Plants Actually 'Scream' When They Are Thirsty, We Just Can’t Hear Them

For generations, plants were described as silent organisms that passively respond to their environment. They grow toward light, extend roots toward water, and adjust chemically to stress, but they were not thought to produce airborne sounds. Recent research has challenged that assumption. Scientists have demonstrated that plants under stress, particularly from drought, emit ultrasonic sounds that humans cannot hear but specialised instruments can detect.

The Discovery: Ultrasonic Emissions From Stressed Plants

In 2023, a study published in the journal Cell reported that plants emit measurable airborne ultrasonic sounds when exposed to stress. The research was led by Lilach Hadany, Yossi Yovel, and colleagues at Tel Aviv University. Their team recorded tomato and tobacco plants placed inside acoustic chambers equipped with highly sensitive ultrasonic microphones. The researchers found that water-deprived plants produced repeated click-like sounds in frequencies between 40 and 80 kilohertz. These frequencies are far above the upper limit of human hearing, which is approximately 20 kilohertz. In controlled experiments, drought-stressed plants emitted dozens of sounds per hour, while well-watered plants emitted almost none.

The team also used machine learning algorithms to analyse the acoustic recordings. The models were able to distinguish not only whether a plant was stressed but also the type of stress, such as dehydration versus mechanical cutting. According to Hadany, the findings resolved a longstanding scientific debate about whether plants emit detectable airborne sounds under stress.

How Do Plants Produce These Sounds?

Plants do not have vocal cords, lungs, or nervous systems capable of intentional sound production. Instead, the leading explanation for these ultrasonic emissions lies in a physical process known as cavitation. Inside plants, water moves upward through specialised vessels called xylem. During drought conditions, tension within these vessels increases as water becomes scarce. Under extreme tension, tiny air bubbles can form and collapse suddenly within the water column. These rapid microevents generate vibrations that propagate through plant tissues and into the surrounding air as ultrasonic clicks.

Botanical research has long documented cavitation in xylem as a sign of hydraulic stress. What the recent study demonstrated is that these cavitation events generate airborne acoustic signals that can be detected at a distance of several meters under laboratory conditions. This means the sounds are mechanical byproducts of physiological strain rather than intentional communication. However, the emissions still contain measurable information about the plant’s condition.

Could Other Organisms Hear Them?

Although humans cannot perceive ultrasonic frequencies, many animals can. Certain insects, rodents, and bats have hearing ranges that extend well into the ultrasonic spectrum. This raises an ecological question: could animals detect and respond to plant stress sounds? Subsequent experimental work suggests that at least some insects may be sensitive to these cues. In related research, scientists observed that female moths altered egg-laying behaviour when exposed to ultrasonic recordings of stressed plants, suggesting that the insects might avoid dehydrated plants, which are therefore less suitable for larvae.

These findings do not prove that plants evolved sound emissions for communication. Rather, they suggest that other organisms might exploit incidental acoustic signals produced by plant stress.

Implications for Agriculture and Monitoring

The discovery of plant ultrasound has potential applications beyond ecology. If stressed crops emit detectable ultrasonic signals before visible wilting, farmers could use acoustic monitoring systems to optimise irrigation timing.

Precision agriculture technologies already rely on remote sensing and soil moisture measurements. Integrating acoustic detection could provide another early warning indicator of water stress. Researchers are now investigating whether field-based ultrasonic sensors can function reliably outside controlled laboratory environments. Because drought is one of the most significant threats to global food production, tools that detect stress before irreversible damage occurs could help reduce crop losses and improve water management efficiency.

Clarifying What “Screaming” Means

The phrase "plants scream when thirsty" is a metaphor. Plants do not experience pain or emotion as animals do. The ultrasonic clicks represent physical consequences of hydraulic failure within tissues. Scientists remain cautious in interpreting the broader ecological meaning of these sounds. The original Cell study concluded that stressed plants emit airborne signals, but it did not claim that plants deliberately use sound as a signalling system.

Future research will examine how widespread this phenomenon is across plant species, how environmental noise influences detectability, and whether long-term ecological interactions incorporate these acoustic cues.

A New Dimension of Plant Biology

The demonstration that plants emit ultrasonic sounds under drought stress expands scientific understanding of plant physiology. What once appeared silent is now known to generate measurable acoustic information during periods of strain.

These findings do not transform plants into sentient beings, but they do reveal that plant life interacts with its environment in more dynamic ways than previously recognised. Beneath the threshold of human hearing, plants undergoing water stress produce real, detectable signals that reflect the physics of survival.