Mycelium growing on the ground

First Signs Of Mycelium Growth

If you’ve finally bought that mushroom kit, but it seems not to be doing anything, it’s easy to think you bought a dud. Don’t worry – most of the action is happening underground!

The first sign of mycelium growth is what looks like little balls of white cotton. However,if you see anything growing, that looks different from that, read on to recognize signs of mold and how you can avoid it.

What Does Mycelium Look Like When It Starts Growing?

Growing your mushrooms is also a lesson in patience. It may feel like nothing is happening until, suddenly, the fruiting body pops up. But before you get to this stage, you might be wondering what the mycelium looks like when it starts growing and how long it takes.

Before the mycelium can start growing, the spawn needs to first grow through the substrate. This process is called incubation. Incubation begins when the mycelium leaps off from the spawn into the substrate.

Spawn is the carrier that holds the strain of mushroom mycelium until you transfer it to your substrate of choice.  So once the mycelium has leaped off the spawn, it expands through the substrate.

Once this mycelium runs into another mycelium, it fuses together. This process continues until the entire substrate becomes one organism.

This process will continue until the mycelium has grown through all the available substrate. In other words, colonization has occurred, and fruiting can be initiated.

The mycelium will look bright white and fuzzy. It might appear like a ball of cotton and quite fluffy to the naked eye.

As soon as you see the first white bits, you might mistake them for mold. However, as it starts to grow, you’ll be able to detect the outline of the mycelium as roots or veins. Overall, it’s very ropey. 

This is easiest to see if it’s growing in a glass jar. Depending on the type of mushroom species you’re growing, the structure of the veins might be more robust or more delicate.

Another telltale sign that the mycelium is growing and that it’s not mold is that it will radiate out from the center.

Mycelium growing looks like white fluff with veins or ropey structure

How Long Does It Take For Mycelium To Show?

Like the growth of mushroom fruit bodies, the time it takes mycelium to grow depends on the specific mushroom species. So, it’s only possible to give average estimates in this post.

Whether you have a self-growing kit or substrate you inoculated yourself, the first signs of mycelial growth should appear within about 5-8 days. Mycelium growth is slow initially, but after 7-8 days, it starts to speed up and grow exponentially.

Mycelium growth can take anything from two weeks to two months. So if you don’t see anything in this period, especially after two months, something might have gone wrong.

How To Know If Its Mold Or Mycelium

Once you start seeing some growth, it’s not always mycelium. Unfortunately, the ideal growing conditions for mushrooms are also the perfect conditions for other fungi, such as mold.

However, mold doesn’t just appear out of nowhere. Instead, it’s usually a sign that contamination occurred somewhere in the process, most likely during inoculation.

It can be challenging to tell mold and mycelium apart. One sign that can help you is the way mycelium grows. Remember that mycelium usually grows in ropey strands. This is called rhizomorphic growth and indicates that the mycelium will most likely produce fruit.

There is also more structure to mycelium. Mold grows more chaotically, and you might find mold in random, unconnected spots.

If you see any other color growth other than brilliant white, this is a sign of contamination. However, mold can be tricky as it can also be a bit white, so don’t judge solely on color.

Some of the most common types of mold that you may encounter are Neurospora crassa (orange bread mold), Cobweb mold, Rhizopus stolonifer (black bread mold/pinhead mold), Trichoderma (green mold), and black mold.

Neurospora crassa (orange mold)

Neurospora crassa is easily detected as it is bright neon orange. The texture of the mold changes slightly as it grows. In the beginning, it might look a bit like orange powder before making more lumpy formations.

You are more likely to encounter this type of mold in the warmer months when it’s hot and humid. It’s also more common in tropical and sub-tropical regions.

Cobweb mold

Cobweb mold looks a bit just like the name implies – like cobwebs. It can be fine or fluffier, and it tends to be light grey. This type of mold can be a little harder to distinguish from mycelium.

Another clue you can look out for is that it’s often found on spoiled fruits. So, if you have some rotten fruits in the room where the mushrooms are growing, and it’s not as brilliantly white as mycelium, you might have some mold on your hands.

Close-up of cobweb mold which looks like a gray web

Rhizopus stolonifer (black bread mold/pinhead mold)

This type of mold can easily be confused with Cobweb mold. However, the main difference is that the pinhead mold has tiny blackheads on the ends of the mycelium strands.

This mold type is one of the most common in the world, so you might have even seen it on rotting fruit before or on stale bread.

Close-up of black bread mold also known as pinhead mold growing on bread

Trichoderma (green mold)

Trichoderma is an umbrella term for more than 80 types of fungi. Trichoderma usually appears in shades of green that range from pale green or olive to dark emerald green. However, it can also appear yellow and often has a white edge and green center.

It’s a very common type of mold found in mushrooms. It’s even referred to as a mushroom grower’s main enemy as it’s so prevalent.

Trichoderma mold growing in a bag

Tips To Avoid Contamination

There is a higher chance of contamination taking place if you are inoculating the substrate yourself. This is only because there are more steps in which contamination can occur.

If you bought a growing kit, experts would already have taken care of that part in a sterile environment. The tips that follow below are more geared towards preventing contamination after inculcation, so for most home-growers, that would apply to their growing kits.

However, although unlikely, even with a growing kit, you might experience contamination that leads to mold. Key areas where this could happen are any spaces where there is exposed substrate.

Fortunately, there are several things you can do to avoid contamination:

  • Open your growing kit as soon as you receive it. Storing it for long might affect the vitality of the mycelium.
  • Don’t over-water your kit. You don’t need to water it, but rather just mist it so it stays moist.
  • Clean the equipment you use to cut open your growing kit. Cleaning your knife with rubbing alcohol would be ideal, but soapy water will also do if you don’t have any alcohol on hand.
  • Don’t store your kit close to the soil and other plants. Plants and gardening areas could release spores into the air.
  • Clean your hands properly and avoid touching the substrate. Millions of little germs on our hands and skin could lead to contamination.
  • Avoid warm and humid weather. If you store your growing kit in an area above 77 ℉ (25°C) with high humidity, mold is significantly more likely to develop. The ideal temperature for growing mushrooms is between 60.8-68 ℉ (16-20°C). However, this optimal temperature depends on the type of mushroom.

Final Thoughts

Depending on the type of mushroom you’ve decided to grow, it will take between a week and a couple of months to show signs of mycelium growth. Usually, when the mycelium is starting to grow, you’ll be able to see a white fluff on the substrate growing from the center and expanding outwards. As it develops, you’ll also be able to note its ropey structure or veins.

Unfortunately, other fungi like mold can grow under the same conditions as the mushrooms you’re trying to grow. That’s why it’s very important to be careful and sterilize your spaces and tools as much as possible. The chance of mold contamination can increase if you’re inoculating the substrate yourself.

If you see growth in patches and in other colors different than white, then it’s possible your kit or substrate has been contaminated with mold, and the fruitbody is unlikely to develop.

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