Humidity and cold shocking prolong mushroom grow kits

Mushrooms in a humid grow room.

You can have as many as five harvests of mushrooms in your own grow kit by maintaining the humidity and trying an extra trick.

The mushroom grow blocks weigh around three kilograms. More than half that weight is water because mushrooms require heaps of hydration. Mushrooms are often between 85 and 95 per cent moisture content, according to researchers at the Punjab Agricultural University in India.

Our grow room requires between 80 and 90 per cent humidity to maintain the moisture content in the mushroom blocks. Otherwise, the mycelium and fruitbodies will dry up and stop growing. It is like humans feeling less productive when we are dehydrated.

JCB Gourmet Mushrooms grow kits include a spray bottle and a humidity tent so you can easily keep the mushroom block hydrated. All you must do is set up your grow block in a cool area out of direct sunlight and maintain the humidity.


You should mist the humidity tent at least two to five times per day as you walk by your mushrooms. A good guide is to see droplets cover around 15 per cent of the humidity tent. The fungi will thrive in that environment.

Too much misting at once could cause water to collect at the bottom of the grow block and become soggy, so it is better to mist more frequently in smaller amounts when you can. Misting three times a day – once in the morning, once at lunch, and once before going to bed – usually does the job, but you can also mist in the afternoon and after supper if you spray in smaller amounts.

Teachers who bring grow kits to school can mist when they arrive and before they leave while having the students mist during the day. They can see how fast the mushrooms grow and learn about decomposition in nature’s circle of life.


Let’s not forget the tastiest part of grow kits: harvesting the gourmet mushrooms. We usually harvest the grow blocks once on each side at our growing facility so we can make space for newer blocks. However, there are still enough nutrients in the substrate for multiple more harvests.

You can harvest on the big sides of the block, the smaller sides, the top and the bottom. All you need to do is keep misting and maintaining a cool temperature.

The blocks will get lighter when the water and nutrients are taken to grow mushrooms. Do not worry if you find the mushrooms are taking longer to grow and the block is noticeably lighter. There is still one more trick you can try.

Cold shocking: the extra trick for more mushrooms

Remove the block from the plastic bag by cutting open the top with scissors or a knife. Submerge it in water for six to ten hours. The substrate will absorb the water and the mycelium will not drown during that time.

You can then place the block on a plate and refrigerate it for another 12 hours. This is called cold shocking the mycelium.

Have you ever taken a cold shower to wake yourself up and feel more productive? The mushrooms sometimes need that wake-up call as well, which is what a cold shock does. It will energize the mycelium to keep growing fruitbodies and produce one to two more harvests.

You can slide the block back in its original bag and tape shut the top once the cold shock ends.

In the end, you can have as many as five or six harvests and multiple pounds of mushrooms over two months. Try it out for yourself by visiting our grow kit page!

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