Laura Beloff's plant seemed to be clicking. She had rigged its roots up to a contact microphone in order to detect faint, high-pitched clicks in the soil. With the help of software she had written for her computer, the frequency of the clicks had been lowered, making them audible to humans. Beloff first had the idea of listening to her plants' roots after reading about experiments by Monica Gagliano. Over the last decade or so, Gagliano, at the University of Western Australia, has published a series of papers that suggest plants have an ability to communicate, learn and remember. She has long argued that scientists should pay greater attention to the fact that plants can transmit and retrieve information acoustically. In a 2017 study, Gagliano and colleagues showed that plants appear to be able to sense the sound of water vibrating via their roots, which may help them to locate it underground. And Gagliano has also raised eyebrows with claims that, in non-experimental settings, she has heard plants speak to her using words. She says that this experience is "outside the strictly scientific realm" and that a third-party observer would not be able to measure the sounds she heard with laboratory instruments. But she is quite certain that she has perceived plants speaking to her on multiple occasions. "I have been in situations where not just me but several others in the same space heard the same thing," she says. But the precise mechanisms through which plants might perceive or sense sound remain mysterious.