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DIY Grain Spawn Kit

Mushroom liquid cultures are mycelium suspended in a liquid growing medium. Liquid cultures provide a convenient way to transfer living mycelium a new growing medium. In this DIY Grain Spawn Kit you'll add your Pink Oyster Mushroom liquid culture to sterilised grain and let it grow into healthy grain spawn. You'll then go through the process of pasteurisering substrate, inoculating it with your home made grain spawn, incubation and finally fruiting your Pink Oyster Mushrooms!

Each species of mushroom is a different growing experience. Even if you have grown mushrooms before, please read the instructions for your kit carefully before proceeding. If you run into any problems please see our FAQ.

Part 1: Inoculating& Incubating Grain

For Part 1 of this project you will need the following materials:

  • Scissors

  • Surface cleaner 

  • Clean towel or kitchen roll

  • Tape

  • Sterilised grain 

  • Liquid culture

Part 2: Inoculating, Incubating & Fruiting Substrate

Step 1: Pasteurise Substrate

You'll need to work in the cleanest space available to you. A freshly cleaned kitchen counter is often a good choice. Be sure to throughly wash your hands and forearms. Use hand sanatiser liberally while you work and consider wearing a mask. This will ensure a better chance of success by reducing competition from other fungi lurking on surfaces or the air.


In addition to your home made grain spawn and the other contents of this kit you will also require a kettle and 1600ml of boiling water. If your kettle does not have measurements you will also require a glass measuring jug.


follow the below steps in order:


  1. Fill the kettle up with 1600ml of tap water and turn it on.

  2. Thoroughly clean a work surface and your hands and forearms.

  3. Pour approx 800ml of freshly boiled water directly on to the substrate inside the filter bag.

  4. Observe any areas that still look dry

  5. Pour approx 800ml of boiling water and pour it directly on the substrate inside the filter bag. Be sure to drench any spots that look dry.

  6. Fold down the top of the filter bag and flip the block of saturated substrate over to help the standing water make its way to dryer substrate

  7. Let cool to room temperature for 6-12 hours.

  8. During this time your substrate will become hydrated and pasteurised. You can flip the bag several times to evenly disperse the water through the substrate.

Step 2: Inoculation

  • Once your substrate is at room temperature, clean your surface and hands throughly

  • Clean the outside of your filter bag.

  • Clean the outside of the spawn container (bag or plastic tub)

  • Working quickly and methodically, open the filter bag and pour the spawn and calcium on top of the substrate.

  • Apply the twist tie tightly at the top of the bag allowing some air space inside the bag to help make the mixing process easier.

  • Thoroughly mix all of the ingredients together. Take your time as evenly distributed spawn will result in faster growth, less risk of contamination and larger volumes of mushrooms.

  • Through the bag, lightly compress the ingredients down before storing the filter bag in the box.

Incubation is the process in which the mycelium digests the substrate, slowly gains enough energy to produce mushrooms. This is best achieved at a constant temperature of between 20-25C but it is important that the bag never reaches over 30C as this will likely kill the fungi. It is also important that incubation is carried out in the dark, as light can be a trigger to tell the mycelium to start growing mushrooms too early. For this reason we suggest that you store your kit inside the box at this stage. Find a dark location between 20-25C to store your box. Check it weekly for signs of mycelial growth.  When most of your substrate is covered in white mycelium it is time to fruit your mushrooms!

Step 3: Incubation

Step 4: Initiating Fruiting

Deflate the block by loosening the twist tie and squeezing out the air. once deflated, tightly re-apply the twist tie.

Choose a spot from which you will grow your mushrooms.

Use a clean knife to cut a cross pattern about 5cm long and wide.

You can choose to grow your mushrooms from just one spot, or from several at once. 

Step 5: Misting

Shiitake prefer to grow in an environment with 80-95% humidity. Because of this, you'll need to gently mist your kit regularly with water from a clean spray bottle. You want to create a humid environment for the mushrooms and to keep their bodies moist, rather than to 'water' them as you would a plant ​​.

  • Before your mushrooms begin to grow, a gentle mist 3 times a week will suffice. 

  • Once you see your mushrooms begin to pin, mist them twice a day and make sure to keep the mushrooms moist as they won't be able to grow if they begin to dry out. 

Step 6: Pinning

'Pinning' should begin within 3 -5 weeks of initiating fruiting. If you haven't seen any pinning after 5 weeks please see out FAQ. Once they have begun to pin, your mushrooms will grow rapidly. Keep the mushrooms moist during this period. 

Step 7: Harvest

Harvest your mushrooms before the edges begin to either flip up or to wrinkle, darken and split. A white dust under your mushrooms means they have started to drop spores. Your mushrooms will be at their most tender if you harvest them before they sporate, but they'll still be perfectly delicious if you don't quite catch them in time. Just don't forget to wipe off your counter! To harvest, twist the whole bunch at the base and pull. Be sure that you have not left any mushroom stem attached to the substrate as this can inhibit the next flush. 

Step 8: Initiating The Next Flush

Did you know that your box has the ability to produce several clusters or 'flushes' of mushrooms over time?


Times between flushes can vary from 3-9 weeks, so be patient and don't forget to keep the humidity up by misting. Your kit may flush several times, but the amount of mushrooms will reduce with each flush and the time between flushes will increase.

Step 9: What to do with your kit when it stops producing mushrooms

Did you know that fungi play a key role in storing carbon? Trees and plants remove carbon from the atmosphere and fungi break down plant waste to create new carbon-rich soil. Clean air, healthy soil and delicious mushrooms: just one of the many ways fungi are incredible!

Once your block has finished flushing, Once your block has finished flushing, you can compost the block and dispose of the fruiting bag in general waste.


We hope you've enjoyed growing your Blue Oyster Mushrooms mushrooms!

We're passionate about sharing the diversity of the fungi kingdom & making more  of its edible & medicinal delights easy to grow. Want to try another strain or learn how to cultivate mushrooms? See our full range of mushroom growing kits and cultivation workshops!

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