All Hail the Oyster Mushroom!

The Oyster mushroom (Pleurotus Ostreatus) is ideal for the beginner mushroom cultivator. It’s a fast growing, vivacious species that will readily grow on an extraordinary variety of materials, they look fantastic, they’re delicious, and it’s easy to make your own spawn to grow them on again and again.
Here we are going to explain how we used an old washing basket to grow these mushrooms on straw. It took about 7 weeks from start to finish and we converting 1kg of straw into 600g of oyster mushrooms in the first flush (the fruiting cycle) and 500g on the second flush.

This species of oyster mushroom is one of the most ubiquitous and vigorous species of fungi on the planet. I have this mushroom to thank for my entry into the kingdom of fungi. I started growing mushrooms after successfully taking a wild oyster mushroom, culturing it on to cardboard then using this “spawn” to inoculate straw. From then on I was hooked and started to explore other techniques for growing all sorts of fungi.
It a nutritious gourmet mushroom containing up to 30% protein and it is high in vitamin C and potassium, and like most mushrooms when exposed to sunlight, even after it has been harvested, it produces vitamin d.

It is also has huge potential to remediate damaged and polluted environments. The Pleurotus Ostreatus is what is known as a saprophytic mushroom meaning that it feeds on decaying organic matter, in this case, woody material containing lignin and cellulose. It is a primary decomposer, beginning the process of breaking down dead wood and returning the nutrients to the soil food web. The oyster mushroom is especially adaptable to many different types of cellulose rich substances. In fact it will grow on an incredible diversity of substrates (the growing medium), almost any ligneous and cellulose rich material.

It has this adaptability because it can produce an enormous array of enzymes to break complex carbon chains. Amazingly, it is being used to denature oil contaminated organic matter reducing petrol-chemical soaked material to organic compost in a matter of months far out performing conventional chemical treatments for oil spills and related pollutants.

Let’s grow mushrooms!

What we describe here is the most simple way to grow these mushrooms. You can’t go wrong. Within a few weeks you will have grown some delightful mushrooms. Once you become experienced in this basic technique you could experiment with more involved methods that can increase yields and expand the amount you produce. These techniques are detailed here on this website, but first let’s look at what you will need to start with oyster mushrooms:

Straw, at least 1kg, cut into pieces or shredded
Gypsum (this is optional but really does help if you can get it)
Oyster Mushroom Spawn (you could buy it or make your own cardboard spawn)

Large cooking pot
“Hay Box” or old duvet (optional)
Probe thermometer
Container (in this case a washing basket could be a polythene bag)

Using just straw is simple as it only involves pasteurisation rather than sterilising the difference being the temperature you have to treat the substrate to reduce microbial competitors and give the fungi your cultivating an advantage.
So firstly, cut the straw into 1 to 2 inch pieces. You could use a strimmer or garden shredder if making a large amount otherwise using scissors works just fine. Soak the straw in soapy water overnight, this help to hydrate the straw and remove dirt and dust which might harbour unwanted microbial life.
After soaking drain the straw then refill the pot with hot, but not boiling water, around 90c. The temperature will drop but bring it up to around 75c and simmer for 30 mins to 1hour. This process of pasteruisation should remove most bacteria and fungi that would otherwise compete with the oyster mushroom. Now drain and leave to cool.
The moisture content is the key a bountiful harvest of mushrooms but excess moisture can encourage contaminants. The important thing to remember here is to avoid liquid pooling in the cropping container create an anaerobic environment. So, basically, not dripping wet is a good rule of thumb.
Now you want to layer the straw and the spawn in the “cropping” container. Add about an inch of straw then the spawn. If you’re using grain you don’t have to use that much per layer, a minimum of 10% the weight of substrate, so, with 2Kg of wet straw you could use 200g of grain. Be sure to press down into the container as you go. You want to make a compact compressed as possible. Remember this fungus grow readily on logs so, in effect, you are trying to mimic these conditions.
Now leave the bag in a dark warm (20c – 25c) place for three weeks until it is a firm whitish block of mycellium. Now it’s ready to fruit!
To initiate the fruiting put the basket somewhere cool and humid. In the picture you see here I hung the basket in our polytunnel in early April. Spraying it to maintain moisture levels. I could go into a lot of detail about the best parameters for fruiting but not here, as I said oyster mushrooms are very resilient and easy to grow so you don’t have to worry too much about this now. If you want more inofrmation it is best to refer to the books listed in our resources page. The main thing is to be sure that you don’t let the substrate dry out. Within a week lots of tiny “pins” will appear this is the name for the primordia, the initial emergence of the mushroom. Some of these will grow into full size mushrooms, most won’t.

Be sure to keep an eye on them, once they start forming primordia they grow fast! Wait until the cap margin starts to unfurl then pull the fruitbody off of the substrate and eat it! I simply way to start experimenting with the flavour and texture of this mushroom is to simply fry it in some butter until it is brown, made even slightly crispy, try it, then you can start seasoning to taste or incorporate it into a particular dish. I’m getting hungry just thinking about!

Making your own Oyster Mushroom Spawn

Using cardboard to “run” mycellium is a simple way of bulking up the mass of mycellium to use when inoculating a suitable substrate. Bare in mind this is only suitable for certain types of fast growing saprophytic mushrooms. Other species within the Pleurotus genus will lend themselves to this technique as well as the Elm Oyster, Wood Blewitt and King Stropharia.
First, soak some cardboard (plain, preferably without printed ink surface) in boiling water; leave to cool; and then drain off the excess water.
Take a healthy fresh specimen and slice thinly.
Once the cardboard has cooled and drained (the cardboard should be wet but not dripping) peel the layers apart and using the corrugated sections lay the thin slices of mushroom in strips in the plastic container. You are trying to create an undulating terrain for the mycellium to grow/run through. Sandwich pieces of the sliced mushroom between layers of the cardboard until the container is full.
Now put the lid on the container but but not completely air tight: place the container in a dark warm place for one to two weeks until the the mycellium has fully colonised the container.
Once you have a container growing a thick white mycellium with a sweet chesnutty aroma you are ready to use it to inoculate your chosen substrate for the mushroom to grow on.

Enjoy and have fun!

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