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YouTube Video on it: https://www.youtube.com/watch?v=WlrC1X0Ybnc

A lot of people like to shake or mix their grain spawn when it is 30 to 50% colonized, but 10% makes much more sense.
If the grain bag is colonizing from a single location such as from the injection port or an agar wedge and you let it colonize to 30% – there were a significant amount of fully colonized grain touching other fully colonized grain: they basically do not contribute to the colonization rate.

If you could calculate how many pieces of grain on average, touch a single piece of grain, you could then opt to mix at that ratio, and once you did mix it – you could have a single fully colonized piece of grain touching uncolonized grain. All of these would be contributing to colonizing the rest of the remaining uncolonized grain.

So, how many pieces of grain is touching a single piece of grain?

We’ve done a small experiment where we soaked a single piece of grain in super glue, and placed it on top of other grain, then we buried it with more grain and gave it a gentle tap to emulate mixing the grain.

Our results show that, on average, a single piece of grain is touching 10 or more other pieces of grain. This would suggest that optimal mixing would occur at around 10% assuming you can properly break apart the colonized grain and mix it effectively and evenly through out the uncolonized grain.

there are a few types of contamination: bacterial, mold and yeasts. Understanding why you got a contamination in the first place can help you prevent it in the future.

Bacterial Contamination

appearence:

bacteria will appear as wet spots, but not just any wet spot. It will be milky and runny. Water can form from condensation and it will be clear. Clear condensation isn’t contamination, just an artifact of the bag. Rarely you may also find starch that has been released from the grain

Left: bag is severely contaminated with a bacteria that produces heat resistant endospores. Notice the milky runny liquid that forms crescent moon 🌙 shakes towards the ground: this is bacteria that has settled in the droplets of water that form as it degrades the starches.

Right: sterile grain. Notice it is dryer but what moisture is present is clear and clean.

Above is an image of grain spawn that has colonized as well as accumulated a significant amount of water at the bottom. This water is crystal clear and a good sign the spawn is not contaminated with bacteria.

smell:

Bacteria will smell very off putting: sour is the smell that first comes to mind, or like the

Behavior:

Bacteria will degrade the starch in the grain which holds onto moisture. Mushroom mycelium and other organisms will also do this, but often these fungi are growing additional structures that can hold onto or utilize the water released better. Bacteria however seem to get suspended in the released water and float around with it, so the free water content in the bag will rise as the bacteria takes over and degrades the starches.

Causes

Bad Inoculant:
Bacteria tends to occur either from bad inoculant that has the bacteria present, such as a spore syringe, LC syringe or already bad grain spawn that had bacteria present unbeknownst to the person inoculating the grain.

Improper Sterilization
If it is not due to contaminated inoculant, it is from improper sterilization of the grain itself. Most simple heat treatments will quickly destroy the spores or actively growing forms of molds, fungi, and yeast as well as the actively growing forms of bacteria. However bacterial endospores are suprisingly heat resistant thanks to the stabilizing agent dipicolinic acid which makes up 15% of their structure. . As most bacteria isn’t spread via particles in the air, tends not to

Mistreatment of gas exchange filters
More true with liquid cultures than spawn bags, but a wet filter patch that isn’t hydrophobic can fail and transfer bacteria into your substrate. This is common with homemade filters for liquid cultures, such as when micropore tape or tyvek is used. Unicorn Bags or other filter patch bags for mycological purposes tend to handle direct liquid contact better as they seem to have a filter made from hydrophobic layers of polyproplyene and teflon (PTFE), with very small pore sizes.

Mold

appearance:

dust, fiber like structures, mycelium of different texture or structure, colors of white, green, red, black, brown, gray and tan.

smell:

Unlike a bacteria, or yeast these won’t have nearly as much smell, but they will have some mild differences from an otherwise fully sterilized bag of grain. Likely if the mushroom mycelium is growing, the smell of the mushroom will overpower the scent of most any molds.

Behavior:

Molds spread both by mycelium and by producing more spores rapidly. You may at first see it in a small localized area but if agitated it will likely spread its spores to other places within the bag.

Causes:

Generally mold spores are easily and rapidly killed by heat, such as pasturizaton. So if you are getting a mold contamination, it is either from your inoculation or a failing component of the bag.

If you inoculated a bag of sterilized grain with a syringe, and the mold is growing where the liquid inoculant went; you likely introduced the mold by using a bad inoculant.

If the bag is not inoculated or it’s growing in a completely separate location, it is likely the bag has failed. The three most common ways are as follow:

1. Improperly attached or damaged filter patch. Improperly attached filters are fairly common due to the highly inert material the filter is made of as it doesn’t seal well with the plastic of the bag. This is often easly detected by squeezing the bag when it is inflated with air; if it rapidly loses its’ air with minimal resistance, check the filter. Alternatively there can be manufacting defects or other damages from handling that can add pin holes into the filter patch. A pin hole may seem small to us, but it’s a wide open door for many spores like trichoderma which have can a spore as small as 0.5 micron.

2. Improper seal
An improper seal can form many ways and be deceptive. It may be sealed at too high of heat and result in small holes at the interface of the bag and seal, it may be sealed at too low of a temperature and only look sealed but failed to properly seal the bag; especially if it is a gusseted bag that four layers of plastic in some areas and two layers of plastic in other areas.

This can happen at both the top of the bag, or the bottom.

3. Improper handling of the bag
Believe it or not, after you send a plastic bag made of one of the more rigdid plastics, polyproplyne, through a heat sterilization treatment, it can become somewhat brittle. If the bag folds in just the right way, it can form very sharp corners that are prone to forming tiny holes; either through being exposed to minor abrasion or just repeated bending.

Additionally, the gussets of a bag are prone to failure and will often fail where the fold meets the inner part of the bag. This is often due to some form of impact such as crushing or dropping the bag, but it can also happen in scenarios where you might have a substance hydrating and expanding inside the bag, a brick of coco coir with water added, or certain types of pellets in certain situations can expand and create enough force to compromise the bag.

Yeasts

Yeasts are fungi, but they behave much more like bacteria in this context. They are however easily killed off by heat and are not a sign of improper heat sterilization. They die well before the endospores even begin to die.

Yeasts alone will often look a good amount like bacteria, and will often have bacteria present. They contaminate bags often due to bad inoculate such as a poorly made liquid culture syringe, or improper inoculation procedures. They may present as white speckles but more often than not they present as an alcoholic or apple-esque vinegar type smell if bacteria is present.

Yeast contamination is often less common in my experience than bacterial or fungal as it most often involves using a bad culture than a bag failure and it seems to be over all larger, less mobile and less ressilant than molds or bacteria.

We were inspired to dedicate this article exclusively to mushroom spawn bags, as some of the terms used in mushroom cultivation might appear daunting to novice cultivators. But what exactly are these bags? What lies within their confines? Fasten your seatbelts and get ready for a comprehensive journey through the necessary mushroom-growing components.

What Is a Mushroom Spawn Bag?

Establishing the concept of a spawn bag marks a robust initial stride in comprehending the essential elements of mushroom spawn bags. Referred to alternatively as mushroom grow bags, these items play a crucial role in cultivating substantial quantities of mushrooms within a confined space.

Constructed from sterile plastic materials, these bags are usually equipped with a filter port to facilitate the exchange of pristine air with the mycelium. Certain variants of these growth bags even arrive pre-packed with the untainted growing substrate. Best spawn bags should possess both breathability and the ability to ease a culture injection via the inoculation port.

Check our article on How To Make Sterilized Grain on your own!

What Are the Features of a Mushroom Spawn Bag?

Spawn bags feature a gusseted design, characterized by inward-folding sides. Additionally, these bags are autoclavable, designed to withstand the high pressure and temperatures within an autoclave or sterilizer. This heat resistance is vital as growers introduce spawn bags into pressure cookers. To prevent any issues with melting, the majority of spawn bags are crafted from polypropylene material.

Moreover, spawn bags serve as effective vessels for containing grains during the sterilization process. Positioned at the forefront of the bag is a filter patch, ensuring a steady inflow of fresh air for the culture while effectively warding off contaminants.

What Can Mushroom Spawn Bags Be Used For?

Spawn bags can be used for multiple different things. They can serve as a valuable tool for generating ample quantities of primary-generation grain spawn within preliminary test batches. These bags can also be used as a fruiting chamber, creating a humid dome good for the mushrooms fruiting phase. That’s not all, they can also be recycled and reused!

Spawn

When creating an initial generation of grain spawn many people opt for mason jars which is okay. However, grain spawns will find greater efficiency when used in grow bags. Opting for a grow bag as your spawn vessel offers the advantage of effortless breaking and mixing of the spawn. This will accelerate the colonization process. Additionally, using grow bags for your spawn can also simplify the task of evenly distributing your spawn onto a bulk substrate.

Read our article How To Make Mushroom Grain Spawn on your own!

Fruiting

Don’t forget that these bags are also referred to as the “grow bags,” thus it’s not surprising that they can be used for fruiting your mushrooms. The bag’s upper portion creates a humid shelter, encouraging mushroom fruiting. It’s important to bear in mind that the interior of the bag might not receive a substantial quantity of fresh air.

Hence, if you choose to employ the bag for mushroom fruiting, it’s important to regularly open the bag’s top to ensure proper fresh air exchange. However, exercise caution and refrain from opening the bag until the block within is fully colonized, as premature opening could lead to contamination.

Repurposing

Truth be told, the best practice is to start your mushroom-growing journey with new spawn bags. However, they can be repurposed for other tasks if they have not been cut open for the fruiting phase. They can be used for pasteurizing casing layers or even the substrate.

While spawn bags can be repurposed, keep in mind that their structure will degrade over time and the filter patch will also become ineffective after multiple sterilization cycles. That’s why the best idea is to start with fresh, brand-new bags.

Mushroom Spawn Bag Specifications

When choosing a mushroom spawn bag, there are a couple of things to keep an eye on, and here’s what:

Filter

Generally, the filter is designated with a micron rating, indicating the pore size of the filter itself. These ratings typically range from 0.2 microns to 5 microns. For applications involving fruiting blocks or spawn bags, it’s advisable to opt for a lower micron rating, preferably not exceeding 0.5 microns.

Material

Spawn bags are available in a spectrum of material thicknesses, typically ranging from 2.2 mil to 4.0 mil. Bags of 2.2 mil thickness serve equally well, there is a slightly higher chance of tearing during regular handling but it’s negligible.

Dimensions

Mushroom spawn bags come in various sizes usually 1.5lbs and 3lbs, if they are pre-made. When choosing a ideal bag size you need to take into account things like the dimensions of your sterilization equipment as well as the grow room.

How To Use Mushroom Spawn Bags

When working with spawn bags always be in a sterile and clean environment wearing latex gloves and a breathing mask. You don’t want to mess up your substrate or the mycelium by introducing them to contaminants. Use rubbing alcohol to clean your gloves and equipment working under the laminar flow hood or in a still air box.

• Start by unsealing your spawn bags and filling them with the substrate of your choice.
• Place the loaded bags in a pressure cooker or a sterilizer and begin sterilizing them.
• Allow the bags to naturally cool down to room temperature.
• Make sure that the bags are sealed properly upon removing them from your pressure cooker or sterilizer.
• The next step is to inoculate your bags.
• Using a syringe inject the culture through the self-healing injection port, making sure that the needle is flame sterilized after each use.
• Place the grow bag in a warm location with indirect lighting.
• Regularly monitor the bag to prevent the substrate from drying out. If it does become dry, inject filtered water using a syringe.
• Wait for the bag to get fully colonized.

There are many ways to make sterilized grain, and each method has its pros and cons especially when considering the scale you are going to operate at. We will go over a few methods we find nice for the small grower, intermediate, and larger scale production.

Easiest Method:

Mix the correct amount of water and Sorghum grain together into the bag or jar of your choosing and pressure cooker for 90 minutes once up to temperature. When the 90 minutes is up, let it cool so it loses all of its pressure, is below boiling, and is at a temperature that allows you to handle the bags or jars. Operate the pressure cooker properly, and do not remove the weight until it is no longer under any pressure (once the safety lock drops).

Give the grain a tumble so that the bottom grain which is slightly more moist will mix with the slightly dryer top grain. Doing this while it is still warm to hot will aid in more even distribution of moisture, but ultimately this step is not needed.

Very easy process but be sure you get the water correct: too dry and it will be slow to colonize, too wet and it will have a bit of excess moisture. Both are generally okay but if you hit the extremes of too dry or too wet it can be problematic.

Here are our recommended amounts of water and Sorghum for this process in useful increments for jars and bags:

1 Pint Jars:
125 grams Sorghum
106 grams Water

1 Quart Jars:
250 grams Sorghum
213 grams Water

3 lbs Bags
760 grams Sorghum
650ml of Water

6 lbs Bags
1520 grams of Sorghum
1300 grams of Water

Sterilized Grain: What Grain Is Best?

For the production of mushroom spawn, Sorghum is probably the best choice.

Interested in buying Sorghum? Click here!

Explanation & Reasoning:

The goal of grain spawn is to provide many points of inoculation, in certain circumstances nutrition that compliments the substrate, and colonize rapidly so that you can have a faster turnover.

In order to provide many inoculating points throughout the bulk substrate, you want a smaller grain as that provides, pound-for-pound, more inoculating points. A single pound of millet for instance will provide vastly more surface area and inoculating points than corn.

Not all grain spawn needs to provide nutrition; such as when growing oyster mushrooms on the master mix. The master mix has plenty and adding more spawn won’t be of much benefit beyond faster colonization times. Often times a large 5 lbs bag of master mix only needs a few tablespoons worth of grain spawn to colonize rapidly and perform well.

However, when growing Psilocybe species on CVG or other bulk substrate, the grain spawn provides most of the nutrition. Instead of a few tablespoons worth, the colonized grain spawn is in a ratio of 25% to 50% vs the bulk substrate.
In this scenario, you’d want a grain that is high in protein, starch, and various fats and minerals.

The best grain is small, highly nutritious, cost-effective, and fast to colonize. We think Milo is the best option as it ranks well in all those aspects, but millet, rye, and oats are also great options.

Corn seems to be trending in the grain spawn scene but I don’t understand the logic beyond that it is visually pleasing when colonized.

Don’t overcomplicate it!

People love to get lost in the weeds with making sterilized grain, and there is a lot of misinformation going around. Some of the biggest misunderstandings come from the idea that the presence of excessive moisture, such as from condensation or burst grains leads to contamination. They do not, but they can make contamination more obvious. Excessive moisture and burst grains are annoying for many reasons; it can make it difficult to shake or break apart once colonized, but they do not cause contamination. Contamination comes from improper sterilization, faulty filters, or spawn bags that let contamination in.
People will often see burst grains once they hydrate the grain and worry that it will cause big issues for them. If they have a good bag or jar and properly sterilize it, the grain will colonize just fine.

The same goes for moisture: even if you have perfectly and evenly hydrated grain, moisture can still form: taking it out of the hot sterilizer and into a colder room is going to cause the moisture to condense on the bag to some degree. This is resolved by letting it reach room temperature and tumbling/mixing the grain.

In the realm of mushroom cultivation, grain spawn goes beyond being a mere puzzle piece within the mycelium assembly – it serves as the entire toolkit, if not the workshop itself! It’s the unsung hero working behind the scenes in our mushroom stories, quietly preparing the stage for the spectacular flourishing of fungi that we all adore. Creating grain spawn is a phase of mushroom cultivation that can involve the entire family and is something you must learn if you want to improve your mushroom-growing skills. The procedure for crafting grain spawn remains nearly identical, regardless of the specific mushroom variety you’re aiming to grow.

The primary purpose of grain spawn is to create a controlled environment where your selected mycelium can thrive and proliferate. This growth happens before you allow it to spread within your fruiting (bulk) substrate. For this endeavor, your grain must be completely sterile. The most convenient method for achieving sterility as a home cultivator involves utilizing a high-quality pressure cooker. Let’s start from the beginning and dive headfirst into the world of grain spawn!

What is Grain Spawn Exactly?

Grain spawn stands as a widely adopted medium for cultivating mushrooms. It is created by sterilizing grains like rye, wheat, or millet, followed by the introduction of mushroom spores or mycelium. Over time, the mycelium proliferates and encompasses the grains, forming a network of fungal cells that can subsequently be utilized to inoculate larger substrates such as sawdust, straw, or wood chips.

This method of using grain spawn has gained popularity in mushroom cultivation due to its comparative ease and cost-effectiveness in contrast to alternative techniques. The grains offer a nourishing foundation for mycelium growth and maturation, with the sterilization process acting as a safeguard against contamination from other microorganisms. Grain spawn proves versatile in nurturing a variety of mushroom species.

How To Make Mushroom Grain Spawn

Grain spawn is the cherished offspring of your mushroom venture, acting as a vital middleman between you and the fungi. This process involves the fusion of sterilized grains with mycelium, the vegetative component of a fungus. Together, they forge a captivating symbiotic relationship, with the mycelium embracing the grains, orchestrating colonization through its intricate network of thread-like cells.

Making Mushroom Grain Spawn In Jars

Let’s break down the process into 5 easy to follow steps that will teach you how to make mushroom grain spawn on your own:

Preparation

The grain will act as the prime nutritional resource for your mycelium. Therefore, handpick it and check if everything is alright.

Soak the Grain

Thoroughly cleanse and soak the grains. To soak the grains, simply place them in a bucket or bowl, cover them with water, and allow them to sit for a span of 12 to 24 hours. Be mindful not to exceed the 24-hour mark, as extended soaking might lead to sprouting. Depending on the type of grain utilized, its volume should increase by approximately 2 to 3 times.

Modify the Jar Lids

You’ll need:

• 12 glass mason jars of approximately 500ml (1/2 quart)
  
• Metal lids for the jars
  
• A screwdriver or a large nail, a hammer, and a wooden block
  
• A small quantity of polyfill

These unique lids are designed to enable you to inoculate the sterilized grain without the need for a laminar flow hood. Simply drill two holes on the lid’s top surface, a bigger one in the center while the other smaller one should be closer to the edge. Once the smaller hole is drilled, apply a small amount of high-temperature silicone sealant over it and allow it to dry completely. This hole will be your inoculation port. Next, insert a small amount of polyfill found in the pillows into the bigger hole. This will provide the mycelium with all the necessary breathing room as it navigates its way through the grains.

Cooking

Once the grain is nice and hydrated gently simmer them on the stovetop. This step serves to fully hydrate the grains and render them tender, making them favorable for the fungi culture. Simply simmer the soaked grains on the stove for approximately 15 minutes. It’s crucial not to overcook them, as extended cooking can lead to grain cracking and the development of mushy grain spawn. Once cooked, place the grains in a sink with a drain cover. Over the course of about an hour, the grains will drain naturally. After this, you can proceed to fill your jars.

Sterilization

Once you’ve filled your jars with grain it’s time to sterilize it. Sterilization is a necessary step that will eliminate all undesirable contaminants present in the grains that could potentially outcompete your mushroom culture. Therefore, investing in a good pressure cooker is always a good idea in the world of mushroom cultivation.

After filling the jars, envelop the lids with aluminum foil to prevent water from dripping into them. Subsequently, proceed to pressure sterilize the jars for approximately 90 minutes at 15 psi.

Inoculation

Once the sterilization is finished and the grain cooled down to room temperature, it’s time to inoculate the jars. Clean the jar lid with rubbing alcohol, take your liquid culture syringe, and flame-sterilize the needle every time before you insert it through the silicone seal on the injection port. This process should be done under a laminar flow hood or a glove box for an extra layer of security.

Colonization

Once the jars have been inoculated, place them in a warm, dim, and adequately humid setting for a span of several days. Occasionally monitor their progress to observe mycelium growth and ensure no contamination has emerged.

If the jar is contaminated you will see green or brown discoloration on the spots where mold is growing. This could mean that the jars weren’t sterilized properly or that the culture is compromised. Within 1 to 2 weeks, your jars will be completely colonized. Good job, you just learned how to make mushroom grain spawn!

How to Make Mushroom Grain Spawn In Bags

Making mushroom grain spawn in bags is yet another simple and straightforward method. To start you will need sterilized grains, water, sealing bags, and a pressure cooker. An atmospheric steam sterilizer can also be used if you possess more advanced equipment.

Preparation

Measure out 760 grams (1.6 lbs) of sterilized grains of your choice. In a clean and sterile environment add 650 grams (1.4 lbs) of water to the grains in a suitable sealing bag. You can learn how to make your own sterilized grain here.

Mix and Seal

Thoroughly mix the grains and water in the bag to ensure even moisture distribution. Seal the bag, leaving some room at the top to allow for expansion during sterilization.

Sterilization

Load the sealed bag into a pressure cooker or atmospheric steam sterilizer. Follow the manufacturer’s instructions for sterilization. If you are using a pressure cooker simply sterilize the grain at 15 psi for 90 minutes.

Inoculation

Allow the bag to cool down to room temperature after sterilization. Make sure that the environment you are working in is as clean and sterile as possible. Preferably work under a laminar flow hood. If you are using regular grow bags with an injection site simply take your liquid culture and inject through the site. Make sure to flame sterilize the needle after every injection to minimize the risk of contamination.

Check our article on how to inoculate sterilized grain bags.

Colonization

The colonization process is the same as with the jar method. Place your bags in a warm and dark place away from direct sunlight, and wait for a week or two until your bags are fully colonized.

Time To Use The Grain Spawn

Once the mycelium has fully colonized your grain spawn, it is ready for use in inoculating mushroom substrates like sawdust, straw, or wood chips. Gently shake your jars to break the grain spawn apart.

For the next step it’s necessary to be in a clean and sterile environment, thus working under a laminar flow hood is the best option. You want to introduce your components in the ratio of 1 part grain spawn to 5 parts substrate. Place your mix into the bag, and clean the air pocket at the top. Vigorously shake your inoculated substrate also known as the “Fruiting Block.” Relax and observe the fruits of your hard work as the substrate is getting slowly colonized by the mycelium.

Final Word

As you can see preparing the grain spawn is pretty straightforward. It indeed is a delicate process requiring special attention to hygiene and sterility. However, armed with the appropriate equipment and knowledge, you can successfully create your own grain spawn and cultivate mushrooms in the comfort of your home!

You may have purchased some of our sterilized grain bags we offer, or made some yourself, and now maybe wondering the best means of inoculating sterilized grain so that you can easily grow mushrooms.

We recommend using a spore syringe or liquid culture syringe, but there are many ways to do so and the best method is always dependent on your situation, the scale you operate on and the equipment you have accessible.

Here is a quick description of how to inoculate our bags using two different methods:

How to Inoculate Sterilized Grain Bags With a Syringe

Be it a liquid culture syringe or a spore syringe, all you need to do is wipe the injection port with an alcohol wipe and quickly but carefully inject the sterile needle into the injection port that comes built into our sterilized grain spawn bags. While it is best practices to do this in a clean room or a Still Air Box; it will work far more often than not in a room, a dusty garage, or anywhere else. This is only true for this method. The moment you cut open the bag to add an agar wedge or grain to grain, you absolutely need a Still Air Box at a minimum, or a Laminar Flow Hood.

if you are reusing the syringe, quick and gentle flame sterilization can be helpful but be warned: shoving a glowing red hot needle into the bag will likely damage the self-healing properties of the injection port.

Another thing that can be harmful to the injection port is aggressively moving the needle in multiple directions. Just inject it, squirt it, and pull back. You can always tumble and mix the sterilized grain bag once it has been inoculated.

How to Inoculate With Agar Wedge or Grain to Grain (G2G) Transfer.

In a very clean area, such as a Still Air Box, or in front of a large laminar flowhood, prepare your area by wiping everything down with a disinfecting or sanitizing cloth. This includes the the bag, your hands that are gloved, and the impulse sealer. The impulse sealer is an absolute must; you cannot effectively close the sterilized grain bags otherwise and expect them to be fully protected from mold spores that are suspended in the regular air.

Carefully cut open the bag by a sterile razor or other cutting instrument; we like to use a sliding paper cutter similar to this one as it provides a clean straight cut as close to the top of the bag as desired.

Separate the bag so that it is open, be careful never to put your fingers or any other device inside the sterile grain bag: it isn’t needed and will only increase your risk of contamination. Carefully and cleanly drop your colonized grain spawn or agar wedge into the opening of the sterilized grain bag and then close it, then seal it with the impulse sealer. Working fast but not clumsy is helpful, but if you ensure that you have good sterile technique and a proper clean setup you don’t need to act too fast.

Checkout our video on Low Tech Method to Easily Grow Oyster Mushrooms at Home

Intro:

By far the easiest mushroom to grow at home is the oyster mushroom. It’s popular as a kit, kits are ready to fruit once holes are cut into the bag and placed in a humid location without much airflow, that would otherwise dry it out. Small kits are highly commercialized, and available at walmart, home depot and other similar stores.

Online bigger kits are available and often more productive: We offer our own ready to fruit kits on our shop.

However, if you’d like to grow oyster mushrooms in a more economical way, on a sizable scale, kits can be too expensive unless you have a good cheap bulk source of ready to fruit blocks.

A good option to grow at home is to use wheat straw; it can be used to grow large quantities of oyster mushrooms without any additional supplementation and without any heat pasteurization or clean work. Heat pasteurization can often be difficult to manage and dangerous, and clean room work can be an expensive barrier of entry to new mushroom growers.

Materials Needed To Grow Oyster Mushrooms on Straw

1. Wheat Straw – ideally shredded. Wheat straw is often smaller and easier to shred and manipulate than barley or other straws, but these will work as well. Pre-shredded wheat straw is often available at Tractor Supply, but it is much more expensive than baled straw.

2. Hi Yield Hydrated Lime – this is a pasteurizing agent and is often available at garden supply stores. Other products also called lime will not work if they are not low magnesium calcium hydroxide.

3. Water – This, combined with the hydrated lime, will hydrate and pasteurize the straw, getting it ready to be inoculated with oyster mushroom spawn, or a kit (either before or after the kit has fruited; so long as it looks healthy)

4. Soaking & Draining Container – this is to let the straw hydrate and pasteurize in the hydrated lime solution. as welll as let it drain once fully hydrated which takes approximately 24 hours to soak, and an hour or two to fully drain.

5. Bag or Container for Colonization – This could be 5 gallon buckets with holes drilled in them, large durable plastic bags, or anything else that can hold a few pounds of hydrated straw.

Steps to Grow Oyster Mushrooms on Straw

1. Get shredded wheat straw – this can either be purchased at places like tractor supply or you can buy bales of straw from a farmer and shred them yourself. This can be extremely messy, and isn’t absolutely needed, but shredding the straw significantly increases yields and makes for a better more compact substrate that is less likely to have problems and colonizes faster.

2. Add and compress the shredded wheat straw into your soaking container. Make sure your container has a means to drain or is small enough that you can easily pour off the water without the straw going with it. You will want to let the straw drain until no more water comes off of it, so make sure it has a sieve or a good drain on the bottom. You will also want something that can hold down the straw so it is fully submerged during the soak.

3. Dissolve hydrated lime in water. Add enough of this solution to completely submerge the straw, again, having something to weight down the straw is a good idea to ensure all of the straw gets properly hydrated and pasteurized. Exact amounts of lime is difficult to provide but 330 grams per 50 gallons of water is the generally recommended. More is often better as excess will be poured off with the solution. That said, as long as the solution is strongly basic and remains strongly basic throughout the soaking process it will work well.

4. Mix prepared straw with oyster spawn – oyster spawn can be purchased and used, or even smaller grow kits can be used to inoculate straw by breaking them up. A grow kit that has already produced fruits but still looks healthy is a great option so long as it is free of obvious contamination such as other unwanted molds. The better the spawn is broken into small pieces and evenly distributed through out the straw, the faster it will colonize. More grain spawn is better as it will provide faster colonization and additional nutrients but we’ve had great success with 4% grain spawn by weight.

5. Place straw and spawn mix into the container which it will fruit from. This could be anything from large ziplock bags, trash bags, 5 gallon buckets, or even very large polytube bags that are 5+ feet tall and 1ft in diameter.

Here are pictures of two vastly different sizes of oyster straw bags.

6. Ensure container has holes for fruiting, approximately every 5 inches over it’s surface. This is important or the oyster mushroom to properly colonize, and for the mushrooms to grow, as they will grow out of these holes. Hole size can vary a good amount ranging from a dime sized hole up to a cut the entire length of the bag. The colonizing substrate needs to breath in order to colonize without contamination. A filter patch is often less ideal than cutting holes. The holes provide air exchange as well as a location for the mushrooms to grow out of the substrate for harvesting.

Shredded Straw VS Regular Unshredded Straw

One might be tempted to skip using shredded straw and instead opt to use straw straight from the bale in hopes of reducing labor, machinery to shred the straw and to avoid the messy dusty nightmare that is inexorably linked to shredding straw.
But, shredded straw has significant benefits both on yield and density of substrate which translates to being able to grow more mushrooms in the same amount of space.
This study: Simplified and Lower Cost Methods for Culinary-Medicinal Mushrooms Cultivation shows that shredded straw can have 4 times the yield as unshredded straw; going from approximately 40% to 170% biological efficiency. One 50 lbs bale of straw can yield 85 lbs of fresh oyster mushrooms if it is shredded, but may only yield 20 lbs if it regular not shredded straw.

Images of Oysters Grown on Lime Pasteurized Straw

Have questions about this process? Just ask!

If you’d like to grow oyster or other mushrooms and need any help or further guidance, please reach out to us.

We would be happy to walk you through anything from a small personal grow using straw or help you hone in a larger commercial project that uses master mix or other supplemented sawdust.

You can get direct help by texting 435-237-2998 or emailing Cameron@spawnmagic.com