This Is Why Mushrooms Grow So Fast

Mushrooms are interesting because they seem to appear out of nowhere. It isn’t uncommon to go to sleep with a well-kept garden and wake up to a full-blown mushroom infestation. But what causes them to appear and grow so quickly?

Mushrooms can grow very quickly if provided with enough water. Their cells enlarge when they absorb water, making it appear as if the mushroom has grown a lot in a short time. They also spread faster if there’s a lot of organic matter in the area.

In the rest of this article, I’ll explain what the optimal conditions needed for mushrooms to grow are, how they grow in size so quickly, and which mushrooms grow the fastest. I’ll also talk about how they spread and what you can do to reduce the number of mushrooms in your garden.

Mushroom Growth Requirements

Mushrooms are classified as fungi, meaning their requirements for growing are completely different from regular plants. For example, plants need sunlight to grow because their cells reproduce through photosynthesis. However, mushrooms can grow fast even in the dark because they don’t use photosynthesis to grow.

Generally, there are two main ingredients that mushrooms need to grow.

Let’s take a look at them.


Water is one of the main ingredients needed for mushrooms to grow. Fungi thrive in damp conditions, so humidity, overwatering, or heavy rains can result in a brand new batch of mushrooms where there weren’t any before.

According to the American Mushroom Institutions, mushrooms are about 90% water. Mushrooms grow by breaking down organic matter to produce energy for cell division. They break down organic material by secreting enzymes, which require high amounts of water.

Organic Matter

While plants use solar energy (sunlight) to produce energy through photosynthesis, mushrooms produce energy through this breakdown of organic material. This organic material can be leaves, wood stumps, animal waste, or dead bodies of insects and animals.

If you’ve got old trees, stumps, leaves, or plants, you’ll likely have mushrooms growing on them after heavy rainfall.

How Mushrooms Grow Overnight

Have you ever woken up to a new mushroom growth in your garden or house? It’s quite common to sleep in a mushroom-free house and wake up to find that your house has been taken over by them.

Generally, the main way plants or fungi grow is through cell division. Cell division is a complicated and energy-consuming process, which is why it can take months or years for a plant to grow. However, cell enlargement is a much simpler process.

In cell enlargement, the cells absorb water and expand. The more water they absorb, the bigger they become. This process takes far less energy and time, so some mushrooms can double in size in just 24 hours. Many mushrooms grow this way in just a few days.

If you’ve had heavy rains or just watered your plants a lot, you might have mushrooms growing just a few hours later. This fast rate of cell enlargement makes it seem like mushrooms just popped up overnight in your house or lawn but they’ve always been there just waiting for the right conditions to grow.

Fastest-Growing Species: Oyster Mushrooms

Mushrooms can grow incredibly fast, doubling in size in just 24 hours. Many mushrooms are ready for harvest just a few weeks after planting them. However, none grow as fast as the oyster mushroom.

Oyster mushrooms are the fastest-growing mushroom species. They’re usually ready to harvest just a week after fruiting. The total cropping period for oyster mushrooms is just 60 days.

How Mushrooms Spread

Another fascinating thing about mushrooms is that they can spread far and wide in very little time. Fungi are notorious for growing everywhere and spreading into all the nooks and crannies. It can be really hard to get rid of them, but understanding how they spread will help you in that task.

First, it’s important to know that mushrooms are simply the reproductive parts of fungi visible above the ground. Most fungi grow underground where you will never see them. In simple terms, mushrooms have the same function for a fungus as fruits have for trees.

Mushrooms help the fungus spread by producing spores. These spores spread through the air to land in other areas, where they develop into a new, individual fungus. One mushroom is capable of producing up to 1 billion spores.

To prevent the mushrooms from spreading, you need to remove them before they produce spores. You can knock them over by hand or remove them with a lawn mower. For particularly stubborn growths, you can try other mushroom removal methods.

How to Permanently Get Rid of Mushrooms

As mentioned before, mushrooms are the reproductive parts of fungal mycelium (the ‘network’ of fungal roots that grow and spread beneath the soil). Since picking mushrooms doesn’t affect the mycelium, the fungus continues to spread beneath the soil, and it may regrow mushrooms after a while.

Mushrooms grow back a few hours or a few days after picking them if there’s plenty of moisture and organic matter. The mycelium beneath the soil produces more mushrooms to spread spores, so removing them doesn’t affect the mycelium itself. As long as the fungal mycelium is intact, it will continue to produce mushrooms.

Normally, picking the mushrooms or mowing them with a lawn mower should be enough to get rid of them completely. However, if you’ve got a persistent mushroom problem, you might need to try other methods.

If mushrooms keep growing back even after picking them, the yard conditions could be encouraging mushroom growth.

This could be caused by:

  • Humidity
  • Shade
  • Organic matter like wood stumps or animal waste
  • Poor soil drainage

You can improve this by cleaning your yard of organic matter or improving soil drainage by adding about 2 inches (5 cm) of sand or pumice into the upper six inches (15 cm) of the soil.

However, if that doesn’t work, here are a few mushroom-killing methods you can try.

Nitrogen Fertilizer

Nitrogen fertilizers break down organic matter much quicker, which limits the nutrients that fungi can feed on. Liquid nitrogen fertilizer is widely used and works on all grass types and can help reduce the number of mushrooms on your lawn.

Vinegar & Water

Mix 1 part of horticultural vinegar with four parts of water. Vinegar gets its characteristic smell from acetic acid, which has been proven to remove and prevent mushroom growth.

Household vinegar will also work when diluted in a 1:1 ratio. However, it can be dangerous for your plants so you can use this only on mushrooms growing on bare soil or wood stumps.

Tea Tree Oil

Tea tree oil has fungicidal properties that can be used to prevent mushroom growth. Normally used as an essential oil, tea tree oil has been proven to have a lot of potential in agricultural contexts as a natural fungicide and pesticide.

Commercial Fungicide

Commercial fungicides are usually much stronger, so they’re perfect for resistant mushrooms. Each product will have specific instructions for safe and effective use so always follow the instructions on the label.

Note: Keep fungicides out of reach of children and pets and limit lawn time after spraying fungicides.

Final Thoughts

Mushrooms grow quickly because they absorb water and enlarge. This process takes less energy and time than cell division, which is much more complex. Mushrooms are also notorious for spreading far and wide, producing up to 1 billion spores from a single mushroom.

Although mushrooms generally grow back if picked, you can use natural fungicidal treatments like vinegar or tea tree oil to remove the fungus. Removing the fungal mycelium will prevent the mushrooms from growing back.

Dr. Moritz Picot

Dr. Moritz Picot is a horticulture enthusiast and the founder of, where he serves as the lead content writer. He established the website in 2022 as a valuable resource for both gardening aficionados and beginners, compiling all the gardening tips he has accumulated over the past 25 years. Alex has a passion for nurturing plants, transforming backyards into inviting spaces, and sharing his knowledge with the world.

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