Finding the Mother Tree: Uncovering the Wisdom and Intelligence of the Forest

by Suzanne Simard

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.

was tapping into the messages that the trees were relaying back and forth through a cryptic underground fungal network.

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.

the most shocking aspect of this pattern—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 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.

How is it possible for them to send warning signals, recognition messages, and safety dispatches as rapidly as telephone calls? How do they help one another through distress and sickness? Why do they have human-l...

the forest is wired for wisdom, sentience, and healing.

the tenacity of the buds to surge with life every spring, to greet the lengthening days and warming weather with exuberance, no matter what hardships were brought by winter.

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.

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.

The mushroom is the visible tip of something deep and elaborate, like a thick lace tablecloth knitted into the forest floor. The threads left behind were fanning through the litter—fallen needles, buds, twigs—searching for, entwining with, and absorbing mineral riches.

Humus is the greasy black rot in the forest floor sandwiched between the fresh litter from fallen needles and dying plants above and the mineral soil weathered from bedrock below. Humus is the product of plant decay. It’s where the dead plants and bugs and voles are buried. Nature’s compost. Trees love to root in the humus, not so much above or below it, because there they can access the bounty of nutrients. But

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.

The replanting was supposed to heal what we’d taken, and we were failing miserably.

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?

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.

under the generous crown of an old Douglas fir,

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.

Mountains to the west were dying where

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.

the prevailing wisdom was that trees only compete with one another to survive. That’s what forestry school had taught me, and it was why my logging company liked fast-growing trees spaced well apart in rows. But that didn’t make sense in this ecosystem where trees and plants seemed to need one another for survival. One extremely dry season, a profound dryness the trees were not adapted to cope with, and they could succumb to the blistering heat. IN THE NICK OF TIME AS USUAL, I arrived at the Logan Lake arena as Kelly’s event was starting.

All three of my odd-duck mushrooms were the fruiting bodies of this group of fungi, which gathered water and nutrients from the soil in exchange for sugars made through photosynthesis from their plant partners.

A two-way exchange. A mutualism.

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.

Adding fertilizers full of minerals and nutrients, or providing irrigation, artificially took care of things, causing the fungi to disappear. When the plants didn’t have reason to spend energy investing in fungi to meet their needs, they cut off the flow of resources.

With a little effort, we could apply a more sustainable method by encouraging the development of the highly coevolved mycorrhizal relationships. Instead, foresters ignored the mycorrhizas, or—worse—killed them with fertilizer and irrigation in the seedling nursery, and focused only on those fungi that damaged or killed big trees, the pathogens. Those parasitic fungal species that infected roots and stems, damaged wood, and sometimes killed trees. The pathogenic fungi could, in short order, cost the industry a big whack of money.

Without the saprophytes, the forest would choke from accumulated detritus, as our towns and cities would from garbage.

All but a few of the world’s plant species—such as those grown on farms that are either naturally nonmycorrhizal or are irrigated and fertilized—require the helper fungi to soak up enough water and nutrients to survive.

The efficiency of clear-cutting felt brutally detached from nature, a discounting of those whom we consider quieter, more holistic and spiritual.

How to protect the forest while it provided us with wood to build our homes, fibers to make our paper, and medicines to cure our ailments. I wanted to be a new breed of silviculturist who honored this responsibility. I

new government policy to get rid of neighboring plants so that conifer seedlings were “free to grow” without competition from anything not-conifer—meaning any native plants, which were viewed as weeds to be eradicated. A policy that had grown from the influence of more intensive American practices that increasingly treated forests as tree farms. And here I was talking about seedlings needing to grow near huckleberries and alders and willows.

Monsanto had invented an herbicide in the early 1970s—glyphosate, or Roundup—that would poison the native plants without affecting the conifer seedlings. Roundup had become so popular that many people used it casually on their lawns and gardens, Grannie Winnie a stubborn exception.

The idea for forest plantations was that killing the leafy plants would free the seedlings from competition, and the companies could then meet their legal obligations for “free-to-grow” stocking.

Now that I knew how to establish a “weeding” experiment, I got a larger contract to test herbicide doses and manual-cutting treatments to kill leafy-green Sitka alder, lance-leaved Scouler’s willow, white-barked paper birch, suckering aspens, and fast-growing cottonwoods. To obliterate purple-flowered fireweed, bunches of pinegrass, and white-topped Sitka valerian. Native plants, including trees, that might impede the growth of coveted planted seedlings—prickly spruce, skinny lodgepole pine, and soft-needled Douglas fir. These three conifer species, especially lodgepole pine, were now planted in nearly every clear-cut across the province because they were lucrative, durable, and fast growing. And the quicker the pesky native trees and plants were killed and free to grow achieved, the sooner the company’s obligation to tend the plantations would be met.

It didn’t matter that the plants provided nests for birds and food for squirrels, hiding cover for deer and shelter for bear cubs, or that they added nutrients to the soil and prevented erosion—they simply had to go. Of no concern was the nitrogen added to the soil by the leafy-green alders, now clear-cut and burned to make way for seedlings. Or that the bunchy pinegrass provided shade for new Douglas-fir germinants, which otherwise ended up baking in the intense heat of wide-open clear-cuts. Or that the rhododendrons protected the smaller prickly-needled spruce seedlings from hard frosts that were much more severe out in the open than under a jigsaw canopy.

No, the thinking was clear and simple. Get rid of the competition. Once the light, water, and nutrients were freed up by obliterating the native plants, the lucrative conifers would suck them up and grow as fast as a redwood. A zero-sum game. Winners take all.

All but one of the treatments would end up failing to improve conifer growth and, no surprise, native plant diversity was lowered. In the case of birch, killing it improved the growth of some of the firs but caused even more to die—the opposite of expectations. When the birch roots had become stressed by the hacking and spraying, they had been unable to resist the Armillaria pathogenic fungus living naturally in the soil. The fungus infected the suffering birch roots and from them spread to the roots of the neighboring conifers. Where white-barked birch was left untouched in the control plots, and continued to grow intermingled with the conifers, however, the pathogen remained subdued in the soil. It was as though the birch were fostering an environment where the pathogen existed in homeostasis with the other soil organisms.

I won a research grant to test whether conifer seedlings needed to connect with the mycorrhizal fungi in soil to survive. I added the twist of exploring whether native plants helped them make those connections, which I proposed to do by comparing seedlings that were planted in diverse communities to those planted alone, in bare earth.

After hundreds of days in plantations and in my weeding experiments observing how plants and seedlings grow together, I sensed that trees and plants could somehow perceive how close their neighbors were—and even who their neighbors were. Pine seedlings between sprawling, nitrogen-fixing alders could spread their branches farther than if they were hunkered under a thick cover of fireweed. Spruce germinants grew beautifully nestled right up to the wintergreens and plantains but kept a wide berth around the cow parsnips. Firs and cedars loved a moderate

cover of birch but shrank when a dense cover of thimbleberry also grew overhead. Larch, on the other hand, needed a sparse neighborhood of paper birches for the best growth and the least mortality from root disease. I didn’t know exactly how the plants perceived these conditions, but my experiences told me to plant the test mixtures with precision. Distances between trees had to be exact,

and the clear-cuts had to be on flat ground for maximum accuracy. Given that British Columbia is a province of mountains, finding thr...

Is connection to the right kind of soil fungi crucial for the health of trees?

On the day I left my experiment, I stopped to absorb the forest’s wisdom. I walked up to an elder birch along the Eagle River where I had collected the soil for transferring to the planting holes. Running my hands across the papery bark stretched across its wide, sturdy girth, I whispered the tree thanks for showing me some of its secrets. For saving my experiment.

The death of fungi in the soil, and the breakdown of the mycorrhizal symbiosis, held answers about why the little yellow spruce in my first plantations had been dying. I’d figured out that accidently killing the mycorrhizal fungi also killed trees. Turning to the native plants for their humus, and putting the fungi in the humus back into the plantation’s soil, helped the trees.

In the distance, helicopters were spraying the valleys with chemicals to kill the aspens, alders, and birches in order to grow cash crops of spruces, pines, and firs. I hated this sound. I had to stop it.

Alder grew in the understory of the native lodgepole pine forests, which had regenerated across the sweeping glaciated interior plateau following the fires ignited by settlers laying railroad and searching for gold in the late 1800s. A century later, these forests were clear-cut with feller bunchers—tractors with a mechanical arm wielding a saw—and the unlucky alders were either crushed by the wheels or cut along with the pines. With the overstory gone, light shined on the sheared-off alder stumps, which sprouted a multitude of new branches and leaves. Water and soil resources abounded. It was alder heaven.

I’d driven through many forests in the years leading up to my master’s to see what these plantations looked like on the inside, getting out of my truck and wading into the alders crowding the road. Once through this wall of green, I’d usually discover pines growing beautifully. But seeing an ocean of alder from the roadside, even if many pines were poking through, was all foresters needed to justify a chemical assault or a literal hack job with saws or clippers. But to what avail? No one knew whether this weeding was improving plantation growth. My experiment aimed to help fill that knowledge gap. I wanted to quantify the competitive effect of the alders and associated plants on the pines. Even more interesting to me was whether the native shrubs might actually collaborate with the pines to help them connect with the soil and create a healthy forest community. To see how—and if—alder might interfere with pine, I had to reduce the abundance of the shoulder-height shrubs to different densities, including total elimination in some plots.