Are Fungi in Wood Chips Harmful?

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Robert Pavlis

This post, Fungi in Wood Chips, was prompted by a picture and discussion on a Facebook group called Australian Native Plant Enthusiasts (ref #3). The discussion was about the harmful fungi that appeared in wood chip mulch used in children’s playgrounds. Off course they posed no real danger–but people were scared. There are a lot of misconceptions about fungi growing in the garden and this post will look at the truth about fungi in wood chips.

Fungi in Wood Chips
Fungi in Wood Chips

Fungi in Wood Chips

Where do the fungi come from? Fungi is a type of organism that is neither an animal nor a plant. They grow just about everywhere, and a lot of different types grow in the soil. Normally we don’t see them, even when we dig in the garden. The reason for this is that they are just too small for us to see them easily. Think of them as very thin long strands of material. They do not have the ability to make food like plants, so they must get their food from other sources and a favorite food source of the type of fungi we are discussing is rotting things.

The wood chips we put into the garden soon start to decompose ie they rot. Fungi find this rotting wood and start to grow like crazy. They love this new home. Before long there are so many strands of fungi in one place that we are able to see it with our naked eye. When we turn over some pieces of wood we see white cottony material.

Where did the fungi come from? Fungi grow from spores which are everywhere; in the air and in the soil. It does not take long and they will find your wood chips.

Soil Science for Gardeners book by Robert Pavlis

If you take a closer look at the wood chips you will find all kinds of different fungi, in various colors. It just happens that the white ones are easier to spot.

Fungi Myths

In this post I am only looking at the fungi found in rotting wood chips.

1) Soil Fungi Kill Plants

Soil contains a lot of different fungi and I am sure some fungi in soil have the ability to harm plants. However, the fungi in wood chips live on rotting wood, not on live plants. They will not kill or even harm your plants.

Note (Nov 2014): The last sentence above came from one of the references given below, but it is not entirely correct. Current research shows that most fungi living in wood mulch will not affect plants, but some do. This is discussed in the comments below and will be discussed in more detail in a future blog post.

2) It can’t be Good for Kids

The original post started because the fungi were found in a play ground and so there was concern for kids. They saw the white fluffy stuff, called it yucky, and assumed it must be bad for you.

Will it harm humans? Fungi are a type of mushroom and we all know that eating the wrong kind of mushroom can hurt us. But who is going to chomp down on a bunch of wood chips and suck out the fungi? I have not seen any evidence that the fungi cause a health.

3) This is Mycorrhizal Fungi

People are starting to become aware of mycorrhizal fungi and now every bit of white fluff in the soil is called mycorrhizal fungi. It is not likely that the white stuff you see in wood chips is mycorrhizal fungi. The fungi on rotting wood is a type that specializes in decomposing wood–it is a different type of fungi. Mycorrhizal fungi live deeper in the soil.

Benefits of Fungi

Ok, so the fungi will not hurt us or our plants, what good is it? Fungi decompose wood chips along with bacteria. As they decompose the wood they convert it to nutrients and put that into the soil, which benefit the plants. The decomposing process also improves soil structure, something most garden soils can benefit from.

The white strands you see is a natural process that is extremely important for soil and our plants. The fungi are native organisms and we should marvel at their efficiency and treat them with respect–leave them alone so they can help you garden.


1) The Myth of Pathogenic Wood Chips:

2) Fungi in Mulches and Compost:

3) Concerns about Fungi in wood Chips:

4) Photo Source: zen Sutherland


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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

28 thoughts on “Are Fungi in Wood Chips Harmful?”

  1. My fungi looks exactly as the picture in this article and IT IS killing my plants. The little spore things in the center are climbing or blowing or however they getting up the plants and staying on my basil, Wild onions that are in a pot and my strawberries to the point of picking bad leaves of EVERY day. I don’t want these removable tiny round center things on my edible plants. Now what?????

  2. I have a big layer of the wood chip fungus on my begonias! I don’t know what to do, I use a mini rake to pull them off. But they keep coming every 2 hours!

  3. I built my first garden last year and this fungi attacked the roots of my cilantro and killed it. It started to pop up all over the rest of the garden and made me nervous it was going to kill my other plants. I know it’s natural and healthy for the garden to have this but I would really rather not worry about any of my plants dying this year. Any recommendations?


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