What is a ‘Substrate’ for growing mushrooms?

Substrate is just a fancy way of saying food for your mushroom. The word ‘substrate’ translates directly to ‘to spread underneath’, for mushroom substrate, it would be the stuff you spread under your mushrooms. A platform, but also food. In ecological terms, a substrate is the substratum that the subject in question is attaching itself to.

But simply, substrate for growing mushrooms just means food.

It’s the ‘base’ nutritional substance that you put your spores (to inoculate) and grow your mushrooms on. And, technically speaking, there might not even be nutrition in your substrate, because some mushrooms, like Oyster Mushrooms, can grow in nutrient scarce substrate.

Typical nutrition for mushrooms involve sugars and other hydrocarbons (like ethanol or more complex chains).

A nutrient dense substrate isn’t always desired, specifically if it’s not sterilized. There are other fungi and bacteria that compete with each other to eat the goldmine of nutrition. Which means if you’re trying to grow something, then you’ll have that compete with everything else, which can be bad- and often you’ll get a mixed bag of stuff that’s might be mixed with mold and is probably not safe to eat.

It is important to note;

That mushrooms, like children, can be picky eaters,
so depending on what you’re growing,
you want to feed it the right food.

Here are a few examples of substrates;

A lot of cellulose or wood such as rotten logs, driftwood, wood chips, etc. can be used as food for specific fungi. There isn’t a lot of nutritional value or sugars for many fungi. So for just dry woodchips with nothing else, you can grow for instance Oyster mushrooms.

There are starter mushroom grow kits that use wooden logs to grow.

Cardboard can be consumed, so you’ll have a nice use for all those amazon boxes.

A fun experiment, but impractical for scalability, is to grow mushrooms on toilet paper. You can also find fun kits online, a great way to learn as a beginner or teach kids something cool.

There’s a lot of fungi that grows on manure or fecal matter, but I personally don’t like that especially if I’m trying to eat what I’m growing.

Coffee bean grounds, straw, gypsum, Coco Coir and Vermiculite are some options.

Some people use beans, and there are all kinds of beans, but also be aware that the beans could sprout making things awkward. You can cook or ground up the beans to mitigate this.

People often use grains, from wheat, barley, rye, and even rice to grow many kinds of mushroom.

Typically, the majority of everything in the universe can probably be consumed by fungi. It just takes much longer to have fungi eat uranium or other heavy metals, but it’s not impossible. For growing purposes, you just gotta find what works best for whatever you’re trying to grow.

As a side note/tip, some people make soups with all sorts of ingredients and use that as a nutrient dense broth that they place over another substrate like grains, wood, soil, etc. to help grow your mushrooms.

Again, the type of mushroom or fungi that you want to grow will influence which substrate you end up using.

And after you have a substrate, there’s all sorts of preparation methods out there, from using the nutrient dense broth to adding other ingredients. Typically though, people sterilize their substrate;

Sterilization of Substrate?

Sterilization just means kill all the germs and bacteria on the substrate. This is accomplished through various methods such as steaming or high heat treatment. People do this before putting their mushrooms spores on the substrate, so that the mushroom you’re trying to grow doesn’t have to compete with other things.

For safety reasons, a lot of people take measures and practices to sterilize the substrate. This is to kill off other germs, bacteria, and other spores that could affect the substrate. If you don’t properly sterilize the substrate, you run the risk of having mold or other types of undesired fungi eating your substrate. Instead of having a competition to grow what you are trying to grow, people kill of the competition through sterilization, heat, steam, and some other options.

Small blurb on Casing Layers,

Sometimes people put a layer of ‘substrate’ on top of their grows, after the mushrooms have colonized the majority of the substrate and right before the fruiting bodies develop.

People call refer to the Casing layer’s substrate as ‘substrate’ because it’s the same material as the substrate. They use the same food.

But it’s a casing layer because it’s ontop of the thing you’re growing, whether it’s plants or mushrooms. So it en‘cases’ it -or puts it in a case.

It’s kind of funny, because you’re putting substrate on top of your grow, and that’s technically a superstrate or supstrate if we were to be linguistically accurate. But, uh, I didn’t write the english language, so cheers.

Thank You,

As a side tip, people have found that microwaveable minute-made rice works really well for a substrate for some types of mushrooms. I forget which ones off the top of my head, but feel free to experiment and try some new things.

If you have any questions or comments, please ask down below. There’s a lot of fancy words that sound big and stuff, but it’s really simple when demystified and anyone can grow their own food. I’m not here to gatekeep, so please ask away.

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