How to Choose the Right Substrates to Grow Mushrooms

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Mushrooms are delicious, nutritious, and quite beautiful if you look closely. If you’re a keen produce grower, you should have a go at cultivating a colony of these beauties. You won’t be planting in soil, and you’ll be inoculating a substrate with spawn. Mushrooms don’t need the same growing conditions that fruit and vegetable thrive.

You can cultivate mushrooms from different substrates like wood logs, cardboard, coffee grounds, coco coir, straw, and master mixes. Most are inexpensive and easy to acquire, depending on the mushroom variety you want to grow.

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If you’re new to the wonderful world of mushroom growing, this may all sound a bit alien and complex, but it doesn’t have to be. By the end of this guide, you’ll be able to approach mushroom growing with confidence, and you’ll know which substrate to go for to get the most fruitful results.

Different Substrates You Can Use To Cultivate Your Mushroom.

Before talking about the substrates, here’s a quick list of mushroom-growing terms that I’ll use in this post and what they mean.

• Substrate – any substance that mushroom mycelium can grow and thrive in, with enough moisture and nutrients to let it fruit and produce mushrooms.
• Inoculate – Introducing the mushroom spawn to the substrate it will be grown in.
• Mycelium – The network of threads that make up most of the fungal organism – the mushrooms themselves are just the tip of the iceberg!
• Colonize – when the mushroom mycelium has taken hold, and you see its white presence all through the substrate.
• Mushroom Grow Bag – A very handy container in which you can mix your spawn and substrate, and watch the magic happen.
• Pasteurize – Cleaning your substrate by immersing it in water at 60c or above for around two hours.

Mushroom growing rule #1 – Different varieties have different needs, so get to know the type you want to grow!

Just like people, mushroom varieties are picky about where they get their nutrition.

I found it helpful to learn that the most common edible varieties (oysters, shiitake, portobello, button) are white-rotters. These guys are pretty versatile and will do fine on the substrates I’ll talk about below.

1. Growing Mushrooms On Wood Logs

Fungi feed on rotting organic matter and are star-players in the process of decomposing wood and releasing its energy back into the forest floor so that it can enrich the earth there.

So it makes sense that one of the easiest and most natural ways to grow your mushrooms is to give them a lovely, tasty wood log to grow on!

Here are a few varieties that I’ve had success with when I’ve used logs as the substrate:

• Oysters
• Shiitake
• Lion’s Mane
• Winecap
• Reishi

Check out my video on the subject for an in-depth look at using logs as your mushroom substrate.

Tips For Using Logs as Your Substrate

• Use logs that are freshly cut from healthy trees. As soon as the inner wood is exposed, fungi and bacteria will move in to colonize it. Make sure your mycelium gets in there first and doesn’t have to fight for its place!
• Mushrooms will do much better on hardwood than softwood. Stick to logs from the likes of healthy beech, birch or oak trees.
• Make sure the logs you use aren’t dry when you inoculate and don’t allow them to dry out as your colony establishes itself, either.
• If you are trying your hand at growing a couple of different varieties, make sure to use separate logs. One colony will always be stronger than the other, and will take over the substrate.

2. Using Cardboards As A Substrate To Grow Mushrooms

Cardboard is an unsung hero for your yard! It’s been used by gardeners for ages as a mulch and as a component in compost.

Plus, it’s a recycled material that happens to be dirt cheap, if not free – who could ask for more?

Cardboard also makes an easy mushroom growing substrate. The fact that it’s so simple and easy to get hold of makes it perfect for use in a family backyard mushroom project.

Which Varieties Can I Grow on Cardboard?

Although most of the wood-lovers I mentioned in the log substrate section can work, I’ve had the best results from oysters.

Oysters have a stronger, more aggressive mycelium and will manage a low-nutrient substrate like cardboard more quickly than the shiitake, which prefers a more nutritious substrate.

Unlike logs, cardboard needs a bit of prep before you inoculate it. Here are a few steps to take to get it substrate-ready:

1. Rip your cardboard up into small strips, a few cm big (kids will enjoy this part. They’re always up for a bit of demolition!)
2. Place it all in a large pot.
3. Cover the shredded cardboard with freshly boiled water, place it out of reach of kids and pets, and keep it at a temperature above 60c for two hours. Allow it to cool to room temperature before handling.
4. Now, squeeze out the excess water, and begin layering the cardboard and spawn into your mushroom bag. Alternate between a layer of cardboard and a layer of mushroom spawn.
5. Seal off the top of your bag
6. Store the inoculated substrate in a dark cupboard for a few weeks, until the contents are white. This is how you’ll know that the mycelium has colonized the cardboard substrate.
7. At this stage, you will need to cut an X shaped hole in the surface of your bag, so that the mushrooms can fruit through it. use a spray bottle to moisten the substrate each day.
8. If you follow these steps, you may well be ready to harvest in around a week’s time.

It’s also great to know you’re using a material that is already recycled and can be added to your compost heap once your mushrooms are done with it.

Because cardboard isn’t a highly nutritious substrate, the yield you get will be on the small side. On the plus side, though, fewer nutrients in the substrate mean less competition from invading fungi.

3. Coffee Grounds Are Perfect For Growing Mushrooms

Coffee grounds are possibly my favorite simple substrate for mushroom growing. Around 18 million tonnes of waste coffee grounds are produced each year globally. The majority of these will end up in landfills.

I’ve written before about re-using coffee grounds in the garden (they’re great for giving your veggies a boost), and it turns out they are superb as a nutritious mushroom substrate, too.

Just like cardboard, coffee grounds are super-easy to acquire. If you want to grow many mushrooms, though, you should ask a local coffee house if you can collect their fresh coffee grounds in bulk.

The best thing about coffee grounds is that the coffee brewing process naturally pasteurizes them, so there’s less prep for you. There’s a time limit, though – after 24 hours, the grounds will get increasingly less clean, so you need to be quick!

Which Varieties Can I Grow in Coffee Grounds?

Coffee grounds are surprisingly nutritious, which means you can try growing hungrier varieties, like shiitake. Of course, good old oysters will do well, too, and so will the typical button mushroom you find in the grocery store.

How to Use Coffee Grounds as a Mushroom Substrate

• Wipe down surfaces with alcohol and wear clean rubber gloves so that no contamination happens.

• Gather your ingredients. Although it’s not essential, I like to mix in some pasteurized straw, chopped up small. This will aerate the substrate, as the tiny grounds can get really compacted.
• Mix your ingredients together by hand in a clean, dry container.
• Place the whole lot into a clean mushroom growing bag, seal the top and store in warm, dark place like an airing cupboard for around three weeks.
• Just like with your cardboard, you’ll witness the mycelium colonizing the substrate and turning it white.
• Cut your X in the surface of the bag, transfer to a window sill or sheltered outdoor spot and mist regularly.
• After around two weeks, you’ll be able to harvest and enjoy!

4. Can You Use Coco Coir and Vermiculite For Growing Mushrooms

Coco Coir is another highly versatile organic material for your garden. Check out my post on some of the coco coir uses.

Coir is another substrate base that was traditionally a waste product, so using it for your mushrooms will boost your green credentials.

Like coffee grounds, coir has tiny particles, so adding vermiculite to the mix can help with aeration and water retention.

Which Types of Mushrooms Can I Grow in Coco Coir and Vermiculite?

Oysters and button or portobello mushrooms will do fine grown in coco coir.

How To Use Coco Coir and Vermiculite as a Mushroom Substrate

• Coir usually comes in a block that needs to be re-hydrated before you put it to work. Since you will need to pasteurize this substrate mix, you can combine the two processes into one step.
• To pasteurize and hydrate, place in a pot of water at 60c or above for two hours.
• Once it’s cooled to around room temperature, you can follow the same steps I described earlier, for using coffee grounds.

Coir and vermiculite are both inert. A cheap way to give your mushrooms the nitrogen hit they crave is to add some coffee grounds to the substrate mix.

5. Straw Is One of the Cheapest and Best Substrates For Growing Mushrooms

Another cheap and cheerful substrate that you can try for your mushroom adventures is straw. For small-scale growing at home, you won’t need too much. A couple of bucketfuls will do fine for getting started.

Straw is one of the most commonly used commercial substrates for oyster mushrooms, so you know you’ll be using a tried and tested method for growing yours.

Here are a few tips to get going:

• Make sure your straw is cut into smallish pieces.
• Pasteurize in a large pot, between 65-82 °C for 1 -2 hours.
• drain the excess water and cool to room temperature.
• Inoculate with mushroom spawn. The spawn should be around 10% of the total mix.
• Grab a mushroom bag, jam it all in there and seal the top.
• Incubate the bag in a warm, dark cupboard for a week or two, until you see the white colonization happening.
• Cut an X in your bag, and move it somewhere fresh and humid.
• Mist the substrate each day for a week or two.
• Harvest time!

6. Master’s Mix For Growing Mushrooms In

Before I wrote this post, I asked mushrooms growers on social media to describe the substrate they would recommend as their favorite. Master’s mix was the overwhelming winner.

87% of the experienced growers I asked for named Master’s Mix as the best substrate for growing oysters, shiitake, and button mushrooms.

I’ve spent a lot of time around keen mushroom growers, both amateur and professional.

They all have slightly different substrate recipes for specific mushrooms, but they all agree on one for growing the most popular edible varieties – the Master’s Mix.

Master’s mix is the stuff of legend for providing just the right substrate conditions to produce enormous colonies. And the best part is, it’s a straightforward recipe!

So, What is This Mysterious Master’s Mix?

T.R. Davis pioneered it at Earth Angel Mushrooms, a simple, 50/50 mixture of hardwood sawdust and soybean husks.

You can buy it ready-mixed, by the bag, but I prefer to source both parts myself and make up the mix that way.

How to make your own Master’s Mix Substrate.

For a decent home crop, these steps have worked well for me:

• 1lb soy hulls (pelleted)
• 1lb hardwood sawdust (pelleted)
• 1.5 liters of water.
• Sterilize all the ingredients in a pressure cooker for three hours at 15 PSI.
• Once cooled, you can mix in your mushroom spawn and substrate together in a mushroom grow bag.
• Seal the top, place in a warm, dark area, and wait a couple of weeks for the mycelium to colonize the Master’s Mix.
• Cut one or to X openings in the bag, transfer to a fresh, humid area and mist every day.
• After to or three weeks you should have a bumper crop ready to harvest!

FAQ’s on Mushrooms

Conclusion On Different Substrates to Grow Mushrooms

I hope this post has de-mystified mushroom substrates for you. As you can see, there are loads of simple substances that common, edible mushrooms will thrive. So, whether you want to whip up a batch of your own Master’s Mix or grab some cardboard or coffee grounds, get stuck in, explore the many substrate options, and enjoy your delicious, home-grown mushrooms.

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