Following along from the previous article (the set-up) we’ll now cover planting your oyster mushrooms into straw logs.
Oysters mushrooms (from the genus Pleurotus) grow on dozens of different materials that we call substrate. Cereal straw is one of the most commonly used materials commercially but I’ve have had good success growing them on sugar cane bagasse, paper, cardboard, dried leaf mulch and brown grass clippings.
Oysters, being one of the most adaptive mushrooms, have the ability to turn cheap, locally available materials into gourmet food and in the process build soil. Sounds good to me!
For your first few projects it’s best to steer clear of hay, lucerne mulch and pea straw as they are too rich and can spoil easily.
Now a bit about mushroom spawn
Simply put, mushroom spawn is small fragments of mycelium from a certain mushroom species (in this case an oyster mushroom) grown on grain. Planting your straw logs involves preparing your medium, mixing through your mushroom spawn and then letting the mycelium grow through the medium. When the mycelium has fully grown through it will then be ready to produce the first of the mushroom crops.
Making mushroom spawn is by far the most technical aspect of mushroom growing and I’d recommend purchasing the spawn to start with. When you become familiar with the process of mushroom cultivation you can take mushroom growing to the next level by doing a course. I had a great experience attending the Milkwood Mushroom Course with Will Borowski and Nick Ritar and would highly recommend it for aspiring mushroom growers.
The Pasteurisation process
Here’s where I get a bit unconventional….
Generally oyster mushroom growers will do one of two things. They’ll heat up bulk amounts of water to ‘cook’ their straw or they’ll wet it down and steam it. The idea behind both methods is to kill off any resident mold, bacteria and microorganisms that will compete with the mushroom mycelium. Needless to say, this process is both time and energy consuming making it quite unsustainable and uneconomical.
Another option that is just starting to get the attention it deserves is a process called lime-pasteurisation.
- Cereal straw or sugar cane bagasse
- Grain Spawn from a very vigorous oyster mushroom variety
- Hydrated lime — aim for the high calcium variety
- A soak tank that can hold all of your straw (avoid aluminum as it pits when in contact with lime)
- A large sack that can hold your straw while you soak it — hessian sacks, onion nets and old pillowcases work great!
- Plastic bags to hold your planted straw.*
*A note on the plastic bag use — this is the one waste product worth finding a suitable alternative for. Plastic buckets with holes drilled in them have been used as a great reusable substitute and are worth experimenting with.
- Fill your drum with water so that your straw will be fully submerged
- While filling, put a double handful of lime into the water to dissolve — be sure to avoid inhaling particles and wear gloves!
- Load your straw into the large soaking sacks, tie closed and place into the tank
- Be sure your straw is fully submerged by placing a heavy weight on top of the bags
- Let your straw soak for 16-18 hours
- After the soak time, remove your straw sacks and set aside to let excess water drain away.
The great thing is that the limewater left in the tank can be re-used over and over again by simply topping up the water and adding more lime. It’s highly alkaline so be careful not to drain the left over water onto sensitive plants or into local waterways!
- Plant your Oyster Grain Spawn into the lime-soaked straw at a rate of 10%. For every kg of spawn you can plant 10kg of wet straw!
- Load your planted straw into the plastic bags and tie closed. Poke a hole every 5-10cm in the bags so that the mushroom mycelium can breathe.
Now we wait
The oyster mycelium will now need to grow through the straw before it has enough energy to produce mushrooms. This process is called the incubation period. To speed this process up place the bags in a warmish area (aim for 18-25ºC) in the dark. If it’s a bit cold, don’t worry, it will just take the mycelium slightly longer to grow.
Check back on the bags now and again to see how they’re going. You’ll know when the mushrooms are ready to grow when the straw is completely covered in the white mushroom mycelium.
Fruiting mushrooms up and away
After the straw is completely covered in the mycelium it’s finally time for your first mushroom crop. Place the bags in dappled shade and keep the humidity high. Have a read of the previous article (the set-up) for the perfect mushroom growing environment.
Mixing through spawn
Pearl oysters growing
Finding mushroom spawn in Australia: