A tree damaged by insects can release chemicals into the air. A nearby plant may detect them and change its own defences. That is an intriguing exchange of information, but does it mean the trees are “talking”?
The answer depends on what we mean by communication. Biologists can study a chemical released by one organism, detected by another and followed by a measurable response. That is a real phenomenon. It does not require words, plans or a wish to help a neighbour.
Signals in the air
Experiments with willows have found that exposure to cues from a damaged neighbour can reduce later herbivore damage. In one experiment, covering the damaged tissue so airborne signals could not pass removed the effect.¹ Such work gives the phrase “plant signalling” a testable meaning.
Yet even here there is a question of interpretation. A plant may release chemicals as a consequence of its own injury, while neighbours happen to use them as information. From the receiver’s point of view, the cue is useful. Whether the sender evolved to warn others is a harder question.
What about the fungal network?
Many trees form partnerships with fungi around their roots. Fungal threads can connect more than one plant, creating what researchers call common mycorrhizal networks. The existence of some connections is not in doubt. What those connections do in complex forests is much harder to establish.
A 2023 review warned that popular claims about these networks often go beyond the evidence. In particular, it found no peer-reviewed published evidence that mature trees preferentially send resources and defensive signals to their own offspring through such networks.² Another review questioned the familiar “mother tree” story of carbon support for seedlings.³
Experiments in pots or simplified plots can show a possible route, but forest soil contains roots, microbes, water movement and many alternative pathways. A changed seedling does not by itself prove that a message travelled through one specific fungal connection. It certainly does not show intention.
A useful word, used carefully
Calling chemical detection “communication” can help explain why plants are not passive fixtures. They sense and respond to their environment, including other organisms. But the metaphor becomes misleading when it turns a forest into a conscious internet where trees knowingly care for relatives.
What would count as proof?
To establish a route of communication, researchers need to rule out alternatives. If two plants change after one is damaged, the second might have detected airborne chemicals, a soil change, altered light or a shared environmental stress. Showing a fungal connection exists is only one step. The experiment must isolate the proposed pathway and show that it changes the receiver’s response.
Intent is harder still. A damaged plant may release a chemical because that helps defend itself. A neighbour may benefit by detecting it. Calling this a warning can be a vivid shortcut, but a warning in ordinary speech suggests a sender trying to help. Evolutionary studies ask whether releasing the chemical benefits the sender under realistic conditions.
Fungi are participants, not passive wires. They take resources and respond to their own incentives. A network diagram that draws a straight line between two trees can hide the living partner in the middle. Reviews of mycorrhizal claims stress how easily complex forest interactions are simplified into an attractive story.²,³
Why the distinction matters
The debate is not an argument that forests are unconnected. They plainly contain interactions among plants, fungi, microbes, insects, soil and air. The issue is whether a particular popular claim is supported by the available experiments.
Better language can preserve the wonder without exaggeration. We can say that damaged plants release compounds, that neighbours may respond, and that fungal partnerships connect many roots. Then we can state what remains unknown about transfer, benefit and intent. Those questions are more interesting than pretending the answers are already settled.
A forest is full of information moving through physical and chemical pathways. Whether a given pathway deserves the word “communication” depends on what we demonstrate, not on how appealing the metaphor sounds.
Curiosity without anthropomorphism
Words such as “talk”, “listen” and “help” make plant research memorable, but they can quietly add motives the data do not show. A better analogy may be a smoke detector: it responds to a chemical cue without sharing our understanding of danger. Plants are far more complex than detectors, but the comparison reminds us to separate detection from intention.
The experimental question remains exciting. If one plant’s damage changes a neighbour’s later defence, researchers can investigate the molecule, route and consequence. Repeating those tests across species and real forest conditions is how a striking observation becomes a reliable ecological account.¹,²
The strongest writing on trees can keep two ideas together: plants are responsive organisms embedded in networks of exchange, and a claim about a specific message route must be demonstrated. Holding both avoids dismissing plant biology and avoids turning uncertain findings into a fairy tale.
The interesting science is richer than the comforting story. Researchers can ask which molecules move, by what route, how a receiver changes and whether the interaction benefits the sender, the receiver or neither. That gives us something more valuable than a slogan: a way to test what forests actually do.