If you are not giving your plants enough water, you may be making them cry! New research has discovered that plants actually make a noise when they are under stress. Using a soundproof chamber and highly sensitive microphones, researchers managed to pick up a sound coming from the plants which resembles the popping of bubble-wrap. The sound is ultrasonic and very high-pitched, so humans cannot hear it. However, the scientists kept lowering the frequency until they were able to detect the sound. For some plants the stress was caused by not watering them, while others were stressed by the physical damage of cutting their stems. The sounds differed according to the type of plant and the stress it was facing.

As a control, they listened to healthy plants to compare their sounds to the damaged ones. The plants with no stress made almost no noise, but when they were later injured or dehydrated their noise levels increased significantly. It is also interesting that the noises started before there were clear signs of dehydration - getting gradually louder over a five day period without water. The researchers are not sure about how the plants emit these sounds, but their theory is that it comes from the bursting air bubbles in the plants’ vascular system.