How Do Mushrooms Grow So Fast?

You’ve probably noticed how mushrooms seem to have appeared in your garden seemingly overnight after a rainstorm. Did they really grow that quick, or did you overlook them previously? If you grow your own mushrooms, is the process also this fast?

Mushrooms spring up so fast thanks to their unique way of growing. Plants and animals grow by cell division which is a relatively slow process. Mushrooms, in turn, grow by cell enlargement. This means they already have a fixed number of cells that blow up like balloons when filled with water if the environmental circumstances are right.

How Do Mushrooms Grow?

It’s important to note that when we say mushroom, we really refer to the part of the mushroom we see above ground. We generally call this the mushroom cap. You can compare it to a fruit. Even though the fruit only took a certain time to become a fruit, there was a long process that happened before this.

While the lifecycle of a mushroom can differ according to the type, each mushroom goes through the same growth cycle.

Unlike plants, mushrooms don’t grow from seeds. Instead, they grow from spores (minuscule cells that you can’t see). Spores are released from the mushroom cap. Once these spores land in a suitable medium, it starts to divide and produce hyphae. Hyphae are like underground roots that absorb water and food.

The hyphae also seek out other underground roots to form mycelium. The mycelium looks a bit like white fluff, and it’s the body of the mushroom. The part of the mushroom that we see above ground is the fruit of this underground body.

Seed growing a fungus and its newborn mycellium

Even though mushrooms will only grow if the circumstances are right, this doesn’t mean nothing is happening underground. The underground mycelium can remain dormant for months, years, or even decades until a mushroom pops out of the ground.

In biology at school, we learned that plants and animals grow by cell division. This is a lengthy process that requires a lot of energy.

Mushrooms grow entirely different. For starters, once the mushroom “fruit” has developed, it already has the number of cells it will have for its entire life cycle. The number of cells won’t increase by division.

The mushroom grows thanks to these fixed number of cells enlarging. Water is needed for the cells to enlarge by swelling up. This means that a mushroom can increase in size as fast as it can pump water into its cells. This is why after a rainstorm you suddenly see mushrooms appearing. 

How Fast Can Mushrooms Grow?

Different kinds of mushrooms grow at different rates, but most grow pretty rapidly, especially if you compare them to vegetables. The environment also significantly influences the speed at which they grow. For example, a dark and humid environment can dramatically affect its growth.

If you are growing your own mushrooms, the substrate you use to produce them also affects the rate at which they grow. The substrate is the bulk material that the mushroom’s mycelium uses for nutrition and energy. If you use a lower nutrient substrate, the whole process will also be longer. Using a high-nutrient substrate will speed up the process.

Shiitake mushrooms, for example, can take 6 months to grow in logs. However, if you grow them on sawdust, they only take between 8 to 12 weeks. Similarly, Lion’s mane mushrooms only take 4 to 6 weeks if grown in bags, but 1 to 2 years if you grow them on logs.

Shiitake mushrooms growing on log
Shiitake Mushroom
Lions mane mushroom growing on log
Lion’s mane mushroom

This doesn’t mean that all mushrooms grow fast. Morel mushrooms, for example, can take 3 to 5 years to grow from the moment the spores are spread until the first colony of mushrooms appears.

However, once the mycelium has formed and the conditions are right, the fruiting period (the last stage of growth) can take only a few days. It’s the unique growth cycle of the mushrooms that give you the impression that all mushrooms grow at lightning speed.

Can Mushrooms Grow Overnight?

The fruiting of a mushroom can happen overnight, especially in areas with a lot of humidity and rain.

You’ll first start to notice round “button caps.” These caps are the densely packed hyphae. Soon after these caps appear for the first time, the cap’s outer covering ruptures, and the stem elongates. This allows the cap to enlarge to its full size.

It’s entirely possible for this process to appear overnight. However, this doesn’t mean that the entire mushroom grew this fast. Remember that the fruiting period is the final part of a mushroom’s life cycle. The mushroom has been growing for an extended period to get to this last stage.

The Phallus indusiatus mushroom is an excellent example of how it can seem that mushrooms grow overnight.  As soon as its outer covering has raptured, the fruit starts to develop. This happens at night as mushrooms thrive in the dark.

Phallus indusiatus mushroom also known as bamboo mushrooms, long net stinkhorn, or veiled lady
Phallus indusiatus also known as bamboo mushrooms, long net stinkhorn, or veiled lady

These fruit bodies enlarge to their full size after about 10-15 hours after emerging from the peridium (the protective layer that encloses a mass of spores in mushrooms).

 Which Are The Fastest Growing Mushrooms?

One of the fastest-growing mushrooms in terms of actual size is the edible Phallus indusiatus we just mentioned. This mushroom is also known as the Bridal veil stinkhorn or bamboo fungus. It can grow four to six inches (10-15cm) per hour to a maximum height of around 10 inches (25cm).

However, the fastest-growing mushrooms that most of us have probably eaten are oyster mushrooms. They are easy to grow, so if you want to try growing mushrooms, oyster mushrooms are your best bet.

Oyster mushroom growing in a forest

The quickest way to grow these mushrooms is by buying a self-growing kit. These kits are already optimized to create the perfect growing environment. This means that the substrate can become fully colonized with the mycelium in around 10-14 days.

You can then harvest your first oyster mushrooms approximately 7 days after fruiting. After the first harvest, another batch should appear every 7-14 days.


Mushrooms grow differently from plants and animals. Instead of cell division, they grow by cell enlargement. By the time the first fruit appears, the mushroom will already have all the cells it needs, contrary to plants which will divide their cells to keep growing. Once the mushroom is in its final stages of growth, it will enlarge its cells with water available in the environment, and the fruit will appear. That’s why it seems like they pop out overnight!

There are several factors that can also accelerate the growth of mushrooms, like the water, nutrients, and light present in the environment. If you’re looking into growing your own mushrooms, this means there are ways you can help your mushrooms grow quicker, like choosing the right room to grow them and the substrates you use to grow them. If you don’t know what type of mushrooms to grow, oyster mushrooms are quick and easy to grow, therefore a great choice for beginners.

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