Plants can't see or hear, but they can recognize their siblings, and now researchers have found out how: They use chemical signals secreted from their roots, according to a new study.

Back in 2007, Canadian researchers discovered that a common seashore plant, called a sea rocket, can recognize its siblings – plants grown from seeds from the same plant, or mother. They saw that when siblings are grown next to each other in the soil, they "play nice" and don't send out more roots to compete with one another.

But as soon as one of the plants is thrown in with strangers, it begins competing with them by rapidly growing more roots to take up the water and mineral nutrients in the soil.