A caterpillar bites into a single tomato plant and an entire field becomes a little deadlier.

It’s easy to underestimate what plants can do. They’re not just passive victims of animal attacks, in need of rescue through barriers and pesticides. They can produce defensive toxins to poison the creatures that try to eat them; the natural pesticides in our food far outnumber the synthetic ones we spray on them. They can also communicate with each other by releasing alarm chemicals into the air. Some of these attract parasites that kill the leaf-eating pests. Others tell neighbouring plants to start upping their own defences.

But the tomato does something different. It releases an airborne chemical that works not as an alarm, but as