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Six Reasons Why Your Mushrooms Are Not Growing

Mushroom Contamination

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Have you ever tried to grow mushrooms but got bad results?  Maybe your harvest was small or non-existent.  Or maybe you have your first grow kit and want to understand some of the potential pitfalls.  Read on, as we will cover the 6 most common reasons why your mushrooms are not growing.  Let’s get into it!

Reason 1: Not Enough Moisture

One of the most important environmental factors for successfully growing any kind of mushroom is moisture. Mushrooms are mostly water, so if you don’t maintain the right humidity level, then their mycelium, or roots, will dry up and won’t survive long enough for the mushrooms to grow.

So before adding your mushroom spawn, or “seeds” to the substrate, or “soil,” give your substrate a thorough soak and squeeze out the extra water. The substrate should retain enough moisture if your mushrooms are growing in an enclosed space like a large plastic tub.

Then, during the fruiting period of your mushrooms, remember to spritz your container or bag multiple times a day, or purchase a humidifier along with a hygrometer to keep a consistent humidity level.

If you don’t maintain the right humidity level, then your mushroom caps will become dry and brittle and may even crack or break.

Remember that if you live in a drier climate, you might need to water more often than the specified instructions if you’re growing mushrooms outdoors. Water retention can improve if you select a naturally shaded area for your mushrooms or if you install shade nettings.

Reason 2: Too Much Moisture

Too much humidity is detrimental to your mushrooms. And if there is standing water where your mushrooms are growing, you may end up with mold and other contaminations.

So don’t overwater your mycelium, and make sure you drain your substrate thoroughly. Another trick is to spritz your substrate with water instead of soaking it, which is the opposite of what you would do if it was lacking moisture. This helps to ensure that no excess water is retained.

Depending on your local conditions and the kind of mushrooms you’re trying to grow, the relative humidity in your growing environment should range from 70 to 90 percent. A hygrometer is a tool that measures the humidity levels in the air and is very helpful when growing mushrooms.

We recommend the following hygrometer:

Govee WiFi Hygrometer 3-Pack H5151: This hygrometer 3-pack comes with three sensors.  Each can connect via WiFi to an app on your phone, making it super easy for you to track the moisture level of multiple grow areas.


Mushroom Farm

Reason 3: Contamination

Contamination is one of the most frequent reasons that your mushrooms don’t grow, and it can cause problems at any stage of your mushrooms’ development.

Contamination happens most frequently because growers have not sterilized and cleaned their equipment. You will get better results if you sterilize all surfaces, tools, and containers in your growing area.

Pollutants like bacteria and mold often thrive in areas where mushrooms are grown because they love environments that are warm and damp. The contaminants will fight your mushrooms for nutrients, which can slow or even halt their growth and development.

Before you mix your spawn with the substrate, make sure the substrate is thoroughly sterilized. No exceptions! If you’re using a pressure cooker to sterilize your substrate, remember to check the pressure often. And if you’re using liquid cultures, always flame-treat the syringe needle before every penetration.

You should also do the same with the scalpel if you’re growing your own spawn when using agar and Petri dishes. Also, remember that the cleanliness and hygiene of the setting where you work are equally important. Wear gloves and a face mask when available and sterilize all equipment with 70% isopropyl alcohol.

Contaminated spores may be carried into rooms with airflow, so try to keep drafts to a minimum by using still-air boxes or tents when working. Remember to also keep your furry pets away! The general rule of thumb is to cause as little disturbance to the growing environment as much as possible. And if you’re a serious mycologist, you may also want to consider a laminar flow hood in your workspace. An excellent choice of flow hoods is:

Msfullsea Vertical Laminar Flow Hood: This flow hood contains a HEPA filter to filter out any contaminants in the air where you are working.

It is also important to learn how various contaminants appear so that you can easily recognize them when they start to impact your growing operation.

Healthy mycelium is white. If you see any pink, green, orange, black, or brown spots, then contamination may be present. To prevent further spread, jars or bags that are contaminated should be removed from your grow area right away.

Reason 4: Impatience

New mushroom growers are always eager to see the fruiting result, and they may make drastic changes to their projects to get their mushrooms to grow faster.

You may run into contamination if your preparations are incomplete, or when you don’t follow a procedure properly. When you rush each step, you increase your failure rate. So before inoculating your substrate, remember to always let it cool fully. And when you begin the pinning and fruiting stage, make sure your mycelium has THOROUGHLY colonized the substrate. Shortcuts never bring about a good outcome.

Understanding the life cycle and fruiting probability of the specific mushroom you’re growing is also helpful. Some mushrooms, like morels, for example, may not fruit for several years. Patience is a virtue and the key to a successful grower.

The idea is to mimic nature and the natural environment of the mushroom you are growing as much as possible. Invest in the correct equipment at the beginning of your growing journey to maximize your chances of success.

If you’re a new grower, you may find the details to be long, complex, and even painstaking. But even seasoned and experienced growers may take multiple tries before getting a successful flush. It’s important to start the process knowing that the results are a bit like baking bread, partially out of your control. Don’t get discouraged if it doesn’t work the first time. Learn, and keep going!

Reason 5: Thermogenesis

When mycelium breaks down organic matter, then your substrate will begin to produce heat on its own, just like compost piles.  And it’s entirely possible that the substrate temperature will rise above the ambient air temperature. When that happens, the heat may be enough to fry your mycelium and to promote the growth of microbes.

Good air circulation in the room or your mushroom’s ambient environment will help prevent the substrate from overheating. Remember to constantly monitor the ambient temperature and allow a buffer for thermogenesis.

The depth of your substrate, and how compact it is, will also affect the temperature and ventilation. If you tightly pack it into the sides of the beds or trays, it will create a more consistent temperature across your substrate.

Mushroom Farming

Reason 6: Wrong environment.

Because mushrooms grow everywhere in the world, each strain of mushroom has its own preferred habitat. Make sure that you do your research on the strain of mushrooms you’re trying to grow, and know the natural environmental factors that the mushroom prefers.

For example, it will be very difficult for you to grow a warm-climate mushroom in cold weather. And if the mushroom prefers wood, using straw instead will quickly lead to failure. The most important factors to consider are air and substrate temperatures, humidity, light conditions, fresh air exchange, and ventilation.

The secret to mastering the art of mushroom growing is to grow them under the right conditions for the strain. Listen and learn from mother nature. Even if it’s not required, a little observation and information can go a long way.

Wrapping It Up

So these are the six main reasons that people are not successful with their mushroom growing efforts.  Keep on top of each of the reasons we describe as you grow your mushrooms, and you will be far more likely to find success!

Check out our video about why your mushrooms might not be growing.

And check out our YouTube channel for lots of other mushroom videos.

If you are a beginner to growing mushrooms, check out our guide Growing Mushrooms for Beginners.

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Why Aren't My Mushrooms Growing


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