You walk past a houseplant a hundred times a week and think nothing of it. It doesn’t move, it doesn’t make a sound, it doesn’t seem to do anything. We file plants away as scenery—the green background against which the real, lively business of animals plays out. They grow, they wilt, they photosynthesise. End of story.
Except it isn’t. Over the last decade, plant scientists have quietly demolished the idea that plants are passive. The new picture is unsettling and a little wonderful: plants sense an astonishing amount about their surroundings, they react to it in targeted ways, they “warn” their neighbours, they trade resources through underground fungal partners, and—at least in some experiments—they appear to learn from experience. A plant has no brain, no nerves, and no eyes. And yet it may be paying far closer attention to its world than you ever paid to it.
The catch, as we’ll see, is that the science here splits sharply into rock-solid findings and seductive overreach. Knowing which is which is the whole game.
The Bias: Why We Wrote Plants Off
Part of the problem is speed. Plants live on a timescale that makes them look inert to us. A vine hunting for a trellis, a root steering around a rock, a seedling tilting toward light—these are real, goal-directed movements, but they unfold over hours and days. Speed up a time-lapse and the same plant suddenly looks like a restless, reaching, almost animal thing.
The deeper problem is that we judge intelligence by our own equipment. No brain, no neurons, no behaviour—that was the assumption. But “no brain” turns out to be a statement about architecture, not about capability. Plants process information using hormones, electrical signals that travel through their tissues, and a chemistry far richer than anything in our bodies. They simply solve the problems of being alive using completely different hardware. We mistook unfamiliarity for absence.
Plants Are Making Sounds (You Just Can’t Hear Them)
Start with the discovery that sounds like science fiction. In 2023, a team led by Lilach Hadany at Tel Aviv University reported in the journal Cell that plants under stress emit airborne sounds. Not metaphorically—actual clicks and pops, in the ultrasonic range between roughly 20 and 250 kilohertz, well above the ceiling of human hearing at about 16 kilohertz.
The researchers recorded tomato and tobacco plants, first in a soundproofed chamber and then in a noisy greenhouse. Plants that were dehydrated or had been cut produced far more of these pops than healthy, untouched ones. More impressively, a machine-learning model could listen to the recordings and tell which kind of stress a plant was under—thirsty versus injured—from the sound alone. The pops could be picked up several metres away.
That raised an obvious question: if the sounds carry information, does anything out there actually use it? A follow-up from the same labs (Hadany’s, working with neuroscientist Yossi Yovel’s) suggests yes. Female moths, which normally lay their eggs on healthy plants so their caterpillars will have plenty to eat, were less inclined to lay eggs on plants broadcasting “distress” sounds. The moths could hear what we can’t—and were making decisions based on it. A quiet field, it turns out, may be quietly chattering.
A crucial note before anyone gets carried away: nobody has shown that the plant is “trying” to communicate by popping. The current best guess is that the sounds are a physical side effect of stress inside the plant’s water-transport system. But side effect or not, the information is real, and the rest of the ecosystem may be listening.
Eavesdropping on the Enemy: Plants That “Hear” Chewing
If passively leaking sound seems unimpressive, consider what plants do with vibration they detect coming in.
In a now-classic 2014 study, Heidi Appel and Rex Cocroft at the University of Missouri recorded the precise vibrations a caterpillar makes as it chews a leaf. They then played those recordings back to Arabidopsis (a small mustard relative) that no caterpillar had touched. The plants that had “heard” the chewing later mounted a stronger chemical defence—producing more of the mustard oils that make their leaves unappetising—than plants played only silence.
The detail that elevates this from curiosity to genuine perception is the discrimination. The plants did not ramp up their defences in response to wind vibrations, or to the vibrations of harmless insects that happened to share some acoustic features with chewing. They responded specifically to the signature of an attacker. That’s not a reflex to “any disturbance”—it’s the recognition of a meaningful pattern, and the pre-loading of a defence in anticipation of a threat that hasn’t arrived yet.
The “Wood Wide Web”: A Beautiful Idea, Hotly Contested
Here is where the story gets famous—and where you should hold on to your wallet.
The foundation is solid. In 1997, ecologist Suzanne Simard published a landmark paper in Nature showing that carbon could move between a paper birch and a Douglas fir through the threads of fungi shared between their roots. Tag the carbon with isotopes, wait nine days, and you find it has migrated from one tree species into another, underground, through living fungal tissue. The existence of these mycorrhizal connections—the so-called “wood wide web”—is not in doubt. Nearly all land plants partner with fungi, and have for hundreds of millions of years.
From there grew the irresistible popular narrative: wise old “mother trees” recognising their own seedlings, deliberately pumping sugar and warning signals to their kin through a forest-wide internet of cooperation. It’s a gorgeous image. It has sold a lot of books.
It is also, according to a pointed 2023 review by Justine Karst, Melanie Jones and Jason Hoeksema in Nature Ecology & Evolution, running well ahead of the evidence. Their analysis argued three things. First, the claim that these networks are widespread in forests rests on field studies too variable and limited to generalise. Second, the claim that resources flow through them to meaningfully boost seedlings has alternative explanations and isn’t reliably demonstrated. And third—most bluntly—the claim that mother trees preferentially feed their own offspring through the network had, at the time of writing, no peer-reviewed published evidence at all. They also documented a “positive citation bias”: the scientific literature kept citing the encouraging results and quietly ignoring the null ones.
Simard and colleagues have published rebuttals, and the debate is live and genuinely interesting. The honest “good to know” takeaway is this: the plumbing is real, but the fairy tale built on top of it is, for now, mostly story. Plants and fungi clearly exchange resources. Whether forests run a benevolent, kin-favouring sharing economy is a separate claim, and a much shakier one.
Do Plants Learn? The Mimosa That Stopped Flinching
The boldest claim of all is that plants can learn—and it’s the one to treat with the most caution.
The poster child is Mimosa pudica, the “sensitive plant” that snaps its leaves shut when touched. Researcher Monica Gagliano built a contraption that dropped potted mimosas a short distance onto a cushioned surface—a jolt that reliably triggered the leaf-folding reflex, but caused no actual harm. After enough harmless drops, the plants stopped bothering to close their leaves. They had, in effect, learned that this particular alarm was a false one. Critically, they would still snap shut in response to a different stimulus, so this wasn’t simple exhaustion. And Gagliano reported that some plants retained the lesson up to 28 days later.
That behaviour, called habituation, is one of the simplest forms of learning, and animals from sea slugs to humans do it. A later, even bolder experiment claimed pea plants could be trained to associate a puff of air with the direction of light—a plant version of Pavlov’s dogs.
So: case closed, plants think? Not so fast. These experiments are striking but contested, and other labs have found the associative-learning results hard to replicate. The cautious reading is that plants can clearly adjust their behaviour based on past experience in surprisingly sophisticated ways. Whether that deserves the word “learning”—with everything that word implies—is exactly the kind of question scientists are still arguing about, and they’re right to.
So Is It “Intelligence”?
This is where a good explainer has to slow down rather than speed up.
There’s a whole field, sometimes called “plant neurobiology,” that has pushed hard on the idea that plants are intelligent, and it has drawn equally hard pushback from mainstream botanists who point out that plants have no neurons, no synapses, and no evidence of anything like an inner experience. Calling root-tip signalling a “brain” or leaf-folding “memory” risks smuggling in claims about awareness that nobody has demonstrated.
The most defensible position sits in the middle, and it’s still remarkable. Plants are extraordinary information processors. They integrate light, gravity, touch, chemistry, vibration and the state of their neighbours, and they convert all of it into adaptive, targeted, sometimes anticipatory behaviour—without a central nervous system to coordinate any of it. That’s not “a plant is just like an animal.” It’s something arguably stranger: a completely different solution to the problem of staying alive in a world that’s constantly trying to eat you.
The Takeaway: Mind the Hype, Keep the Wonder
The fun of this topic is also its trap. The genuine findings—stressed plants emitting informative sounds, plants distinguishing an attacker’s chewing from the wind, real underground exchange between roots and fungi—are remarkable enough on their own. They don’t need to be inflated into talking, feeling, scheming forests, and when they are, the science suffers for it.
So the next time you walk past that houseplant, you can drop the assumption that nothing is happening. Something almost certainly is: a quiet, chemical, electric, achingly slow attentiveness to light and water and damage and time. It isn’t thinking about you. But it is, in its own alien way, keeping track of the world. And that may be the most “good to know” thing of all—that intelligence was never the only interesting thing a living organism can do.