What Do Trees Say to the World? Plant Communication Through Underground Mycorrhizal Networks

Can trees communicate with each other?
Is it possible that a forest is not just a cluster of plants, but a network of relationships and information exchange — functioning similarly to the internet?
Just two decades ago, such questions might have been dismissed as poetic metaphors. Today, they are the subject of intensive scientific research that is reshaping how we understand the plant world.

At the heart of this revolution lies mycorrhiza — the symbiosis between plant roots and soil fungi.
Through microscopic fungal threads known as hyphae, vast underground networks are formed, connecting trees, shrubs and other plants in a complex web of interdependence.
Scientists refer to this phenomenon as the Wood Wide Web — a “forest internet” of sorts.

Research shows that through these networks, trees can:

exchange water, sugars and minerals,
transmit warning signals — for example, when under attack by pests,
support their offspring and even cooperate with other species.

What’s more — some studies suggest that plants can recognise their “relatives” and adjust their communication accordingly.

What are mycorrhizal networks?

Mycorrhiza is one of the most widespread — yet underappreciated — phenomena in nature.
It is a symbiotic relationship between plant roots and soil fungi, which benefits both sides:
the plant gains improved access to water and minerals, while the fungus receives sugars produced by photosynthesis.

What was once thought to be a local relationship — “one fungus, one plant” — is now known to be something far larger.
Studies have shown that the hyphae of a single fungal individual can connect dozens, or even hundreds, of plants of various species, forming a continuous underground network through which both resources and signals can be exchanged.

Types of mycorrhiza: how does the cooperation work?

There are several main types of mycorrhiza:

Ectomycorrhiza – found mostly in broadleaf and coniferous trees (e.g. oaks, beeches, pines). The fungal hyphae wrap around the outside of the roots, forming a “sheath”.
Endomycorrhiza (arbuscular) – the hyphae penetrate the interior of root cells. This is the most common form, found in over 80% of plant species.
Ericoid, orchid and other types – less common, highly specialised forms, often crucial in extreme environments.

What does the network look like?

Mycorrhizal hyphae are microscopic, thread-like structures that can:

penetrate soil much deeper and wider than plant roots,
connect individuals of the same species as well as entirely different plants,
transport water, phosphorus, nitrogen, zinc, manganese and other micronutrients.

Studies in Canadian forests have shown that a single mycorrhizal network may span hundreds of trees and shrubs, and the mycelium of the largest fungi (e.g. Armillaria ostoyae) can cover over 9 square kilometres and be more than 2,000 years old.

Mycorrhiza is not the exception — it is the rule

It is estimated that mycorrhizal associations are present in:

over 90% of land plant species,
all temperate, boreal and tropical forests,
a large proportion of agricultural crops, grasslands and tundra.

This means that without mycorrhiza, most plants simply would not survive.
And that nearly every forest on Earth is, in reality, a connected, interdependent web of organisms — both visible and hidden beneath the surface.

How Does Plant Communication Work?

If we imagine a forest as a social network, then mycorrhiza is its nervous system.
Thanks to it, plants are able to communicate with one another, passing on information about threats, environmental stress or available resources.
Although this “conversation” doesn’t take the form of words or sounds, it relies on complex chemical and electrical signals that spread through the mycelium much like impulses in a neural network.

Warning Signals

One of the best-documented forms of plant communication is the warning system.
How does it work?
When a tree’s leaves are attacked by pests (e.g. aphids), the tree begins to produce chemical compounds (phytohormones and volatile organic compounds) that:

trigger defence mechanisms in other parts of the same plant,
are transmitted through the mycelial network to neighbouring trees — which can then “pre-emptively” increase tannin production, alter the chemical composition of their sap, or thicken their leaf cuticles.

Research example:
In an experiment published in Ecology Letters (2013), pines receiving signals through a mycorrhizal network “anticipated” pest attacks and activated their defence mechanisms faster than trees disconnected from the fungal web.

Resource Sharing: Sugars, Water, Minerals

Communication through mycorrhiza is not just about signals — it also includes resource sharing.
Trees growing in favourable conditions (e.g. fertile soil, good sunlight) can pass on excess sugars to weaker neighbours, especially if they are their offspring.
During drought, the mycorrhizal network may transport water from wetter to drier areas.
Among species with different nutrient absorption capacities, the network acts like a system for exchanging microelements.

This is not pure altruism — the fungus acts as a “mediator” and often regulates the flow, maintaining balance within the ecosystem.

Mother Trees and Their Offspring

Research by Prof. Suzanne Simard in the forests of British Columbia has shown that large, old trees (so-called mother trees) form preferential connections with young seedlings that are their genetic offspring.

They:

send them more sugars and minerals,
protect them from drying out,
pass on “environmental memory” — e.g. information about past stress.

As a result, young plants connected to the mother’s network have a better chance of survival and faster growth.

Electrical and Biochemical Impulses: Plant Electromessaging?

Recent studies show that electrochemical impulses — very similar to nerve signals in animals — can also travel through mycorrhizal hyphae.
Some research teams suggest that:

these impulses respond to environmental changes,
they may encode information about the direction and nature of a threat,
different species of fungi may use “different languages” of communication.

This is still an area of exploration, but one thing is certain: the mycelium is not just a conduit — it is an active element that communicates with the plant.

Trees as Social Beings?

When we hear that trees “recognise their kin” or “support their offspring”, it’s easy to fall into anthropomorphism. But science is increasingly showing that within mycorrhizal networks, processes occur that resemble social behaviour — although driven not by emotion, but by evolution and chemical communication.

Preferential Support: Mother Trees and Selective Aid

In temperate and boreal forests, older trees have been observed to more frequently transfer resources (e.g. sugars, nitrogen) to:

young individuals of the same species,
genetically related seedlings,
plants showing signs of stress (drought, shading).

This doesn’t happen by chance.
Mycorrhizal networks are plastic and responsive to signals from the environment.
The mycelium “knows” which plant is asking for help — and trees may allocate resources preferentially, increasing the survival chances of their own genetic lineage.

Do Trees Recognise Their Relatives?

Research by Simard and her team indicates that trees can distinguish which plants are their offspring.
In experiments:

seedlings connected to the mother tree via a shared mycorrhizal network grew faster,
they received more resources than unrelated individuals in the same network,
they showed higher chlorophyll content and metabolic activity.

This suggests the existence of recognition and selective support mechanisms — analogous to nepotism in animal societies.

Inter-Species Cooperation

Interestingly, cooperation is not limited to trees of the same species.
In many ecosystems:

birches provide carbon to firs during low-light periods,
pines share mycorrhiza with larches, which in turn support understory shrubs,
the mycelium connects herbaceous plants and trees, creating a multi-species community of exchange.

This is not altruism, but mutual benefit — the more stable and diverse the ecosystem, the greater the survival chances of each of its elements.

What If a Forest Is a Collective Organism?

If we accept that trees recognise relatives, cooperate, warn each other and support regeneration — then we must rethink how we perceive a forest.
Not as a collection of individual trees, but as a networked structure of life, functioning more like an organisation than a set of individuals.

Forests are increasingly being described as “superorganisms” — systems that possess:

memory (e.g. through persistent mycelium and transmitted information),
resilience (to environmental stressors),
capacity for planning and adaptation (through selective support, growth regulation, and shared resource management).

Does a Forest Have Rights?

If we accept that forests function as social systems, the question of ethics arises.
Is cutting a part of the mycorrhizal network merely a forestry operation — or a violation of the integrity of a living organism?
Should trees, as beings capable of communication and cooperation, have a right to protection not just as resources, but as entities in their own right?

Such questions are becoming increasingly common in public debate — for example, in discussions about recognising rivers, mountains or ecosystems as legal persons.

The Importance of Mycorrhizal Networks for Ecosystem Health

Mycorrhizal networks are not only the “forest internet”, but also its immune, circulatory and regenerative systems.
Without them, the ecosystem loses its cohesion — both physically and functionally.
It is thanks to mycorrhiza that the forest can maintain balance, adapt to changes and recover after disturbances.

Soil Stabilisation and Quality Improvement

Mycorrhizal mycelium:

binds soil particles, preventing erosion,
increases humus content and microbial activity,
supports the formation of soil aggregates that retain water and air.

As a result, the soil around trees becomes more fertile, permeable and resistant to degradation — particularly important in conditions of water shortage or the use of heavy forestry equipment.

Boosting Plant Immunity

Mycorrhiza acts as a natural buffer against disease and stress:

mycorrhizal fungi compete with pathogens for space and resources,
they increase plant cell resistance to infections,
they help plants cope with abiotic stress: drought, pH fluctuations, heavy metal excess.

Some mycorrhizae even form protective symbioses, releasing antibiotic substances or altering conditions in the root zone to suppress harmful microorganisms.

Water Retention and Drought Mitigation

Mycorrhizal networks enhance the soil’s ability to retain water, and also:

extend root reach through fungal hyphae,
improve access to capillary water,
enable plants to draw water from deeper soil layers.

Thanks to this, forests with well-developed mycorrhizae are much more resistant to drought and heatwaves — which is critical in the face of climate change.

Restoring Degraded Areas

Mycorrhiza plays a key role in rewilding and land rehabilitation:

restores soil biological activity,
supports the growth of pioneer species and natural succession,
works faster than mineral fertilisers or artificial soil improvers.

In many rewilding projects, mycelium is introduced intentionally — for example, through seed coatings with fungal spores or by transplanting seedlings already colonised by symbiotic fungi.

Can the Wood Wide Web Be Destroyed?

Yes.
And it happens more often than we think.
Although mycorrhizal networks are invisible and may seem resilient due to their underground nature, they are actually extremely sensitive to mechanical, chemical and ecological disruption.
And their restoration — if possible at all — takes decades.

Logging and Industrial Forest Use

The greatest threats to mycorrhizal networks include:

clear-cutting of large forest areas,
heavy forestry machinery that damages the humus layer and soil structure,
post-clearcut monocultures lacking the diversity needed for complex fungal networks.

In managed forests, the model of “cut – plant – harvest” often dominates. But in this approach, there is no time to rebuild the underground relationships.
As a result, we get young, species-poor forests prone to drought, pathogens and soil degradation.

Soil Chemicalisation and Fertiliser Overuse

The use of mineral fertilisers, pesticides and herbicides destroys mycorrhiza in several ways:

acidifies or salinises soil, altering fungal habitat conditions,
reduces the plant’s need for symbiosis (since nutrients are provided externally),
directly kills the fungal network and associated microorganisms.

Over time, this leads to soil dependency on artificial inputs, degradation of biological structure, and the loss of natural plant defence systems.

Loss of Biodiversity

Mycorrhizal networks develop best in environments where:

many plant species are present,
there is age and structural diversity,
the soil is not frequently disturbed.

Monocultures (e.g. spruce or pine plantations) that lack this diversity form poor, one-dimensional networks that are easy to disrupt and difficult to restore.

What About Restoration?

Although there are attempts to restore mycorrhiza:

inoculating seedlings with fungal spores,
“forest soil transplants” (i.e. moving mycelium from natural forests),
use of commercial mycorrhizal preparations,

there is still no technology that can fully recreate a naturally formed mycorrhizal network — with all its complexity, hierarchy and interspecies connections.

It’s like trying to rebuild a city by copying only the pipes and wires — without its people, relationships or history.

The Future of Plant Communication Research

Just 30 years ago, the idea that plants could communicate was considered science fiction or a poetic metaphor.
Today, we have hundreds of peer-reviewed studies confirming that the plant world is a system of information exchange — and that mycorrhiza is one of its key tools.

But this is only the beginning.

New Technologies: Electrodes, Spectrometers and 3D Mycelium Mapping

Modern plant communication studies increasingly use advanced technologies:

electrodes in soil that record electrical impulses in mycelium,
mass and isotope spectrometry to track specific compound movement between plants,
soil tomography to create 3D maps of mycelium and root networks.

Thanks to this, scientists are beginning to see the logic and directionality of flows within mycorrhiza — they are not random, but functionally optimised.

Plant Neurobiology? Yes, It Exists

In recent years, a new field has emerged: plant neurobiology, which explores how plants process stimuli, make decisions and respond to their environment.
Even without a nervous system, plants can:

detect touch, light, magnetic fields, sound,
store “stress memories” (e.g. drought),
change their behaviour depending on context and experience.

Some researchers go further and claim that plants show traits of proto-consciousness — the ability to produce integrated, adaptive responses to their surroundings.

Artificial Intelligence and Forest Network Modelling

Thanks to AI and machine learning, we are beginning to simulate:

the behaviour of mycorrhizal networks under different environmental conditions,
the impact of specific decisions (e.g. logging, planting certain species) on information and resource flow,
the evolution of the forest as a collective organism.

In the future, these tools could help us plan forestry and rewilding in a way that respects the communicative functions of ecosystems.

Will We Talk to Plants?

It may sound like science fiction — but researchers are working on systems that allow:

translating chemical and electrical plant signals into forms understandable to humans,
recording “plant emotions” (e.g. stress, relaxation, activation),
even initiating dialogue with a plant via electrodes and interfaces.

The goal is not to create a “talking tree”, but to better understand its needs, alerts and reactions.

A forest is not just a collection of trees.
It is a network of life — a living, dynamic and intelligent structure built on cooperation, exchange, and response to change.
Mycorrhiza is its foundation: an invisible thread that connects not only roots, but also intentions, reactions and the survival of the entire community.

As scientific understanding grows, we begin to realise that:

plants are not passive — they listen, respond, learn, and support one another,
mycelium is not just a symbiont, but the architect of information and resources in the ecosystem,
destroying mycorrhizal networks means losing the forest’s immune and communication systems — and rebuilding them can take decades.

If we accept that forests are networks of relationships,
we must also change how we protect them.
Planting trees is not enough.
We must preserve and nurture their connections — just as we care for social bonds, culture, and memory.

Because only when we learn to truly listen to what the forest is saying,
will we begin to understand how to truly help it.