Some people talk to their plants. These plants talk to each other.
Like it or not, Facebook, Instagram, and other digital messaging services have become an intimate part of many of our lives. In fact, we collectively send 10 billion messages per day over Facebook!
If we suppose that the average message is five words long (disclaimer: I have no idea if that's true, but it feels about right) and a novel is 50,000 words long, that means we collectively write enough to fill over a million books per day!
Would it surprise you if I said plants were just as chatty?
And if they're talking so much, what are they saying?
Well, here's a couple samples of what a tree would say, if a tree could post to Facebook.
"Watch out for those giraffes!"
Acacia trees are thorny, green, and a favorite snack for elephants, antelopes, and giraffes. With so many big, voracious herbivores, you'd think they'd all be stripped bare in a day!
But it turns out acacias have a kind of mass alarm system.
When a giraffe comes up and starts munching on acacia leaves, the victimized plant releases a bunch of ethylene gas. Any other acacias that "smell" it know it means danger and start pumping their leaves with nasty, poisonous chemicals to shoo the predators away.
And it's not just acacias. Sagebrush, willows, poplars, and tomatoes also seem to warn each other of attacks. Sometimes the messages even work across different species, although there's also evidence that different plants may use different chemical languages to encrypt their messages.
The messages don't just work over the air, either. Other studies have found that plants can communicate warnings through webs of underground fungal hairs (known as mycelium) that can reach across entire forests. It's like a big, fungal internet!
"Careful, I'm sick! Don't you catch it too!"
Speaking of the fungal Internet — evidence suggests that plants might use it to do more than just shout about predators. They might share health tips too.
In 2010, researchers in China discovered that tomato plants might use this fungal internet to warn each other when they're sick.
The researchers planted a bunch of tomatoes, let the fungal Internet grow between them, then purposefully got one of the plants sick. Lo and behold, the sickie's hooked-up neighbors started taking defensive precautions like activating anti-disease chemicals.
"Help me out here, wasps!"
Ever heard the adage: "The enemy of my enemy is my friend"? Well, some plants believe in that whole-heartedly.
We're not the only ones who love to munch on corn. Caterpillars also love to chow down on corn plants and, like the acacias, if a caterpillar starts to chow down on a corn plant, the plant will release chemical scents into the air.
But instead of warning other corn plants about the caterpillars, these scents are targeted at other insects — caterpillar-loving parasitic wasps. The scent is like a giant dinner bell for the wasps, shouting: "Caterpillar here! Come and get it!" The plants can even have specific scents for specific types of caterpillar!
And it's not just corn — a bunch of other plants do this too, including cotton and tobacco. That's not to mention all the other ways plants communicate with animals (like flowers).
We're just starting to understand how plants communicate.
OK, OK, time to stop anthropomorphizing a bit. A tree isn't going to start speaking to you, no matter how sophisticated these signals are (or what movies want us to think).
"We are used to thinking of humans as the only organisms that are really perceptive. And now we're finding that – wow – plants can even do this.” — Professor Richard Karban
Trees are still trees. They don't have brains and are not intelligent, at least in the way most of us would think of intelligence.
And there are still a lot of questions and things to study. For example, professor Richard Karban, who is studying communication in sagebrush, says plants probably aren’t actually trying to broadcast every message. Instead, if they are signaling, they might just be trying to talk to closely related family members — with other plants eavesdropping in. So instead of a vegetable Facebook, the average forest might be more like the vegetable NSA.
But the fact that we're listening in at all is incredible. And maybe one day, scientists may be able to decipher these vegetable languages.
Imagine if, instead of spraying pesticides, we could "tell" plants to beware of bugs. A lot more work needs to be done before that though.
"It's an extremely difficult code and a really difficult problem," Karban said.
But he added that it helps us understand the world around us.
"We are used to thinking of humans as the only organisms that are really perceptive," he said. But as we've learned more, we've realized that many different animals are capable of taking in the world. "And now we're finding that – wow – plants can even do this. I think it is changing our view about what organisms are capable of ... and that by itself is pretty cool."