1. About your GROWTUB
Your GROWTUB mushroom kit is packed with substrate, moisture and mycelium spawn, ready to colonise. The tub is transparent to allow you to observe the mycelium spreading through the tub until it is fully colonized. Each GROWTUB is labelled with the oyster mushroom species, batch number and the date on which it was packed. It takes 10 - 20 days from packing to colonise fully. Keep the GROWTUB in a warm place with at least 60% humidity during colonisation, but avoid direct sunlight. When the GROWTUB is fully colonised, it is ready to fruit. Do not remove the lid or add water to the tub.
2. Prepare for Fruiting
Pick a place where you are going to fruit the GROWTUB. We summarise the ideal fruiting conditions below:
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Light: Oyster mushrooms prefer bright, indirect light—think of the light in a shady room or under a tree canopy, where they would grow in nature.
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Temperature: Ideal fruiting range is 18–24°C. Some varieties tolerate slightly cooler or warmer temperatures, refer to the growing conditions page.
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Humidity: Needs 85–95% humidity to form healthy mushrooms.
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Airflow: Gentle fresh air is important—avoid sealed cupboards or airless spaces. Mushrooms breathe air and release carbon dioxide (CO₂)—avoid a build-up of CO₂, which will cause the mushroom fruit bodies to grow tall stems and small caps.
3. Start Fruiting
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Place the GROWTUB in a humid environment as described above. This could be:
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A greenhouse tent or humidity dome
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A large clear plastic bag with air holes
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A bathroom with daily misting
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A kitchen counter or other suitable space in your house
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- Remove the microporous tape covering the holes in the GROWTUB from 50% of the holes in the tub.
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Mist 2–3 times a day with clean water, aiming around the hole, not directly soaking the mushrooms.
4. Watch for “Pinning”
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Within 5–10 days after placing the GROWTUB in fruiting conditions, you should see tiny mushroom buds (“pins”) forming.
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Keep humidity high during this stage—if pins dry out, they will stop growing. The baby mushroom are very fragile and you have to keep them moist at this stage.
- After pinning, the mushrooms will grow bigger every day until they are ready to harvest.
5. Harvest
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Harvest when the caps are still slightly rolled under but fully formed—usually 5-7 days after pinning.
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Gently twist or cut mushrooms off at the base, taking care not to damage the mycelium.
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Don’t wait too long—over-mature mushrooms drop spores and lose quality.
6. Second & Third Flush
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After harvesting, rest the GROWTUB for 5–7 days in a humid environment.
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If the inside of the GROWTUB appears dry, open the lid and spray the top of the mycelium gently with cold water. Excess water will drain from the holes at the bottom of the GROWTUB.
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Repeat the same fruiting process for 2–3 flushes until the mycelium and substrate is exhausted. Each consecutive flush will be smaller.
7. On to the Garden
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When your GROWTUB stops producing, remove the mycelium block from the tub and break up the block and add it to your garden soil or compost, or use as bedding cover.
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Oyster mycelium helps improve soil structure and may still produce small mushrooms outdoors.
Tips for Success:
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If your environment is very dry, create a mini-greenhouse using a clear bag or plastic tub.
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Avoid direct sunlight—it can overheat and dry the mushrooms.
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Keep temperature and humidity as stable as possible for best yields.