Finding the Mother Tree: Discovering the Wisdom of the Forest

by Suzanne Simard

what I found was not what I had grown up to understand. Instead I discovered vast landscapes cleared of trees, soils stripped of nature’s complexity, a persistent harshness of elements, communities devoid of old trees, leaving the young ones vulnerable, and an industrial order that felt hugely, terribly misguided. The industry had declared war on those parts of the ecosystem—the leafy plants and broadleaf trees, the nibblers and gleaners and infesters—that were seen as competitors and parasites on cash crops but that I was discovering were necessary for healing the earth.

I set out on scientific expeditions to figure out where we had gone so very wrong and to unlock the mysteries of why the land mended itself when left to its own devices—as I’d seen happen when my ancestors logged with a lighter touch.

The trees soon revealed startling secrets. I discovered that they are in a web of interdependence, linked by a system of underground channels, where they perceive and connect and relate with an ancient intricacy and wisdom that can no longer be denied.

“The trees soon revealed startling secrets…in a web of interdependence, linked by a system of underground channels, where they perceive and connect and relate with an ancient intricacy and wisdom.” P.4

I conducted hundreds of experiments, with one discovery leading to the next, and through this quest I uncovered the lessons of tree-to-tree communication, of the relationships that create a forest society.

The evidence was at first highly controversial, but the science is now known to be rigorous, peer-reviewed, and widely published. It is no fairy tale, no flight of fancy, no magi...

One of the first clues came while I was tapping into the messages that the trees were relaying back and forth through a cryptic underground fungal network. When I followed the clandestine path of the conversations, I learned that this network is pervasive through the entire forest floor, connecting all the trees in a constellation of tree hubs and fungal links. A crude map revealed, stunningly, that the biggest, oldest timbers are the sources of fungal connections to regenerating seedlings. Not only that, they connect to all neighbors, young and old, serving as the linchpins for a jungle of threads and synapses and nodes.

that it has similarities with our own human brains. In it, the old and young are perceiving, communicating, and responding to one another by emitting chemical signals. Chemicals identical to our own neurotransmitters. Signals created by ions cascading across fungal membranes. The older trees are able to discern which seedlings are their own kin. The old trees nurture the young ones and provide them food and water just as we do with our own children. It is enough to make one pause, take a deep breath, and contemplate the social nature of the forest and how this is critical for evolution. The fungal network appears to wire the trees for fitness. And more. These old trees are mothering their children.

When Mother Trees—the majestic hubs at the center of forest communication, protection, and sentience—die, they pass their wisdom to their kin, generation after generation, sharing the knowledge of what helps and what harms, who is friend or foe, and how to adapt and survive in an ever-changing landscape. It’s what all parents do. How is it possible for them to send warning signals, recognition messages, and safety dispatches as rapidly as telephone calls? How do they help ...

The scientific evidence is impossible to ignore: the forest is wired for wisdom, sentience, and healing. This is not a book about how we can save the trees. This is a book about how the trees might save us.

Mist crept through the clusters of subalpine firs, coating them with a sheen. Light-refracting droplets held entire worlds. Branches burst with emerald new growth over a fleece of

I touched some feathery needles, comforted by their softness. Their stomata—the tiny holes that draw in carbon dioxide to join with water to make sugar and pure oxygen—pumped fresh air for me to gulp.

I was entrusted with the job of assessing established plantations—seedlings put in to replace harvested trees.

I picked one of the tiny mushrooms. The bell-shaped elf caps of the Mycena were dark brown at the apex and faded into translucent yellow at the margins, revealing gills underneath and a fragile stem. The stipes—stems—were rooted in the furrows of the bark, helping the log decay. These mushrooms were so delicate it seemed impossible they could decompose a whole log. But I knew they could. Those dead cottonwoods along the riverbank in my childhood had fallen and sprouted mushrooms along their thin, cracking skin. Within a few years, the spongy fibers of decayed wood had completely disappeared into the ground. These fungi had evolved a way to break down wood by exuding acids and enzymes and using their cells to absorb the wood’s energy and nutrients.

Extending downward in the tiny crater still holding the remains of the mushroom’s stem were fine yellow threads, the strands braiding into an intricately branching veil of fungal mycelium, the network that blankets the billions of organic and mineral particles making up the soil.

these root tips were glowing yellow, like lights on a Christmas tree, and they ended in a gossamer of mycelium of the same color. The threads of this streaming mycelium looked close to the same color as those radiating into the soil from the stems of the Suillus mushrooms, and from my pocket I took out the one I’d picked. I held the clump of root tips with its cascading yellow gossamer in one hand and the Suillus mushroom with its broken mycelium in the other. I studied them closely, but I could not tell them apart.

My instinct has always been to listen to what living things are saying. We think that most important clues are large, but the world loves to remind us that they can be beautifully small.

No matter the lifestyle, these fungal branching filaments, called hyphae—along with the mushroom fruit they spawned—appeared to be only a smattering of the vast mycelium in the soil.

I washed the soil crumbs from the rest of the root tips. I’d never seen such a rich bouquet of fungus—certainly not this brilliant a yellow, plus white and pink too—each color wrapped around a separate tip, bearded with gossamer. Roots need to reach far and in awkward spaces for nutrients. But why were so many fungal threads not only sprouting from the root tips but blazing with a palette like this? Was each color a different fungal species? Did each do a different job in the soil?

The seedlings had shown me the textures and tones of the forest’s underworld. Yellows and whites and shades of dusty pink that reminded me of the wild roses I grew up with. The soil where they had found purchase was like a book, one colorful page layered on the next, each unfolding the story of how everything was nourished.

I lifted a branch to uncover a young tree, just as I’d picked garbage off the flowers trying to bloom under the trash piles in the hills above the neighborhood when I was a child. I knew the importance of these gestures.

Some little velvety firs had been orphaned near the stumps of their parents and were trying to recover from the shock of their loss. Their recuperation would be arduous given the slow shoot growth since the harvest. I touched the tiny terminal bud of the one closest to me. Some white-flowered rhododendrons and huckleberry shrubs had also ducked the zip of the saw. I was a part of this harvesting of lumber, this business of chopping down trees to clear the spaces where they were free, wild, whole. My colleagues were drawing up plans for the next clear-cuts, to keep the mill going and their families fed, and I understood this need too. But the saws wouldn’t stop until whole valleys were gone.

The crew that had done the planting to replace the harvested elder firs had inserted prickly spruce seedlings, now ankle high. It might seem odd not to replace the subalpine firs they’d taken down with more subalpine firs. But spruce wood is more valuable. It’s tightly grained, resistant to decay, and coveted for high-grade lumber. Mature subalpine-fir timber is weak and punky.

The government also encouraged planting the seedlings in garden-like rows to ensure no patch of soil was left bare. This was because timber grown in grids of evenly spaced trees yielded more wood than scattered clumps. At least in theory. By filling in all the gaps, they figured they could grow more wood than occurred naturally. With every corner chockablock, they felt justified in bigger harvests, in anticipation of future yields. And logical rows made everything more countable. Same rationale as my Grannie Winnie planting her garden in rows, but she worked the soil and varied her crops over the years.

The first spruce seedling I checked was alive, but barely, with yellowish needles. Its spindly stem was pathetic. How was it supposed to survive this brutal terrain? I looked up the planted row. All the new seedlings were struggling—every single sad little planting. Why did they look so awful? Why, in contrast, did the wild firs germinating in that old-growth patch look so brilliant? I pulled out my field book, wiped needles off the waterproof cover, and cleaned my glasses. The replanting was supposed to heal what we’d taken, and we were failing miserably. What prescription should I write?

shading a seedling and flicked it into the shrubs. Using a makeshift envelope fashioned from drafting paper, I collected the seedling’s yellow needles. I was grateful to have my own desk in an alcove set off from the map tables and boisterous offices where men made deals and negotiated timber prices and logging costs; decided what patches of forest to cut next; awarded contracts like banner ribbons at a track meet. In my tiny space, I could work on the plantation problems in a secluded peace. Maybe the seedling’s symptoms would be easy to find in the reference books, since yellowing can be caused by myriad problems. I tried to find any seedlings that were healthy, but to no avail. What was triggering the sickness? Without a correct diagnosis, the replacement seedlings would likely suffer too. I kicked myself for glossing over the problem, taking the easy way out for the company. The plantation was a mess. Ted would want to know if we were failing to meet the government requirements for reforestation at this site, because not succeeding meant a financial loss. He was focused on meeting the basic regeneration regulations at minimal cost, but I didn’t even know what to suggest. I pulled another spruce seedling from its planting hole, wondering if the answer might be in the roots, not the needles. They had been buried tightly in the granular soil, where it was still moist in late summer. Perfect planting job. The forest floor scraped away, the planting hole plunged into the da...

I picked up a piece of bark shading a seedling and flicked it into the shrubs. Using a makeshift envelope fashioned from drafting paper, I collected the seedling’s yellow needles. I was grateful to have my own desk in an alcove set off from the map tables and boisterous offices where men made deals and negotiated timber prices and logging costs; decided what patches of forest to cut next; awarded contracts like banner ribbons at a track meet. In my tiny space, I could work on the plantation problems in a secluded peace. Maybe the seedling’s symptoms would be easy to find in the reference books, since yellowing can be caused by myriad problems. I tried to find any seedlings that were healthy, but to no avail. What was triggering the sickness? Without a correct diagnosis, the replacement seedlings would likely suffer too. I kicked myself for glossing over the problem, taking the easy way out for the company. The plantation was a mess. Ted would want to know if we were failing to meet the government requirements for reforestation at this site, because not succeeding meant a financial loss. He was focused on meeting the basic regeneration regulations at minimal cost, but I didn’t even know what to suggest. I pulled another spruce seedling from its planting hole, wondering if the answer might be in the roots, not the needles. They had been buried tightly in the granular soil, where it was still moist in late summer. Perfect planting job. The forest floor scraped away, the planting hole plunged into the damp mineral earth below. Just as instructed. By the book. I inserted the roots back into the hole and checked another seedling. And another. Every one of them packed exactly right in a slit made by a shovel and backfilled to eliminate the air gaps, but the root plugs looked embalmed, as if they’d been shoved into a tomb. Not a single root seemed to get what it was supposed to do. None was sprouting new white tips to forage in the ground. The roots were coarse, black, and plunging straight to nowhere. The seedlings shed yellow needles because they were starving for something. There was an utter, maddening disconnect between the roots and the soil. By chance a healthy subalpine fir had regenerated from a seed nearby, and I uprooted it to compare. Unlike the planted spruce, which I’d plucked like a carrot out of the soil, these sprawling fir roots were anchored so tightly that I had to plant both feet on either side of the stem and pull with all my might. The roots finally ripped out of the earth and—a parting shot—sent me stumbling. The deepest root tips had refused to unglue from the soil, no doubt in protest. But I brushed the humus and loose dirt off the torn roots I’d claimed, pulled out my water bottle, and rinsed off the remaining crumbs. Some of the root ends were like the fine tips of needles.

A complete replanting using the same kinds of seedlings and methods—shovel planting one-year-old plug stock that is mass-produced in nurseries—felt like the cheapest way for the company to go, but not if we had to keep returning because of the same dismal result. Something different needed to be done to re-establish this forest, but what? Plant subalpine fir? No nurseries had it available for planting, and it wasn’t considered a future cash crop. We could plant spruce seedlings with bigger root systems. But the roots would still die if they couldn’t sprout strong new tips. Or we could plant them so their roots touched the yellow fungal web in the soil. Maybe the yellow gossamer would keep my seedlings healthy. But the rules required that the roots be planted in the underlying granular mineral soil, not the humus—figuring that the grains of sand, silt, and clay held more water late in the summer and therefore offered a better chance of survival—and the fungus mainly lived in the humus. Water, it was thought, was the most crucial resource that soils needed to supply roots so seedlings would survive. There seemed a very low chance of a change in policy so we could plant the roots in a way that they could reach the yellow fungal threads.

I wished I had someone to talk to out here in the forest, to debate my growing sense that the fungus might be a trustworthy helper to the seedlings. Did the yellow fungus contain some secret ingredient that I—and everyone—had somehow missed? If I didn’t find an answer, I’d be haunted by turning this clear-cut into a killing field, a graveyard of tree bones. A brush field of rhododendrons and huckleberries instead of a new forest, a burgeoning problem, one plantation dying after another. I couldn’t let this happen. I had seen forests grow back naturally after my family had logged near my home and knew it was possible for a forest to recover from a harvest. Perhaps it was because my grandparents had cut only a few trees in a stand, opening gaps where nearby cedars and hemlocks and firs could readily seed in, the new plants easily connecting to the soil. I squinted to spot the timber edge, but it was too distant. These clear-cuts were huge, and perhaps their size was part of the problem. If they had healthy roots, surely trees could regenerate in this expanse. So far, though, my job consisted of overseeing plantations with little chance of turning into anything resembling the towering cathedrals once here.

Kelly shouted, “Jiggs fell in the outhouse! Jiggs fell in the outhouse!” over and over, too excited to stop. I crowded in with the men and peered through the wooden hole. Jiggs was paddling in the slop, baying louder when he saw us, too far down in the pit to be reached through the narrow hole. The men would need to dig next to the outhouse, widening the pit underneath, enlarging it until they could reach him.

Before any ground was broken, Grampa cleared away the mushrooms. Boletes, Amanitas, morels. He placed the most precious—the orangey-yellow funnel-shaped chanterelles—under a birch for safekeeping. Their apricot aroma stood out even over the drifts from the outhouse. He picked the honey-brown flat-capped Armillarias, which were centered in icing-sugar halos of spores. These were not good eating, but the cascade of them around the white-barked birches told him the roots might be soft and easy to break through. The men started digging, raking the leaves, twigs, cones, and feathers into a pile. This sweep revealed an underlying congealed mat of partially decomposed needles, buds, and fine roots. Obscuring these dismembered pieces of forest were brilliant-yellow and snow-white fungal threads coating the collage of detritus, almost like the gauze covering my scraped knee. Through the pores in this fibrous quilt crawled snails and springtails, spiders and ants. To get to the earth’s innards, Uncle Jack sliced his pickaxe through the fermenting layer as thick as the axe-head was wide. Underneath this carpet gleamed the humus, so thoroughly decomposed that it looked like the paste of dark cocoa, sugar, and cream that Mum mixed to make us hot chocolate.

Jiggs was reduced to whimpers. Grampa grabbed a pickaxe and chopped into the cake of rhizomes. The roots were almost impenetrable, forming an interwoven basket of earthen tones. Muted shades of white, gray, brown, and black. A warm palette of umber and ochre.

Uncle Jack and Dad made their way through the humus layer and started into the mineral soil. By now the entire forest floor—the litter layer, and then the fermented and the humus ones—had been cleared from an area two shovel blades wide next to the outhouse. A thin bleached layer of sand gleamed, so white it looked like snow. I would later learn that most soils in this mountain country had surface layers like this, as if drained of all life by heavy, percolating rains. Maybe beach sand is so pale because storms quench it of the blood of bugs and the guts of fungi. Among these blanched mineral grains, an army of roots was threaded with an even denser thicket of fungi, sapping the upper soil horizon of any other nutrients that might remain. Another shovel’s length deeper, and the white horizon gave way to a crimson layer.

It was as though the pulsing arteries of the soil had been revealed, and I was the first witness. I inched closer to see the details of the new layer, mesmerized. The grains were the color of oxidized iron coated in black grease. They looked made of blood. These new clods of soil looked like whole hearts. The going got tougher. Roots the size of my dad’s forearm jutted in all directions, and he hacked them with his shovel.

Every root looked tenacious in its unique way, though their common job was to graft the trees to the earth. White papery birch, purple-red cedar, reddish-brown fir, black-brown hemlock. Keeping the mammoths from tipping over. Tapping the water that ran deep. Creating pores for water to trickle through and bugs to crawl along. Allowing roots to grow downward to access minerals. To keep the outhouse hole from caving in. Making it hard as hell to dig through. Shovels were thrown down in favor of the axes to chop through the woody foundation of the forest. Then the spades were used again, only to encounter boulders speckled white and black. Rocks of all sizes, some as big as basketballs and others small as baseballs, wedged into the earth like bricks cemented into a wall. Dad ran to the boathouse for a crowbar. Taking turns, the men levered each rock out of its tight nook—turning, scraping, coaxing. It dawned on me that the gritty soil was a pile of pulverized rock grains. Beaten down by fall rains, dried to dust in summer. Frozen and cracked in winter, then thawed in spring. Eroded by water trickling over millions of years.

Later I sat on the shore and threw driftwood into the water for Jiggs to fetch. He had no idea, nor did I, that his adventure had opened up a whole new world for me. One of roots and minerals and rocks that made up the soil. Fungi, bugs, and worms. And water and nutrients and carbon that ran through the soil and streams and trees.

Those summers in the floating camps on Mabel Lake are where I learned the secrets of my ancestors, fathers and sons who spent their lives felling timbers, a history knitted into our bones. The inland rain forests my family had logged seemed indestructible, the big old trees the keepers of the communities. What mattered was that loggers once stopped and carefully gauged and evaluated the character of individual trees to be cut. Transportation by flumes and rivers kept cuttings small and slow, whereas trucks and roads exploded the scale of operations. What was the timber company of the Lillooet Mountains doing so completely wrong?

The hand falling, horse logging, and river drives left the forests capable of vibrant, renewed life. Clearly much had changed from what I knew to what my industry and I were doing now. I stared out a window in the Woodlands office and thought about my plantations. There were many ways to improve—sow more locally adapted seed in the nursery, grow bigger seedlings, prepare the ground more meticulously, plant sooner after logging, remove competing brush. But the clues told me the answer lay in the soil and how the seedlings’ roots connected to it.

I looked at the dead-forest-standing. I was thrilled to be working in this venerable expanse; I didn’t even mind figuring out how to log some trees. But obliterating whole tracts in one fell swoop would leave little foundation to help the forest recover. The trees grew in clusters, with the eldest and largest—one meter in girth, thirty meters in height—in the deepest part of the hollows where the water collected, with younger trees of various ages and sizes close by. Like chicks clutched around a mother ptarmigan. The grooves of their bark housed tufts of wolf lichen, easy for the deer to nibble in winter. Buffaloberry and soapberry shrubs grew between rocks. Bright-red Indian paintbrushes, purple silky lupines, pale-pink Calypso fairy slippers, and candy-striped coralroot traced the roots fanning out from the tree boles. None of these herbs would thrive after a clear-cut. What the hell was I doing here?

“You see those big pumpkins?” Ray asked, referring to some large firs outside the line of our square. He thought we should take them. The bosses would be pleased—an extra bonus of prize trees. I pointed out that they were well away from the cutting-permit borders. Including them would be illegal. Not only were big elder trees an important seed source for the open ground, they were favorite perches for birds, and I’d seen bear dens under the necks of the roots.

We walked to one of those forbidden elders, and I wanted to shout at it to run. I understood the pride of claiming what was grandest, the temptation—green-gold fever. The handsomest trees captured top prices. They meant jobs for the locals, mills staying open. I checked out this one’s immense bole, seeing the cut through Ray’s eyes. Once you start hunting, it’s easy to get addicted. Like always wanting to snag the tallest peaks. After a while, your appetite can never be sated.

I wanted to scream at the top of my lungs. Instead I rerouted the line and cried inside at my weakness. At the timberline where a magnificent fir stood, my shoulders tightened. A curtain of cow parsnip and willows obscured the avalanche track, but the air was still. I quickly hung the pink ribbon so the tree fell inside the boundary. In a week, it would be lifeless. Delimbed, bucked, and piled along a road right-of-way, waiting to be loaded onto a truck. Ray and I rerouted all the borderlines. We condemned another ancient. And another. And another. By the time we were done, we’d stolen at least a dozen elders from the edges of the avalanche tracks. When we took our break, he offered me chocolate chip cookies and said he had made them himself. I declined and wrapped the nylon chain into a figure eight, using my boot and knee as anchors. I floated the suggestion that we could convince the company to leave some firs in the middle of the block to spread their seed. I blurted, “You know, the way they sometimes leave the big seed trees in Germany.” “We only clear-cut around here.” When I tried to explain that where I’d grown up, we’d log small patches, and the dragged logs churned the floor to make a bed for fir seeds to germinate, Ray countered that if we left some lone firs, the wind would blow them over, and the bark beetles would move in. “And the company will lose a pile of money,” he added, frustrated that I just didn’t get it.

Ted told me we would just plant pine. “But there’s no lodgepole pine up there,” I said. “Doesn’t matter. It’ll grow faster, and it’s cheaper.”

But Douglas fir and ponderosa pine were both better than the spruce and subalpine fir at minimizing water loss, helping them cope with the drought. They did this by opening their stomata for only a few hours in the morning when the dew was heavy. In these early hours, trees sucked carbon dioxide in through the open pores to make sugar, and in the process, transpired water brought up from the roots. By noon, they slammed their stomata closed, shutting down photosynthesis and transpiration for the day.

I sat eating an apple under the generous crown of an old Douglas fir, the seedlings on the outskirts of its apron a sign that the ground was cool and moist. The brown furrowed bark absorbed the heat and protected the tree from fire. It was thick, too, to prevent water loss from the underlying tissue, the phloem, which transported the photosynthetic sugar water from the needles to roots in an inch-thick ring of long tubular cells. The orange bark of the ponderosas also protected the parasol-crowned trees from the fires that swept through every twenty years or so. These seedlings were growing happily where there was barely any water, while my seedlings in the Coast Mountains to the west were dying where there was plenty.

I glanced at an ant crawling over from a nearby nest as tall and wide as my seated silhouette. The nest quivered with thousands of workers. Moving, stacking, and stockpiling millions of Douglas-fir needles that littered the forest floor. The ants also carried spores of brown decay mushrooms on their legs and in their fecal pellets into the nest, accelerating infection and decomposition of the needles, which settled and stabilized the thatch. And into stumps and fallen trees, aiding decay otherwise hindered by the summer drought. I remembered the saprotrophic oyster mushrooms at Mabel Lake, their smooth, creamy caps attached to the fallen leaves and logs of dead birch trees. Trees that had been killed by the pathogenic honey mushrooms. The oyster mushrooms, their decay skills so efficient, also killed and digested bugs to meet their needs for protein. Mushrooms were as varied as their roosts, and they were masters at multitasking.

Somehow, in the ravines and hollows of this parched valley, the saplings and seedlings sprinkled around the Douglas firs and ponderosa pines seemed fine—without the benefit of a deep taproot of their own yet. Could the old trees be helping the young ones by passing them water through root grafts? Grafts were unions where roots of different trees spliced into a single root, with phloem shared in common, like veins grown together in a healing skin graft.

Trembling aspen are unique in that many stems of the same individual spring from subterranean buds along a shared network of roots, and I wondered if the aspen copses were accessing water from the ravines and passing it upslope through their shared root systems. Like a fireman’s brigade.

What were the fungal threads of this odd-shaped mushroom doing, and how were they helping the coral fungus make a living? I rubbed the threads between my thumb and index finger. They were gritty. Moist soil particles clung to the mycelia. The threads might have a role in gathering water from the labyrinth of pores in the soil. In this climate, any water still in the ground would adhere to soil particles with the strength of cement. In the sparse woodlands, where trees only grew in depressions and gullies, water was obviously limiting where they could get a toehold. I wondered if these tiny mushrooms might be helping not only themselves but the trees in need of water or perhaps nutrients where the trees were surviving the cold. If I rode my bike to those high-elevation forests across the valley, would I find the Suillus pancake mushrooms there too, as I had in the Lillooet Mountains? In places with plenty of water, maybe the pink and yellow and white threads were delivering nutrients instead of moisture to the trees. I put the coral fungus into my pocket with the puffball. More puzzling was the question of whether the multitude of silky fungal threads fanning through the clay could explain how water moved from the big trees to the more shallow-rooted plants. Were those threads, which looked like an underground spider’s web, joining trees and plants together to capture much-needed moisture for the whole community? Were the puffball and coral fungus involved?

I dug through sheets of hard clay, each layer cloaked in black fans of fungal threads. I held a clump close to my eye and saw the tiny threads growing straight into the soil pores. Working my knife through the layers, I realized that every single sheet was coated in the fungal network. I hit a soft spot, as if I’d poked a cooked potato, and carved through the clay until a dark, round truffle stared back at me, its black rind fissured. I swept aside the surrounding soil, as though I were on an archeological dig looking for shards of bone, until I could get my fingers all the way around the tuber. As the hole grew to the size of my foot, I uncovered a fungal strand flowing out of the truffle. It looked like a thick black umbilical cord, wiry and tough, and made of many individual fungal strands twisted and packed together like ribbons around a maypole. The strands themselves came out of the black fans caking the clay sheets before knitting themselves into one. The cord was packed into the clay, so I chiseled off more soil to see where it went. With about fifteen minutes of work, I followed it to a whitish-purplish cluster of fat Douglas-fir root tips. I poked the tips with my knife—they had the same softness and texture as a mushroom. I stared at the excavation, my mind whirling. The cord was linking the fungal-coated root tips of the Douglas fir to the truffle. The tips were also the source of the fungal threads fanning over the soil pores. The truffle, the cord, the hyphal...

But why would the fungus give up its water to the tree roots? Maybe the tree was so parched, with such a deficit from transpiring water through its open stomata, that its roots sucked the water from the fungus like a vacuum cleaner. Or a thirsty kid drinking through a straw. This exquisite underground mushroom system sure looked like the lifeline between the tree and the precious water in the soil.

Scientists had recently figured out that mycorrhizal fungi helped food crops grow because the fungi could reach scarce minerals, nutrients, and water that the plants couldn’t.