Fungi in the garden – some revelations

The Fly Agaric grows under oak near our house, Image by Rowena Millar

Rowena Millar, Cornwall Wildlife Trust's (currently Non-Roving) Wildlife Reporter, continues to show us how to make the best of our gardens for wildlife. With Autumn the perfect time to look for fungi, Rowena shares how you can encourage fungi in your garden and some all-important ID tips.

Fungi, along with bacteria, are the hidden heroes of our gardens.

If you listen to gardeners’ questions on local radio, you will know that queries like “how damaging are the toadstools that appeared in my garden and how do I get rid of them?” crop up frequently, rather like mushrooms.

The answers have, I hope, moved on from ‘apply fungicides’ or ‘dig them out and change the soil’ to a more tolerant approach, but a check online reveals that many sites give advice about treating ‘infected’ soil, replacing topsoil and/or removing deadwood and mulch. In short, fungi are still seen as a problem.

Fungus on an old tree stump

Fungus that appeared on an old tree stump in the garden, image by Rowena Millar

The opposite of a problem

At last, however, the role of fungi in soil ecology is starting to be understood, throwing into doubt the wisdom of digging, treating and otherwise disrupting the earth. Farmland in the UK and around the world has become impoverished or even lost because we have not understood the intricate flows of communication and cooperation that go on out of sight. Fungi do far more than decomposing organic matter.

We now know that fungi build soil structure, producing a gluey protein (glomalin) which sticks particles together, helping to store carbon, and generally improving the health and productivity of soil. Phosphorus, calcium, magnesium, nitrogen, potassium (see ingredients listed on bags of fertilisers), zinc, copper and iron are all accessed – for plants – by mycorrhizal (root-like) fungi.

Fungi fed plants before roots evolved, and developed a symbiotic relationship with plant roots many millions of years ago. Fungal mycelium is comprised of networks of thread-like hyphae. These spread underground, help plant roots take in nutrients and connect plants, enabling them to feed each other, and to send chemical messages such as warnings of attack. Fungi protect plant roots once inside, even producing natural antibiotics. They can also make plants more resistant to drought. Read more about fungi and their symbiotic relationship with plant roots via the linked article. 

Diagram depicting interplant communication of tomato plants through underground mycorrhizal networks

Experiment that demonstrates interplant communication of tomato plants through underground mycorrhizal networks, Image sourced by the Sustainable Food Trust

Why do they do this? Plants make carbohydrates, and feed sugars to the fungi. About 80% of all plants form associations with fungi, according to various sources online.

Looking at fungi

If you are expert in fungi ID, feel free to skip this section. We all know that some delicious fungi are highly distinctive, but many edible species look similar to inedible or poisonous ones. Although you shouldn’t eat fungi unless you are sure what they are or have an expert with you (e.g. on an official fungus foray), that needn’t stop you investigating them.

So do stop to take a closer look. The visible fruiting bodies are also made of threadlike fibres. They are easy to photograph close up, as they don’t run or fly away, and they don’t even tend to sway in the wind. Photograph fungi from the side and below as well as from above.

Where is your fungus growing? What does it smell like, and is the top slimy, dry, smooth, scaly or waxy?

Look at the shape and colour of the stalk or stem as well as the cap. If you break a piece off, does the mushroom stay the same colour or does it change colour where it is damaged? Or is it just a brightly coloured cup? Is it part of a clump? Is it woody, a blob or a gelatinous mass? Are there any distinctive spots or other markings?

Does the stem have a ring or skirt around it, or does it sit in a soft sac (volva) the shape of an eggshell with the top broken off?

Look under the cap (if it has one) to see whether there are lines of soft gills radiating out from the centre. There may be a spongy underside, or take the smooth (sometimes slimy or dusty), solid form of some of the bracket fungi. There may be dense, soft spikes like stalactites (a hedgehog mushroom). If the cap is rounded, it may be an earthball, a spore-puffing puffball or stinkhorn, for instance, or it may not yet have opened out – the caps of classic ‘toadstool’-shaped mushrooms change from round to flat as they age.

The closer you look, the more interesting each fungus becomes. You will soon want to look them up – some have fantastic English names, from ‘Destroying Angel’ to ‘Silky Piggyback’. If your fungus turns out to be a slime mould instead, they are even more fascinating – intricate shape-shifters that can move around.

Do stop to take a closer look... look at the shape and colour of the stalk or stem as well as the cap.

Do fungi damage the garden?

The Royal Horticultural Society (RHS) describe the vast majority of fungi as ‘harmless and often beneficial’, citing the only problems being large bodies of fungi pushing through tarmac or lifting paving slabs as they expand. Occasional species smother young seedlings, or stink (the stinkhorn Phallus impudicus), adversely affect the appearance of a well-manicured lawn, or cause concern by being poisonous (if children or pets are likely to eat them, just remove the fruiting bodies).

Honey fungus

Interestingly, honey fungus (Armillaria species) are mentioned on a different RHS page, with more susceptible trees and shrubs listed, the advice being to remove and destroy the infected root and stump, then insert a physical barrier around the area. My advice is not to panic. Some plants, such as rhododendron, lilac and privet, can be susceptible to honey fungus, especially if they are old and the soil is badly drained, but often, you can live with it. Remember that many other fungi, such as Sulphur Tuft (Hypholoma fasciculare) are also honey-coloured!

Fungi in compost

Fungi can break down all sorts of things, including the woodier bits of compost. They work together with bacteria and invertebrates, making food for your soil. Don’t bother buying fungal compost accelerants; there are so many natural fungus spores around, they will find a heap, given the right ingredients. My compost ingredients consist of hay and straw bedding, with gloppy messes from the ducks along with guinea-pig-dropping-soiled newspaper, weed stems and leaves, lawn mowings, shredded wood, non-cooked vegetable kitchen and a little cardboard from mushroom containers. Fallen leaves, shredded wood and untreated wood shavings are stored in a separate airy chickenwire container, where a different cohort of fungi might be at work. Learn more about home composting and creating your own garden compost on the Garden Organic website or watch the video below. 

Fungi on plants

Black spot, mildews, blight, rust, and clubroot are, admittedly, caused by fungi. Keep your plants in optimum conditions (something you learn with research and experience) and tolerate fungi if the plant’s life is not in danger.

In the case of blight, grow the most resistant varieties, grow early potatoes, grow tomatoes indoors, and completely remove all stems and leaves near the first hint of disease. Spray every inch of the plant, including the undersides of leaves, with one part full-cream milk to ten parts water (traditional Bordeaux mixture – copper sulphate with slaked lime – is now banned in the UK as it harms wildlife). If blight gets into the stems, pick all the tomatoes and make chutney or ripen unripe ones in drawers or boxes with a ripe banana or apple. Destroy blighted plants (not by composting).

If you have a stumpery or pile of dead wood or logs for wildlife, you may well grow some lovely fungal bodies to feed your garden wildlife.

Fruiting fungi on lawns and in flowerbeds

Of the thousands of fungi in the soil keeping your garden healthy, few will produce visible fruiting bodies. If any come up, the best thing is to enjoy their beauty.

We have had the odd garden fungi experience. One year, we accepted the free offer of a truckload of spent mushroom compost (watch out – this may contain 10–15% peat, at the expense of peatland habitats). We spread it all along a bed on one side of the garden, and were surprised by an abundant crop of mushrooms the next year.

Another time, a shaggy inkcap appeared in a flowerbed. I identified it, cooked it, ate it, and sadly never saw one again. More recently, a brilliant turquoise mushroom appeared in the dark under a big piece of wood leaning against my husband’s workshop door (see picture below). Wow.

turquoise fungi species against garage door

A turquoise fungi species appeared by the garage door, Image by Rowena Millar

A healthy garden

We can encourage fungi like this:

  • Avoid using chemical plant foods on soil, as they can damage sensitive fungal structures, preventing plants from reaching nutrients already locked up in the earth. Chemical applications in agriculture can nourish or protect crops, but the crops may not build up their own strength and immunity.
  • Minimise cultivation of soil. Build soil up with compost on top rather than disturbing fascinating underground networks. Make a planting hole by all means, but don’t damage your back and your soil structure by overdoing the digging.
  • Keep soil covered, helping to minimise erosion or flood damage. Meadows and woodland edges are great, and you can pack food crops in with other edible plants and herbs in a way that benefits the plants, the soil and the grower too.

Can fungi save the world?

Fungi offer a solution to rebuilding the world’s degraded soils, and gardeners and landowners can play their part (see above). Our part can be achieved by protecting soil and allowing trees, shrubs, and a wealth of other plants, mosses, lichens and liverworts to grow.

Fungi have a great past, present and future in medicine, in food production (mushrooms and yeasts), perhaps even in the manufacture of clothing and household goods. The most valuable use of fungi may be in rendering pollutants harmless (even biodegrading nappies and tarmac?) and keeping our natural world alive and intact – from beneath and from within.

A final thought

Fungi are genetically closer to humans than they are to plants – we evolved together for a while then branched off. We are part of the mycelium of life on this planet.

Further information on fungi

Use our Species A-Z Fungi page to identify the species that you see, as well as heading over to The Wildlife Trust's website to learn more about where you can find fungi.

More information on wildlife gardening