Mushroom Magic in the Great North Wood

Sam Bentley-Toon

Enter the weird and wonderful world of fungi in south London's Great North Wood.

Mushrooms and toadstools have long been associated with the supernatural. Their habit of popping-up overnight, seemingly from nowhere, and then almost as quickly dissolving back into obscurity, gives them an air of sly mystery. Their ability to be both delicious and deadly, sometimes both, lends them a malign glamour, while their ability to produce altered states and mystical experiences has imbued them with a quasi-religious significance to some. The Great North Wood, with its mix of secondary and ancient woodland, is a fungal treasure trove and at their peak in autumn you can barely take a step without seeing some new mycological delight emerging from a rotting log or poking out from under a carpet of dead leaves. 

Fungi, being somewhat immobile and plant-like, were once considered to be part of the plant kingdom. In fact, we now know that they are more closely related to animals and because they can’t produce their own food using energy from the sun they must, like animals, go on the hunt for food in the form of other living or once-living things. The food-harvesting part of fungi is the mycelium: a web of super-fine threads that penetrate soil and wood digesting and absorbing organic molecules. The charismatic and colourful structures we recognise as fungi are just part of the organism; they are the fruit bodies whose function is to produce and disperse spores. 

Many fungi eat dead plant material which makes them a vital part of all ecosystems because they allow the nutrients which would otherwise be locked up in dead plants to be made available again for other plants. One theory suggests that the rich coal deposits laid down in the carboniferous era were a result of a lag period between the evolution of lignin, an incredibly tough molecule that gives wood it’s hardness, and the evolution of fungi that could digest it. Before fungi evolved the necessary enzymes, there was nothing around that could decay wood. This led to a huge wood pollution problem with wood stacking up all over the place for several million years before eventually becoming fossilised as coal. 

False death cap in Biggin Wood

False deathcap Amanita citrina in Biggin Wood

The other great role that fungi play in ecosystems is a result of their intricate association with living plants. Over 90% of plants have a symbiotic relationship with so-called mycorrhizal fungi which can attach themselves to plant roots. The fine fungal threads massively increase the surface area of plant roots allowing them to more efficiently absorb water and nutrients. The plants repay the fungi for this service by giving them a significant proportion of the sugars they make in their leaves through photosynthesis. A healthy woodland will have an incredibly complex mycorrhizal network with hundreds of trees and fungi connected in what has been called the wood wide web.  

Mycorrhizal networks have been shown to facilitate tree communication. Trees that are under attack by leaf-eating insects can send a chemical message, via their fungal symbionts, to warn nearby trees of the impending danger and cause them to flood their leaves with unpalatable tannins. Young trees, growing beneath the shady canopy of their parents are unable to photosynthesise effectively and must rely on a drip-feed of sugars from nearby adult trees, administered via their mutual fungal friends, until they can at last emerge into the light. 

One particularly charismatic genus of mycorrhizal fungi are the amanitas. This group includes the deadliest mushroom in the world – the death cap Amanita phalloides – as well as it’s less poisonous lookalike the false death cap Amanita citrina (pictured above). The most instantly recognisable member of the genus is the fly agaric Amanita muscaria (pictured in the header). Fire-apple red and covered in little-white spots, this is the classic toadstool of fairy tales and folklore. It is thought to be the active ingredient in an ancient hallucinogenic drink called soma which was consumed in ancient India and Iran. It has also been used for its psychedelic properties by Siberian shamans who avoided some of its toxic side-effects by drinking the urine of reindeer who had ingested the mushroom. Shamans would give fly agarics as gifts for winter solstice and it has been suggested that the mushroom may have inspired Santa’s red and white costume. The species favoured partner tree is birch, but you can also find it growing amongst oak and pine. My colleague, and fellow Great North Wood project officer, Chantelle spotted the one pictured here from the van window on the way back from a volunteer workday in Dulwich Wood. 

cotw

Chicken of the woods Laetisporus sulphureus in Spa Wood

Another fungus we find commonly growing in the Great North Wood is chicken of the woods Laetiporus sulphureus (pictured above) so called because it is said to taste like chicken! Chicken of the woods grows in wavy-edged tiers that emerge from dead or living trees, often oak, and disperse their spores through tiny pores on their underside, rather than from gills like a classic mushroom. The scientific species name – sulphureus – comes from the dazzling bands of acid yellow and orange that ripple across its surface. Equally vivid in colour, the beautifully named amethyst deceiver Laccaria amethystina (pictured below) is another mycorrhizal species that associates with beech and oak. It’s related to the common deceiver which is so called because of its variable and changeable appearance which can make it difficult to identify. 

Amethyst deceiver in Low Cross Wood

Amethyst deceiver Laccaria amethystina in Low Cross Wood

The giant parasol Macrolepiota procera (pictured below), with its dinner-plate sized cap held aloft on a long sinuous stalk (or stipe), is perhaps the most statuesque mushroom we find in the Great North Wood. It can be distinguished from similar species by the snakeskin patterning on the stipe from which it derives the nickname: snake’s-hat. This fungus is one of nature’s recyclers, feeding on leaf litter and other dead plant material, which it breaks down into molecules that can be reabsorbed by plants.  

Fungi are a crucial element of the woodland ecosystem, but we’ve noticed that there’s some parts of the Great North Wood where they are unable to thrive. In heavily trampled areas the soil appears to be too compacted and eroded to sustain the delicate network of fungal threads that make up the wood wide web. We see a lot less fungi in these areas and we wonder if in the long term the trees may suffer without their mycorrhizal partners or nutrient recyclers. In some places we’ve erected fencing to exclude trampling feet and in time we hope a rich community of fungi will return to these areas along with woodland wildflowers and new generation of young trees. 

Parasol in One Tree Hill

Parasol Macrolepiota procera in One Tree Hill

This blog has barely scratched the surface of the huge diversity of fungi that flourish across the Great North Wood living landscape. Fungi are notoriously hard to identify but a little bit of effort goes a long way and it can be very rewarding when you start to recognise a few species. If you are keen to learn more it’s worth investing in a good guidebook: The Mushroom Collins Gem by Patrick Harding is a great place to start. Next time you are in the woods keep your eyes peeled for these captivating organisms and perhaps even have a go at identifying some of them! 

Note: We do not recommend harvesting mushroom to eat in the Great North Wood. Not only is there a very real risk of poisoning unless you know exactly what you are doing but in these small urban sites there is a risk of over-harvesting which may have an impact on fungus populations or the other wildlife that eats them.