Growing mushrooms in a bag is one of the easiest ways to cultivate homegrown mushrooms. If you’ve ever tried one of the boxed, mushroom-fruiting kits available online or in specialty stores, then you may already have some experience with growing mushrooms in a bag. That’s because the kits frequently include clear polypropylene bags filled with growing mediums that have been inoculated with mushroom spawn. As a result, by the time a mushroom growing kit makes it to you, that bagged substrate is almost fully colonized by bright white mycelium—the fungal organism which ‘fruits’ by putting out loads of tasty mushrooms. Still, relying on a pre-packaged grow kit isn’t the only way to grow mushrooms at home. With a few supplies and close attention to detail, you can cultivate many different kinds of mushrooms—and a lot more of them—economically in bags. Keep reading to learn more.
Why grow your own edible fungi
High in fiber, protein, vitamins, and minerals, edible mushrooms are good for you—and they’re just plain good! When you grow your own, you have regular access to a plentiful supply of fresh fungi for cooking or freezing or dehydrating for later. You can also grow a lot of mushrooms in a small amount of space. Plus, you can grow them indoors, year-round. Growing mushrooms in a bag is a great alternative to wild foraging, especially if you aren’t a confident wild mushroom hunter.
Why growing mushrooms in a bag is a great way to get started
Commercial farmers who produce mushrooms on a large scale frequently grow their mushrooms in bags which have been designed to help optimize conditions for fungal growth. Many of these bags maintain their integrity after being sterilized in hot water and include other features which have been developed to boost overall success rates and mushroom yields.
Fortunately, the same bags that commercial growers rely on are plentiful and inexpensive enough for hobby mushroom growers to use as well. Sometimes called ‘mushroom grow bags’, ‘mushroom fruiting bags’, or ‘mushroom spawn bags’, they’re lightweight, take up little space, and can expand to accommodate the growth of the tiniest mushroom ‘pins’ into the mature, finished product.
What kind of mushrooms can you grow in a bag?
When it comes to the types of mushrooms, growing mushrooms in a bag affords a ton of flexibility. Some of the edible fungi that will fruit on a sterilized growing medium include reishi and lion’s mane, as well as the oyster mushroom. The Italian or phoenix oyster, pink oysters, golden oysters, and pearl oysters, among others, are all well-suited for growing and fruiting inside grow bags. Just keep in mind that not all mushrooms make good candidates. For instance, because red wine cap mushrooms need contact with soil in order to fruit, they won’t thrive inside a bagged, sterile growing medium.
First, decide on the type of mushroom you’d like to cultivate. Then you can either develop your own mushroom spawn or you can obtain a ready-to-use mushroom spawn product. Think you want to develop your own mushroom spawn? In that case, purchase a syringe pre-filled with mushroom spores—the result of a specialized liquid culture process. Otherwise, most commercial mushroom growers also sell ready-to-use mushroom spawn which you mix with an appropriate substrate. See chart below for supply details:
What type of bag do you need?
As you learn more about mushroom cultivation—and specifically about growing mushrooms in a bag—you may see the terms “mushroom grow bag” and “mushroom spawn bag” used interchangeably, but those terms aren’t exactly the same.
- Mushroom spawn bags are used early in the mushroom-growing process to encourage tiny mushroom spores to develop into a mycelial network—the rootlike fungal organism which eventually produces mushrooms. These specialty bags can withstand high heat and often also include an injection port through which fungal spores are introduced via a sterile needle.
- Mushroom grow bags are used later in the mushroom-growing process and their main purpose is to encourage the mycelium—that rootlike fungal network—to mature and fruit. Technically, you can use many different kinds of containers for mushroom fruiting. However, bags with a Micron filter patch, like these Unicorn 0.5 micron filter mushroom grow bags, confer some important benefits. Chief among them? They allow for fresh air exchange while simultaneously keeping potential contaminants out.
If you’re a beginner, using a mushroom grow bag as a kind of fruiting chamber for pre-supplied grain spawn is a good project to start with. And, once you get the hang of that, you might want to develop your own mushroom spawn using mushroom spawn bags. Find the step-by-step instructions for each of these processes below.
The best substrate for growing mushrooms in a bag
Some of the very best substrates for growing mushrooms in a bag include hardwood sawdust; chopped straw or straw pellets; shredded, woody debris; or a mixture of some of these. Or use a pre-made product like Fast Fruiting Mix. What you choose depends in part on the kind of mushrooms you intend to cultivate.
The substrate you choose feeds the developing mycelium and acts as a kind of scaffolding for it to colonize. When it’s time for the mycelium to fruit, the substrate also provides physical support. In other words? It gives the mushrooms being produced something to hang onto as they mature.
Like healthy soil, a good substrate should be able to hold moisture as well as pockets of air. It should also contain carbon, nitrogen, and other nutrients. Mixing remnants of spent grains like wheat bran or soy hulls can help to provide a boost of these essential nutrients. Here are some good mushroom-substrate combinations to try:
Other materials you’ll need
Aside from 1) mushroom bags 2) mushroom spores (for producing your own mushroom spawn) or grain spawn (for fruiting mushrooms) and 3) the substrate of your choice, you’ll need a few other items for successfully growing mushrooms in a bag.
Recall that if you are just starting out, it’s best to use a mushroom grow bag with filter patch to cultivate mushrooms from pre-supplied mushroom spawn. (Incidentally, when comparing mushroom grow bags, you may notice they feature a range of different filter patch pore size ratings. A bag with a 0.2 micron filter patch will keep many potential contaminants out. And, it also allows for less air exchange than, say, a bag with a 0.5 micron filter patch will.)
If you plan to cultivate mushrooms from pre-supplied mushroom spawn, you’ll need:
- Disposable, surgical-style gloves
- Large pot for heat pasteurization
- Candy thermometer (optional)
- Twist-ties, zip ties, or rubber bands
- Spray bottle filled with distilled water
If, instead, you plan to develop your own mushroom spawn via a spore syringe, you’ll need:
- Disposable, surgical-style gloves
- A pressure cooker or similar device to sterilize your mushroom spawn bags and substrate
- Twist-ties, zip ties, or rubber bands
- Isopropyl alcohol
- Lighter (optional)
- Spray bottle filled with distilled water
Step by step instructions for growing mushrooms in a bag
Best for beginners, here are the basic steps you’ll need to take when growing mushrooms in a bag. (See the next section for step-by-step instructions on cultivating your own mushroom spawn using a spore syringe.)
One more thing: although it is possible to pasteurize your growing medium using cold water, the following hot water method is a bit quicker. And it doesn’t require the addition of vinegar, bleach, lime, or other chemicals.
- Bring large pot of water to a boil and then reduce heat. When water temperature reaches 150 to 160 degrees F (65.5 to 71 degrees C), add the substrate materials of your choice to the hot water. Keep it submerged in the pot and hold in this temperature range for at least one hour.
- Turn off heat and allow water to cool completely.
- Drain off water and, wearing gloves, pick up handfuls of your growing medium and gently squeeze out excess water. (Ideally, your growing medium should be moist, but not sopping wet.)
- Again with clean, gloved hands, open your commercially prepared mushroom spawn package. Remove chunks of the spawn material and carefully mix it with your now-pasteurized substrate.
- Once combined, remove the spawn-and-substrate mix from the pot and carefully pack it into one or more mushroom grow bags. (Leave enough room towards the top that you can easily seal the bag shut.)
- Finally, gather the open bag’s top flaps and secure with a twist-tie, zip tie, or rubber band.
- Place mushroom grow bag in a warm, dark place to allow the mycelium to colonize the new substrate completely. (See ‘Where to keep to keep your mushroom bag’ for details.)
Step by step instructions for cultivating mushroom spawn using a liquid spore syringe
Ready for something more advanced? When producing your own mushroom spawn using a spore-filled syringe, cleanliness is paramount. In fact, your growing medium must be sterile—not simply pasteurized. (Having access to a clean room or a still air box will boost your success.)
- Moisten growing medium and place in mushroom spawn bag(s) designed to withstand high heat. (Follow bag manufacturer’s directions regarding fill levels.) Fold and tuck bag openings so that they remain shut during sterilization process.
- With your bags elevated just above the water in the bottom of your pressure cooker, sterilize at 15 psi for two to two-and-a-half hours. (Your aim is to heat the substrate to just over 250 degrees F or 121 degrees C.)
- Allow spawn bags to cool completely. Before removing bags from the pressure cooker, wash your hands well, put on disposable gloves, and wipe your gloved hands and work surface with isopropyl alcohol.
- The pressure cooking process vacuum-seals the bags. As an added measure, use a heat sealer or isopropyl alcohol-cleaned twist-tie, zip tie, or rubber band to ensure the top of the bag remains closed.
- Wipe the outside of the spawn bag’s injection port with isopropyl alcohol. Open the spore syringe package and follow the manufacturer’s instructions. (Some syringes come with caps and separately packaged sterile needles which you’ll attach once you’re ready to inject.)
- Remove the needle’s protective cap. (Optional: use a lighter to heat sterilize the tip of the needle.) Stick needle halfway through the spawn bag’s injection port and push the plunger to release the spore material. Once you remove the needle, the self-healing injection port closes up.
- Place mushroom spawn bag in a warm, dark place to allow mycelium to form and grow.
Where to keep your mushroom bag
You’ll want to keep your mushroom grow bag in a warm, dark place until mycelial colonization of the entire substrate is complete. The ideal incubating temperature range is between 60 and 75 degrees F (15.5 to 23 degrees C.) Once you see the delicate mycelium wending its way throughout your grow bag, it’s time to induce fruiting. To do this, move your grow bag into a warm area which gets bright, indirect light. High humidity levels are also necessary for mushroom production, so, you’ll want to use scissors to cut at a small “X” on at least one side of your bag. Then, fill a clean spray bottle with distilled water and hit the cut areas with a couple of light sprays once or twice each day.
How long does it take before mushrooms grow?
Growing mushrooms in a bag does require a little patience. If you are developing your own mushroom spawn inside a mushroom spawn bag, this part of the process can take a month or more. If, on the other hand, you mixed ready-to-use spawn with a suitable bulk substrate inside a mushroom grow bag, the process can go much more quickly.
How long it’ll take before the mycelium spreads and begins to fruit depends on multiple factors. These include mushroom variety, the size of your grow bag, ambient storage temperature, and humidity levels. When you see the beginning of “pins”—tiny, new mushrooms—you’ll be harvesting within a week or two. (Pro tip: For the best taste, harvest mushrooms before their rounded caps begin to flatten out with age.)
In the bag!
Follow a few best practices and you’ll discover that growing mushrooms in a bag is not only an intriguing process, but a rewarding one, too. When you grow your own mushrooms at home, you can opt for many different varieties, rather than just settling on the usual standbys available in those small, mushroom-fruiting box kits. You can also grow a much greater quantity of mushrooms very inexpensively.
Remember, if you are new to mushroom cultivation, you might first want to try fruiting mushrooms in a mushroom grow bag using commercially prepared grain or sawdust spawn. Once you’ve had some success with that method, you can take things to the next level. This means producing your own mushroom spawn by injecting the appropriate spore material into specialized mushroom spawn bags containing a sterilized substrate. Remember to match the mushroom types you want to grow with the right growing media. Also be careful to avoid contamination and you’ll end up with multiple flushes of delicious mushrooms to add to omelets, soups, stir fries, and more.
For more information on indoor food growing, check out these articles:
- How to grow oyster mushrooms at home
- Growing wine cap mushrooms: A beginner’s guide
- Learn how to grow pea sprouts and shoots inside your home
- 11 Easy indoor food gardening projects
Did we answer your questions about growing mushrooms in a bag?