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June 28, 2022

How to grow mushrooms: 4 tips for after harvest 'grow kit' care

How to Grow Mushrooms and care for the grow-kit AFTER harvesting. If you show it some love it will keep performing for many months to come.

After harvesting the mushrooms, there are a couple of things you will need to do to prepare the grow kit for its second, and subsequent flushes. This guide on how to grow mushrooms is just one of many on our website to help beginners through to advanced mushroom growing.

If you care for it, the grow kits should continue fruiting for many months. However, the yield may go down as nutrients are depleted from the substrate of the mushroom fruiting block. See the tip below, to keep it going longer.

You may also need to do this if you had a failed flush, where all your mushrooms stalled. In which case, we call this re-setting the bag. If you have experienced a stall, please refer to this article about mushroom growing problems.

1. Clear the airholes

Run your hand over the outside of the bag to clear the holes of any debris and nubby bits like pin-sets that failed to grow, or stem stumps from harvested mushrooms. You may need a knife to clear them. We want these airholes clear so it gets plenty of fresh air and space to grow next time.

2. Check if it needs Rehydration

Weigh the bag and compare its new weight to its original weight. The difference is the water loss. Generally, it will not need rehydration until after its second or third harvest.

  • Half the weight of the bag is water. So, for instance, if you purchased a 4kg bag that means 2kg (or 2 litres) is water
  • If you harvest 700g from that 4 kg bag that's just under 700ml of water right there! Most of the weight of the mushrooms is water.
  • If the bag now weighs in at 3kg. This means the bag has lost 700g of water to the fruit and 300g to evaporation from the holes.
  • This means it only has 1 litre of water left, which should be enough for the second flush, but it may struggle for the third. At some stage, it will need a drink.
  • Also note: a loss of 300g to evaporation would be fairly high and may indicate that it is in a spot that could be too dry.

3. How to Rehydrate

Once it's lost about 70% of its water it's time for it to take a dunk. Generally, this should not be needed until after the 3rd flush (or possibly the 2nd if you have it in a dry location). Do this by...

  • Soak it in a bucket (bath or sink) of water for a few hours.
  • Put a weight on top to submerge it.
  • When you pull it out, put a small hole in the bottom to help it drain.
  • Re-weight. Aim to get it to about 80% of its original weight.
  • While it's soaking, and if required, try finding a better spot for it.
  • Tap (or town supply) water is fine. If chlorine or fluoride has been added it will not adversely affect the grow kit.

4. Do not oversoak

This is one of the few things that will harm the mycelium and may cause mould. 

  • If you are unsure, weigh it every hour, during the soak, to get a sense of how long it may take.
  • You may need to put a few small holes at the bottom to help it drain.
  • The idea is that the substrate becomes damp, not 'wet.

More Tips: How to Grow Mushrooms

Keep it growing for longer

We have had customers say that they have kept their grow kits happily performing by adding some nutrition to the bag after 4 months.

  1. Dilute some liquid (seaweed) fertilizer
  2. Use a metal straw and a large syringe
  3. Inject it into various places within the centre of the bag

Do not overdo it as the nitrogen in the fertilizer may damage the mycelium. We would also recommend doing this before the soaking.


Now you know everything you need about how to grow mushrooms and success for subsequent flushes. If you do a good job caring for it, it should reward you for many months. We have had customers give us feedback that theirs are still producing after 10+ months. Let us know how you do!

Further reading

How to grow mushrooms article from this NZ Life

How to grow mushrooms: from Stuff (lifestyle section)

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