When first starting out growing mushrooms people new to the hobby often encounter problems with contamination. Whether it’s molds, bacteria, or some combination, it can be frustrating and disheartening to see your hard work go to waste. To combat this let’s look at where contamination comes from and how to avoid it.

What Is Contamination?

In short contamination is competing fungi and bacteria. When you setup a fungiculture or mushroom substrate you’re preparing a nutrient rich environment for you mushrooms to grow. Unfortunately, this is exactly what makes contamination possible. These high nutrient environments are the perfect place for microorganisms to grow and if they get in, they will.

Where Does Contamination Come From?

In short, everywhere.

Contaminates can be in the air, on surfaces, or in our substrate from the start. Think about all the things you need to do keep your house clean. The air is teaming with dust, spores, and microbes. While you can’t see it, contamination is all around us.

The reason these microbes are a problem for us now is because we’ve given them the perfect places to live when we setup our fungiculture. If open air touches the surfaces we work on or the growth medium itself there is a chance of introducing contamination.

How Likely Is Contamination?

Now that you know contamination sources are all around you you might wonder how common actual contamination is. How frequently will contamination be a problem?

The answer is: it depends. Air quality, sterile technique, and materials all effect contamination rates. Your setup will be unique to you.

So, If there’s contaminates everywhere why don’t we get contaminated mushrooms every time?

The reason we don’t see this in every case, even when working in open air, is because not every microbe is going to colonize your growth medium. When growing mushrooms you are trying to make the perfect habitat for fungi, so this reduces the viability of other microorganisms in that medium. Additionally, event though open air is full of microbes, it has 10 times less microbial load than outside air on average.

How contaminated is my

If you were to leave a few petridishes or agar plates out open to the air in your home for 30 minutes, you would be able to see how much contamination is present. In some homes it’s more than others. Once the plates grow, you might get a few spots indicating minor contamination chances, or your plates might be covered, which means you should deep clean your home.

Avoiding Contamination of Mushroom Cultures

If you want to keep your cultures clean you need to keep your work area clean. Before you do anything that involves growth medium or transferring spores you need to clean the area you’re working in, if not your whole house. If you have mold in your bathroom, those spores are in the air in your home!

A clean house will make your chances of success much higher and likely also make you happier. Everyone likes a clean house, mushrooms included.

In addition to cleaning doing things like taking out the trash, removing or storing open food, and replacing your HVAC filters regularly can all help lower the chance of contamination.

Choosing a Work Area

When considering contamination choosing the right work area is critical. Typically you will want to work in a room without carpet with easily cleanable surfaces. Kitchens and bathrooms are usually the first choice if you don’t have any better suited work areas available. Choose an area that is away from vents and never work next to a garbage disposal or full trash can.

Preparing a Work Area

When you are ready to work make sure to wipe down your area with a 10:1 mix or isopropyl alcohol. Additionally, spray down the outside of your containers and tools before you begin working. It may also be a good idea to close vents in the room you are working to reduce the chance of dust being introduced to your clean area.

Upgrade your Workspace

While the above tips can help you work in relative ease, you still have the risk of contamination from time to time. To cut these risks even further you can upgrade your workspace and construct a glove box, get a laminar flow setup, or even build a clean room if you have the space and resources. These are all things you would consider as you scale up. The glove box is the easiest place to start as it’s a minimal investment and can dramatically reduce contamination when used properly.


Contamination is everywhere, but if you’re vigilant you can reduce the number of contaminates you encounter. Proper cleaning and good aseptic technique can save you a lot of time and money. Don’t waste your time taking risks when you can easily do things that will help you succeed early on.