This instructable presents a simplified method of growing oyster mushrooms using hydrogen peroxide or agricultural lime rather than hot water or steam to pasteurize the straw substrate. For most home mushroom cultivators this should be easier to deal with than heat and more reliable than doing without pasteurization.
If you are new to mushroom cultivation or if you want links to many other mushroom instructables, you may want to read the background material at the end of this one.
Step 1: Materials
Clean table – For a work surface. Cover it with plastic sheeting if it shouldn’t get wet. I prefer to work outside because of the water involved in the process.
An oyster mushroom “grow kit” - consisting of a bag of oyster mushroom mycelium, usually on straw. I obtained mine from Smugtown Mushrooms at a workshop in Brooklyn. They are a friendly, helpful and reliable source based out of Rochester, New York. I have also obtained mycelium and other supplies from Fungi Perfecti based in Oregon, another excellent source. I used pearl oysters, (Pleurotus ostreatus) an aggressive wood decomposer that is relatively easy to culture. The species could possibly have unique traits that are particularly well suited to the methods used here. Other species and strains are available. I would suggest choosing yours based on the temperature of the space where you will grow them. I think it is quite likely that these techniques will work across the genus. I welcome comments from all who try it!
One-Step – This is a no rinse hydrogen peroxide sanitizing agent used for cleaning beer brewing equipment. Here it is used to pasteurize the straw.
Agricultural lime – Powdered, not granular. This is another way to pasteurize the straw without heat, as described by Peter McCoy in Radical Mycology. It works by raising the pH beyond what most mushroom competitors tolerate. It works for oyster mushrooms but may raise the pH too high for some other species.
Burlap – My local hardware store had plain brown burlap. It can also be ordered from Fungi Perfecti.
Straw – A clean fresh bale or portion of one. You will use less than half of it so it’s good to have a use for the rest, such as mulch.
Plastic sheeting – Polyethylene, as used for drop cloths for painting, etc. I prefer clear so I can see what is going on with the culture.
Zip ties – For holding the rolls of plastic/mycelium/straw/burlap together. Long ones are nice but you can daisy chain shorter ones to do the job.
Rubbing alcohol – Either 70% or 91% is fine.
Paper towels - For wiping down surfaces and equipment with rubbing alcohol to kill potential contaminants.
Disposable gloves – Protect your hands from irritants. Protect your cultures from contaminants.
Knife or razor blade - To cut x-marks in the plastic for the mushrooms to grow through.
Step 2: Pasteurize the Straw and Burlap
Wipe a clean a 5 gallon plastic bucket with a paper towel moistened with rubbing alcohol. Cut four pieces of burlap to approximately 2 feet by 3 feet. Fill the bucket with straw. Top with two of the pieces of the burlap folded to fit in the bucket and weighted down with a clean rock. Add One-Step dissolved in warm water at the 1 tablespoon per gallon rate recommended on the container for sanitizing beer brewing equipment until the straw and burlap is completely submerged. Wait about 24 hours before proceeding with step 2.
As above but rather than One-Step use powdered agricultural lime mixed with water at about ¼ cup per 5 gallon pail of water, or until the pH rises to 12 or 13 if you have a meter to measure it. This is a fairly caustic solution, so wear disposable gloves and keep it off your skin and out of your eyes.
Step 3: Set Up Your Work Surface
I find it best to work outside at this point because it’s a wet job. Wearing disposable gloves wipe the surface of a clean table with a paper towel moistened with rubbing alcohol. (Alternately, if you don’t have a smooth non-porous waterproof table, cover it with plastic sheeting and wipe that.) Then cut an approximately 2 ½ foot by 4 foot piece of plastic sheeting, put it on the table and wipe that.
Step 4: Make the Mushroom Rolls
Take a piece of the wet burlap from the bucket and spread it out on the plastic. Cover it with about half of the straw from the bucket. Let it drain a bit. Take about ¼ of the bag of oyster mushroom mycelium, break it apart, and spread the bits out on top of the straw. Roll the burlap/straw/mycelium up like a bedroll. Then roll this up in the plastic sheeting. Secure the roll with zip ties. If the zip ties you have are too short, you can daisy chain several together to do the job. Cut about half a dozen approximately 2 inch X’s in the plastic covering of the roll with a wiped knife or single edge razor blade. These allow a little air exchange and give the mushrooms spots to emerge. Repeat steps 2 and 3 to make 3 more rolls. Set these upright in an area of appropriate temperature for your oyster strain. Mist the rolls occasionally, especially the X’s so they don’t dry out.
Step 5: Watch for Primordia
When tiny pinhead mushrooms, primordia, start to appear at the X’s, hang the rolls up, and mist them at least daily, more often if possible.
Step 6: Harvest Your Mushrooms
Harvest developing mushrooms before they get really huge (and tougher) and start dropping white spores all over the floor.
Step 7: Enjoy!
Enjoy! There are many ways to prepare mushrooms, but don’t pig out on your first batch. Always go a little easy if a food is new to you. Probably it deserves to be prepared by itself, lightly fried in butter or in the oil of your choice, and seasoned with a little salt and pepper.
Step 8: Background
Much like growing plants, the complexity of the process of growing mushrooms depends on where in the life cycle you choose to jump in. Seeds can produce a lot of plants, but you have to wait for them to germinate and give them the time, nutrients and sunlight they need to grow. Many people grow annual flowers from seed, but fewer attempt oak trees. Most people let the nurseries do that and buy the tree when it is several feet tall. Mushrooms reproduce by spores. Spores are far tinier than seeds and don’t contain stored food to give the germinating fungus a head start. Because they are tiny and because mushrooms produce huge quantities of them the spores can be very widely distributed. But if they don’t germinate in exactly the right place they will die. People in attempting to grow mushrooms from spores or from tissue culture must provide the right conditions and also keep out competitors such as bacteria and fungi. So sterile culture techniques involving things like autoclaves or pressure cookers, petri dishes and agar, or sterile liquid or solid media are used. This is more complicated than sprouting most seeds. But some cultivators are devoted to this process. It’s how tiny cultures are expanded from agar to grain, and then to many bags of less nutrient dense media like enriched sawdust or straw. It’s also how new strains can be isolated and developed. Several Make Instructables address some of these techniques:
This one uses pressure cooker sterilized jars with media and spore syringes. Species is not specified.
This is an interesting one involving making a spore print from an unknown species of wild mushroom on hot water pasteurized cardboard. It relies on the observation that most competitors don't grow well on cardboard.
This starts from agar culture or alternately from a grain master culture and expands the mycelium on grain. It involves pressure cooker sterilization and construction and maintenance of a clean room. Not for the faint-hearted! There is a sequel.
Involves sterilizing jars with media in a pressure cooker and inoculating with spore syringes. Species specified are Shaggy Mane, Lion's Mane and P. cubensis.
Many mushroom growers prefer to deal with the grow out rather than the spore or tissue culture portions of the life cycle. Commercial cultivators sell opportunities for home growere to do this in the form of kits.These kits can be used as is, or they can be expandedon pasteurized substrates. The requirement for sterilization is somewhat relaxed at this point. It is enough to give the main competitors a serious setback by using heated water, stem, or , as described in this instructable, hydrogen peroxide or agricultural lime on the substrate.The substrate is less enriched than the agar, grain, or liquid media most often used in earlier stages, so the competing bacteria and molds have a reduced advantage.
Most of the following instructables deal with growing mushrooms from a source of actively growing mycelium such as a commercial grow kit, and expanding it to media like straw, enriched sawdust, or coffee grounds. I've also included a couple that use bits of the bases of mushrooms as a starting point. While this is in a sense, tissue culture, it is not sterile tissue culture, so I thought it fit best here:
Making Mycelium by ashleyscarborough in cardboard
Uses cut pieces of the base of a King Oyster mushroom on unpasteurized cardboard. The instructable follows the process through mycelium colonization of the cardboard.
Shiitake, oyster and lion's mane mushrooms on enriched sawdust and gowing out of fancy water-jet cut boxes. Pasteurization by boiling
Oyster mushrooms on cardboard using grain spawn.
Two strains of oyster mushrooms grown out on pasteurized straw. Bases and stems cut up and mycelium grown from them on unpasteurized cardboard. This is used to inoculate the next batch of straw.
Cut up oyster stem butts to coffee grounds, then used to inoculate pasteurized straw.
This is basically part two of How to Grow Oyster Mushroom Spawn (Low Tech). It's really quite a complicated large scale operation invoving a clean room and many bags of pasteurized sawdust. Not for the timid!
Oyster mushroom spawn on coffee grounds.
Shiitakes on a log (which really belongs in the my next section) and oysters on a roll of toilet paper (!). Shows how to build fancy plexiglass boxes to house the cultures. What the author refers to as spores looks like grain spawn.
Sensor, ultrasonic mist generator, Arduino (!). Old McDonald did not farm mushrooms this way. A treat for the right maker, I think.
The last category of instructables here involves outdoor culture on logs or woodchips. A fresh log is relatively free of mushroom competitors such as other mushroom species, bacteria, and mold. So if you poke holes in it, inoculate them, and seal them up that log may grow your mushrooms. The right species of mushroom must be matched to the right kind of log, and it does take time for the mushrooms to appear. Also, some mushroom species can be grown outdoors on wood chips because they are aggressive enough to beat out competitors. I have had the experience, however, of getting a very nice crop of something that I definately did not intentionally plant. It came with the chips. So those who grow mushrooms outdoors need to have a very good knowledge of what their intended crop looks like, what its spoore print looks like, etc., just like in picking wild mushrooms. Here are a number of instructables dealing with outdoor cultivation:
Shiitakes and oysters on oak using plug spawn. Good coverage of the process.
This is an overview, followed by sequel instructables A through F:
"Part A: Making a Mushroom log, Sterilizing Grain. Day 1 (2-3 hrs)
Part B: Making a Mushroom log, Transferring Mycelium onto Grain. Day 2 (30 minutes)
Part C and D: Making a Mushroom log, Bulking up Grain Spawn (2-3 weeks later)
Part E: Making a Mushroom log, Transferring Spawn onto fruiting substrate (2-3 weeks later)
Part F: Making a Mushroom log, Harvesting and caring for your finished log"
So this really starts with from the beginning, and doesn't get to inoculating the log until Part E. This is excellent for someone wishing to go through the whole process, but for those satisfied with buying plug spawn, parts E and F are sufficient.
This shows how to make oyster mushroom logs starting with oyster mushrooms from the grocery store. The bases of these are cut up and used to inoculate cardboard that has been pasteurized with hydrogen peroxide. This is the only mention I have found of using hydrogen peroxide for this purpose in an instructable. I could have missed some, of course. I am very much a fan of this. The colonized cardboard is sandwiched between log sections. Very simple and elegant.
Good instructions on settting up an outdoor Garden Giant (Stropharia rugosa-annulata) patch on woodchips. No results yet, so we are waiting for the sequel!