The Hidden Helpers: Mycorrhiza and Fungi in the Garden

Mushrooms in the Garden: Helpful Friends or Troublemakers?

Fungi are remarkable organisms — neither plants nor animals, but a kingdom all of their own. Unlike plants, they don’t photosynthesise but feed on organic matter. And unlike animals, they don’t actively consume food; instead, they break it down with enzymes before absorbing it. Biologically, fungi are actually closer to animals, though they share traits with both kingdoms of life.

Turkey Tail (Trametes versicolor) / Photo by James Lindsey, Ecology of Commanster, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3565096

Fungi: Different Strategies and Ways of Life

Turkey Tail (Trametes versicolor) / Photo by James Lindsey, Ecology of Commanster, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3565096

Some fungi break down dead organic matter, and can even decompose coarse material such as wood and leaves. These decomposers play a vital role in turning organic matter into humus, enriching the soil in the process. Examples include ink caps, birch polypores and field mushrooms.

Roots with mycorrhiza / Photo by Ellen Larsson, R. Henrik Nilsson, Erik Kristiansson, Martin Ryberg & Karl-Henrik Larsson (2005), Approaching the taxonomic affiliation of unidentified sequences in public databases – an example from the mycorrhizal fungi, BMC Bioinformatics, 6:178. DOI: 10.1186/1471-2105-6-178, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=459872

Mycorrhizal Fungi: A Partnership Between Fungus and Plant

Roots with mycorrhiza / Photo by Ellen Larsson, R. Henrik Nilsson, Erik Kristiansson, Martin Ryberg & Karl-Henrik Larsson (2005), Approaching the taxonomic affiliation of unidentified sequences in public databases – an example from the mycorrhizal fungi, BMC Bioinformatics, 6:178. DOI: 10.1186/1471-2105-6-178, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=459872

Another strategy is symbiosis with plants — a cooperative relationship where both partners benefit. The fungi form connections with plant roots, taking in sugars from their hosts. In return, the plants receive water and nutrients. These are known as mycorrhizal fungi, and examples include chanterelles, porcini and truffles.

Powdery mildew /Image by Heizer, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=42754

Fungal Diseases and Parasitic Fungi

Powdery mildew /Image by Heizer, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=42754

Finally, there are the parasitic fungi – pathogenic species that attack and damage other living organisms. They draw nutrients from their hosts, often causing the leaves – and eventually the whole plant – to die back. Fungal diseases such as powdery mildew, grey mould and rust are a serious problem, particularly in agriculture and home gardens.

Which Mushrooms Grow in the Garden?

A wide range of fungi with different roles can appear in the garden. You might spot them in borders, on the lawn, on dead wood, or even on your plants. Some are beneficial to the garden ecosystem, while others can cause serious damage.

Mushrooms in the Garden – Good News or Bad Sign?

It all depends on which type of fungus you have in your garden.

Decomposer and mycorrhizal fungi – the kinds that form visible fruiting bodies – are signs of an active mycelium in the soil. Many gardeners assume that’s a bad thing, but in fact a healthy mycelium offers plenty of benefits: it improves nutrient uptake for plants and helps build humus-rich soil. Mycorrhizal fungi are therefore particularly valuable, promoting a diverse and healthy plant community.

Some fungi, however, can point to imbalances in the soil such as waterlogging, compaction or over-fertilisation. As a rule of thumb, an occasional mushroom in a bed or pot is nothing to worry about. But if they start appearing in large numbers, it’s worth checking what’s going on beneath the surface. The fruiting bodies themselves aren’t the problem – they’re more like indicators, giving you clues about what’s happening underground.

Pathogenic fungi, on the other hand, are a different matter. These can infect plants and cause them to die back, so you’ll need to act quickly if you spot signs of disease. You can find out how to recognise whether it’s a plant disease in this article.

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What Are Mycorrhizal Fungi – And Why Are They So Special?

As mentioned earlier, mycorrhiza refers to a symbiotic partnership between plants and fungi that benefits both sides.

The fungus colonises the plant’s roots, forming a close connection. It takes in sugars from the plant, since fungi can’t photosynthesise or produce their own food. This is also why some fungi have evolved as parasites, simply taking what they need. In return, the fungus releases enzymes that make nutrients in the soil more available, particularly phosphorus, and passes them on to the plant. Without mycorrhiza, most of the phosphorus in the soil would remain locked away and unusable by plants.

If your plants show signs of phosphorus deficiency, it might indicate that your soil is out of balance and lacks enough mycorrhizal activity.

The mycorrhizal network itself is enormous – around 85% of all land plants live in symbiosis with these fungi. Through this underground web, not only fungi and plants are linked, but also plants to one another, sharing information and resources. The mycelium can even transmit signals through the soil that help other organisms respond to changes in their environment. It’s often compared to an underground internet connecting life below the surface.

Understanding Mycorrhizal Symbiosis in the Garden

As mentioned earlier, the mycelium of mycorrhizal fungi can link many plants across several square metres, creating a much larger surface area for nutrient and water uptake. This brings a number of clear benefits for the plants.

It’s worth noting that mycorrhizal fungi most commonly form partnerships with trees and shrubs rather than with vegetable crops. As a result, mycorrhiza is often absent from vegetable beds. This is also because these fungi are highly sensitive to soil disturbance and don’t cope well with regular digging or cultivation.

Advantages of Mycorrhizal Symbiosis

• Improved nutrient and water uptake during dry spells. The mycelium spreads across a wide area, collecting water and nutrients that the plant’s roots alone couldn’t reach, and making them available when needed.
• Enhanced soil chemistry and nutrient availability. Mycorrhizal fungi release enzymes around the roots that slightly lower the pH, boosting biological activity in the soil. This process also helps make phosphorus available to plants — at a neutral pH, it tends to form salts that roots can’t absorb.
• Stronger plant health and resilience. A lively, fertile soil is closely linked to healthy, vigorous plants. Greater microbial activity improves nutrient exchange, while humus compounds further support plant strength and disease resistance.
• Early warning system for plants. Mycorrhizal networks can even transmit signals through the soil, alerting neighbouring plants to pests or stress factors. This gives them time to prepare and strengthen their natural defences.

Do not dig up the soil!

Practical Tips: Encouraging Mycorrhiza

Do not dig up the soil!

For a healthy mycelium to develop, avoid digging and heavy soil cultivation, as this can disrupt the fungal network. It’s far better to mulch or apply compost to feed the soil from above — the principle behind the No-dig method.
It also helps to include plenty of native and mycorrhiza-friendly plants in your garden. Finally, remember that these symbiotic relationships form to prevent nutrient deficiencies. If you apply too much fertiliser, such valuable partnerships won’t develop — the plants simply won’t need the fungi’s help.

Mushrooms in the Bed: What Should You Do if They Suddenly Appear?

Almost every gardener has probably gone out into the garden and spotted a mushroom in a border or plant pot. So the question is: should you cut it off or leave it be?

First, it’s worth knowing that the fruiting body – the mushroom you see above ground – is only a tiny part of the fungus. Even if you remove it, the mycelium beneath the surface remains. For that reason, I usually just let the mushrooms grow quietly and do their thing.

If they start spreading extensively, you can cut back the fruiting bodies to limit further growth – but it’s also important to look at the underlying cause. The mushrooms themselves aren’t the problem. When fungi or plant diseases spread too much, it’s always worth asking: why is this happening?

• Could the soil be too wet or compacted?
• Have you recently added fresh organic matter, such as compost or mulch?
• Might the balance of the soil be out of sync?

Once you’ve identified the cause, you can take the right steps – for example, adjust your watering routine or improve the soil structure. Please avoid using fungicides, as they harm all fungi in the soil ecosystem – and, as you’ve learned in this article, many of them are hugely beneficial in the garden.

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