How To Grow Mushrooms Indoors: 5 Steps to Follow

Swear by the shiitake? A glutton for buttons? Think the oyster is the pearl of the mushroom world? 

Mushroom-lovers, did you know that it’s possible to grow mushrooms indoors?

Creating an indoor mushroom garden can be extremely rewarding – not only will you (hopefully!) get tasty mushrooms to eat, you will also learn a lot about this fascinating fungi in the process. They are also low-maintenance compared to many houseplants.

As you construct your indoor mushroom farm, remember that different types of mushrooms like different growing mediums, including straw, hardwood sawdust and even coffee grounds! All mushrooms agree that the cool, dark and damp make a good home.

Here you will find all of the essential information for growing mushrooms at home, from how to prepare the growing material (or substrate) to what on earth mycelium is.

This guide has been put together after intense research into how to grow mushrooms indoors specifically and is focused on giving you a shortcut to mushroom success.

This handy guide is split into four helpful sections: need-to-knows, the care guide, a step-by-step mushroom growing guide, and other useful information.

Table of Contents

• What Is Key Mushroom Terminology?
• What Is a Mushroom Growing Life Cycle?
• Can You Grow Mushrooms Indoors?
• Which Is the Best Variety for a Beginner Mushroom Grower?
• Which Location is Best?
• Do Mushrooms Need Light?
• Is Substrate Necessary?
• Step 1: Preparation
• Step 2: Spawning (inoculation)
• Step 3: Incubation
• Step 4: Cropping
• Step 5: Harvesting
• What Recipes Are Best?
• FAQ

What Is Key Mushroom Terminology?

Spores: Similar to pollen in plant-speak.

Spawn: Similar to seeds in plant-speak – this is the easier way to grow mushrooms at home. Get your mushroom spawn online or from a garden center.

Substrate: The material which mushrooms can grow in and get nutrients from (like soil for a plant). 

Mycelium: The part of the fungus which grows underground, like a root system, and is white in color. Mushroom mycelium are much more complex than plant roots – they absorb nutrients, can spread to help the mushroom move to find more space and some varieties can even pass messages along them.

What Is a Mushroom Growing Life Cycle?

Understanding how mushrooms grow is key for success.

Mushrooms have a continuous life cycle – the Circle of Life, mushroom-style – which makes them one of the most rewarding things to grow. 

Let’s start with the mature mushroom releasing spores.

1. A mature mushroom releases spores from its gills (the frilly section found underneath the mushroom cap). Each mushroom can produce hundreds of thousands of spores!
2. A male and female spore then have to combine to form a spore that can germinate into a mushroom.
3. The mycelium (a fancy word for mushroom root system) absorbs the nutrients necessary for growth and the mushroom begins to develop into a visible thing.
4. The mushroom starts to emerge from the soil (at this point it is called a hyphal, or baby mushroom), and before too long it will reach maturity and the life cycle begins again. The part of the mushroom above the surface is the edible part. In essence it’s like the fruit, whereas the rest of the “plant” – the mycelium in this case, largely remains unseen underground or within a host tree.

Can You Grow Mushrooms Indoors?

There are many varieties of mushroom that can be grown indoors, from the frilly and appropriately-named Lion’s Mane mushroom to the tall and spindly Enoki mushroom. 

Given that each type of mushroom has slightly different requirements, let’s focus on three simple – and delicious! – varieties: button, oyster and shiitake. 

Button mushroom: Button mushrooms – the most popular mushrooms – are white or very pale gray-brown all over, except for their brown gills. They are native to the grasslands of North America and Europe. Their caps can reach 15cm in width. (There are several button look-alikes that are poisonous, including the aptly-named Destroying Angel which have pure white gills.

Oyster mushroom: Oyster mushrooms get their name from their gray-brown color and oyster-shaped cap. They have an extremely short, or non-existent, stem and grow in clusters. Oyster mushrooms have a mild flavor – some say that they taste a little like seafood. There are different varieties of oyster mushroom that come from around the world, but the most common – the pearl – grows to between 5cm and 25cm in length.

Shiitake mushroom: Native to East Asia, this variety is a darker brown with small caps (usually between 5cm and 10cm). They often have a wrinkled appearance and a longer stem than button or oyster mushrooms. Shiitake are one of the most flavorful and meaty mushrooms.

Which Is the Best Variety for a Beginner Mushroom Grower?

Oyster mushrooms are the best mushrooms for beginners to grow. 

Oyster mushrooms are simple to grow because they are happy with many different substrates (growing materials), including coffee grounds! They are also very fast growing and are hardy against dangerous pathogens like blue mold. 

Bonus: they require very little input from you!

Oyster mushrooms also come in lots of wonderful varieties, including:

• Pearl: The standard variety of oyster mushroom. They are light gray with very little stem and a relatively small cap.
• King: The largest oyster mushroom. They grow thick white stems and brown caps. Unlike other oysters, they grow individually.
• Golden: Golden oysters are bright yellow and have a more aromatic flavor than the standard pearl.
• Blue: Although not a vibrantly colored mushroom, the blue oyster has a slight blue tint amongst its gray. They have thicker brown caps (a little like a chestnut mushroom) and lighter gills.
• Pink: They are bright pink (though the color fades when cooked) and have a pretty ruffled appearance. Pink oysters tend to be tougher and more pungent.

Which Location is Best?

All varieties of mushrooms love cool, dark and damp conditions. Selecting a place where conditions can be easily maintained is important – mushrooms love consistency. A basement, garage or cabinet would be perfect.

Avoid keeping your mushrooms near wood furniture as the damp can spread. Particularly don’t keep your mushroom under the stairs – as Phil does in Modern Family – as it may result in a step collapse.

Top tip: Shiitake mushrooms need to be grown in an indoor fruiting chamber (or outside on a log in a shady spot). You can actually make your own fruiting chamber at home. Fruiting chambers can also be used to successfully grow other varieties of mushrooms indoors.

Darkness

Mushrooms do not need complete darkness (other than during the initial incubation period). Though as they grow under a tree canopy or in the shadow of a rock in the wild, they do need some darkness.How to create these conditions indoors:

• Choose a place with no windows, such as a cupboard or basement.
• Cover your mushrooms with a black bin liner.

Damp

Mushrooms like damp, moist conditions during their growing phase. They need a substrate (growing material) that has lots of moisture as well as moisture in the surrounding air.

How to create these conditions indoors:

• Keep the substrate moist by adding water to stop it going dry. Or cover your mushrooms with a damp towel.
• Use a humidifier to keep the air moist.
• Choose a spot without draughts or heaters as these can alter the moisture in the air.

Temperature

Mushrooms rarely grow in warm places and generally prefer a cooler climate. This is why mushrooms are rarely seen in the hot summer season, and usually make their appearance in spring or fall.

Aim for 70°f (21°c) for spawning (the beginning of the mushroom cycle), then 55°f (13°c) for growing.

How to create these conditions indoors:

• Pick a cool place like a garage or basement.
• Keep your mushrooms out of the sunlight.
• If you are growing mushrooms outside, aim for your mushrooms to make their appearance in either spring or fall. Keep them in a well-shaded area.

Do Mushrooms Need Light?

Mushrooms will put up with a little indirect light (this can help mimic the sun and encourage them to grow upwards), but light isn’t necessary. 

A grow light can help your mushrooms to grow upwards, making harvesting easier. Keep your grow light far enough away from your mushrooms so that it doesn’t impact the temperature.

Keep your mushrooms away from windows. Windows provide too much light for mushrooms and can also cause nasty draughts.

Top tip: Shiitake mushrooms can survive with some indirect light. But white button mushrooms need no sunlight at all.

Is Substrate Necessary?

Mushrooms often need nutrient-rich substrate (growing material) and enjoy slight acidity – around 5 pH to 6.5 pH is great. (Though oyster mushrooms can survive up to pH 8.) 

If you opt for one of the following substrate options, you won’t need to worry about the acidity levels or adding in nutrients.

Substrate options

• Straw – best for oyster mushrooms.
• Coffee grounds – another option for oyster mushrooms.
• Composted manure – ideal for button mushrooms.
• A log – best for shiitake mushrooms.
• Untreated hardwood sawdust – another option for shiitake mushrooms.
• Decaying leaves – for outside mushroom growing only.

How to Grow Mushrooms Indoors: Step-by-Step

Step 1: Preparation (substrate)

It is important to prepare your substrate (growing material) before you add the spawn.

Top tip: If you opted for sawdust, make sure it’s untreated hardwood sawdust, so that it has the right nutrients.

How to prepare your substrate:

1. Add enough water to the substrate to make it damp, but not soaking.
2. Sterilize the substrate to avoid other microorganisms growing, such as molds which can harm the mushrooms or competing bacteria. See the sterilization options below.

How to sterilize your substrate:

Option 1: Sterilization

Sterilization aims to expose the substrate to really high temperatures and pressure to eliminate other microorganisms.

The best way to sterilize your substrate is to use a microwave. Simply divide up the substrate (so it will fit in your microwave), place it in a microwaveable bowl and add water until the substrate is thoroughly wet, but not massively dripping. Then heat it on the highest heat level your microwave has until the excess water has boiled off. Your substrate should remain slightly damp after its visit to the microwave. Repeat until you have done all the batches of substrate.

You can also use an oven, but this is more likely to burn the substrate and it will need rehydrating after.

Option 2: Pasteurization

Pasteurization aims to get rid of the contaminants that might hinder the growth of your mushrooms.

Submerge your substrate in boiling water for an hour to kill off other bacterias and molds.

Step 2: Spawning (inoculation)

Inoculation involves adding your mushroom spawn to the substrate (growing material).

1. After sterilizing your chosen substrate, put the substrate in a large baking tray. Add enough to cover the bottom with a thin layer.
2. Use a sterilized (boiled) utensil to mix the mushroom spawn (which you can pick up easily online or at most garden centers) into the substrate.
3. Heat the spawn and substrate mix to 70°f (21°c) on the stove top (the hob is better than the oven as you need to check it doesn’t go above 70°f ). This is the best temperature to encourage growth while keeping the mixture slightly damp.
4. Leave the spawn and substrate mix in the baking tray or transfer it into a growing container – a bucket, a planting tray, a large plant pot – anything you like!

For tips on how to inoculate your shiitake using a log or hardwood substrate, see the FAQs.

Step 3: Incubation

Once your mushroom spawns have been inoculated (added to your substrate), they need an incubation period.

1. Put the container into a completely dark place for three weeks, such as a closed cupboard. Pick a spot that is dark but not as cold as the later growing spot (room temperature is fine for this phase). 
2. Keep checking that the mixture is not completely drying out. Add water to keep the substrate moist when needed.
3. After three weeks you should see a white fuzz covering the substrate. The mycelium (mushroom root system) will have formed below the soil.

Step 4: Cropping (fruiting)

Now comes cropping:

1. Move your container to your planned dark, damp growing place. This should be around 55°f (13°c) and certainly not above 70°f (21°c).
2. Cover the growing mushrooms with a light layer of the substrate (remember to sterilize the new substrate first). 
3. Spray the mixture in the container with water so that it is damp, but not soaking. Try covering the container with a damp towel to reduce water loss.
4. If you spot dark green, brown or blue mold growing (it looks like the kind you see on bread), remove the infected areas of the substrate and throw them away.

Top tip: Make harvesting easier by using a grow light to mimic the sun – this will encourage the mushrooms to grow towards the light, making them easier to pick.

Step 5: Harvesting

Most mushroom types will grow much faster indoors compared to outdoors. After a few weeks you should see small mushrooms appearing. (For oysters this will be around 14 days, for shiitake 8-12 weeks and for button mushrooms 3-4 weeks. Mushrooms grown in a log can take up to 6 months to reach this stage.)

Top tip: Leaving button mushrooms for longer than 4 weeks will result in brown mushrooms (portobello) developing instead. 

1. Continue to keep the mushrooms in a moist, cool, dark atmosphere.
2. When you start to see mature mushrooms (you can eat them from any size), harvest them with a sharp knife by cutting the base of the mushroom. Don’t pull them out with your hands as this will damage the mycelium under the soil and prevent new growth.
3. Once harvested, other mushrooms will appear quickly – harvest as they appear.
4. Growth will eventually stop. Add more spawn to the existing growing area to enjoy more mushrooms!
5. Rinse your mushrooms before eating or cooking them. They can be stored in the fridge for a week at the most.

What Recipes Are Best?

Now you have nurtured and harvested your mushrooms, it’s time to decide how best to enjoy them! 

Here are some simple and delicious recipes to help you make the most of your mushrooms:

• Mushroom risotto – a wonderfully creamy and rich risotto which tastes best with white button or oyster mushrooms. 
• Mushroom soup – a delicious and warming soup is a firm favorite in most households in the winter months. If you have timed your growing right, you can use your white button mushrooms for this. Swap the chicken stock for vegetable or mushroom stock to make your soup vegetarian. 
• Shiitake stir fry – shiitake mushrooms can work in any type of stir fry, adding a real depth of flavor. This recipe combines your mushrooms with broccoli and noodles to make a healthy stir fry. 

FAQs About How to Grow Mushrooms

Is it better to grow mushrooms outdoors or indoors?

It’s possible to grow great mushrooms indoors and outdoors. 

The benefit of growing them indoors is that they avoid contamination with wild spores and other bacteria, and they are less exposed to sunlight and the horrors of outdoor life.

Growing your mushrooms outdoors will only work if you have a very shaded and damp outdoor space.

Is it possible to grow mushrooms on logs indoors?

Growing mushrooms on a log (especially shiitake mushrooms which like logs) indoors is a little trickier than growing them on a log outside.

The log needs to be kept damp throughout, so it will require more watering than other substrates. You will also need to drill into the logs to put inoculation dowels (which have the spores in them) into the wood.

Should I buy a mushroom growing kit?

A mushroom growing kit is great for a beginner or anyone with little spare time. The substrate comes ready prepared (though it will still need sterilizing) so you don’t need to worry about acidity levels or nutrients such as nitrogen. 

It is possible for gardeners with reasonable experience to grow mushrooms without a kit.

What might kill my mushrooms?

Keeping your mushrooms in light, dry and warm conditions will upset them terribly. Aim for as close to 13°c (55°f) as possible. Keep the substrate damp throughout the process. Also watch out for other contaminants (like molds) that might outcompete your mushrooms – sterilizing the substrate should help you avoid this issue.

Ready to “Spawn” Your Own Mushroom Babies?

Growing mushrooms indoors can be hugely rewarding, fascinating and good fun! Watching the baby mushrooms emerge out of the substrate will make your sterilizing efforts and patience very much worthwhile. Finally celebrate your mushroom growing success by cooking a delicious and nutritious mushroom-based meal.

Key Tips to Remember

• Each mushroom variety is different and needs a different substrate, so do your research.
• All mushrooms like the cool, dark and damp.
• Sterilize your substrate at the beginning of the process to avoid other contaminants outcompeting your precious mushrooms.
• Rinse off your mushrooms before consuming.

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