• How to use grain spawn to grow delicious mushrooms

    How to use grain spawn to grow delicious mushrooms

    Have you just purchased a two kilogram bag of Forest Fungi organic wheat grain spawn? Here is a simple guide to learn how to grow gourmet mushrooms using Forest Fungi Grain Spawn. The grain spawn is ready to be used to inoculate your fruiting substrates.  Once the substrate is inoculated, in a matter of weeks you will be eating delicious gourmet oyster mushrooms! To prepare your fruiting substrate, you will need to either pasteurise, sterilise or lime wash it. Please read below to select a technique best suited for you


    Popular choices for fruiting substrates include sugarcane mulch, hardwood sawdust, wheat straw, other cereal grain straws and even coffee grounds. I like a combination of sawdust and oaten chaff.


    Equipment required

    1. Substrate medium
    2. Bucket or esky big enough to hold substrate
    3. Large pot to heat water to 80 degrees Celsius
    4. Your chosen fruiting vessel (e.g. bucket with holes, plastic bag or cardboard box)

    Time required: 1 – 2 hours


    Pasteurising your substrate involves heating your substrate to between 60 – 80 degrees Celsius for 1 – 2 hours. An easy way to achieve this is to load your substrate into a bucket or esky and cover with hot water 80 degrees Celsius and leave for 1 – 2 hours. Drain off excess moisture and when cool enough to handle mix grain spawn throughout at a ratio of 1:5 up to 1:10 and load into your chosen fruiting vessel (e.g a bucket with holes, mycobag or plastic bag).


    Equipment required

    • A Pressure Cooker, or large vessel to steam the bags in, such as 200L drum.
    • Forest Fungi Filter patch bags


    If you choose to sterilise your substrate, you need to heat your substrate to 121 degrees Celsius for 1 – 2 hours. To achieve this, you need to use a pressure cooker that reaches 15psi. 

    An alternative method involves steaming for up to 12 hours, which although technically is not sterilising for our purposes it is sufficient. A common method is to use a 200 litre drum with a fire/gas stove underneath and 10 – 20 litres of water inside the drum, with the substrate packed in bags raised above the water line. A lid is loosely placed on top but not secured. A hole is drilled in the lid, to allow pressure to escape, and to allow a thermometer to be inserted into the drum When substrate is cooled mix grain spawn at a ratio of 1:5 up to 1:10



    Time required:

    4 - 24 hours

    Equipment required

    1. Wood ash or Hydrated lime with low magnesium content (<10%)
    2. Bucket to mix lime with water
    3. Another vessel or bucket to soak substrate in lime water mix
    4. Your chosen fruiting vessel (e.g. bucket with holes, plastic bag or cardboard box)


    Your fruiting substrate can also be treated by drastically altering the ph. To achieve this, you can use wood ash from your fire place or hydrated lime. Make sure you use a hydrated lime with low magnesium content (<10%). This is my preferred method for growing oyster mushrooms because it is quick, cheap and easy. I like to dissolve 4 cups of wood ash (or 1/2 a cup of hydrated lime ) in 20 litres of water (be careful when handling hydrated lime as it is very caustic and can cause burns). Then I place my substrate in a large bin and completely cover with the lime water. Leave for between 1-24 hours then drain off excess fluid. You can reuse this fluid a few times, but the pH will drop, so add more ash/lime.

    Benefits of lime and/or wood ash treatment:·

    • Cheap and easy·
    • No special equipment required
    • Adds calcium to the substrate

    Drawbacks of lime and/or wood ash treatment:

    • Care needed when using as hydrated lime is highly caustic

    Mix grain spawn throughout at a ratio of 1:5 to 1:10 and load into your fruiting vessel.

    Caring for your Oyster Mushroom culture

    One you have spawned your substrate with your grain spawn, you need to protect it from insects, slugs, birds and rodents. I allow my bags to colonise inside my shed-they are tolerant of a wide range of temperatures. You do not need to keep them in the dark. The mycelium is white and should cover the substrate within a few weeks. If you are using bags, when you see small mushrooms (primordia) forming, cut a hole into the bag to allow the mushrooms to grow out from. You can cut the top off the bag as well. If you wish to grow the mushrooms in your garden, you can remove the bag and bury the substrate once it is fully colonised. Alternatively, you can leave the bag on but opened, and place in the garden under a plant for shade. Your culture will be happiest when kept moist. For me, this involves either spraying with a hose 3 or 4 times a day. You can use humidifiers, small greenhouses, hand misters or even just sit the substrate in water if you have removed the bag. The Mushrooms will appear when they are ready. This is in response to several factors, including: using all the available food in the substrate; a change in temperature; exposure to changes in oxygen levels (triggered by opening the bag); thunder storms; and I believe there is a correlation with the moon. The first flush of mushrooms is often the biggest. The next two crops usually occur within 2 months. At this stage I put my spent substrate either in the chook pen, or cover it with sawdust in the garden, and get more mushrooms! Watch this space for upcoming blogs on how to use your spent substrate bags, incorporating them into your mycopermaculture garden (or simply your garden)...