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Lesson 2

Make a grow bag

The classic bag: hardwood pellets, soy hull pellets, a little straw and grain spawn. A step up from the easy methods, and the way most good harvests are grown.

Please read first. Soy hulls are rich food, for mould as well as mushrooms, so this mix must be properly sterilised in a pressure cooker, not just boiled. Work clean: wash your hands, wipe every surface and tool, and add the spawn in still air. If you see green, black, pink or orange patches, or smell something sour or rotten, throw the bag out and start again.

What it suits

Most wood-loving mushrooms grow well on it, including oyster, lion's mane, chestnut, shimeji and enoki. It is not the best mix for shiitake.

You need

  • Hardwood pellets and soy hull pellets, half and half. Pellets made for growing mushrooms are the safer choice.
  • A small handful of chopped straw, to keep the mix airy (optional)
  • Water
  • Grow bags with a filter patch
  • A pressure cooker that reaches 15 PSI
  • Grain spawn of the mushroom you want to grow
  • A still air box or a flow hood, gloves and surface spray or wipes

Steps

Amounts below make one bag of about 2.3 kg.

  1. Soak 2.5 cups of soy hull pellets overnight in 700 ml of water. Boiling water speeds this up.
  2. Pour another 700 ml of water over 2.5 cups of hardwood pellets and leave for 30 minutes, then break them up.
  3. Mix the two together, with the handful of straw if you are using it. Squeeze a handful: if more than a drop or two of water comes out, it is too wet.
  4. Fill the grow bag, fold the top over and sterilise it in the pressure cooker for 2.5 hours at 15 PSI. Follow your cooker's own safety instructions.
  5. Let the bag cool inside the closed cooker. This can take up to 8 hours. Spawn added while the mix is warm will die.
  6. Wash your hands, wipe everything down, and work in a still air box or in front of a flow hood. Add grain spawn at about 10% of the bag's weight, mix it through and seal the bag.
  7. Keep it warm and dark until it is white all through. For oysters, 22 to 24 °C is ideal; above 25 °C is too warm. How long it takes depends on the mushroom.
  8. When it is fully white, it is ready to fruit. Cut it open and mist it, following the M.U.S.H. guide for your mushroom.

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