Have you ever wanted to grow your own mushrooms at home? I’m not talking about the “magic” mushrooms. I’m talking about the delicious gourmet mushrooms that can cost you upwards of $15 to $20 a pound.
Well, Here, I am going to try to show you how to grow your own Oyster mushrooms at home. This is a very easy set of instructions that starts with pasteurizing your straw (substrate), and then inoculating your straw with the mycelium of your choice. After that, all your mushrooms need is a bit of care, but YOU will need to be patient and let the mushrooms do what they do best, to grow, and fruit for you.
Now let’s get started.
How to Pasteurize Straw for Growing Mushrooms
Learning how to pasteurize straw is necessary if you want to start growing certain types of mushrooms on your own. Although it may seem daunting at first, this article will take you through the ins and outs of straw pasteurization.
Cereal straws (not hay) such as oat or wheat are used as a base, or substrate, upon which mycelium grows. Mycelium is a thread-like collection of cells that represent the vegetative growth of a fungus. Much like you need an apple tree to produce apples, you need healthy mycelia to produce mushrooms.
Pasteurization is simply the process by which amounts of microscopic competitors in a substrate are reduced. This gives the mycelium an advantage over harmful organisms, allowing it to take over the substrate and eventually produce mushrooms.
So how does one prepare straw? There are a variety of different methods, with hot water being the most common. There are other ways as well, such as using cold, steam, or certain chemicals.
Let’s go over straw pasteurization for growing mushrooms in greater detail.
To Pasteurize or To Sterilize? That Is the Question…..
When learning how to grow mushrooms, you may come across the term ‘sterilization’. Yet for substrates such as straw, you want to pasteurize them, not sterilize.
To pasteurize means to reduce the amount of harmful competing organisms. When the process is over, there is still some micro-activity going on in the substrate, usually in the form of beneficial bacteria.
To sterilize means to remove all living organisms in a substrate. When you’re done, there should be nothing left alive. This process is usually done with chemicals or very high heat and pressure, such as with the autoclave on the right.
Sterilizing simply leaves the straw too susceptible to contaminants. Without the beneficial bacteria to guard against foreign competitors, the substrate becomes a free for all for anything to grow.
Having beneficial microorganisms left over allows you to inoculate the straw without using special sterile procedures. Thus you can do it outside in the open air without a flow hood or fancy equipment.
Think of it like having a house sitter when you’re away. Sterilizing is like leaving the doors unlocked with no one home. Pasteurizing is like leaving a friend at your house. Someone may still break in, but it’s less likely.
Straw Pasteurization in hot water
This is by far my favorite method of pasteurization. It does not require any chemicals, or additives which could take residence in your straw, leaving it as organic as the straw you started with.
Most articles insist that before using this technique, you should first cut your straw into 1 to 3 inch segments. I find it easier to first pasteurize the straw and then cut it into smaller pieces. Doing so has some advantages and also some disadvantages. For example, the advantage will be the softer straw which will be kinder to your hands and your scissors. The disadvantage is that you could contaminate your straw after it has already been pasteurized. In order to balance both sides, and especially if I know my mycelium is a slow grower type, I sometimes will boil the straw per instructions below, let it cool, cut the straw down to size, then boil it again for half as long as instructions requires.
Pasteurization occurs between 160 and 180 degrees Fahrenheit. Anything more than that and you risk killing good bacteria and allowing the bad to bloom.
With a hot water bath, you pasteurize by soaking the straw in 160-degree water for an hour. You can do whatever you want to accomplish this, but here are common methods for larger and smaller amounts of straw:
Small Scale:
- Fill the container of your choice half way with water. Make sure it has at least twice as much volume as the volume of Straw you are going to use. Bring to a boil, and then back the heat off by about 1/3. Check the temperature with a meat thermometer.
- Keep adjusting the heat and checking the temperature until it stays within a stable 160 – 170 range. This may take some time but be patient. It is an important step in this process.
- Put your straw into a nylon mesh bag. You can get one online or in most stores, usually near the laundry supplies. Only use as much straw as can be submerged in the water.
- Put the straw bag in the pot with something heavy on it so the whole thing is covered in water. Let the whole thing sit for an hour, keeping an eye on the water level and temperature.
- After an hour, remove the bag and put it in a strainer. Be careful as the water and straw will be very hot. You may want to wear rubber gloves.
- Allow the bag to drain and cool to room temperature or at least below 90 Degrees Fahrenheit. Use immediately.
Larger Scale:
- This is the same basic principle, only with a larger pot and heat source. Start by filling a clean, food-grade container, such as a 55 gallon metal drum, half full with water.
- Heat the water in the container until it stays constant at around 160 degrees Fahrenheit. The heat source can be a gas burner or something else, just make sure it’s safe. Use a long thermometer to measure the temperature. Do not lean on the container or try to reach too far to measure temperature.
- Put the straw in a laundry or wire mesh basket. Submerge it in the hot water for one hour, keeping an eye on the water level and temperature.
- After an hour, remove the straw and lay it on a clean table or plastic tarp to cool and drain. Make sure the straw has cooled to below 90 degrees and use immediately.
Note: The large-scale hot water bath requires extra caution. You’ll be working with a lot of hot water and a heat source. Make sure everything is safe, secure, and sturdy. Do not take any chances. Keep in mind that wet straw coming out of the container is hot and very heavy. Depending on the amount you use, lifting it out of your container may be a two-person job. If you think you might need help, then ask a friend to help out. In return you can give him some mushrooms, or a mushroom straw log to grow.
Alternatives to Preparing Straw
Are the above methods too much work? Does the idea of babysitting a water bath of straw make you yawn?
If you don’t want to pasteurize straw you can still grow mushrooms. Here are some ways around it:
- Use a different substrate – Straw is just one way of growing mushrooms. You may find using logs or wood chips more gratifying.
- Buy a mushroom grow kit – If you just want to grow a few mushrooms without a lot of hassle and preparation, a mushroom growing kit is for you. These convenient blocks of sterilized and enriched sawdust require little maintenance beyond some water and patience.
- Buy it – It may sound like cheating, but you can buy bags of pasteurized straw over the Internet. They’re more expensive, but you’ll save time and effort. A good option if you’re just starting out or only want to do a few mushroom experiments. Definitely not cost-effective for the large-scale grower.
Whatever method you use, pasteurized straw makes for a great mushroom substrate. With the right attitude, it’s an easy and fun part of growing mushrooms.
How to inoculate your substrate
I suggest you start this part before or while you are pasteurizing your straw (substrate).
To do this step, you first need to prepare your tools and your area.
Preparations
Fist you have to make sure you have all your tools and ingredients ready. To do this, you’ll need:
-gloves
-Rubbing alcohol
-paper towels
-Clear, or slightly opaque food grade bags (to make at least a 6” diameter log)
-Black or thick light filtering bags (large enough to cover the clear bags when filled without restricting air flow)
-Tie strings or Zip Ties that can handle 10-15 pounds of weight hanging from them.
-Mycelium (leave it in its original sealed container)
-A fork (long enough to reach into the mycelium container and pull out everything.
-Last but not least, pasteurized, cooled straw.
Once you have all the items listed above, you’re ready to start.
First, you need to choose the proper work area. Choosing the right work area is very important. I suggest, as a guide line, you choose a place that is clean, and away from traffic, drafts, or pets. It should be well lit, or have plenty of light available if and when needed. You have worked hard to make sure your substrate is pasteurized, so you want to make sure it remains that way until the mycelium has had a chance to colonize it. Having the right lighting is also important to prevent mishaps.
What you need to do now is to clean your work area. First, put on your gloves. Next, pour some alcohol on your gloves and rub them together as if you were washing your hands under a faucet, making sure all surfaces of the gloves are wet and rubbed together.
Now, take a couple of paper towels and pour a generous amount of rubbing alcohol on them (Remember that dry paper towel will not sanitize your area). Use the soaked paper towel and wipe down the entire work surfaces and about a foot (30 cm) beyond. If you are working near the walls, make sure you wipe down about two feet above your work surface. Let the area dry for a couple of minutes.
While your work surfaces are drying, pour some rubbing alcohol on to a new paper towel and start wiping down all the tools you will be using (scissors, knives, etc). Make sure you wipe them down very well, leaving no un-sanitized surfaces or hidden areas.
Now you are ready to bring out your straw and mycelium. I prefer using mycelium grown on wild bird seed. The wild bird seeds are much easier t work with and will quickly mix into the straw.
When ready, take one of the clear bags, open and fold the edges outward until you have about 6 inches (15 CM) left to the bottom of the bag. Take a handful of straw and spread it at the bottom of the bag, creating an even layer covering the entire bottom of the bag. Tap the straw down to remove excess air from the straw.
Once you have tapped down the straw, take the fork and scoop up some mycelium from its container. The rule of thumb is the weight of your mycelium media should be between 10-20% of the weight of the straw. You can adjust these numbers as you wish. Obviously, the more mycelium you add, the faster the log will be occupied and ready to bloom. But be careful not to overcrowd the mycelium in the straw.
Once you have spread the first scoop of mycelium on your layer of the straw, grab another handful of straw and spread it on top of the mycelium seeds. Tap down the straw to remove excess air. Repeat these steps till you have filled the bag about 6-8 inches from the top.
Now grab your twisty tie or any other type of tie you have chosen. Hold the bag closed with one hand while pressing the straw down with the other hand. Do this till most of the air has escaped from the top of the bag. Do not press too hard or you might run the chance of tearing the bag.
Now close the bag, wrapping your ties around the neck. Once you’re done, grab your clean knife or blade and make about 6-8 holes around the log, making sure each hole is at least 2” away from the closest hole.
You’re almost done. All you have left to do is to put the log in the darker bags and setting them aside, for a few weeks, in a dark, out of the way, cool (not cold) place. Make sure you don’t tie the second bag closed. The log needs to stay in darkness, but at the same time, it needs air circulation. During this stage your mushroom log will be exhaling Carbon Dioxide and if it can’t get rid of it, it will definitely kill the mycelium.
Check your log at least once a week and make sure it is in the dark, gets air circulation, and it is not dried out. If you see signs of drying out, spray it with clean drinking water. I don’t recommend straight tap water because of the amount of Chlorine, Chloramine, Sulfur, and other chemicals you might be introducing to your log.
Within a few days of inoculation, you should see signs of mycelium growth. Keep the log in the same conditions until the log is completely covered with mycelium. If you don’t see mycelium growth after a week or two, something has gone wrong. Check your log for signs of mold or other contaminants. If your log smells like anything but fresh forest air after a rain, some part of the process was not done properly.
Once your mycelium has colonized the entire log, and there are no dark or colorful patches on your log, you are ready for the next stage. Move your log out of the darker bag and set it on a plate in a well lit, very low draft area where it can get at least 6 hours of indirect every day. Make sure your log doesn’t see direct sunlight at all. If this happens, you could kill the mycelium very quickly. Now grab a clean, sterilized knife or blade, and increase the size of the holes in your bag. Do this by creating a cross cut (like a plus sign) at each hole. Do not cut the openings to more than one inch (2.5 Cm) in each direction.
After about two to three weeks at this stage, you should start seeing small growth, known as pin heads, growing out of your mushroom. From here on, the growth is usually very rapid. Within a few days you will have full sized mushrooms, ready to be picked and enjoyed.
Start picking those babies off your bags and enjoy! You’ll probably get more than one flush from a bag, so after it’s done water them thoroughly and let them rest in darkness for a week or so. Then your logs are ready for round 2. Continue this “cycling” until the bag stops producing mushrooms or mold has set in. Once that happens, take your mushroom log to the compost pile, or bury it in a cool moist place. Sometime, you get a couple of additional bloom cycles that way.
I promise you, the first time you taste your own home grown mushroom, all commercially grown mushroom will taste like cardboard.
If you need more info or if you have specific questions, please send me an email and I will be more than happy to answer your questions.
Just a few things to keep in mind:
- Pay close attention to the moisture level in your straw bags. Too dry and your mycelium will die; too wet and mold will start to grow. If you see a lot of standing water, poke some extra holes in the bottom for drainage.
- When growing oyster mushrooms and most other species, the mycelium is a white color. If you see large patches of red, black, blue, brown or green then you’re looking at mold. As painful as it is, you should discard your bag as you could make yourself sick.
- You don’t need complete sterility for this method but do pay attention to cleanliness. Wash your hands, lay your straw out on a clean tarp, and don’t hang your bags over the cat litter box.
- Research the species you want to grow before you begin. Some do better on wood than straw. Others may need a certain temperature range for incubation. Knowing these specifics will increase your success rate.
- Be cautious when pasteurizing straw on your own. The burner is hot, and wet straw is very heavy. Asking a friend to help will make it more fun and be safer. Bribe them with the promise of delicious mushrooms.
- Some people mix some leached cow manure in with the straw and spawn. Most mushrooms thrive on this. Use a ratio of about 3:1, or three parts straw to 1 part manure.
Don’t be discouraged if nothing happens your first time. Everyone fails at this at one point or another. Read some more and refine your methods. Try, try again!
Happy Gardening!
Pops
2013
Maple Creek Farm PNW 