The Forest That Talks: What Trees Really Share Underground

Under the forest floor

Stand in a forest long enough and the visible world begins to slow down. The canopy moves in the wind. A seedling waits in the shadow of a much larger tree. Fallen leaves disappear into the soil. Nothing appears to travel between the two trunks.

Then imagine the underground view.

Roots branch outward. Fungal threads stretch through pockets of soil, slipping around particles and touching surfaces that roots cannot reach. Some fungi live in relationships with trees, receiving carbon-rich compounds derived from photosynthesis and helping their hosts access nutrients. A single fungal body may connect roots belonging to different plants. [S007; S008]

This is where a fascinating scientific question becomes an irresistible story: if plants are physically connected, can they help one another? Could an older tree support a younger one? Can a forest carry information that no individual tree could obtain alone?

The temptation is to answer immediately. But the real research is more interesting if we leave those questions separated for a moment.

The experiment that changed the conversation

In 1997, Suzanne Simard and colleagues published a field study on paper birch and Douglas-fir seedlings. The researchers used carbon isotopes to follow carbon movement and reported bidirectional transfer, with net gain by Douglas-fir under the conditions investigated. Their results suggested a role for mycorrhizal fungal connections, and shading influenced the observed transfer. [S007]

This was not a fantasy about sentient trees speaking in words. It was experimental ecology, trying to trace atoms through an extraordinarily difficult environment.

That distinction matters. An isotope can reveal where a labelled chemical element appears later. It does not directly reveal an intention. The presence of labelled carbon in a neighboring plant does not, by itself, tell us whether the donor gave it away on purpose, whether the transfer improved the recipient's survival, or whether every forest behaves similarly.

The experiment made a possible underground pathway tangible. It did not settle every claim that would later be attached to the word network.

What a fungal connection is

Mycorrhiza means a relationship between fungal organisms and plant roots. In many cases, fungi gain access to carbon from a plant while providing enhanced access to nutrients or water-related benefits, although costs and benefits vary by species, conditions and ecological context.

The fungal filaments are called hyphae. They form mycelial structures that can spread through soil. When a common mycorrhizal network links several plants, it offers a possible route along which material may move. [S008; S009]

But there are three easily confused propositions:

First, fungal structures can connect more than one plant. Second, substances can move across some of these systems. Third, one plant deliberately sends resources or warnings to another, perhaps favoring its offspring. The first proposition is not the same as the third.

The same is true of a road. A road can connect two houses. Goods can travel along it. Neither fact demonstrates that one household is deliberately supporting the other.

We need evidence for the connection, evidence for the transfer, and separate evidence for ecological benefit or directional choice.

The mother-tree story and its appeal

The idea that an older forest tree might nourish its younger relatives is almost perfectly suited to human imagination. It turns a landscape into a family. Large trees become guardians. The forest ceases to be a collection of competing organisms and becomes a community with memory and concern.

There are reasons this language became popular. Forests are not just random trees standing close together. They contain countless relationships: competition for light, fungal partnerships, insect herbivory, microbial exchanges and chemical responses to damaged neighbors. Some of these relationships can increase survival under certain conditions.

Yet a narrative can become much more confident than the experiment beneath it.

In 2023, Justine Karst, Melanie Jones and Jason Hoeksema examined three widely repeated claims: common fungal networks are ubiquitous in forests; they routinely move resources in ways that improve seedlings; and mature trees preferentially support their offspring or send warning signals through these networks. They argued that field evidence was too limited or ambiguous for the first two broad generalizations and that peer-reviewed evidence did not support the last claim as popularly stated. They also documented a problem of positive citation bias. [S008]

This is not a declaration that fungal networks never matter. It is a challenge to claims made at a scale stronger than available demonstrations justify.

Why the critics are not the end of the story

A later perspective by Merckx and colleagues in 2024 approached the issue from an unusual angle: plants that receive carbon from fungi instead of making all their own through photosynthesis. Such mycoheterotrophic plants provide evidence that underground fungal relationships can be a genuine route for substantial resource transfer. The authors argued that these organisms offer an underused window into how common fungal networks operate. [S009]

That response does not establish a vast, intentional forest-wide communication grid. It does show why the entire subject cannot be dismissed with one skeptical headline.

The interesting question is not whether every claim under the phrase wood-wide web is true or false. It is which transfers happen, through which organisms, in which habitats, and with what measurable consequences.

A forest containing mycoheterotrophic plants may reveal something about fungal-mediated carbon nutrition. A forest of two photosynthetic tree species poses different questions. The same metaphor can hide very different processes.

Can a forest warn itself?

Underground signaling is only one part of the story. Plants can also react to airborne chemicals released by other plants.

In a classic 1983 study, damaged poplars and sugar maples showed changes in leaf defensive chemistry, while some nearby undamaged plants changed as well. The authors discussed airborne cues as a possible explanation. Later research developed stronger approaches to volatile-mediated responses, including studies of induced defensive resistance. [S010; S011]

That process may sound like communication. But scientists still debate the exact evolutionary meaning of the word. A chemical released by a wounded plant can serve as a cue to a neighbor whether or not the emitter evolved to benefit the receiver. An insect may even intercept that information.

Think of smoke from a fire. You may learn that danger is nearby. The fire did not intend to send you a warning.

The analogy is imperfect, but it helps separate information from conscious messaging. Chemical cues can carry useful information without requiring a plant to think in human terms.

Why networks are difficult to prove

Researching the underground is not like photographing a road intersection. If researchers dig up soil, they may destroy the very filaments they want to study. If they use barriers, those barriers can alter water, nutrient and microbial conditions. If they measure isotope movement, they have to consider alternative routes, including soil processes and microbial mediation. [S008]

A greenhouse experiment may give excellent experimental control while missing important forest complexity. A field experiment may capture genuine ecological processes but struggle to exclude competing explanations.

That tension is not a failure of science. It is the normal difficulty of studying an intricate living system. Better evidence requires several kinds of method pointing to the same mechanism, not a single photograph of a fungal thread attached to two roots.

The intelligence question

Now return to the word talks.

If a fungal network carries material, is the forest behaving intelligently? That depends on the meaning of intelligence. If the term describes an adaptive system that changes in response to information, some plant and fungal processes qualify under a broad functional definition. If it means an inner experience of deciding to care for another organism, the same experiments do not demonstrate that.

The dispute is partly biological and partly philosophical. The 2026 historical review by Paolo Pecere notes that these questions are not new. Charles and Francis Darwin used striking analogies for root behavior in the nineteenth century, and later researchers disagree about how far to take them. [S013]

The danger lies in sliding between definitions without noticing. A tree that adjusts physiology to a neighbor's cue is impressive. Calling it a forest internet is memorable. Calling it a loving parent making voluntary gifts is another claim entirely.

What an extraordinary discovery would look like

Picture a future study that follows a mature tree, a seedling and a genetically identified fungal network through several seasons. It independently verifies connections, excludes alternative pathways, measures resource flow, shows a reproducible benefit to the recipient and compares related and unrelated seedlings under controlled conditions.

Such a result would substantially strengthen a specific claim about selective support. It still would not prove that a tree experiences parental love. But it would improve what we can responsibly say about how ecological relationships function.

The distinction protects discovery. When we insist that every intriguing effect already means consciousness, we make it harder to recognize the genuinely unexpected mechanisms still waiting in soil.

The story beneath the story

The forest is connected. That is not merely a metaphor. Its organisms exchange matter, alter each other's surroundings and respond to a shared environment.

What remains unsettled is the extent to which particular fungal networks function as dependable communication and support systems across natural forests. The answer will not be a simple yes or no for every species and ecosystem.

There is a quieter wonder here: trees have survived for hundreds of millions of years without minds, limbs or speech like ours. They are embedded in networks of life we can measure only imperfectly. The more carefully we investigate, the more complicated their world becomes.

The next time you stand over a seedling in the shade, you do not need to imagine a secret conversation to feel the mystery. You can ask a more difficult question: what is moving beneath your feet, and how would we know? [S007; S008; S009]