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All You Need to Know About Aerial Mycelium, Mushroom Pinning and Aerial Hyphae

What Is Aerial Mycelium - Does It Delay Mushroom Pinning - Aerial Hyphae Or Vegetative Mycelium - Curative Mushrooms

When it comes to discussions about mycelium type, you’ve probably heard the terms rhizomorphic and tomentose and their association with mushroom pinning, but then, there comes another term, “aerial mycelium.”

So what is it? Is it a third type of mycelium? Where does it fall between rhizomorphic and tomentose?

How does aerial mycelium delay mushroom pinning? Is aerial mycelium a good or a bad thing?

In this article, we will answer the most commonly asked questions about aerial mycelium including how it affects mushroom growth.

What is Aerial Mycelium: Meaning and Definition

What is Aerial Mycelium Explained - Curative Mushrooms

Mycelium is a network of hyphae that grow from mushroom spores in a substrate with plenty of nutrients. In certain conditions, hyphae may grow upward or outward from the surface of the substrate.

This outward growth is called “aerial hyphae.” Coming from the term “aerial” which means “existing, happening, or operating in the air.” A network of outward hyphal growth is collectively termedaerial mycelium.”

In appearance, it presents as loose cotton balls or cauliflower growth above the substrate. Unlike molds, aerial hyphae are bright white and do not overgrow overnight.

Is cobweb mold growing on your substrate or is it mushroom mycelium?

1. Vegetative Mycelium vs Aerial Mycelium

Aerial Mycelium vs Vegetative Mycelium - Delayed Mushroom Pinning - Curative Mushrooms

In contrast to aerial mycelium which grows above the substrate, there is what you call substrate mycelium.

Also called as penetrative mycelium, it is the portion that penetrates the substrate and absorbs nutrients.

Simplified Diagram Penetrative Hyphae, Surface Hyphae, Aerial Vegetative Hyphae, Aerial Reproductive Hyphae - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms
Simplified diagram of the growth of filamentous fungi on solid substrates. The different types of hyphae present are indicated.

Basically, this is the main mycelium that develops from the germinating spores. That is why it is also termed as “primary mycelium.”

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Next, we have surface mycelium which is obviously the mass of hyphae growing right on the surface of the substrate.

Then there goes the aerial vegetative mycelium which is the non-reproductive mass of hyphae growing right above the substrate’s surface.

Last is the aerial reproductive mycelium which produces spores.

Meanwhile, some scholarly articles only describe two types of mycelium.

Vegetative mycelium as the mass of non-reproductive hyphae penetrating the substrate. Then, aerial mycelium as the reproductive outward hyphal growth.

Given that, they refer to vegetative mycelium as the “primary mycelium” and aerial mycelium as the “secondary mycelium.”

2. Aerial Hyphae Definition and How Does It Form

How does aerial mycelium form - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

Firstly, aerial mycelium may grow as an extension of the substrate mycelium. It may start occurring when the substrate is only partially colonized or when it has reached full colonization.

Often, growers cannot tell whether they are seeing aerial mycelium or already the formation of primordium before the Fruiting Phase.

This confusion stems from the fact that both growths characterize an appearance of extended mycelium.

Primordium (plural primordia) also referred to as pinhead is the earliest identifiable stage of development of a fungus’ fruiting body.

3. What Does Mushroom Pinning Look Like?

How do you tell mushroom pinning from aerial mycelium? - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

Give it a little time and see if more branching hyphae stem in a few days. With no noticeable tiny pins, the mycelium in your growing room or medium might not be pinning at all.

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In other words, the conditions in your mushroom growing kit are not optimal and you need to do some adjustments.

Usually, the overgrowth of aerial hyphae is caused by two correlated conditions: poor air exchange and excessive humidity.

Branching outside the substrate is like the mycelium’s cry for fresh air.

Fresh Air Exchange and Humidity - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

However, it is unclear if all mushroom-bearing fungi go through aerial hyphae phase. Or if it is an abnormal growth that prevents pinning.

In other scholarly articles, it was described that after the primary substrate mycelium has been established, aerial hyphae are formed. From that form, it may develop into reproductive structures such as fruiting bodies.

Probably, in healthy mushroom growth, aerial hyphal growth is supposed to be short-lived before it starts pinning.

So aerial mycelium has earned its bad reputation because its overgrowth and stagnation are associated with delayed pinning.

4. How Do Aerial Mycelium Affect Mycelium Pinning and Mushroom Growth?

For the mycelium to produce good pin sets, you need to tweak the conditions like adjusting humidity and controlling air temperature.

You may introduce fanning to encourage airflow and prevent CO₂ buildup. Also, you can just limit misting with water spray bottle, to bring down moisture and humidity.

According to mushroom expert “TVCasualty” in the Mycotopia forum:

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“… aerial mycelium is a sign of high Relative Humidity (not necessarily too high, just somewhere above 90%). In the case of most home growers, this would also usually occur in conjunction with high carbon dioxide.

(This is because) most people don’t build complex automated FAE systems. They either end up with air that’s a little too dry (but very fresh), or with 90+% rH but is a little stagnant. It’s far better to err on the side of too dry but fresh air.”

shiitake mushrooms, oyster mushrooms, white button mushrooms - mushroom growing parameters or conditions - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

There is no universal growing process for all mushrooms at home. So parameters for optimal mushroom development vary depending on the strain you’re growing.

But commercialized mushroom strains (such as shiitake mushrooms, oyster mushrooms, or white button mushrooms) can fruit in the following approximate conditions:

  • Humidity
    • 80% to 95% Relative humidity
  • Fresh Air Exchange (O2 vs. CO2 levels)
    • 4 to 6 fresh air exchanges per hour
  • Temperature
    • 50°F to 70°F (10°C to 21°C)
  • Lighting
    • 12-hour cycles of light/dark

Poor Fresh Air Exchange and little yield - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

Aerial mycelium overgrowth, as a result of poor air exchange, may delay your mushroom pins. A lot of growers report ending up having flush of mushrooms with stunted growth or stems that are too long.

While others have little mushroom yield or not going through the pinning phase at all.

5. Is Aerial Mycelium Rhizomorphic or Tomentose?

Is aerial mycelium rhizomorphic or tomentose? - What is Aerial Mycelium - Does It Delay Mushroom Pinning - Curative Mushrooms

There is no strict rule in terms and definitions when it comes to mushroom growing. The meanings of some terms have not yet been established.

Thus, growers often rely on reading discussions and asking around online forums. Then, from there, discover new words that best describe their mushroom appearance…

until those words become “FORuMALLY” widely accepted terms, such as calling any string-like growth as rhizomorphic and a fluffy growth as tomentose. 😉

So if your aerial mycelium looks like string-like growth, call it rhizomorphic aerial mycelium. No one can judge you.

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Rhizomorphic vs Tomentose Mycelium - Is Fluffy Growth Better - Curative Mushrooms

Key Takeaways:

  • Aerial mycelium a.k.a. secondary mycelium grows from the surface of the substrate or the primary mycelium.
  • Substrate mycelium, vegetative mycelium, or primary mycelium is the portion of the mycelium that penetrates the substrate.
  • Though not necessarily bad, overgrowth and stagnation of aerial mycelium often correlates to delayed pinning and inferior mushroom growth.
  • Lastly, improving Fresh Air Exchange seems to prevent further aerial mycelium growth and encourages pinning.



Curative Mushrooms has to post the standard FDA Disclaimer…The statements made regarding medicinal mushrooms have not been evaluated by the Food and Drug Administration. The efficacy of these products has not been confirmed by FDA-approved research. Curative Mushrooms is not making claims intended to diagnose, treat, cure or prevent any disease. All information presented here is not meant as a substitute for or alternative to information from healthcare practitioners. Please consult your healthcare professional about potential interactions or other possible complications before consuming the medicinal mushrooms. The Federal Food, Drug and Cosmetic Act requires this notice.


This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Curative Mushrooms nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement or lifestyle program.



Always looking for ways to improve the health of myself and my family led me to the discovery of medicinal mushrooms and the numerous health benefits they have on the body. My mission is to spread this knowledge and help as many people as possible.

This Post Has 6 Comments

    1. Hi, Vernon. Aerial mycelium might be a signal for pinning or delayed pinning. You can transfer to a fruiting chamber and introduce fanning and misting.

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