Sounds of the undergrowth
26 May 2025
Is sound more important to plant life than we think? Sarah Philip investigates
From the call of a bird to the chirp of a cicada, sound is everywhere in nature. Yet plants – lacking obvious organs for emitting and receiving sound – are rarely thought of in terms of their acoustic abilities.
Over the years there have been many exaggerated or unsubstantiated theories about plant perception: of plants communicating with each other, perceiving or responding to human speech or emotions, and even receiving signals from outside the universe¹. The idea that plants make and can even hear sounds might at first seem like a theory that belongs among these fanciful ideas, but recent research suggests that the tiny, high-frequency sounds that plants make or reflect can influence other organisms, and possibly even other plants.
Listening to leaves
The first person to record audible acoustic signals from plants was John Milburn² in 1966. He recorded vibrations from the leaves of dehydrated castor bean plants and ferns using an amplifier and loudspeaker. Milburn described the sound as a sharp click, and went on to discover that when leaves are dehydrated, air bubbles block the flow of water, which creates clicking sounds. However, the sounds were infrequent and extremely quiet. Further research by Milburn and others³ led to the discovery that the predominant sounds plants produce are actually ultrasonic – i.e. of higher frequency than the upper limit of human hearing (20kHZ and above).
During drought, pressure builds in the xylem (the tubes transporting water from the roots to the rest of the plant). This causes dissolved air in the water to expand, forming air bubbles that reduce the plant’s ability to transport water. When the air bubbles burst they make ultrasonic sounds. This process of air bubbles forming and popping is known as cavitation. Similar stress responses happen in plants that are cut or infected, leading them to generate slightly different ultrasonic signals.
In 2023, Lilach Hadany and her team at the University of Tel Aviv recorded plant sounds strong enough to be captured from a distance for the first time⁴. Previously, vibrations were recorded from very close range using sensors on or within the plant itself.
“The fact that we were thinking about the potential for communication drove us to record sounds from a distance,” Hadany says. Her team used tomato and tobacco plants as they are sensitive to drought and their soft stems mean they produce much clearer acoustic emissions than plants with rigid, woody stems, such as rosemary. To compare how different types of stress impact the sounds plants make, they prepared plants that were dehydrated and those that had been physically damaged by cutting.
They found that both dry and cut plants produced airborne sounds that could be detected by microphones from distances of up to five metres. The ultrasonic clicks sound like bubble wrap being popped, but at a higher frequency, according to Hadany. The pops they recorded could be as loud as human speech and occurred in rapid bursts, compared with almost silent healthy plants that produced fewer than one sound per hour.
In general, cut plants emitted fewer sounds than plants deprived of water. The team found that cutting plants meant air was released from the stem more quickly, resulting in fewer air bubbles and fewer sounds.
There were also noticeable differences in pitch and volume. On average, both cut tobacco and tomato plants produced higher-pitched sounds than their dry counterparts. Tomato plants, however, typically produced lower-pitched sounds than tobacco plants, possibly due to the diameter of their xylem. The results were not as straightforward when it came to volume. Dry tomato plants produced a softer sound than dry tobacco, but cut tomato plants resonated more loudly than cut tobacco.
The team created machine learning algorithms to help analyse their data. This enabled them to successfully distinguish between different plant conditions and species based solely on their acoustic signals. They also found that virus-infected plants produced ultrasonic emissions that could be detected from a distance, but did not analyse these sounds in detail.
Moths and plant noise
Hadany’s research has since moved on to trying to understand if other organisms might be able to interpret and use these sounds for their benefit. Animals such as moths and mice are most likely to respond, as they interact with plants and have hearing in these ranges. In a recent study⁵ the same team found female moths preferred to lay their eggs on tomato plants that were thriving and silent rather than on drought-stressed plants producing high-pitched sounds. The team then placed two healthy plants on opposite sides of a room, but played dehydrated plant sounds next to one of the plants through a speaker. Once again the moths preferred the plant without stress noises, suggesting sound has an impact on the moths’ egg-laying decisions. The team even deafened moths to ensure their decision was primarily based on acoustic sounds. In this case moths did not show a preference for either plant.
When fellow researchers removed the plants and put the moths in a room with a box playing plant stress noises and a box not playing the noises, the moths were drawn to lay their eggs near the high-pitched sounds. One potential explanation for this is that the drought-stressed signals were the only reliable indicators of a plant in the room and the moths preferred to lay their eggs on a dehydrated plant than none at all.
Recording equipment listening in to plant sounds at the University of Tel Aviv
The moths in this set of studies showed a clear preference for certain signals, despite having been raised in a lab with no prior exposure to plants. “The acoustic interactions between insects and plants seem deeply rooted in moths’ genetics and highlight the evolutionary significance of these signals,” says Rya Seltzer, an entomologist at the University of Tel Aviv, who led this study.
Seltzer suggests other insects with ultrasonic hearing might also be able to detect and react to plant sounds, given that they provide a reliable indicator of plant stress and the health of their food source or nesting place.
Plant hearing
Is it possible that plants could also detect such signals? Being able to detect stress in nearby individuals would enable plants to respond physiologically, such as by conserving water or boosting defences against disease. Hadany says they are now testing the possibility that plants use mechanoreceptors in their cell membranes to detect sound vibrations from their neighbours.
Earlier studies⁶ have suggested plants’ drought tolerance increases when exposed to loud, synthetic white noise for hours at a time. Other studies have suggested that sound can alter the expression of key genes, the release of hormones and the photosynthetic state of plants⁷,⁸, although these involved strong sound waves that are not likely to be found in nature.
Plants may also be able to respond to sound through their roots. In a series of experiments in 2017, Monica Gagliano, a professor in evolutionary ecology at the University of Western Australia, demonstrated that plant roots can bend towards the sound of water⁹ in order to reach it. Her team also found that the roots of corn plants emit low-frequency acoustic emissions, and grow towards the source of sounds played in the same frequency¹⁰.
Some have theorised that mechanoreceptors in plants might form part of an important sensory network that provides signals about touch, growth, gravity and sound, but aside from the studies above, there is little other data on plant ‘hearing’, and no current understanding of how plants might do this.
“The hypothesis that these sounds could be used as informational signals by animals or other plants remains speculative and requires further confirmation,” says Laura Arru, a plant biologist from the University of Modena and Reggio Emilia, who was not involved in the studies above. “We cannot rule out the possibility that plants themselves might detect these ultrasonic vibrations, provided they are at an appropriate distance and under the right conditions.”
Acoustic expertise
Plants’ noise-making abilities may be limited to bubbly clicks, but their ability to reflect or manipulate sounds can be quite sophisticated. Many plants, like the balsa tree, have evolved bell-shaped flowers¹¹ to reflect the sounds of echolocating pollinators, making the plants stand out in the forest soundscape. The bell shape reflects a distinct subset of the frequencies bats emit and sustains the echoes of this sound for longer. The benefits are mutual: bats rely on the plant’s nectar and fruit, while the plants depend on bats to take their pollen to another flower.
Ralph Simon, a biologist at Nuremberg Zoo, found that the cactus Espostoa frutescens¹² does something quite different: sound-absorbing hairs around its flower absorb sound at the frequencies of bat echolocation calls. The acoustic contrast with the echoes of surrounding flowers makes the flowers stand out and helps bats locate them. “It’s a unique acoustic contrast enhancement mechanism,” Simon says. “We suspect other cactus species may have similar adaptations.”
Other plants are involved in what is called ‘buzz-pollination’ – only releasing pollen upon vibration at the particular frequency made by a pollinating bee’s wings.
Pollination is not the only reason plants reflect sound. The pitcher plant (Nepenthes hemsleyana)¹³ has unusually curved and elongated leaves that effectively reflect bat calls to advertise its identity as a roosting nest. The bats are then able to easily find and identify a nest with a favourable climate. In return, bat droppings provide additional nitrogen to the plant – a crucial resource, as they grow in nutrient-poor soil. “It was fascinating to discover an acoustic coevolution between bats and plants outside of a pollination context,” Simon says.
Knowing plants make sounds that affect animals – and potentially even other plants – shows there may be a hidden level of interaction in nature that must be understood and explored further.
Future research might look at other ways that species respond to plant sounds. There’s also interest in whether plants produce sounds beyond signals of drought, disease and physical damage, and the possible effects these could have on other organisms. For instance, do the sounds produced as roots grow have an impact on the growth of other plants? Could we enhance these interactions to bring greater benefits to certain crops or to dissuade crop pests?
To help explore these ideas, scientists including Hadany are trying to create a database of the sounds plants make under different circumstances, starting with the ultrasonic emissions they’ve already discovered. “Plant sound can be important,” she says. “It opens a very interesting way of looking at the world.”
Sarah Philip is a freelance writer who is particularly interested in science and nature.
1) Tomkins, P. The Secret Lives of Plants (Penguin, 1975).
2) Milburn, J. & Johnson, R. The conduction of sap: II Detection of vibrations produced by sap cavitation in Rincinus xylem. Planta. 69(1), 43-52 (1966).
3) Nardini, A. et al. Talk is cheap: rediscovering sounds made by plants. Trends in Plant Science. 29(6), 662-667 (2024).
4) Hadany, L. et al. Sounds emitted by plants under stress are airborne and informative. Cell. 186(7), 1328-1336 (2023).
5) Seltzer, R. et al. Female moths incorporate plant acoustic emissions into their oviposition decision-making process. BioRxiv (2024).
6) López-Rivera, I. & Vicient, C. Drought tolerance induced by sound in Arabidopsis plants. Plant Signalling and Behaviour. 12(10), e1368938 (2017).
7) Gagliano, M. et al. Tuned in: plant roots use sound to locate water. Oecologia. 184(1), 151-160 (2017).
8) Gagliano, M. et al. Towards understanding plant bioacoustics. Trends in Plant Science. 17(6), 323–325 (2012).
9) Helverson, D. et al. Echoes of bat-pollinated bell-shaped flowers: conspicuous for nectar-feeding bats? Journal of Experimental Biology. 206(6), 1025-1034 (2003).
10) Simon, R. et al. An ultrasound-absorbing inflorescence zone enhances echo-acoustic contrast of bat-pollinated cactus flowers. Journal of Experimental Biology. 226(5), jeb245684 (2023).
11) Simon, R. et al. Bats are acoustically attracted to mutualistic carnivorous plants. Cell. 25(14), 1911-1916 (2015).
