• How to make Supplemented Sawdust Substrate

    How to make Supplemented Sawdust Substrate
    Here is a basic Forest Fungi supplemented sawdust substrate formula for growing many wood loving mushrooms. The ratios of ingredients can vary.
    • 40 Litres hardwood sawdust (I use Eucalyptus sp.)
    • 10 Litres oat chaff (optional, aids colonization with longer fibres)
    • 10 Liters bran (or other Nitrogen supplements)
    • 2 Litres Gypsum (Calcium Sulfate)

    Forest Fungi Supplemented Sawdust

    A supplemented sawdust mix Mix with enough water to bring close to field capacity-where if you squeeze a handful hard enough, you'll just get a drop of moisture. I just mix in a cement mixer, then tip the lot into a bin. I tip the bin on its side with a trolley and allow excess moisture to drain off. When no more liquid drips out, I upend the bin, then start loading it into fruiting vessels (filter patch bags or glass jars with filters).  

    How to make supplemented sawdust

    In the case of filter patch bags, I fold them like this, then tape them (masking tape or duct duct tape both work).

    Spawn bag 2kg

    You can pressure cook them at 15 psi for 2 hours, I fit 4 or 6 bags in my All American 921 pressure cooker,. Or steam them in a big drum, such as this set up with a 200 Litre drum.

    Pasturisation Drum

    We put a metal grill on top of some bricks or ceramic pots, add about 15 Litres of hot water, then stack the bags allowing spaces between the bags for steam to penetrate. I get 30-40 bags in, then put the lid on-but make sure you have a hole drilled through the lid! You don't want to build any pressure in this set up. Plus you can slide a thermometer through the hole and measure the temperature. Get a fire going underneath, such as a gas burner, and steam for 12-24 hours.     When cool, add 1 cup of spawn per bag, then close the bag using an impulse heat sealer, or tape or twist ties. Keep your bag somewhere out of direct sunlight until you start to see little mushrooms forming. A bit of sunlight when they start forming is good.


     I have shelves on wheels, which I move under cover or put shade cloth on the top if it is too hot. This allows me to use rain and wind and sun to minimize costs and pests. I cut the top off the bags and allow mushrooms to form from the top.If I see clusters forming on the sides, I cut a hole for them to grow out of.

                Forest Fungi Golden Oyster Mushroom                

    The exception is for Shiitake, which I take the bag whole bag off when the block has gone brown. Here are some down by the dam-they have fruited 4 or 5 times in the last 9 months, unprotected.


    Keep the block somewhere you can mist it 3 or 4 times a day-they like moisture, so if it is very dry, consider a small greenhouse. I just place the blocks in the garden under a plant, where they get shade and regular water, or on racks under my carport. The first mushrooms should be ready within a month for most species, but some species can take almost a year! The blocks should give 2 or 3 flushes within a few months, then it can be buried in the garden, where you'll often get further flushes.