Introduction

This guide will show you how to prepare straw for mushroom cultivation, maximising production capacity whilst using a portable system anyone can employ. I will be using a 20L bucket (I now use a large tote instead, as shown in the video) of water and a sous vide to create a hot water bath which pasteurised straw at an optimal temperature range.

I believe this method offers an efficient and accessible way to produce straw substrate for mushrooms without the need for large-scale farming equipment, such as barrel drums and propane burners, which are commonly used on commercial mushroom farms but may not be practical for home growers.

We will walk you through preparing straw for growing mushrooms and discussing each step: preparing, hydrating, pasteurising, and inoculating 40 litres of straw, detailing a process that maximises your production capacity. 

This technique is designed to be scalable, allowing you to adjust the volume of straw based on your willingness to put in the effort.  By following these instructions, you can efficiently prepare a larger quantity of straw in less time and with reduced energy consumption right in your own home. 

Requirements

Large Tote or Bucket (get these from a local store amazon is a rip off).

Sous Vide or bucket heater.

Barley Straw.

Pillow Cases.

Choosing The Correct Straw.

Straw serves as an excellent substrate and is known for its rapid colonisation and potential for high yields. Below is a list of straws which can be used for mushroom cultivation:

• Wheat Straw: Wheat straw is one of the most popular choices due to its wide availability and excellent structure for mushroom growth. It's known for its ability to retain moisture and provide a suitable environment for mycelium to thrive.
• Rye Straw: Similar to wheat straw, rye straw is also a great option for mushroom cultivation. It offers a good nutrient profile and is particularly favoured for growing species like oyster mushrooms.
• Oat Straw: Oat straw is another excellent substrate, appreciated for its nutrient content and structure. It's suitable for a variety of mushroom species and is often available in agricultural areas.
• Barley Straw: Barley straw can be used for mushroom cultivation, especially for species that don't require as rich a nutrient environment. It's effective for growing oyster mushrooms and is also commonly available.
• Rice Straw: In regions where rice is a major crop, rice straw serves as a good substrate for mushroom cultivation. It's especially used in the cultivation of specialty mushrooms in Asian countries.
• Sugar Cane Mulch (Bagasse): While not technically a straw, sugar cane mulch, or bagasse, is a byproduct of sugar cane processing and can be an effective substrate for mushroom cultivation due to its high cellulose content.

Chop The Straw.

Begin by cutting or chopping the straw into smaller pieces, typically 2-4 inches long.

This size increases the surface area for mycelium to colonise and makes it easier for the mushroom roots to penetrate and spread throughout the substrate.

Smaller straw pieces ensure more uniform hydration and pasteurisation whilst also allowing you to fit more substrate into each bucket which should increase overall yields.

I tip all of my straw out into a bucket then cut it up using electric garden trimmers which I use only for this purpose. Repeatedly move the straw around ensuring all of the large pieces are cut down to size. Be careful not to put your hand in the bucket while running the trimmer, I have done this inadvertently a few times and cringed after.

Alternatively you could use a grass strimmer which is quicker and messier, however mine is rather dirty so I just take the extra time using a handheld trimmer.

Finally once complete, pack the straw into pillow cases.

Hydrate The Straw.

Soak the chopped straw in water to fully hydrate it. This step is crucial because mushrooms require a moist environment to grow. The soaking period can vary, but typically it ranges from 12 to 24 hours. 

Straw takes time to fully hydrate due to its cellulose and lignin content, which are somewhat hydrophobic, and its structure filled with air pockets. These factors slow down water absorption.

However, there's a handy trick for those on a tight schedule: adding a bit of dish soap to the water used for hydrating straw can speed up the process to 2 hours. This simple addition alters the water's surface tension, enhancing its ability to penetrate the cell walls and air pockets in the straw more quickly.

This has nothing to do with cleaning the straw or getting rid of contamination; it is a step to hydrate straw fast.

To prepare your straw with the dish soap method, fill up a bucket with approximately 10 litres of water and add about 2.5 to 5 teaspoons of dish soap. This ratio aligns with the recommended 1-2 teaspoons of dish soap per gallon (3.8 litres) of water. 

Finally once the allotted time has passed, drain away any excess water into a drain, don't worry about getting rid of all the suds the mycelium can cope with. 

Move onto the next step: pasteurisation.

Pasteurise The Straw.

Pasteurising the straw is essential to kill off any unwanted bacteria, fungi, or pests that could compete with your mushroom mycelium.

You can pasteurise straw by submerging it in hot water at around 140-170°F (60-77°C) for 1 to 2 hours.

This process eliminates contaminants while preserving the beneficial microorganisms that support mushroom growth.

To do this we will be using a 20L bucket and a sous vide, first I fill up my bucket to around half way with hot water from my tap (this speeds up the process and conserves energy as the sous vide does less heating).

Attach the sous vide onto the side of the bucket and turn it on, set the sous vide to run within pasteurisation temperatures, I normally set around 70c for 1 – 1.5 hour/s.

The sous vide will likely complain that there is not enough water in the bucket to start.

Now place the first pillowcase of straw into the water bath and put a dumbbell or weight on top of it to hold thestraw down, the water will rise. Press start and the sous vide will begin.

The sous vide will alert you when it has reached temperature then again when it has completed the allotted heating time.

Wearing a heat resistant rubber glove, remove the pillow case from the water and hold it above the water for a brief minute allowing it to drain, move it over into the second bucket temporarily.

Place the second pillowcase of straw into the bucket, with the weight on again, top up the bucket with hot water as required until the sous vide will run again. Reusing as much of the water as possible, it is already hot meaning the sous vide can start straight away. Set off your second batch.

Now take the bucket with the pasteurised straw and drain away excess water from the bucket, I then place the pillow case over the top of the bucket (balancing on a piece of wood) to then allow water to evaporate off the straw, leaving it here to cool down.

Repeat this process for every pillowcase of straw prepared. Try to recycle as much of the water as possible to avoid wasting energy / water on the process.

After a few hours all of the pillow cases will be pasteurised.

This technique can be scaled using more buckets and a second sous vide, whether that is economical in comparison to using a 55 gallon drum and propane tank is up to you to decide but it is definitely a portable solution which can be packed away at the end of the day, great for the novice or urban farmer.

Inoculate Straw.

Once the straw has cooled to room temperature and is properly drained, it's time to introduce the mushroom spawn. Mix the spawn thoroughly with the straw to ensure even distribution. 

This step is where you inoculate the substrate with the specific type of mushroom you wish to grow.

After mixing, pack the inoculated straw into growing containers, such as bags or buckets, and maintain them in a controlled environment to encourage mycelium growth and mushroom production.

Colonisation & Fruiting.

After the inoculation stage, the real transformation begins, typically taking between 7 to 14 days for the straw substrate to be fully colonised by the mushroom mycelium, depending on your room's climate. 

It's best to keep the substrate in a spot that's consistently at room temperature and out of direct sunlight for optimal growth.

Normally Oyster mushrooms can do this within 2-3 weeks.

If you're managing multiple substrates, spacing them out is crucial to prevent overheating, as the metabolic activity of mycelium generates heat, which can be detrimental in excess.

A sign of contamination is often a bad smell or the appearance of colourful mold. Oyster mushrooms give off a sweet smell like aniseed, contamination smells like feet or rancid. 

Such substrates are best disposed of to avoid any risk of spreading contaminants. 

However, in most cases, you'll see a promising spread of white mycelium covering the substrate.

Once colonisation is achieved, the substrate is exposed to conditions that trigger mushroom fruiting. This typically involves changes in temperature, light exposure, and often increased air exchange or humidity. 

These environmental cues signal the mycelium to produce mushrooms, the fruiting bodies. For Oyster mushrooms this will involve placing the fruiting containers outside in the fresh air and waiting for the mushrooms to produce.

Indoor cultivation might necessitate a shift in conditions to trigger fruiting, like introducing light, adjusting the temperature, and increasing humidity. 

A simple setup can suffice for indoor grows, with regular misting to maintain humidity. A fan for indirect air flow can also simulate natural conditions, promoting healthy growth.

For those looking into more controlled cultivation, exploring different grow chamber setups could be beneficial. 

Each variation caters to different needs and can help maintain the ideal conditions for mushroom growth.

Harvest.

Now's the moment you've been waiting for—harvest time, which arrives roughly 21 to 40 days post-inoculation, varying with the mushroom species you're cultivating.

To harvest, either cut the mushroom cluster at its base using a knife or gently twist it off by hand. From a 10L bucket, you can expect to harvest at least 0.27 kg of mushrooms, though yields can vary based on the mushroom variety.

For oyster mushrooms, the ideal harvest time is just before they release their spores, signalled by the edges of the caps beginning to curl upwards.

 A powdery coating on the mushrooms means they've already dispersed their spores.

While not harmful, regular exposure to high concentrations of oyster mushroom spores can lead to allergic reactions in some individuals, particularly in indoor environments.

Second Flush.

After you’ve harvested your first flush of mushrooms, leave the mushrooms to rest for a week or so, then, soak the buckets in water overnight to prepare a second flush. The mushroom will go dormant for a while but they will produce for up to 6 months depending on amounts of substrate and conditions. I have had buckets freeze over winter then thaw and produce during the thawing stage, however these did not taste as good as the first flush.

This final step marks the culmination of your mushroom cultivation journey, allowing you to reap the rewards of your dedication and care.

Which Mushrooms Grow Best On Straw?

For those new to mushroom cultivation, oyster mushrooms come highly recommended as the ideal choice for growing on straw, thanks to their ease of cultivation.

Every strain of oyster mushroom, from the striking blue and golden hues to the vibrant pink, elegant pearl, robust phoenix, and majestic king oyster varieties, thrives on straw substrates.

Others include:

• Pioppino Mushroom
• Enoki Mushrooms
• Lion's Mane Mushroom
• Shiitake (only straw adapted strains however).