Imagine walking through a forest and suddenly discovering that the silent giants around you are actually chatting away, crying out when they’re thirsty, and warning each other about danger. It sounds like science fiction, but researchers have found that trees and plants do make sounds — ultrasonic “screams” that we can’t hear but that reveal a hidden world of plant communication. This groundbreaking discovery is reshaping how we think about plant life and opening doors to revolutionary farming techniques.
The Silent Forest Isn’t So Silent After All
What if I told you that every time you walk past a stressed plant, it’s essentially screaming for help? The plant sounds resembled pops or clicks, and a single stressed plant emitted around 30-50 of these clicks per hour at frequencies of 40-80 kHz and seemingly random intervals, but unstressed plants emitted far fewer sounds. That’s right — your tomato plants are literally talking, but at frequencies so high that only dogs might pick up on their distress calls. Think of it like a dog whistle, but for plants in crisis.
Stressed tomato plants make distinctive clicking noises that can be picked up by ultrasonic microphones. In this clip, scientists condensed the sounds and brought them into the range of human hearing. When researchers first played these recordings at human-audible frequencies, people described it as sounding like someone furiously tap dancing on bubble wrap. When lowered into a range that human ears can detect, these stress-induced pops sound like someone furiously tap dancing across a field of bubble wrap. It’s both fascinating and slightly unsettling to realize we’ve been surrounded by these invisible conversations our entire lives.
The discovery challenges everything we thought we knew about the plant kingdom. “These findings can alter the way we think about the plant kingdom, which has been considered to be almost silent until now,” the study authors wrote. Scientists have been studying plants for centuries, measuring their growth, analyzing their chemistry, and understanding their biology — but nobody thought to simply listen to them until recently.
The sounds were about as loud as a quiet conversation but were mostly between 40,000Hz and 60,000Hz, which is too high pitched for human hearing which only goes up to about 20,000Hz. To put this in perspective, these plant sounds are in the same frequency range as bat echolocation calls. While we humans are completely oblivious to this acoustic drama, many animals around us are probably tuning in to this botanical radio station every day.
When Plants Get Thirsty, They Get Chatty
The most remarkable discovery is how dramatically plants change their vocal behavior when stressed. The mean number of sounds emitted by dry plants was 35.4 ± 6.1 and 11.0 ± 1.4 per hour for tomato and tobacco, respectively, compared to healthy plants that rarely make any noise at all. It’s like the difference between a person humming quietly to themselves versus someone shouting for help every few minutes.
Water-stressed plants started emitting more rapid noises before visible signs of dehydration, such as the browning of leaves, began appearing. The sounds peaked after five days without water and dropped off as the plant dried up completely. This means plants are essentially sending out SOS signals long before we can see any obvious signs of distress. It’s their version of calling for help while they still have the energy to do so.
Different types of stress produce different acoustic signatures too. Interestingly, sounds were different depending on the cause of the stress. Researchers were able to train a machine-learning algorithm to accurately differentiate between unstressed plants, thirsty plants and cut plants. Think of it like having different alarm sounds on your phone — one for text messages, another for calls, and yet another for emergencies. Plants appear to have their own version of this acoustic coding system.
Stress from drought—brought on by up to ten days without water—elicited about 11 squeals per hour from the tobacco plants, and about 35 from the tomato plants. What’s particularly interesting is that tomato plants seem to be much more “talkative” when stressed than tobacco plants. It makes you wonder if some plant species are just naturally more vocal than others, like how some people are chattier than others.
The Science Behind Plant “Screaming”
So what’s actually causing these sounds? The exact mechanism behind these noises is unclear, but the authors suggest that it might be due to the formation and bursting of air bubbles in the plant’s vascular system, a process called cavitation. Picture a straw filled with water — when you suck really hard and the water column breaks, it creates tiny bubbles and makes noise. That’s essentially what’s happening inside stressed plants.
In drought-stricken trees, this increased pressure can cause the water column to break, allowing dissolved air to form bubbles that block water flow. These events are called cavitations, and while trees can withstand some, too many can be deadly. It’s like the plant’s circulatory system getting air bubbles — not only does it make noise, but it also disrupts the flow of nutrients and water throughout the plant.
In this article, we resolved the rapid development of all cavitation bubbles and demonstrated that each ultrasound emission was linked to the nucleation of one single bubble, whose acoustic energy is an increasing function of the size of the conduit where nucleation occurred and also of the hydric stress. We modelled these observations by the fact that water columns in conduits store elastic energy and release it into acoustic waves when they are broken by cavitation bubbles. Think of it like a tiny explosion happening inside the plant every time a water column snaps under pressure.
What’s fascinating is that this isn’t just random noise — there’s actual information encoded in these sounds. However, in a decibel (dB) range below that associated with cavitation, a close relationship was found between UAE intensities and stem radius changes. The plants are essentially broadcasting real-time updates about their internal condition, like a biological status report that other organisms might be able to interpret.
It’s Not Just Tomatoes — Many Plants Are “Talking”
“We found that many plants — corn, wheat, grape, and cactus plants, for example — emit sounds when they are stressed,” Professor Hadany said. The research extended far beyond just tomato and tobacco plants. In additional experiments, the team successfully recorded sounds from diseased tomato plants infected with tobacco mosaic virus, and captured the cries of a slew of other stressed plants, such as wheat (Triticum aestivum), corn (Zea mays) and pincushion cactuses (Mammillaria spinosissima). It seems like vocalization under stress might be a universal plant trait we never knew existed.
Even woody plants like trees participate in this acoustic world. UAE was continuously recorded on the stems of mature field-grown trees of Scots pine (Pinus sylvestris) and pubescent oak (Quercus pubescens) at a dry inner-Alpine site in Switzerland over two seasons. These aren’t just small garden plants making noise — we’re talking about massive trees that have been silently broadcasting their stress levels for who knows how long.
Different plant species seem to have their own acoustic “personalities.” And each plant species had a recognizable “voice.” A machine learning algorithm the team created could tell the difference between clicks from tomato plants and tobacco plants. It’s like each species has developed its own dialect in this ultrasonic language. Imagine if we could eventually create a plant translation app — “Your tomato is saying it needs water, but your basil is complaining about too much sun.”
What’s particularly intriguing is that the sounds aren’t limited to drought stress. Plants also make noise when they’re physically damaged, infected with viruses, or facing other environmental challenges. This suggests that acoustic emission might be a fundamental response to various types of biological stress, not just water shortage.
Machine Learning Cracks the Plant Code
They developed machine learning models that succeeded in identifying the condition of the plants, including dehydration level and injury, based solely on the emitted sounds. Scientists have essentially created a plant translator using artificial intelligence. The team fed these recordings into a machine-learning algorithm — an AI system used to identify patterns in data — and found that the trained algorithm had about a 70% success rate in distinguishing the sounds made by different plants exposed to different stressors. That’s pretty impressive accuracy for what amounts to plant mood detection.
The AI system can differentiate not just between different types of stress, but also between different plant species. The SVM classifier with scattering network for feature extraction achieved ∼70% accuracy for each of the four pairs (Figure 1F red line), significantly better than random when distinguishing between tomato and tobacco plants under various stress conditions. It’s like having a sophisticated listening device that can tell you not only that a plant is stressed, but exactly what kind of stress it’s experiencing and what species is making the sound.
The algorithm could even differentiate between plants when they sat in a noisy greenhouse, filled with the sounds of people talking and building renovations next door. This is particularly impressive because it means the technology could work in real-world agricultural settings, not just in perfectly quiet laboratory conditions. The practical applications become much more realistic when the system can filter out background noise and focus on plant signals.
What makes this even more remarkable is that the machine learning models were trained to recognize subtle differences in acoustic patterns that might be completely imperceptible to human ears, even if we could hear at those frequencies. The AI is essentially becoming fluent in a language we didn’t even know existed until recently.
Who Might Be Listening in the Wild?
The frequency of these sounds is too high for human ears to detect, but they can probably be detectable by other organisms such as insects, mammals, and possibly other plants. However, they should be audible by dogs, who can hear up to 45,000Hz, or cats, whose hearing goes all the way up to 64,000Hz. Your pets might actually be more aware of your houseplants’ emotional states than you are!
Insects like moths, or mammals such as mice bats, can hear plants. This opens up fascinating possibilities for ecological interactions we never considered. Nearby insects may realise that the clicking plant is vulnerable to attack. Imagine if stressed plants are essentially advertising their weakness to potential predators — it would be like wearing a sign that says “I’m sick, please don’t eat me” but having the opposite effect.
This means that even if they aren’t intentional, the clicks could carry information useful to other plants or animals. Other plants might respond by reducing their water use. The idea that plants might be eavesdropping on each other’s distress calls and adjusting their own behavior accordingly is mind-blowing. It would represent a form of plant community awareness that we never suspected existed.
“It’s possible that other organisms could have evolved to hear and respond to these sounds,” Professor Hadany said. Evolution tends to take advantage of any available information source, so it’s entirely plausible that some organisms have developed the ability to interpret these plant sounds over millions of years. We might be discovering just the tip of an enormous acoustic ecosystem iceberg.
Revolutionary Applications for Modern Agriculture
Intentional or not, detecting those sounds could be a step forward for agriculture, potentially offering a new way to monitor water stress in plants, the study’s authors propose. If microphones in fields or greenhouses picked up certain clicks, farmers would know their crops were getting dry. This could revolutionize precision agriculture by providing real-time, non-invasive monitoring of crop health before visible symptoms appear.
According to Ponomarenko, the findings could lead to the design of a handheld device that allows people to diagnose stressed trees using only microphones. Such a device may be particularly important if droughts become more common and more severe, as many global warming models predict they will. Imagine farmers walking through their fields with acoustic sensors, getting instant feedback about which plants need attention — like a stethoscope for crops.
For instance, he envisions a device that would attach to a tree and constantly listen for sounds of thirst. If needed, the device could then trigger an emergency-watering system. This level of automated plant care could prevent crop losses and optimize water usage, which becomes increasingly important as water resources become scarcer globally. It’s like having plants directly connected to their own life support systems.
The technology could also help identify plant diseases early. Since infected plants produce different acoustic signatures than healthy ones, farmers could potentially detect outbreaks before they spread throughout entire crops. This early warning system could save billions of dollars in agricultural losses worldwide and reduce the need for chemical treatments.
The Technology Behind Plant Listening
Microphones designed to detect and record ultrasonic waves were placed approximately 10cm away from the subject plant. The recording equipment isn’t particularly exotic — it’s similar to the ultrasonic microphones used in bat research or industrial applications. Although the researchers gathered these recordings by setting microphones about 4 inches (10 centimeters) away from the plants, they suggest that these ultrasonic sounds could potentially be heard by mammals and insects with great hearing from 9.8 to 16.4 feet (3 to 5 meters) away. This range makes practical field applications much more feasible.
To investigate plants’ airborne sound emissions, Khait et al. constructed a reliable recording system, where each plant is recorded simultaneously by two microphones; first, they recorded plants within an acoustic box and developed machine learning algorithms to classify the recorded sounds; then they tested the system in a greenhouse, while monitoring physiological parameters of the recorded plants. The researchers were meticulous about eliminating false positives and ensuring the sounds were actually coming from the plants themselves.
So the researchers ordered sound-dampening acoustic boxes and tucked them in the basement away from the lab’s hustle and bustle. Inside the hushed boxes, thirsty tomato plants emitted about 35 ultrasonic clicks per hour, the team found. The careful experimental setup was crucial for proving that plants were the actual source of these sounds, not just background noise or equipment artifacts.
The beauty of this technology is its relative simplicity and low cost compared to other plant monitoring methods. Traditional agricultural sensors often require physical contact with plants or soil, but acoustic monitoring can be done remotely without disturbing the plants at all. It’s completely non-invasive, which means it won’t interfere with natural plant behavior or growth patterns.
Frequency Patterns Tell Different Stories
The mean peak sound intensity recorded from dry plants was 61.6 ± 0.1 dBSPL and 65.6 ± 0.4 dBSPL at 10 cm, for tomato and tobacco, respectively, and the mean peak frequencies (frequency with maximal energy) of these sounds was 49.6 ± 0.4 kHz and 54.8 ± 1.1 kHz, respectively. The mean peak intensity of the sounds emitted by cut plants was 65.6 ± 0.2 dBSPL and 63.3 ± 0.2 dBSPL at 10.0 cm, for tomato and tobacco, respectively, and the mean peak frequency was 57.3 ± 0.7 kHz and 57.8 ± 0.7 kHz, respectively. Each type of stress produces its own acoustic signature — like having different ringtones for different types of problems.
Within a low-dB range (27 ± 1 dB), UAE regularly increased and decreased in a diurnal rhythm in parallel with ΔW on cloudy days and at night. These low-dB emissions were interrupted by UAE abruptly switching between the low-dB range and a high-dB range (36 ± 1 dB) on clear, sunny days, corresponding to the widely supported interpretation of UAE as sound from cavitations. Plants seem to have daily acoustic rhythms, getting louder or quieter depending on environmental conditions and time of day.
The frequency analysis reveals that different plant species operate in different acoustic ranges, almost like they’re using different radio channels. This natural frequency separation might prevent acoustic “interference” between species and could be an evolutionary adaptation to maintain clear communication channels in diverse plant communities.
