Why are there mushrooms in my compost?

Sometimes we get asked about the appearance of toadstools in SylvaGrow. If you see fungi in your compost, don’t panic! They’re our friends.


From time to time, depending on climatic conditions, you may see mushrooms in your peat-free compost. For many people, this can be a concern. We are often told mushrooms and fungi are bad. They are associated with rot and poisons – not things we want on our plants, especially if we are growing edibles. However, recent scientific discoveries have shown us a little more about the amazing world of fungi, and we now know that most fungi are incredibly beneficial to plants.

What are mushrooms?


Let’s start by dealing with the difference between the terms ‘toadstool’ and ‘mushroom’.
‘Mushroom’ is frequently used to define fungi that are edible, and ‘toadstool’ is a more general term for fungi with a stem and a cap. In fact, there is no scientific difference between them, and the terms can be used interchangeably.

Mushrooms are the fruits of certain types of fungi. Just like apple trees bear apples, fungi bear mushrooms. Most fungus is under the soil and invisible to the naked eye. So, the chances are that there are still fungi even if you don’t see mushrooms.

Why are there mushrooms in my peat-free compost


Peat-free compost differs from peat-based compost in that it is not inert. Peat-free compost such as SylvaGrow is a thriving ecosystem full of microscopic life. Peat on the other hand, is formed from decomposed plant remains that offer no food sources to microbes, created in conditions with very little air, which makes it almost entirely devoid of life.
Scientists and gardeners are just beginning to understand the benefits of the microbial life – including fungi – that live within healthy soil and compost.

Fungi are beneficial to plants


Many people believe that fungi feed on their plants. Whilst one or two species will do this (most notably honey fungus), most plants and fungi have an incredible symbiotic relationship. The plant voluntarily gives some of its sugars to the fungi; in return, the fungi can extend the plant’s root system many times. This helps our plants to source nutrients and water in the soil. The fungi can also help the plant to fight off pests and diseases by forming a protective barrier around the roots. This is of huge benefit to the plants.

Are the mushrooms poisonous?


We don’t recommend eating any mushrooms unless you are 100% sure that they are edible. But most mushrooms in the UK are harmless unless eaten in large quantities. So, if there are mushrooms present in your soil, even if they are in contact with an edible plant, they are unlikely to hurt you or the plant. We recommend rinsing any produce before consumption, but this is good practice whether there are mushrooms or not.

What are the mushrooms feeding on?


Mushrooms feed on the organic matter in the soil. Usually, this is in the form of dead leaves and other dead matter. However, some are supplied by living plants in something called root exudates. These are little parcels of carbohydrates that the plants send down through the roots to feed the soil life in exchange for nutrients and protection from pests and diseases.

What should I do if I find mushrooms in my compost?


You don’t need to do anything. Seeing mushrooms is a great sign that you have healthy soil. They will not affect your plant’s growth. However, if you have a lot of mushrooms, they may crowd your plants, in which case you can pick them out and get rid of them. This won’t take away the benefits to your plants. Just make sure to wash your hands before you next eat.