Why Is My Mycelium Growing So Slow? (9 Prime Reasons With Easy Cures)

The problematic predicament of slow mycelium growth is a familiar and frustrating reality for many dedicated growers of culinary or medicinal mushrooms.

If unchecked, it can significantly delay your harvest, so eat into your profits or supply of healthy homemade mushrooms. But, do you know why is your Mycelium growing so slow?

Sadly, many factors can cause their growth to slow, turning the usually exciting cultivation process into a painstakingly slow game of wait-and-watch.

Understanding and addressing this issue in mushroom cultivation is pivotal to ensuring optimal mushroom yield. This is what brings us to the crux of our topic today.

Why is my mycelium growing so slow

You can look forward to understanding the key aspects influencing mycelium growth, from substrate composition to environmental conditions. Furthermore, we will equip you with actionable advice to help maximize your mycelium’s growth rate and overall mushroom yield.

Why is my mycelium growing so slow?

There are multiple reasons why mycelium growth tends to be slower than usual. To understand them better, let’s delve deeper into each of these factors.

The Perils of Inadequate Air Exchange

Insufficient air exchange is one of the most common reasons behind slow mycelium growth. Mycelium requires oxygen to grow and colonize the substrate. When air exchange is insufficient, oxygen levels drop and carbon dioxide (a byproduct of mycelium metabolism) builds up.

This imbalance can stunt the mycelium’s growth and lead to an eventual stall, causing the growing process to slow down.

Impact of Unfavorable Environmental Conditions

The environment within which the mycelium grows is pivotal in determining the growth rate. Some key environmental factors include temperature, light, and humidity.

Each mushroom variety has specific environmental needs; if these requirements are not met, the mycelium’s growth could take a hit. For instance, if the temperature drops below or climbs above the optimal range for a specific type of mycelium, its growth will slow or even halt.

Impact of Unfavorable Environmental Conditions

Consequences of Disturbing the Substrate

Lastly, the substrate — the material mycelium grows — should remain undisturbed for optimal growth. However, if the substrate is frequently disturbed or moved around, it can disrupt the mycelium’s delicate growth routine.

Mycelium needs a stable setting to establish itself and spread across the substrate. Any interruptions to this process can result in slower growth rates.

Understanding and addressing these three key factors can greatly enhance your mycelium’s growth rate and optimize your overall mushroom yield.

The Troubles of Using Bad Spawn

Spawn is the mycelium-infused medium that kickstarts the mushroom cultivation process. It’s similar to the seed for a plant. Therefore, using high-quality spawn is paramount for healthy mycelium growth.

Poor quality or contaminated spawn can drastically slow the growth process or inhibit it altogether. It could introduce mold or other harmful contaminants to your substrate that not only compete with mycelium for nutrients but can also prevent the formation of a healthy mycelial network.

The Need for Patience

While it might not seem like a direct contributing factor, impatience can often be an obstacle to cultivating mycelium effectively. Mushroom cultivation is a process that calls for immense patience.

Often, growers get anxious if they do not see immediate results and make unnecessary changes or take extreme measures which can, ironically, cause the process to slow down further.

It’s important to remember that mycelium growth is a slow, gradual process and rushing it or constantly intervening can be counterproductive.

Considerations for Different Varieties

Different mushroom varieties have different incubation rates; therefore, not all mycelium will grow at the same pace. By their very nature, some types take longer to colonize the substrate.

As a grower, it’s important to understand and respect the unique growth characteristics of each variety. So, if your mycelium is growing slowly, it might be because your chosen variety has a naturally slow incubation time.

The Importance of Sterility

Sterility is another crucial aspect for fostering suitable conditions for mycelium growth. Mycelium is highly susceptible to contamination, particularly from molds and bacteria.

These contaminants compete with the mycelium for nutrients, potentially stifling the growth of the mycelium. So, ensure that your growing environment is as sterile as possible – from the substrate and the spawn to the tools and the containers used.

The Role of Moisture

Last but not least is the aspect of moisture. A well-hydrated substrate is key for mycelium to grow effectively. It uses the water in the substrate for metabolic processes necessary for growth. If the substrate has too little moisture, the mycelium can desiccate and growth can slow down.

Conversely, too much water can create conditions conducive for harmful bacteria or mold to thrive, negatively impacting mycelium growth.

Possible Nutritional Deficiencies

Apart from the factors mentioned, the growth rate of mycelium could be affected by nutritional deficiencies in the substrate. The substrate serves as a source of nutrients for the mycelium to grow, and if the essential nutrients are lacking, the mycelium may either grow slowly or not grow at all.

Possible Nutritional Deficiencies

Typically, nitrogen, along with a host of other nutrients, is vital for mycelium growth. A lack of these nutrients can lead to slow or deformed mycelial growth. Therefore, using a substrate with a balanced nutrient profile will lead to healthier and faster mycelium development.

By maintaining keen observance on the factors above, you can navigate the cultivation process to ensure optimum mycelium growth and garner a satisfying mushroom yield. Mycelium is a living network, and understanding its needs is the first step towards successful mushroom cultivation.

How long does it take for mycelium to start growing?

Mycelium growth commences after you inoculate your substrate with spores and place them under ideal conditions. The incubation period for mycelium to start growing, especially if the conditions are right, can vary depending on the species but generally takes 2 to 4 weeks.

This is when spores germinate and grow into healthy mycelium. If the compost is colonized in the growing room, it is usually left there so the mycelium stays intact, with the optimal time for colonization generally falling between 16 to 19 days.

How long does it take for mycelium to start growing

However, these timeframes are only general guidelines as the exact duration can vary based on various factors, including environmental conditions, cleanliness, and the mushroom species.

Always ensure the substrate is kept in ideal temperature conditions for incubation, as recommended for the specific type of mushroom being grown.

How can I speed up mycelium growth?

Here are some ways to speed up mycelium growth:

  1. Ensure optimal air exchange: Mycelium needs sufficient oxygen and low levels of CO2 to grow efficiently. Ensure the growing area allows adequate air exchange to meet these requirements.
  2. Maintain appropriate environmental conditions: Keep the growing environment within the optimal temperature, humidity, and light range for the cultivated variety of mycelium.
  3. Select a nutritious substrate: Use a balanced nutrient profile to ensure that your mycelium has access to the nutrients necessary for healthy growth.
  4. Minimize substrate disturbance: Avoid disturbing the substrate while the mycelium is growing. Keeping the environment stable will encourage mycelium to grow more quickly.
  5. Use good-quality spawn: Starting with high-quality spawn is essential to promoting fast and healthy mycelium growth.
  6. Maintain sterile conditions: Keep the growing area, tools, and containers as sterile as possible to minimize the risk of contamination and competition, which could slow down mycelium growth.
  7. Control moisture levels: Ensure that the substrate is well-hydrated but not overly wet, as excess moisture can create conditions that promote bacterial growth and hinder mycelium expansion.

Remember, following best practices for mushroom cultivation and being patient is crucial, as speeding up mycelium growth can only be achieved within natural limits for a given variety.

What is the best food for mycelium growth?

The best food for mycelium growth would vary somewhat by species, but mycelium needs a rich and balanced nutritional diet for healthy growth. Depending on the species, the most optimal nutrients come from a mix of carbon, nitrogen, vitamins, and minerals:

  1. Starch or Sugars: Mycelium needs a carbon source for energy; sugars such as sucrose or starchy substrates can provide carbohydrates.
  2. Proteins: Nitrogen is pivotal for growth and protein synthesis in mycelium. Nutrient components like peptone and tryptone boost growth.
  3. Mineral Salts: Calcium (Ca2+) also plays a significant role in mycelial growth.
  4. Vitamins: Certain vitamins like folacin are also crucial for mycelium growth.
  5. Yeast Extract: Yeast extract, rich in B-vitamins, is often used to supplement the growth medium for general nutrient support.

Finally, it’s important to note that the optimal culture medium and nutrient requirements for mycelial growth may differ according to the specific strain used. All the mentioned components should be modified according to the specific species of mushroom being cultivated for optimal growth.

Mycelium not growing after inoculation

If you’re noticing that your mycelium is not growing despite having inoculated your substrate, there could be several potential reasons:

Mycelium not growing after inoculation
  1. Substrate Moisture: Mycelium needs a moist environment to thrive. If the substrate is too dry or the humidity levels are too low, the mycelium might not grow.
  2. Quality of Spawn: It’s possible that the spawn used for inoculation is not high quality or was stored improperly, resulting in poor or no growth.
  3. Temperature and Other Environmental Factors: Optimal growth conditions include the appropriate temperature and light. The mycelium may not grow if these are not observed.
  4. Contamination: Contamination can hinder the growth of the mycelium. Keep the growing area, tools, and containers sterile.
  5. Time: Patience is key. According to some experienced growers, it’s not uncommon to see growth only around the 3-5 day mark, sometimes longer.

So, it’s highly important to maintain optimal conditions for your mycelium to thrive. If these conditions aren’t met, the mycelium may not grow even after inoculation.

frequently asked question (FAQs)

Does mycelium need light to grow?

Mycelium does not require light for growth. It primarily relies on the nutrients in the growth medium for sustenance.

Does mycelium need to be in the dark to grow?

Mycelium doesn’t necessarily need darkness to grow. However, it prefers lower light conditions during colonization.

Does heat make mycelium grow faster?

Yes, heat can expedite mycelium growth, but only to a point. Each species has an optimal temperature range for growth. If the temperature surpasses this optimal range, it can kill the mycelium.

What is the best temperature for mycelium growth?

The best temperature for mycelium growth is generally between 24-27°C (75-80°F), but this may vary depending on the species.

Does sunlight help mycelium growth?

Not directly. While mycelium doesn’t use sunlight to grow, light can trigger a mycelial network to start fruiting, the stage when mushrooms appear.

Does humidity help mycelium grow?

Yes, mycelium requires a high-humidity environment to grow well. The humidity level can vary based on the mushroom species.

Does sugar help mycelium grow?

Yes, sugar can be used as a carbohydrate source for energy, aiding in mycelium growth. However, care must be taken not to overuse sugar as it can promote the growth of unwanted organisms.


Mycelium growth rate can be influenced by several factors, from the quality of the spawn to the climatic conditions. Care must be taken for optimal results to provide the right balance of moisture, temperature, and nutrients.

Remember, each mushroom species may have different requirements for optimal growth. It can be a delicate balancing act to create the perfect environment for your mycelium.

Still, by understanding these factors, you can better troubleshoot slow mycelium growth and improve your mushroom cultivation success.

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