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How to Keep Your Mushroom Jars Toasty (For Everyone Who Loves Fungi!)


Okay, fungi fans, let's talk mushrooms! After adding spores to your jars, they need to be cozy and warm. Paul Stamets, the Mushroom Master, says in his book "The Mushroom Cultivator" that the perfect temperature is between 84-86 degrees Fahrenheit. But watch out, because if it goes above 106 degrees, your mycelium will say goodbye-lum!

Also, remember, mycelium produces heat as it munches on the grains, so we don't need to hit 84-86 degrees exactly. A comfy range of 75-80 degrees will do just fine.

You should keep in mind that Paul Stamets also recommends keeping the grains at a relative humidity of 90% as well. So, keeping the jars inside the MiniTub after you've inoculated with spores or liquid culture will help you maintain that range.

Heating Mats: The Good, the Bad, and the Deadly

Heating mats sound like a great idea, right? Wrong! They're relatively inexpensive. They don't take up a lot of room. They appear to be a good idea but I'm here to tell you: stay clear from heating mats.

These mats can overcook your mycelium or even prevent your spores from germinating. If you must use one, keep it at least six inches away from your jars.

We're not exactly sure why they don't work but according to dozens who have used them, they only slow down the mushroom-growing process. Below, you'll see what we recommend instead.

The Best Ways to Keep Your Mushroom Jars Warm (No Sweaters Required)

There are several ways to warm up your jars. You also need to keep in mind that maintaining a high relative humidity can help your mycelium colonize your grains even more quickly.

Here are some ideas, from cheap to a bit pricey:

Move your jars higher in your house.

Since warm air rises, putting the jars in a cabinet in a room that stays toasty could work. For example, a kitchen cabinet above an appliance might do the trick.

Use a hot water bottle and a cooler.

If you've got these lying around, this method might be perfect for you. Check out this video for a step-by-step guide:

You can get yourself this hot water bottle on Amazon. Bonus! Use it to keep your toes warm in bed during the winter too. It's amazing. 5-Stars.

Heat up a small room with a portable heater.

Be careful with this one, though! Make sure to follow all safety instructions to avoid accidents. If you're up for the challenge, here's a heater with good safety ratings:

Crank up the thermostat!

Turning it up by just 5 degrees could help speed up the growing process. Keep in mind that this could be expensive, depending on your home size and energy source.

Buy an egg incubator.

Sounds weird, right? But trust us, they work like a charm! Set the incubator to the right temperature, add a little bit of water to the bottom tray and you're good to go.

They usually cost between $60-$150.

I use the Vevor White Reptile Incubator and love it:

I've used products like this and have had success as well. Check it out here:


I highly recommend purchasing a temperature monitor. This will help you keep a close eye on your fungi and ensure that they are warm and happy.

I use the Govee Wi-Fi thermometer and couldn't be happier.


The best solution for you depends on your budget and how quickly you want results. Better temperature control means faster growth, but if you're on a budget, patience is key. Whatever you do, try and steer clear of heating mats.

And a wireless thermometer can give you the peace of mind you need during all steps of the mushroom growing cycle!

Choose an option that fits your needs and get ready to watch your mushrooms thrive!

Happy growing!


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