Fungi, friend or foe?

How the fungi you find in your garden are helping your plants thrive

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Field mushrooms and grass

Now autumn has set in you may have noticed that there are a lot of mushrooms around or spotted them growing near the plants in your garden, allotment, local park or even amongst your houseplants.  

If you’re concerned about seeing toadstools around your plants, you aren’t alone. However, their presence is likely to do your garden some good.  

Fungi are not plants, as life forms, they are closer to animals. Plants and fungi are however intrinsically linked and many plant species can’t survive without their fungal counterparts. To understand this better, let’s examine a few fungi fundamentals. If you already know all about spores, fruiting bodies and mycelium, skip to our section on ‘mycorrhizal fungi’ to learn about the connection between plants and fungi.  

  

scarlet waxcap toadstools
Scarlet waxcap, hygrocybe coccinea, iStock/adrianam13

What are mushrooms? 

Mushrooms are the 'fruiting body’ of a fungus. They are the part that we can see above the ground, although most fungal matter lives beneath the earth. This part underground Is called ‘mycelium’. It’s a network of fine threads that run through many kinds of living tissue and organic matter, such as wood, soil and compost. These threads are usually microscopic but can spread across vast distances. In fact, the world’s largest living organism is a fungus in the US, which covers 2385 acres. 

The function of a mushroom is to help its fungus reproduce. The process is quite complex and varies between species but simply put, mushrooms disperse spores from which, when they land on the ground, more mycelia can begin to grow.

mycelium on log
Mycelium, rizomorph mycelial cord on dead wood, empire331/ iStock

Why can I see mushrooms growing around my plants? 

Fungi produce mushrooms at different times of the year depending on the species, but many of them prefer damp and humid conditions, which is why we see so many in Autumn. An increase in rainy weather combined with some final sunny spells trigger many fungi to ‘fruit’.

 

Here are a few UK native species you might see in your garden:

Giant puffball
Giant puffball, Calvatia gigantea,
Liberty cap mushrooms
Liberty cap, Psilocybe semilanceata, herraez/iStock
Fairy ring mushrooms
Fairy ring mushroom, Marasmius oreades, Anna Nelidova/ iStock,
Shaggy ink cap mushroom
Shaggy ink cap, Coprinus comatus, EstuaryPig/iStock
Field mushrooms
Field mushroom, agaricus campestris, herraez/ iStock

Helpful fungi, harmful fungi

The majority of fungi species are ‘saprobic’ which means they ‘feed’ on dead organic material, so they are unlikely to negatively affect your living plants. Without these fungi, everything would be buried under piles of rotting wood and leaves, so really, they are actually a great help to gardeners.    

Occasionally, saprobic fungi can adversely affect garden plants due to extensive mushroom growth able to smother young seedlings. Some people find mushroom growth amongst their plants unsightly, if you have stinkhorns growing in your lawn, the scent can be unpleasant.

However, it is the few species of fungi that are ‘pathogenic’ which can be truly troublesome. These fungi cause diseases and attack plants, feeding on live wood. Species like this to look out for are honey fungus (Armillaria) and silver leaf (Chondrostereum purpureum).

Honey fungus mushrooms
Honey fungus, Armillaria mellea, Vincent Ryan/ iStock

If you are concerned about these species growing near your plants, it is important to have them identified. There is no chemical treatment that you can use on these fungi and removing them will require the destruction of any material they have infected. 

What’s the difference between plants and fungi? 

Many factors distinguish plants and fungi from each other, but the most distinct is how they fuel their growth. Plants ‘photosynthesize’ by taking up water and nutrients from the soil along with CO2 from the air and using sunlight to turn this into ‘food’.

In order to grow, fungi don't photosynthesize like plants or consume food the way animals do. Instead, they secrete enzymes from the growing tips of their mycelia, which breakdown matter outside of them. They then absorb this pre-digested material as their food and grow into the space it has left.

White mycelium growing
Mycelium, Alexander_Volkov/ iStock

Mycorrhizal fungi

The word ‘myco’ is Greek for fungus and ‘rhiza’ is Greek for ‘root’. Together they form the word ‘mycorrhizal’.  

Many plants are unable to absorb all the nutrition and water they need to grow by themselves. This is why 80% of plants are believed to have a relationship with ‘mycorrhizal fungi’. When a plant and a fungus species have a ‘mycorrhizal relationship’ it means that the fungal mycelium sheathes itself around the roots of the plant. The two organisms then ‘trade’ food sources with each other.

Mycorrhizal fungi provide their plant partners with nutrients they need, such as nitrogen, phosphorous, zinc, copper and water. After a long sizzling summer when plants are particularly thirsty, their mycelial networks work harder than usual to provide them with sufficient water. This is why we see an abundance of mushrooms in Autumn, following very hot summers.  

Fly agaric mushrooms
Fly agaric, Amanita muscaria 

Plants return the favour by giving carbon to their fungal partners, in the form of simple sugars. This is one of the reasons fungi are so essential in combating the climate crisis. Many trees have mycorrhizal relationships with fungi and some species aren’t able to reach maturity without them. So, not only are fungi fantastic at carbon sequestering, they also support the growth of forests, which are essential carbon sinks.

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