Helen Macdonald,

When the trees turn gold, it’s time to go out gathering mushrooms. Naturalist Helen Macdonald enters the weird, wonderful and sometimes lethal world of woodland fungi

“Hunting for mushrooms can feel surprisingly like hunting animals, particularly if you’re looking for edible species.”

It’s raining hard and the forest air is sweet and winey with decay. I’m walking with Nick, an old friend and former PhD advisor, emeritus professor of the history of science and amateur mycologist. For the past 15 years I’ve accompanied him on autumn mushroom hunts; today we’ve come to Thetford Forest in Suffolk.

We’re carrying trugs, traditional English wooden baskets of willow and sweet chestnut, to hold our prizes – perhaps tiny fungi with hair-fine stalks, lumpy shelves broken from the trunks of rotting trees, masses like discarded round pillows, or splayed red starfish arms emerging from the ground.

Hunting for mushrooms can feel surprisingly like hunting animals, particularly if you’re looking for edible species. Searching for chanterelles, I’ve found myself unconsciously walking on tiptoe across mossy stumps as if they might hear me coming. It doesn’t work well if you walk around and try to spot them directly. They have an uncanny ability to hide from the searching eye. Instead, you have to alter the way you regard the ground around you, concern yourself with the strange phenomenology of leaf litter and try to give equal attention to all the colours, shapes and angles on the messy forest floor.

Once you’ve achieved this relaxed and faintly predatory gaze, brilliant wax-yellow chanterelles often pop out from behind leaves and twigs and moss, and now they look quite unlike the false chanterelles growing beside them. Nick says that with enough experience “you can reliably tell, at least for the commoner species, what the thing is, even if they are enormously variable, and you could not begin to explain how”. He has been an enthusiastic mycologist since his teens and has the names of at least several hundred species committed to memory.

INVISIBLE BODIES

Mushrooms are the fruiting bodies of fungi that live as networks called mycelia, made up of tiny branching threads. Some are parasitic, others feed on decaying matter and many are mycorrhizal, growing in and around plant roots and sharing nutrients with their host. Picking a mushroom doesn’t kill the fungus; in a sense, you’re merely plucking a flower from a hidden, thready tangle that may be vast and extraordinarily ancient. One honey fungus in Oregon in the US covers almost four square miles and is thought to be nearly 2,500 years old. Soon Nick and I come across scores of mushrooms set in ragged half-circles, their broad tops like cooling milky coffees among dead leaves. They’re cloud caps, a common species here, and considered toxic.

We walk on. Nick spots a yellowish gleam in the long grass. This one is more interesting. He crouches beside it and, frowning, gently pulls it free of moss and grass. “Tricholoma

sulphureum,” he says, with satisfaction. Mycologists generally use scientific names to describe fungi, as their common names vary. The mushroom he holds is sometimes called the sulphur knight or the gas agaric. He offers it to me, gesturing that I should smell it, and an unpleasantly sulphurous tang makes me wrinkle my nose. He stows it in the basket.

DISTURBING VISIONS

I am not very good at identifying fungi, but I am better than I used to be. Over the years I have not only learned to identify a few species by looking at them or smelling them, or seeing the colour their cut surfaces turn, but I’ve become more and more intrigued by the curious place they occupy in our imaginations. We’ve been foraging and eating mushrooms for millennia, and they still have the power to disturb us, to conjure the deepest human mysteries of sex and death.

Nineteenth-century sensibilities were especially horrified by the common stinkhorn, a fetid fly-attracting species that bursts out of a membranous egg into a shape well described by its scientific name, Phallus impudicus. In her later years, Charles Darwin’s daughter Henrietta went into the woods to collect stinkhorns for the express

“Mushrooms still have the power to disturb us, to conjure the deepest mysteries of sex and death”

purpose of bringing them back to be “burned in the deepest secrecy of the drawing-room fire, with the door locked; because of the morals of the maids”, according to a memoir by her niece. Our continuing pieties about sex are reflected in the way some modern field guides describe the distinctive odour of mushrooms such as Inocybe as “unmentionable” or “disgusting” rather than the more accurate spermatic.

FRIEND OR FOE?

The unpredictable flowering of beautiful alien forms from rotting wood, dung or leaf litter in a forest moving towards winter is a strong and strange conjuration of life-in-death – in Baltic mythology, mushrooms were thought to be the fingers of the god of the dead bursting through the ground to feed the poor. But mushrooms have a more direct relationship to mortality. Many of them, of course, are deadly. You might survive after eating a destroying angel or death cap, but to do so you’ll probably need a liver transplant. What’s more, the particular toxicity of fungi is as mysterious as the forms they take. A mushroom can contain more than one kind of toxin, and the toxicity can change according to whether it has been cooked, how it has been cooked, whether it has been eaten with alcohol or fermented before ingestion. Mycologists talk about poisonous fungi the same way herpetologists talk of ‘hot’ snakes: with more than a modicum of transgressive relish.

If you’re collecting fungi to eat, your expertise in identification is all that keeps you from death or serious illness. There’s a daredevil side to the activity, a sense of staking your life against terrifying possibilities. Today’s vogue for wild foods, spurred by famous foraging chefs and a nostalgic desire to reconnect with the natural world, has resulted in popular guides that feature a selection of edible and poisonous species. Nick thinks many of these are irresponsible, even dangerous. “They don’t explain the full range of things you might be running into,” he warns. Many toxic fungi closely resemble edible ones, and differentiating each from each requires careful examination, dogged determination and often the inspection of spores stained and measured under a microscope slide.

DEFYING THE EXPERTS

Puzzling out tricky specimens is satisfying in itself: if you call on Nick the evening after a fungus expedition, you’ll find him at a table spread with fungi, several frighteningly expensive volumes on mycological identification, a microscope and a magnifying lens, and he’ll be wearing an expression of joyous, fierce concentration. “For some species, the colours are unbelievably variable,” he enthuses about one group, the Russula, “and they get washed out by rain, and then the exact distribution of the warts on their spores is an alternative. So you’re doomed, as an ordinary citizen. Because the colours won’t do it, and you haven’t got a powerful enough microscope.”

Fungi force us to consider the limits of our understanding: not everything fits easily into our systems of classification. The world might be, it turns out, too complicated for us to know.

After a couple of hours, the rain is beginning to ease. We’re soaked but triumphant. Nick’s trug is full of small, difficult and poisonous species. Mine is heaped with edibles, including crab brittlegills whose shining caps are the colour of toffee apples. We start to make our way back to the car through a dense stand of pines. The air is damp and dark in here. Taut lines of spider silk are slung between their flaking trunks; I can feel them snapping across my chest. Fat garden spiders drop from my coat on to the thick carpet of pine needles below. I’m about to step back on to the path when something catches my eye under a tree a few yards away. I know instantly what it is, though I’ve only ever seen it in books. “Cauliflower fungus!” I cry, and run up to it. It’s a pale, translucent, fleshy protuberance the size of a soccer ball that seems to glow in the dripping shade, its complicated folds an unnerving cross between boiled tripe and a sea sponge. Looking at it, I remember its Latin name, Sparassis

crispa, and that it is parasitic on conifers. And also that it is fragrant and delicious when torn and simmered in stock. I sit down on the wet ground to regard it more closely.

SUBTERRANEAN LIFE

We are visual creatures. To us, forests are places made of trees and leaves and soil. But all around me now, invisible and ubiquitous, is a network of fungal life, millions of tiny threads growing and stretching among trees, clustering around piles of rabbit droppings, stitching together bush and path, dead leaves and living roots. We hardly know it’s there until we see the fruiting bodies it throws up when conditions are right. But without fungi’s ceaseless cycling of water, nutrients and minerals, the forest wouldn’t work the way it does, and perhaps the greatest mystery of mushrooms for me is in how they are the visible manifestations of an essential yet unregarded world.

I reach forward, break off half the brittle, furled mushroom and place it in the basket, eager to taste this souvenir from a place full of life hidden from our own. Helen Macdonald is the author of H is for Hawk. Winner of the

Samuel Johnson Prize for non-fiction, her 2014 memoir became a bestseller. Helen’s new book Vesper Flights is a collection of 41 essays about our relationship with the natural world (published by Jonathan Cape in hardback, ebook and audio download).

See Helen Macdonald on BBC iPlayer

Is there a wild side to Britain’s busiest road? In the BBC Four programme The Hidden Wilds of the Motorway, Helen searches for wildness and natural beauty within sight and sound of the M25.

“If you’re collecting fungi to eat, your expertise in identification is all that keeps you from death”