New research has shown that plants may not be as silent as we thought. When in distress, plants make faint popping or clicking sounds at ultrasonic frequencies—far beyond what human ears can hear. These sounds increase when the plant is stressed, which could be one way plants communicate their distress to the world.
In a recent study, scientists found that stressed plants emit sounds that animals might hear and respond to. According to evolutionary biologist Lilach Hadany from Tel Aviv University, “Even in a quiet field, sounds are all around us, but we don’t hear them. Some animals, however, can pick them up, creating the possibility for acoustic interaction.”
Plants might be using these sounds in unexpected ways. They interact constantly with insects and other animals, many of which rely on sound for communication. It’s unlikely that plants would ignore this major avenue of interaction, as animals use sounds to find food, attract mates, and sense threats.
Under stress, plants release strong smells and even change color or shape to send signals to other plants and animals. These visible and aromatic signals can tell nearby plants to boost their defenses or attract animals to fight off pests. Now, this study adds sound signals to the mix of plant defenses, suggesting they may be communicating even more than we realize.
To explore this theory, Hadany and her research team first showed that plants can hear sound. They then asked: Could plants produce sounds too? They decided to test this with tomato and tobacco plants under different conditions.
First, they recorded the sounds of plants under no stress to get a baseline. Then, they recorded plants that were either dehydrated or had been cut. These sounds were recorded both in a soundproof chamber and in a normal greenhouse environment.
What they found was striking. When plants experience stress, they emit clicking sounds—especially when dehydrated. The more stressed the plant, the more sounds it makes, even before showing visible signs of distress like wilting. Using machine learning, the team trained an algorithm to distinguish between sounds from healthy, cut, or dehydrated plants and could even identify which plant species was making each sound.
The researchers found that plants like wheat, corn, and grapes all make similar sounds, suggesting that sound production is widespread among plants. These ultrasonic sounds travel up to 3.3 feet (about a meter) from the plant and may help animals detect plants in distress.
There’s still a lot to discover. For instance, scientists aren’t sure how plants produce these sounds. One possible explanation is a process called cavitation, where air bubbles in the plant’s stem pop, much like when people crack their knuckles.
It’s also unknown if other stressors, like extreme temperatures, pathogens, or UV exposure, might cause plants to make more noise. Future research will explore these possibilities to see if other conditions prompt this sound-based signaling.
This discovery opens up intriguing possibilities for humans too. If we can “listen” to plants in distress, farmers might know when plants need water before they show visible signs. This could lead to better, more efficient plant care.
But are other plants listening? Previous studies have shown that plants can respond to sounds by enhancing their drought resistance, so it’s plausible that plants are aware of these sounds. Hadany’s team is investigating whether plants and animals respond to these ultrasonic sounds in nature, which could reveal a fascinating new dimension of plant communication.
