On February 2nd, 1966, Ex-CIA analyst Cleve Backster hooked up his houseplant to a polygraph machine and, according to him, found astounding results. In his 1968 book, Primary Perception: Biocommunication With Plants, Animals, and Inanimate Objects, Backster writes extravagant claims regarding the abilities of our leafy friends, writing that they were telepathic and could understand human thought.

​

Shortly after, his research was deemed nothing more than science fiction.

 

But Backster did get something right: there’s a lot more going on in the world of plants than we realize.

​

They can talk.

​

Some can count and listen.  

​

Some can even remember. 

​

Research has given a lot of answers about the hidden world of plants, but it has also raised a bigger question: are plants intelligent?

​

That’s exactly what the Society of Plant Signaling and Behavior has been trying to prove since 2005. According to their website, plantbehavior.org, members host an annual symposium people who are set to show the line between plant and animal may be much more blurred than we think.

​

So we’re going to look at three factors that support their theory: communication, perception, and memory.

​

Let’s start with a massacre.

​

In the 1980’s, South Africa’s Limpopo Savannah experienced a drought. It wiped out all of the plant life, except for one species: the acacia tree.

Much to the relief of game preserve owners, the acacia singlehandedly allowed their kudu, a deer like species, to survive.

​

And then something interesting happened. Large amounts of Kudu began to die at an alarming rate for no particular reason.

​

Scientists came in to figure out what was going on and found out that the cause of death was extremely high levels of a natural chemical called tannin. They compared numbers across multiple preserves and learned that the more populated an area was, the greater the chances kudu would die.

​

So who was the who in this kudu whodunnit? The very same thing that kept them alive: the acacia.

Investigation showed that this species knows when it’s being over utilized and, in response, skyrockets its tannin production to four times the normal amount—lethal to the kudu.

​

But they also found that nearby trees—trees that were damaged very little or not at all—underwent the same change. 

​

They discovered that the acacia tree not only could tell when enough grazing was enough, but it also told its neighbors to protect themselves as well.

​

Interplant communication like this is not uncommon—especially when species are being attacked.

​

But with communication comes the need for something to communicate.

​

How are plants saying, “Hey, this is happening to me?” It requires the ability to perceive, and believe it or not, plants have more perception than you think.

​

Point number two: plants are very aware of their surroundings. 

​

According to scientists, plants have 15 more senses than humans to monitor the complex world around them. They can be aware of not only light and taste and touch, but some can also hear through vibration.

​

The natural enemy of the mousear cress is the cabbage butterfly caterpillar, which can raze through a plant within a matter of days. When being attacked, like the Acacia, the cress will ramp up levels of mustard oil to repel caterpillars away.  

​

According to a study in science journal Oecologia, researchers exposed a few of these plants to a two-hour long audio recording of a caterpillar eating.

​

And what did the plant do? It reacted. Mustard oil levels shot through the roof in response to a vibration that moved the leaves up and down one ten thousandth of an inch.

​

What made the experiment so remarkable was that they repeated the process with different sounds—wind, other insects. And the cress did nothing. The experiment suggests that some plants are able to perceive sounds and make decisions based on what they’re hearing.
 

Let’s draw our attention to the Venus fly trap—a species Charles Darwin said was the most wonderful plant in the world. (Note, this was before the boom of recreational marijuana use.) But while Darwin never had the munchies, the fly trap certainly does.

​

As the name suggests, this species catches and digests flies, along with slugs, butterflies—really anything that wanders into the plant’s mouth.

​

And if plants eating animals isn’t wild enough, take a look at how they do this.

​

The Venus Fly Trap has three hairs on each jaw that, when stimulated enough, sends an electric action potential down the entire plant. The message signals the plant to push water into the top of the plant so the jaws shut, and the fly trap spends the next one to two weeks absorbing the fly.

​

Now, it takes a large amount of energy for the fly trap to close—it’s exhausting work. So exhausting, in fact, that the plant can only open and close a few times before it loses this ability altogether.

​

So it wants to make sure there’s something for it to eat.

And we didn’t know how they did this until January 2016, when the University of Wurzburg published a study in Current Biology that revealed that the Venus fly trap systematically counts the number of times those hairs are triggered, and performs actions accordingly.

​

The first time a hair is triggered nothing happens. It’s too soon to tell, it could be a piece of leaf, speck of dust. And if nothing happens within 20 seconds, the plant resets.But if the hair is touched again within that time period, well, now we’re cooking. 

​

So the trap gets a second signal, and closes completely in one tenth of a second.

​

A third touch primes the plant for digesting. 

​

And a fifth will trigger the release of digestive enzymes, and the more hairs that are touched, the more enzymes delivered—so, ironically, the harder the fly struggles, the faster it will be digested.

​

So, what can we take away from this study? Two things: one, if you find yourself stuck inside a Venus fly trap, for the love of God, don’t panic. And two, according to science, at least one species can not only keep track of time, but can also count certain stimuli in order to optimize energy use.

​

And so all plants, to some degree, have this awareness of their surroundings. They perceive and make decisions based off of those perceptions. But those responses have been ingrained since they were seeds, they’re instinctive. The Venus fly trap, the mousear cress have been doing this for thousands of years.

​

What happens if a plant encounters a new stimulus? Can they learn a response? Can they store a memory of the stimulus?

​

And that brings us to our third aspect that the Society of Plant Signaling and Behavior says supports the idea of plant intelligence: memory.

​

In 2014, Doctor Monica Gagliano and fellow colleagues at the University of Western Australia.  published a study in a journal Oecologia.

​

This study involved a plant called Mimosa pudica—also known as the sensitive plant, or the shame plant. It’s a novelty among plant collectors because when the plant is disturbed, the leaves will immediately fold inward.

​

And nobody really knows why, the best guess is that it’s a defense mechanism to scare off whatever’s trying to eat it.

​

But Gagliano didn’t care about why the plant closed; she wanted to see if the mimosa could learn to stop closing.

​

What she did was drop these test plants about 60 times. As expected, the first few times, the mimosa closed up instantly.

​

But as the drops went on, the plants slowly stopped responding, until they didn’t react at all.

​

Were they tired? No. When the mimosa plants were picked up and shaken, they shut immediately.

​

They learned that being dropped didn’t have damaging consequences, and quit curling up in self-defense.

​

Now here’s where the memory part kicks in: the drops were performed again, 28 days later, and there was no response whatsoever. The plant remembered.

​

The study concluded that plants could “learn” long-lasting behaviors by storing the botanical equivalent of a memory and keep that memory for more than a month.

​

When Gagliano presented her findings, she was met with ridicule and dismissal. In fact, many scientists consider plant neurobiology as a whole to be nothing more than kabuki.  

​

But it’s important to understand that they aren’t trying to prove plants are sentient.

Gagliano wrote something in her studies that sums up the Society of Plant Signaling and Behavior’s thesis pretty well:

​

“Plants may lack brains and neural tissues, but they do possess a sophisticated…signaling network in their cells, similar to animals’ [neural] processes.”

​

And we’ve seen that over and over again in these studies: the communication between acacia trees, the cress’s perception of certain sounds and the fly trap’s perception of stimulus, and finally, the mimosa’s ability to remember.

​

Furthermore, What may seem like pseudoscience is being applied to practical situations. Farmers are using these botanical communication skills to tweak farming practices, so that crops can better defend themselves. Researchers at the University of Tokyo are utilizing the slime mold’s ability to detect nearby food sources to build public transportation models.

​

 And with growing support, these findings are slowly shifting from the impractical to the innovative.

 

No, plants can’t actually talk. And they certainly can’t read your mind. But if Cleve Backster knew plants had some level of communication, perception, and memory? He’d probably wet his plants.

​