation through the bag once it’s sealed up (we’ll go through the sealing process in a minute).
The presence of the air filter is important. It keeps any airborne microorganisms from getting into the grow bag and contaminating the mushrooms.
It’s important for the grow bag to be strong enough to handle pressure because the last thing we want is for our mushroom-growing ecosystem to spill out of the bag due to an untimely tear.
Some growers use tubs, buckets, or other appropriate containers instead of grow bags. While these are all viable options, I recommend sticking to grow bags if you’re a beginner.
They’re just infinitely more convenient and practical. The transparent plastic allows you to get a complete view of everything that’s going on within the bag. The portability of the bag is also a big plus.
Once you’ve grown your first batch of mushrooms, you can explore using the above containers to grow mushrooms on a larger scale. You don’t necessarily need to make the switch, though. Grow bags are perfectly fine for large-scale mushroom farming.
Grow bags come in varying sizes and thicknesses. For a 5-pound (2.27 kg) recipe, a standard 18 by 8-inch (46 x 20 cm) grow bag is perfect. You can also go for a larger grow bag since any excess plastic can be folded up.
Either way, grow bags are relatively inexpensive and readily available online.
5. Start With Inoculation
Okay. We have everything we’ll need – mushroom spawns, suitable substrate, and a grow bag. What now?
We will now mix everything up.
You could do all the mixing in the grow bag itself, but I advise against it. It’s far more practical to prepare the final mixture in a separate container and then transfer it into the grow bag.
This will also allow you to make any adjustments along the way.
Here’s what you need to do:
- Add about 1 kilogram (2.2 pounds) of your substrate to a tub or bucket. Ideally, straw or wood pellets. As we discussed earlier, factory-processed pellets are already pasteurized and safer to use.
- Add approximately four full cups (960 ml) of water. This should be a little over one liter or 36 ounces of water. You can use hot water to rid the substrate of any lurking microorganisms, but that’s optional.
- Wait for half an hour. Allow the substrate to soak up all the water you’ve added.
- Add 180 g or ¾ cup of your mushroom spawns to the mixture. Mix everything up with your hands.
You can add the above ingredients in greater or lesser quantities, but I recommend sticking to the ratios I’ve provided to get the best results. The recipe above is for a standard 5-pound (2.27 kg) mycelium cake.
Adding too much or too little water can hurt your crop yield. A practical way to check whether the newly prepared mycelium cake is well-hydrated is by grabbing some in your fist and squeezing. No more than a few drops of water should drip out.
If a substantial amount of water leaves the substrate, it’s overhydrated. Add some more substrate to the mix to even things out, or wait for the existing one to dry out some more. If no water drips out, the substrate is too dry and needs more water.
Once you’ve given the mixture a thorough mix, you can scoop it up and place it in the grow bag.
You should leave some empty space at the top of the grow bag – the top 30% of the bag should be optimal. This will allow for better air exchange, which promotes mushroom health and crop yield.
You can fill more of the bag if your mycelium cake consists of straw as the primary substrate. Straw forms larger chunks and allows more air into the cake. In any case, don’t fill the bag to the point where the air filter ends up blocked off by the mycelium cake. Mycelium needs fresh air to grow.
Sealing the Grow Bag
Once you’re done putting everything in the grow bag, you’ll need to seal it up. Grow bags typically don’t have a built-in sealing mechanism, so you’ll have to be a little inventive here.
I recommend using a wire or zip tie. Simply twist the bag at its top end and wrap it with wire.
You can purchase an impulse sealer if you plan on upscaling your mushroom-growing hobby to a part-time business. These devices conveniently seal the grow bag using heat and pressure. However, they cost upwards of $100, so they’re only worth getting when using grow bags regularly.
For most hobbyists and beginners, a wire will suffice.
6. Wait for the Mycelium To Colonize
At this point, everything is in place. All that’s left is to wait for the mycelium to grow and colonize the entire substrate.
The mycelium is a network of fungus colonies that feed on the nutrition in the substrate to grow into mushrooms. The more nutritious the substrate, the faster the mycelium will grow.
You’ll first see the mushrooms as one or more white spots. With time, those white spots will increase in number and size.
The time it takes for the white spots to spread over the entire substrate will depend on the type of mushroom you’re growing. For instance, oysters mushroom mycelium takes an average of three weeks to fully colonize your standard five-pound substrate. On the other hand, Shiitake mycelium may take two to three months.
You must wait for colonization to complete before proceeding to the next step. If you rush things, you may end up with a contaminated cake. At the very least, the quality and quantity of your eventual harvest will be compromised.
You should also know that while most mushroom varieties have white mycelium, a few don’t. For example, the Shiitake mushroom’s mycelium starts to show white patches and turns brown once it has colonized most of the available substrate.
Keep the Grow Bag in a Cold and Dark Room To Speed Things Up
Mycelium is a fungus colony; it doesn’t need light to grow. Rather, it prefers being kept in the dark during the colonization phase.
Mycelium grows best at 68-75°F (20-24°C). This is typical room temperature for most people, so keeping the grow bag anywhere around the house is safe, provided it’s out of direct sunlight. The mycelium will likely be fine if the surrounding temperature falls outside the above range by a few degrees.
Still, I would be especially wary of keeping the grow bag in a room that’s too hot. Since grow bags are relatively well-insulated, a build-up of trapped heat could end up cooking the fungal colonies inside out. Not to mention, Mycelium produces its own heat during colonization.
So to be safe, stick with temperatures below 75°F (24°C). The cold isn’t nearly as dangerous. In fact, you can cut a day or two off the time it takes the mycelium to fully colonize the substrate by keeping the grow bag in a cold, dark room.
7. Trigger the Fruiting Process
Mushrooms are fruit produced by fungi when humidity increases to a certain level. This happens naturally in the wild as the seasons come and go. However, the fruiting process doesn’t have to happen naturally when growing mushrooms indoors because that would take longer.
Once colonization is complete, you can initiate the fruiting process through a sudden change in humidity (and airflow). To do that, you need to artificially expose the mycelium to increased humidity levels.
There are a few rules you need to observe when triggering the fruiting process:
Cut a Cross Into The Side of the Grow Bag
Use a pair of sterile scissors to cut a cross-shaped incision into the side of the grow bag. To sterilize the scissors, dip them in alcohol-based disinfectant or bleach diluted to 10% concentration with water.
The incision will expose the now-ready mycelium to the outside world, allowing for increased airflow through the bag. This will also be the opening through which our mushrooms will grow.
Some gardeners recommend making holes at the bottom of the grow bag to allow for drainage and airflow. There’s an entire debate to be had about that.
For now, I don’t recommend you make any holes on incisions other than the one primary cross, especially if you’re sticking to the standard 5-pound (2.27 kg) cake recipe I detailed above.
If you’re working with a larger grow bag containing a 10-pound (4.54 kg) mycelium cake, you should make two X-shaped incisions. Other than that, everything else remains the same.
Remember to make both incisions on the same side of the bag. Otherwise, you won’t be able to lay it on either side; you’ll have to ensure it always stays upright.
Also, do not make the incision until the mycelium has fully colonized the substrate, i.e., it’s all white. If you make the cut too early:
- The mycelium won’t move onto the fruiting stage. It’ll keep colonizing the remaining substrate like normal, except the substrate will dry out faster.
- The uncolonized part of the substrate will be extra vulnerable to contamination by mold and bacteria.
So if you’re unsure, wait another day or two. The primed mycelium will yield a better harvest.
Avoid Opening or Cutting Off the Top of the Grow Bag
Some mushroom growers open or cut off the top of the bag instead of making an incision at the side. This works too, but I don’t recommend it.
Cutting off the top of the bag allows for too much ventilation, which causes the substrate to dry out faster than it should. Mushrooms are 70-90% water by mass, so a lack of water in the substrate will likely lead to a smaller crop.
It’s also not advisable to water the mycelium cake once it is in the mushroom growing phase either, so focusing on water retention is your best bet.
What you should do, instead, is curl up most of the empty space at the top of the grow bag. Remember my earlier advice about leaving space in your grow bag for the colonization phase? That empty pocket of air has served its purpose and now needs to be closed up.
This is to prevent any mushrooms from growing upwards into that empty space. We want all the growth to come out through the cross-shaped incision so we can harvest it quickly.
Mist Regularly With a Spray Bottle
Mycelium fruit in high humidity. A practical way to replicate this fruiting trigger at home is to regularly mist the contents inside the grow bag with a water spray bottle.
Expose some of the mycelium cake by pulling open the flaps created by the X-shaped incision and give the exposed contents a thorough misting. Be careful not to overdo it, though. Mushrooms aren’t meant to be watered. The misting is intended to keep the insides of the grow bag humid.
As for how often to do this, I recommend misting twice a day under normal conditions. If it’s especially hot and dry where you live, you may want to mist more frequently to make up for the quicker water loss.
8. Keep Your Mushrooms in Favorable Fruiting Conditions
Once you’ve triggered the fruiting process, the mycelium will go through a process known as pinning. This is a several-day-long process that involves the mycelium clumping up and forming pins near the incision.
Eventually, these pins will grow and evolve into beautiful mushrooms. This will take some time, so you’ll have to be patient.
If your mycelium cake isn’t producing any pins, the environmental conditions may not be correct. If the pinning halts midway, a lack of humidity is the likely culprit.
Here’s a rundown of the ideal fruiting conditions for mushrooms:
Light
You shouldn’t expose the mushrooms to direct sunlight. Doing that might cause them to shrivel up and die.
Remember, mushrooms don’t need sunlight like regular plants because they’re incapable of photosynthesis. This is also the reason they’re non-green plants. Green plants have a green pigment known as chlorophyll, which absorbs sunlight and uses it to carry out photosynthesis.
Mushrooms don’t use photosynthesis to convert nutrients into energy. They just snack on whatever non-living organic matter they can find in their substrate.
Nevertheless, mushrooms need some light to grow, primarily during pinning. The light can be either sunlight or light from a grow lamp.
Exposing mushrooms to light-intensity UV light as they grow also has a nutritional benefit. It raises their Vitamin-D content considerably, making them an even healthier superfood than they already are.
I recommend placing your grow bag a few feet away from a window sill. That way, it will get enough indirect light to induce some excess Vitamin-D production without harming the mushrooms. This indirect sunlight is also important for a secondary reason; it discourages mold growth.
Humidity
High humidity slows down water loss, which is crucial if you want a bountiful harvest. At this point, you’re hopefully already misting your mushrooms twice daily to keep them hydrated and moisturized.
You may think that misting won’t affect the humidity remarkably, but it does. The water vapor released gets trapped inside the grow bag, raising relative humidity to much higher levels than the outside room.
Still, I recommend raising the humidity level further by running a humidifier. This electronic appliance releases water vapor into the air, steadily raising the humidity level in a room.
And just in case you’re wondering, running a humidifier and misting won’t create too much humidity for your mushrooms. Mushrooms are completely different from most houseplants in how much humidity they need.
For comparison, most houseplants sit well in 40 – 60 % humidity. On the other hand, most mushrooms need a minimum of 70% humidity to stay in good shape. Some mushroom species need a minimum of 85% relative humidity to initiate pinning, while others thrive in humidity as high as 95%.
Airflow
Airflow becomes a more important consideration in this stage since growing mushrooms need oxygen. On the other hand, high carbon dioxide levels in the air hamper growth.
With poor airflow, you’ll get a smaller harvest. Fruition will also take longer; it may not initiate at all if there’s too much CO2 in the air. Not to mention, stale air increases the likelihood of mold growth.
You can tell if your mushrooms are suffering from oxygen deprivation if they start growing longer and thinner to the point where their proportions look unnatural. Healthy mushrooms should be plump and full.
To avoid airflow issues, keep your grow bag in an open space, preferably near a window. You can also keep the grow bag at a more central spot as long as you rest it near an open window for a few minutes every day or two.
Optional: Consider Keeping Your Mushrooms in a Fruiting Chamber
A fruiting chamber is a container built to replicate the perfect conditions required for mushroom growth. They feature high humidity, good airflow, some light exposure, and a contaminant-free environment – essentially, everything a mushroom could ask for.
You don’t have to transfer your mycelium cake to a fruiting chamber to reap the benefits. You can simply place the grow bag (with all the contents still inside) in the fruiting chamber.
Keeping your mushrooms in a fruiting chamber means you won’t have to mist them regularly. The remaining part of the process will be much more autonomous, although you should check on the mushrooms from time to time to see if any problems need attention.
You can find fruiting chambers as commercial products in the market or build your own in a DIY fashion.
9. Cut Off the Mushroom Crop When It’s Ready
After about a week or so of consistent misting, you’ll notice tiny mushrooms. These baby mushrooms will now grow relatively quickly. You can expect them to be fully grown adults within the upcoming weeks and months. Once the mushrooms are fully grown, you’ll harvest the crop.
Now, how do you tell when it’s time to harvest? Timing is important. Harvest too soon, and you miss out on potential crop size. Do it too late, and the mushrooms will release tons of spores.
The free-flying pores are a problem for several reasons.
- They fall onto the mycelium colony and put a hamper on the upcoming mushroom growth. The next crop will be weaker and smaller than it would have been.
- The pores will land on your mushrooms and make them visually unappetizing.
- They pose a health risk to those who suffer from respiratory disease or spore allergies.
The spore-riddled mushrooms are still safe to consume, though. Mushroom spores are edible regardless of whether they’re inside or outside the parent mushroom.
You should harvest your mushrooms once the caps have formed, but the veils remain intact. Allow the caps to open up, but don’t wait for them to flatten out completely.
For most mushrooms, the veil will darken in color slightly right before it tears. That’s your cue to harvest the crop.
Harvesting is pretty simple. All you need to do is grab the crop firmly at its base and twist sharply. The stem will break off and leave behind only a tiny stump – no mushroom wasted. You won’t have to apply much force.
If the crop doesn’t break off easily, you might be trying to harvest it too early. Try again in another few days.
You could also use a sterile knife or a similar cutting instrument. Not necessary, though; you can usually just twist the mushrooms off easily.
10. Enjoy Your Homegrown Mushrooms Fresh
And there you have it! A homegrown batch of fresh mushrooms, ready for consumption or storage.
Mushrooms usually stay fresh for a few days before they go stale or get taken over by mold. You can extend their lifetime by refrigerating or freezing them. Mushrooms will last about a week in the fridge, which is plenty of time to use them in your favorite recipes.
Do not eat mushrooms that have gone bad. As with most other foods past their due date, you can get severe food poisoning by eating stale mushrooms. The only thing you can do with stale or rotten mushrooms is to use them as compost.
Tips for Using Homegrown Mushrooms in Your Favorite Recipes
You can add mushrooms to just about anything. Their versatility in cooking is incredible. From fried foods to vegetable mixes, mushrooms add flavor, texture, and substance.
Mushrooms are one of the most nutritious foods. They’re rich in antioxidants and low in calories, which makes them a super healthy, diet-friendly food option.
If you want the most out of your mushrooms in terms of health and nutrition, I recommend microwaving or grilling them before use.
A recent study by Scientists from the Mushroom Technological Research Center of La Rioja discovered that frying and boiling considerably reduce the antioxidant activity in mushrooms. Grilling and microwaving, on the other hand, retain antioxidants far better.
Why should you care about retaining antioxidants? Well, they help protect your cells from free radicals.
Some chemistry knowledge is required to understand why your cells need protection against free radicals, so I’ll give you the toned-down version of the explanation: Free radicals are highly reactive particles freely moving about your body. They steal electrons from other particles.
Things get problematic when free radicals steal electrons from DNA. This leads to all sorts of problems, including mutations, cancer, and faster aging.
Tips for Freezing Homegrown Mushrooms for Long-Term Storage
Mushrooms can be frozen and kept in the freezer for up to 12 months before they go bad.
Before you store them, clean off any surface dust or dirt using a simple brush.
Don’t store your mushrooms in the freezer immediately after washing them. Doing so will cause them to become mushy, and the surface moisture may attract mold.
Instead, wait for the mushrooms to dry off. Once fully dry, place them in an airtight plastic bag and seal the bag with as little air as possible.
11. Be Ready for a Second Crop
The mycelium colony in your grow bag will likely remain healthy and active after producing its first mushroom crop. After you harvest this first crop, expect to see new growth.
A new batch of mushrooms will grow over the next few weeks.
Most of the time, you can expect to get at least two healthy, full-sized harvests followed by some residual mushroom growth from the above recipe.
Cleaning Up
Once the mushrooms stop growing, the mycelium cake will have been spent. Instead of disposing of it, add it to your compost bin. It makes for a highly nutritious fertilizer that works well for garden or house plants that could use the extra fuel.
As for the grow bag, you cannot reuse it for your next mushroom care preparation because the X-shaped incision on its side will allow contaminant entry. You will have to dispose of it.
Common Mistakes to Avoid When Growing Mushrooms in a Grow Bag
Before I wind up this guide, let me highlight some of the most common mistakes mushroom growers tend to make so you know to avoid them.
Seeing your crop go bad halfway through the growing process would be heartbreaking, so it’s worth looking these over!
Contamination
Throughout this guide, I’ve strongly emphasized the importance of using sterile equipment and sterile growing material for mushroom growing. All of this boils down to keeping your mushrooms free from other microorganisms that will grow and feed on the mushrooms, rendering them inedible.
Contamination is the most common reason why mushroom harvests end up failing. It can happen at any stage of the growing process, so you need to be careful every step of the way.
The leading cause of contamination remains unsterilized substrate. The second leading cause is improper care techniques, such as unnecessarily exposing the mycelium cake to the air. Remember, airborne mold, yeast, bacteria, and similar microorganisms are always floating around us.
Overwatering
Overwatering is a menace to both green plants and mushrooms alike. Too much water in the growing media cuts off access to oxygen, which almost all lifeforms need to survive.
Overwatering has the potential to kill healthy mushrooms and ruin what would otherwise have been a fruitful harvest. As you’ll notice, the only time we water anything in this guide is in the preparation stage, when we wet the dry substrate and add mushroom spawn to create our mycelium cake.
As long as you follow the proportions above, your mycelium cake won’t dry out midway through the process unless you live in an exceptionally hot and dry environment. Even in these conditions, watering is still not recommended; the solution would be to move your grow bag to a cooler, more humid room. If anything, you can be more intense with the misting to keep humidity levels higher.
Heat and Sunlight
Mushrooms need neither. Definitely avoid direct sunlight, and make sure you keep your mushrooms at or below their recommended temperature range.
Mushrooms generate their own heat through metabolism, which worsens any temperature-related problems. Not to mention, grow bags feature a decent degree of insulation, which causes heat to stay trapped inside for longer.
Final Thoughts
To summarize:
- Acquire mushroom spawn, a suitable (and pasteurized) substrate, and a grow bag.
- Prepare the mycelium cake by adding mushroom spawn to a hydrated substrate.
- Add the mycelium cake to the growing bag.
- Place the bag in a cold, dark room and wait for colonization to complete. The mycelium cake will turn white all over.
- Make an incision on the side of the grow bag and start misting the exposed cake twice daily. Mushrooms will grow through the incision.
- Harvest when the mushrooms are fully grown. This will take several weeks.
- In another few weeks, harvest the second crop.
