Make Supplemented Sawdust Substrate

Here is a Forest Fungi basic formula for learning how to grow 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 kgs Gypsum (Calcium Sulfate)

A supplemented sawdust mix

Supplemented sawdust - method

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).  

Make supplemented sawdust
Making your bags with supplemented sawdust mix

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

How to fold mushrooms bags

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 below with a 200 Litre 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 hours.

When cool, add 1 cup of spawn per bag, then close the bag using an impulse heat sealer, or tape and twist ties.

Fruiting your delicious mushroom bags: 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. 


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