In April 2022, a computer scientist named Andrew Adamatzky, who runs the Unconventional Computing Laboratory at the University of the West of England in Bristol, published a paper in Royal Society Open Science with a strange claim buried in dry statistical language. He had inserted microelectrodes into the fruiting bodies and mycelial mats of four fungal species, including the oyster mushroom Pleurotus djamor, and recorded trains of electrical spikes. Some spikes clustered into patterns lasting minutes. Adamatzky, working from analogies to linguistics rather than neuroscience, counted what he called a vocabulary of roughly fifty distinct spike shapes and suggested the patterns resembled something like words.
Most mycologists treated the paper as interesting and wildly overinterpreted in equal measure, which is a fair summary of where this entire field sits right now. But Adamatzky’s electrodes were picking up something real: fungal hyphae carry ionic current, the same basic physics that lets a nerve cell fire. And that fact connects to a separate, better documented body of research on plants that, together, adds up to a genuinely startling possibility. Trees under attack generate electrical signals. Fungal threads running between their roots can carry current. The question that has consumed a small but serious corner of plant science for over a decade is whether those two facts combine into something like a warning system, a forest wired for distress calls that travel not through air, but through soil.
The Aphid Experiment That Started the Argument
The clearest experimental hint came out of the University of Aberdeen in 2013. A researcher named David Johnson, along with Zdenka Babikova and colleagues, grew bean plants in pots connected only by strands of mycorrhizal fungus, the symbiotic threads that fungi extend into plant roots in exchange for sugar. Some pots were connected by fungal networks; others were physically separated by mesh fine enough to block roots but also block fungal hyphae, or wrapped in plastic to block airborne chemical cues entirely.
When Babikova’s team infested one plant with aphids, neighboring plants connected by fungal threads began producing volatile defense chemicals, the same compounds that repel aphids and attract aphid predators, before any aphid touched them. Plants isolated from the fungal network did not respond. The paper, published in Ecology Letters, did not claim electricity was the messenger. It left open whether the signal traveling through the hyphae was a hormone, a peptide, a stress-related chemical, or something electrical. But it proved the fungal thread itself was doing the work, not the air and not the soil water around it.
The signal that saves a neighboring plant might be a voltage spike, or it might just be sugar.
That ambiguity, whether the fungal network is a chemical pipeline or an electrical wire or both, is exactly where the science still sits twelve years later. Nobody has definitively shown an electrical impulse leaving one tree’s roots, crossing a fungal hypha, and triggering a measurable defense response in a second tree in an intact forest. What researchers have shown, piece by piece, is that every component of that chain is individually plausible.
How a Bite Becomes a Voltage Spike
Inside a single plant, electrical signaling is not speculative at all. When a caterpillar bites a leaf on Arabidopsis thaliana, the lab mustard plant that functions as biology’s stand-in for “generic plant,” the wound triggers a wave of electrical depolarization that races through the vascular tissue at roughly one centimeter per second, reaching distant, untouched leaves within two minutes and priming them to produce defensive chemicals before the caterpillar arrives. Simon Gilroy’s lab at the University of Wisconsin-Madison, working with Masatsugu Toyota, mapped this in a 2018 Science paper by engineering plants with a fluorescent calcium sensor, watching a wave of calcium light up the plant like a fuse burning outward from the wound.
The trigger for that wave sits in a family of genes called glutamate receptor-like channels, GLRs, first linked to long-distance leaf-to-leaf signaling by Edward Farmer’s group at the University of Lausanne. When insect saliva or mechanical damage ruptures plant cells, glutamate leaks out, GLR channels sense it and fly open, calcium floods in, and the resulting shift in membrane voltage propagates outward the way a nerve impulse does, cell to cell, without any single cell needing to know what caused it. It is a genuine electrical signal, measurable with the same kind of electrode you would use on a heart or a neuron, running through a system that has no neurons at all.
What Happens Where the Root Meets the Fungus
The open question is what happens when that electrical wave reaches the very end of the root, where a fungal hypha is fused into the plant’s cortical cells as part of the mycorrhizal symbiosis. A hypha is a tube one hundredth the width of a human hair, its cytoplasm bounded by a membrane studded with ion channels, not unlike a plant cell’s own membrane. Adamatzky’s spike recordings, along with earlier work from the 1990s and 2000s on electrical activity in fungal mycelia by researchers studying wood-decay fungi, establish that hyphae can and do generate and propagate voltage changes along their length, likely tied to nutrient transport and growth rather than communication.
A mycelial thread is not a wire, but it moves current the way a wire does.
Whether a depolarization wave arriving from a stressed tree’s root can cross into that fungal membrane and continue propagating, rather than simply dissipating at the boundary, has not been directly recorded. Suzanne Simard, the University of British Columbia forest ecologist whose decades of work on what she calls “mother trees” made the phrase “wood wide web” a household term after her 2021 book Finding the Mother Tree, has documented carbon, nitrogen, and stress-related compounds moving between Douglas fir trees through shared fungal networks, with older, larger trees preferentially supplying resources to younger, related seedlings. Her tracer studies used radioactive and stable isotopes, not electrodes, and measured chemical transfer over hours and days, not electrical transfer over seconds. It is a real, repeatedly replicated phenomenon. It is also a slower and chemically different mechanism than what Adamatzky’s fungal spike recordings or Farmer’s and Gilroy’s plant electrical waves describe.
| Signal type | Speed | Medium | Evidence strength |
|---|---|---|---|
| Electrical wave within a single plant | ~1 cm/sec, minutes to reach whole plant | Vascular tissue, GLR channels, calcium | Well established, directly recorded |
| Chemical transfer between trees | Hours to days | Shared mycorrhizal hyphae | Established via isotope tracing, debated in scale |
| Electrical spiking within fungal mycelium | Seconds to minutes per spike train | Hyphal membrane ion channels | Directly recorded, function unclear |
| Electrical signal crossing tree to fungus to tree | Unknown | Proposed continuous circuit | Not yet directly observed |
The Wood Wide Web Has a Credibility Problem
You should know that not everyone in forest ecology is comfortable with how far this idea has already traveled in the public imagination. In 2023, Justine Karst at the University of Alberta, with Melanie Jones and Jason Hoeksema, published a review in Nature Ecology & Evolution auditing the scientific literature behind “wood wide web” claims and found something uncomfortable: many widely cited statements, including the claim that common mycorrhizal networks are ubiquitous in forests and reliably transfer resources in ways that benefit seedlings, rest on a small number of studies that get cited far more often than their actual findings support. Karst’s team found that only a minority of forest tree species have even been confirmed to share fungal networks at all under field conditions, and that lab pot experiments, like the Aberdeen aphid study, do not automatically scale up to a mixed, windy, fungus-competitive forest floor.
Overstating the wood wide web doesn’t help the science. It just makes better headlines.
That critique does not undo Babikova’s aphid results or Simard’s isotope work or Adamatzky’s electrodes. It reframes them. Each is a real, published, peer-reviewed finding, obtained under specific and sometimes narrow conditions. What has not been done, and what would settle the electrical question directly, is planting electrodes in the roots of two trees connected by a documented mycorrhizal network in an actual forest, wounding one, and watching for a voltage change in the other on a timescale that rules out wind, chance, or coincidental chemical drift through groundwater. That experiment is technically brutal. Field electrodes drift, hyphae are microscopic and fragile, and forests are full of competing electrical noise from soil chemistry and moisture. Nobody has published it.
What Would Actually Prove It
The organization most likely to eventually attempt something close to that experiment is SPUN, the Society for the Protection of Underground Networks, founded in 2021 by Toby Kiers at Vrije Universiteit Amsterdam. SPUN’s stated mission is mapping the world’s mycorrhizal networks at scale, sampling soil across continents to build the first global atlas of which fungal species connect which plants and how densely. That mapping work is aimed at conservation, not electrophysiology, but it is building the exact infrastructure, verified maps of which trees are actually fungally connected to which others, that any future electrical field study would need as a starting point. You cannot test whether a signal crosses a network you have not first confirmed exists.
Until that experiment happens, the honest state of the science is this: plants unambiguously generate electrical signals when wounded. Fungal hyphae unambiguously carry electrical current and generate their own spike patterns. Fungal networks unambiguously transmit some kind of signal, chemical at minimum, that changes the defensive behavior of neighboring plants without any direct root contact. Nobody has yet closed the loop and shown the middle step, the crossing from plant electrical wave into fungal electrical wave and back out into a second plant, actually happening. The forest almost certainly has a way of talking to itself. Whether any of that conversation is electrical, in the sense a neuroscientist would recognize, or whether the electricity Adamatzky and others are recording is just the fungus doing its own unrelated business while chemicals do the real work of the warning system, is the specific, answerable, unanswered question sitting at the center of this entire field.