May 30, 2018

Plant Parade

Do you really need a brain to sense the world around you? To remember? Or even learn? Jad and Robert, they are split on this one. Today, Robert drags Jad along on a parade for the surprising feats of brainless plants. Along with a home-inspection duo, a science writer, and some enterprising scientists at Princeton University, we turn our brain-centered worldview on its head through a series of clever experiments that show plants doing things we never would've imagined. Can Robert get Jad to join the march?

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ALVIN UBELL: Testing one, two. This is the headphones?






LATIF NASSER: How is that? Better?


ROBERT: Oh, much better.


JAD: This is Radiolab.


ALVIN UBELL: Can I interrupt?




ALVIN UBELL: Could I say ...


LARRY UBELL: Me first. Me first. Because if I let you go it's gonna be another 20 minutes until I get to talk.


ROBERT: A little while back, I had a rather boisterous conversation with these two guys.


ROBERT: First of all, like, who are you?


LARRY UBELL: I'm Larry Ubell.




ALVIN UBELL: And I'm Alvin Ubell.


ROBERT: So you are related and you're both in the plumbing business?


ALVIN UBELL: Are we related?


LARRY UBELL: Yes, we are related. But we are in the home inspection business.




ROBERT: They're father and son. It's a family business.


LARRY UBELL: We are the principals of Accurate Building Inspectors of Brooklyn, New York.


ALVIN UBELL: And I've been in the construction industry ever since I'm about 16 years old. I'm 84.




LARRY UBELL: I'm not giving my age. [laughs]


ROBERT: And I wanted to talk to them because, as building inspectors they -- there's something they see over and over and over.




ALVIN UBELL: All the time.


ROBERT: That is actually a clue in what turns out to be a deep, deep mystery.


JAD: Which -- which is what, exactly?


ROBERT: Let us say you have a yard in front of your house. Yours is back of your house, but let's make it in the front.


JAD: Okay.


ROBERT: And right in the middle of the yard is a tree.


ALVIN UBELL: And the tree happens to be a weeping willow.


ROBERT: And not too far away from this tree, underground, there is a water pipe.


ALVIN UBELL: A perfectly good pipe.


ROBERT: Connecting your house to the main city water line that's in the middle of the street. But the Ubells have noticed that even if a tree is 10 or 20, 30 yards away from the water pipe, for some reason the tree roots creep with uncanny regularity straight toward the water pipe.


ALVIN UBELL: The tree will wrap its roots around that pipe.


ROBERT: Around and around and around.


ALVIN UBELL: In a tangling of spaghetti-like, almost a -- and each one of those lines of spaghetti is squeezing a little bit. Each one an ounce, an ounce, an ounce, an ounce, an ounce. Eventually over a period of time, it'll crack the pipe like a nutcracker.




ROBERT: The Ubells see this happening all the time.


LARRY UBELL: Yeah, and I have done inspections where roots were coming up through the pipe into the house.


ROBERT: Into the house?


ALVIN UBELL: It's amazing.




ROBERT: This happens to a lot of people. It's almost as if these plants -- it's almost as if they know where our pipes are.


JAD: I see what's happening.




JAD: Are you bringing the plant parade again? Is that what -- is that what this?


ROBERT: Well, of course I am.


JAD: It's like every time I close my eyes, you're coming at it from a different direction.


ROBERT: I do! I do!


JAD: With the plant parade.


ROBERT: And I met a plant biologist who's gonna lead that parade. She's done three experiments, and I think if I tell you about what she has done, you -- even you -- will be provoked into thinking that plants can do stuff you didn't imagine, dream they could do.


JAD: Hmm.


ROBERT: I know -- I know you -- I know you don't. But let me just -- let me give it a try.


JAD: Okay. I'm game.


ROBERT: So let's go to the first. This is the plant and pipe mystery.


MONICA GAGLIANO: Hello, finally!


ROBERT: Hello! Hello, at long last.


ROBERT: Now, you might think that the plant sends out roots in every direction. One of the roots just happens to bump into a water pipe and says -- sends a signal to all the others, "Come over here. Here's the water."


JAD: Right.


ROBERT: But that scientist I mentioned ...


MONICA GAGLIANO: My name is Monica Gagliano. I'm a research associate professor at the University of Sydney.


ROBERT: She took that notion out of the garden into her laboratory.


MONICA GAGLIANO: Yeah, tested it in my lab.


ROBERT: She took some plants, put them in a pot that restricted the roots so they could only go in one of just two directions, toward the water pipe or away from the water pipe. Now the plants if they were truly dumb they'd go 50/50. It'd be all random.


JAD: Right.


ROBERT: But after five days, she found that 80% of the time, the plants went -- or maybe chose -- to head toward the dry pipe that has water in it.


MONICA GAGLIANO: A plant that is quite far away from the actual pipe. How does it know which way to turn and grow its roots so that it can find the water?


LARRY UBELL: All right, if she's going to do this experiment, most likely she's going to use cold water. She's not gonna use hot water because you don't want to cook your plants, you know? And it's more expensive. Why waste hot water?


ALVIN UBELL: You have to understand that the cold water pipe causes even a small amount of water to condense on the pipe itself. On the outside of the pipe.


LARRY UBELL: It's kind of like a cold glass sitting on your desk, and there's always a puddle at the bottom.


ALVIN UBELL: The glass is not broken. There's not a leak in the glass.


LARRY UBELL: It's not leaking. The water is still in there.


ROBERT: So there is some water outside of the pipe. It's condensation.




ROBERT: So what they're saying is even if she's totally sealed the pipe so there's no leak at all, the difference in temperature will create some condensation on the outside. And it's that little, little bit of moisture that the plant will somehow sense.


ALVIN UBELL: If you look at a root under a microscope, what you see is all these thousands of feelers like hairs on your head looking for water.


ROBERT: These sensitive hairs he argues, would probably be able to feel that tiny difference.




ROBERT: But Monica says ...




ROBERT: Absolutely not. She made sure that the dirt didn't get wet, because she'd actually fastened the water pipe to the outside of the pot. So it wasn't touching the dirt at all.


JAD: Wait. So the -- this branching pot thing.


ROBERT: Uh-huh.


JAD: The part where the water pipe was, the pipe was on the outside of the pot?


ROBERT: That's right. Outside.


JAD: And the plant still went to the place where the pipe was not even in the dirt?




JAD: That is strange.


LARRY UBELL: Or it's just the vibration of the pipe that's making it go toward it.


ALVIN UBELL: They would have to have some ...


ROBERT: Maybe there's some kind of signal? Different kind of signal traveling through the soil? Monica thought about that and designed a different experiment.


MONICA GAGLIANO: Again, if you imagine that the pot, my experimental pot.


ROBERT: With the forked bottom.


MONICA GAGLIANO: Yeah. But then have ...


ROBERT: Two very different options for our plant. On one side, instead of the pipe with water, she attaches an MP3 player with a little speaker playing a recording of ...


MONICA GAGLIANO: The sound of water.


ROBERT: And then on the other side, Monica has another MP3 player with a speaker. But this one plays ...




ROBERT: So she's got her plants in the pot, and we're going to now wait to see what happens. Remember that the roots of these plants can either go one direction towards the sound of water in a pipe, or the other direction to the sound of silence. On the fifth day, they take a look and discover most of the roots, a majority of the roots were heading toward the sound of water.


MONICA GAGLIANO: Exactly. Exactly.


JAD: So they just went right for the MP3 fake water, not even the actual water? Just the sound of it?


ROBERT: Just the sound.


LARRY UBELL: That -- that's -- that's interesting.


ALVIN UBELL: That's interesting.


LARRY UBELL: That is interesting.


ROBERT: But what -- how would a plant hear something? Like, they don't have ears or a brain or anything like, they couldn't hear like we hear.


JENNIFER FRAZER: Well, maybe. They definitely don't have a brain. No question there. But they do have root hairs.


ROBERT: This is Jennifer Frazer.


JENNIFER FRAZER: I am the blogger of The Artful Amoeba at Scientific American.


ROBERT: And she was willing to entertain the possibility that plants can do something like hear.


JENNIFER FRAZER: So what do we have in our ears that we use to hear sound?


ROBERT: Little hairs!


JENNIFER FRAZER: Little hairs.




JENNIFER FRAZER: Right? And if you go to too many rock concerts, you can break these hairs and that leads to permanent hearing loss, which is bad. So maybe the root hairs, which are always found right at the growing tips of plant roots, maybe plant roots are like little ears. Maybe each root is -- is like a little ear for the plant. I don't know.


JAD: That is cool. That is definitely cool. If a plant doesn't have a brain what is choosing where to go?


ROBERT: I don't think Monica knows the answer to that, but she does believe that, you know, that we humans ...


MONICA GAGLIANO: We are a little obsessed with the brain. And so we are under the impression or I would say the conviction that the brain is the center of the universe, and -- and if you have a brain and a nervous system you are good and you can do amazing stuff. And if you don't have one, by default you can't do much in general.




MONICA GAGLIANO: It's a very biased view that humans have in particular towards others.


ROBERT: I think if I move on to the next experiment from Monica, you're going to find it a little bit harder to object to it. We need to take a break first, but when we come back, the parade that I want you to join will come and swoop you up and carry you along in a flow of enthusiasm.


[ASHLEY: Hi. This is Ashley Harding from St. John's, Newfoundland, Canada. Radiolab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of Science and Technology in the modern world. More information about Sloan at]


JAD: Three, two, one, Jad.


ROBERT: Robert.


JAD: Radiolab.




JAD: So today we have a triptych of experiments about plants.


ROBERT: Mm-hmm.


JAD: That apparently -- jury's still out. Are going to make me rethink my stance on plants.




JAD: So we're up to experiment two now, are we not?


ROBERT: That is correct. So we are going to meet a beautiful little plant called a mimosa pudica, which is a perfectly symmetrical plant with leaves on either side of a central stem. This peculiar plant has a -- has a surprising little skill.


MONICA GAGLIANO: Yeah. A reflex.


JENNIFER FRAZER: An anti-predator reaction?


MONICA GAGLIANO: Like a defensive mechanism.


JENNIFER FRAZER: As soon as it senses that a grazing animal is nearby ...


ROBERT: If a nosy deer happens to bump into it, the mimosa plant ...


MONICA GAGLIANO: Folds its leaves.


ROBERT: Curls all its leaves up against its stem.


JENNIFER FRAZER: The whole thing immediately closes up and makes it look like, "Oh, there's no plant here. Just a boring set of twigs. Nothing delicious at all."


ROBERT: So the deer's like, "Oh, well. Never mind.




AATISH BHATIA: That's so eerie.


ROBERT: So that voice belongs to Aatish Bhatia, who is with Princeton University's Council on Science and Technology. We showed one of these plants to him and to a couple of his colleagues, Sharon De La Cruz ...


SHARON DE LA CRUZ: This guy or this guy?


ROBERT: And Peter Landgren.


PETER LANDGREN: Oh, that's neat!


ROBERT: Because we wanted them to help us recreate Monica's next experiment.


MONICA GAGLIANO: I created these horrible contraptions.


JENNIFER FRAZER: Apparently she built some sort of apparatus. I guess you could call it a mimosa plant drop box.


ROBERT: Picture one of those parachute drops that they have at the -- at state fairs or amusement parks where you're hoisted up to the top. Except in this case instead of a chair, they've got a little plant-sized box.


JENNIFER FRAZER: Into which she put these sensitive plants.


ROBERT: So the plants are now, you know, buckled in, minding their own business. And then Monica would ...




ROBERT: Just about, you know, seven or eight inches.


MONICA GAGLIANO: Landing very comfortably onto a padded base made of foam. So no plants were actually hurt in this experiment.


ROBERT: [laughs]


ROBERT: But the drop was just shocking and sudden enough for the little plant to ...


JENNIFER FRAZER: Close all its leaves.


ROBERT: Then Monica hoists the plant back up again and drops it again. And again. And again. And after not a whole lot of drops, the plant, she noticed, stopped closing its leaves.


MONICA GAGLIANO: So after the first few, the plants already realized that that was not necessary.


ROBERT: She thinks that they somehow remembered all those drops and it never hurt, so they didn't fold up any more. They learned something.


MONICA GAGLIANO: Exactly, which is pretty amazing.


JAD: Couldn't it just be an entirely different interpretation here?


ROBERT: Like what?


JAD: The plants have to keep pulling their leaves up and they just get tired. They run out of energy.


JENNIFER FRAZER: Yeah, it might run out of fuel. Exactly. It's a costly process for this plant, but ...


ROBERT: She figured out they weren't tired. Because after dropping them 60 times, she then shook them left to right and they instantly folded up again.


JENNIFER FRAZER: It would close up.


JAD: Oh!


ROBERT: So it's not that it couldn't fold up, it's just that during the dropping, it learned that it didn't need to.




ROBERT: That's a -- learning is something I didn't think plants could do.




ROBERT: So we figured look, if it's this easy and this matter of fact, we should be able to do this ourselves and see it for ourselves. So that's where these -- the scientists from Princeton come in: Peter, Sharon and Aatish. They designed from scratch a towering parachute drop in blue translucent Lego pieces.


AATISH BHATIA: So this is our plant dropper. And we can move it up, and we can drop it.


ROBERT: So we strapped in our mimosa plant.


PETER LANDGREN: Little seatbelt for him for the ride down.


ROBERT: And then ...


AATISH BHATIA: All right. And then someone has to count.


ROBERT: I'll count.


ROBERT: And then we let it drop.


ROBERT: Five, four, three, two, one, drop!


ROBERT: And we dropped it once and twice. Again. And again. We waiting for the leaves to, you know, stop folding. We dropped. We dropped. But it didn't happen.


JAD: It was curling each time when it ...


ROBERT: Every time. It just kept curling.


JAD: So you couldn't replicate what she saw.


ROBERT: Nothing happened at all. So we went back to Monica.




ROBERT: We, as you know, built your elevator.


MONICA GAGLIANO: I heard. [laughs]


ROBERT: We told her what we did.


ROBERT: What happened to you didn't happen to us. Now, can you -- can you imagine what we did wrong?


MONICA GAGLIANO: Like for example, my plants were all in environment-controlled rooms, which is not a minor detail. They're not experiencing extra changes, for example. I don't know if that was the case for your plants.


ROBERT: No, I -- we kept switching rooms because we weren't sure whether you want it to be in the high light or weak light or some light or no light.


MONICA GAGLIANO: I wonder if that was maybe a bit too much. Was it possible that maybe the plants correctly responded by not opening, because something really mad was happening around it and it's like, "This place is not safe."


ROBERT: Truth is, I think on this point she's got a -- she's right. One time, the plant literally flew out of the pot and upended with roots exposed.


AATISH BHATIA: This feels one of those experiments where you just abort it on humanitarian grounds, you know?


ROBERT: So I think what she would argue is that we kind of proved her point. We were so inconsistent, so clumsy, that the plants were smart to keep playing it safe and closing themselves up. And she goes on to argue that had we been a little bit more steady and a little bit more consistent, the plants would have learned and would have remembered the lesson. Because what she does next is three days later, she takes these plants back into the lab.


MONICA GAGLIANO: The idea was to drop them again just to see, like, the difference between the first time you learn something and the next time.


ROBERT: Like, would they figure it out faster this time? Or maybe slower?




ROBERT: So she takes the plants, she puts them into the parachute drop, she drops them. And she says this time they relaxed almost immediately. They remembered what had happened three days before, that dropping didn't hurt, that they didn't have to fold up. So they didn't.




ROBERT: And then she waited a few more days and came back. They still remembered.




ROBERT: Few more days.


MONICA GAGLIANO: Yeah. And it was almost like, let's see how much I have to stretch it here before you forget.


ROBERT: Eventually, she came back after ...




ROBERT: 28 days!




ROBERT: And they still remembered. They still did not close when she dropped them. That's what she says.


ANNIE MCEWEN: What was your reaction when you saw this happen?


ROBERT: That's producer Annie McEwen.


ANNIE: This retention of knowledge?


MONICA GAGLIANO: My reaction was, "Oh ****!" That was my reaction. Because the only reason why the experiment turned out to be 28 days is because I ran out of time. So they might remember even for a much longer time than 28 days.


JAD: Well, supposing that she's right.




JAD: Where would the -- a little plant even store a memory?


ROBERT: Well, that's what I asked her.


ROBERT: Like, I don't understand -- learning, as far as I understand it, is something that involves memory and storage. And I do that in my brain. That's the place where I can remember things. In my brain.




ROBERT: Yes, I do!




ROBERT: Is a brain -- I think.




ROBERT: Is your dog objecting to my analysis? That's okay.


MONICA GAGLIANO: Picasso! Pics! Picasso! Enough of that! [laughs]


ROBERT: [laughs]


MONICA GAGLIANO: Picasso, enough of that now. Sorry!


ROBERT: Actually, Monica's dog leads perfectly into her third experiment, which again will be with a plant. But it was originally done with -- with a dog.


JENNIFER FRAZER: So Pavlov started by getting some dogs and some meat and a bell.


ROBERT: Science writer Jen Frazer gave us the kind of the standard story.


JENNIFER FRAZER: And his idea was to see if he could condition these dogs to associate that food would be coming from the sound of a bell. So he brought them some meat.


ROBERT: They would salivate and then eat the meat.


JENNIFER FRAZER: Then he would bring them the meat and he would ring a bell.


ROBERT: And again, drooling, eating.


JENNIFER FRAZER: And he would repeat this.


ROBERT: Ring, meat, eat. Ring, meat, eat. Ring, meat, eat.


JENNIFER FRAZER: Finally, one time he did not bring the meat, but he rang the bell.




JENNIFER FRAZER: Sure enough ...


ROBERT: The dogs began to drool.


JENNIFER FRAZER: They had learned to associate the sound of the bell ...


ROBERT: Which has, you know, for dogs has nothing to do with meat.


JENNIFER FRAZER: With when they actually saw and smelled and ate meat.




ROBERT: It got Monica thinking.


MONICA GAGLIANO: Would the plant do the same?


ROBERT: Could a plant learn to associate something totally random like a bell with something it wanted, like food?




ROBERT: Monica says what she does do is move around the world with a general feeling of ...




ROBERT: What if? So she decided to conduct her experiment.


MONICA GAGLIANO: Pretty much like the concept of Pavlov with his dog applied.


ROBERT: But instead of dogs, she had pea plants in a dark room.




ROBERT: And for the meat substitute, she gave each plant little bit of food. In this case, a little blue LED light.


MONICA GAGLIANO: Light is obviously representing dinner.


ROBERT: So light is -- if you shine light on a plant you're, like, feeding it?


MONICA GAGLIANO: Yeah, plants really like light, you know? They need light to grow. So otherwise they can't photosynthesize.


ROBERT: So for three days, three times a day, she would shine these little blue lights on the plants.


JENNIFER FRAZER: From a particular direction.


ROBERT: And she noticed that ...


JENNIFER FRAZER: Unsurprisingly ...


ROBERT: The plants would always grow towards the light.


ROBERT: And the salivation equivalent was the tilt of the plant?


MONICA GAGLIANO: Exactly. And then I needed to -- the difficulty I guess, of the experiment was to find something that will be quite irrelevant and really meant nothing to the plant to start with. Like the bell for the dog.


ROBERT: So after much trial and error with click and hums and buzzes ...


MONICA GAGLIANO: All sorts of randomness.


ROBERT: She found that the one stimulus that would be perfect was ...


ANNIE: A fan.


MONICA GAGLIANO: A little fan. The same one that are used in computers like, you know, really tiny.


ROBERT: She determined that you can pick a little computer fan and blow it on a pea plant for pretty much ever and the pea plant would be utterly indifferent to the whole thing.


MONICA GAGLIANO: The plants didn't care.


ROBERT: Then she placed the fan right next to the light so that ...


MONICA GAGLIANO: The light and the fan were always coming from the same direction.


ROBERT: And with these two stimuli, she put the plants, the little pea plants through a kind of training regime. Little fan goes on, the light goes on. Both aiming at the pea plant from the same direction, and the pea plant leans toward them. Then she takes the little light and the little fan and moves them to the other side of the plant. Turns the fan on, turns the light on, and the plant turns and leans that way.


MONICA GAGLIANO: Yeah. Fan first, light after. And moved around, but always matched in the same way together.


ROBERT: Fan, light, lean. Fan, light, lean. Fan, light, lean. Same as the Pavlov. The bell, the meat and the salivation.


MONICA GAGLIANO: So then at one point, when you only play the bell for the dog, or you, you know, play the fan for the plant, we know now for the dogs, the dogs is expecting. So it's predicting something to arrive.


ROBERT: And Monica wondered in the plant's case ...


MONICA GAGLIANO: If there was only the fan, would the plant ...


ROBERT: Anticipate the light and lean toward it?


MONICA GAGLIANO: Or would just be going random?


ROBERT: After three days of this training regime, it is now time to test the plants with just the fan, no light. So Monica moves the fans to a new place one more time. They're switched on. And the pea plants are left alone to sit in this quiet, dark room feeling the breeze.




ROBERT: The next day ...


MONICA GAGLIANO: I remember going in at the uni on a Sunday afternoon.


ROBERT: And she goes into that darkened room with all the pea plants.


MONICA GAGLIANO: So, you know, I'm in the dark.


ROBERT: But she's got a little red headlamp on.




ROBERT: And she moves about the room.


MONICA GAGLIANO: To have a look ...


ROBERT: Peering down at the plants under the red glow of her headlamp.


MONICA GAGLIANO: And then I saw ...


ROBERT: That these little plants ...


MONICA GAGLIANO: My little peas ...


ROBERT: Had indeed turned and moved toward the fan, stretching up their little leaves as if they were sure that at any moment now light would arrive.


MONICA GAGLIANO: And it's good it was Sunday. And I remember it was Sunday, because I started screaming in my lab. It was like, Oh, I might disturb my plants!" I go out and I thought there's no one here on Sunday afternoon. I can scream my head off if I want to. And so I was really excited. I was like, "Oh, my God! These guys are actually doing it." And so of course, that was only the beginning. Then we actually had to run four months of trials to make sure that, you know, that what we were seeing was not one pea doing it or two peas, but it was actually a majority.


ROBERT: So you just did what Pavlov did to a plant. You got the plant to associate the fan with food.


MONICA GAGLIANO: Yep. Pretty much.


ROBERT: But once again I kind of wondered if -- since the plant doesn't have a brain or even neurons to connect the idea of light and wind or whatever, where would they put that information? Like, how can a plant -- how does a plant do that?


MONICA GAGLIANO: I don't know. I don't know yet. But what I do know is that the fact that the plant doesn't have a brain doesn't -- doesn't a priori says that the plants can't do something. There are multiple ways of doing one thing, right?


ROBERT: Huh. So we're really -- like this is -- we're really at the very beginning of this.


MONICA GAGLIANO: Yeah, I know. This way there is often more questions than answers, but that's part of the fun as well.


ROBERT: Monica's work has actually gotten quite a bit of attention from other plant biologists.




ROBERT: And some of them, this is Lincoln Taiz ...


LINCOLN TAIZ: I'm a professor emeritus of plant biology at UC Santa Cruz.


ROBERT: ... say they're very curious, but want to see these experiments repeated.


LINCOLN TAIZ: It's a very interesting experiment, and I really want to see whether it's correct or not.


ROBERT: Us, too!


ROBERT: He's got lots of questions about her research methods, but really his major complaint is -- is her language. Her use of metaphor.




ROBERT: For example, words like ...




ROBERT: Or ...


LINCOLN TAIZ: Learning behavior.


ROBERT: And this? He's not a huge fan of.


LINCOLN TAIZ: Yes. If you get too wrapped up in your poetic metaphor, you're very likely to be misled and to over-interpret the data. I mean, I -- it's a kind of Romanticism, I think. You know, it goes back to anthropomorphizing plant behaviors.


ROBERT: Mm-hmm.


ANNIE: But I wonder if her using these metaphors ...


ROBERT: Again, producer Annie McEwen.


ANNIE: ... is perhaps a very creative way of looking at -- looking at a plant, and therefore leads her to make -- make up these experiments that those who wouldn't think the way she would would ever make up. And therefore she might, in the end, see something that no one else would see. Is it ...


ROBERT: This is like metaphor is letting in the light as opposed to shutting down the blinds.


ANNIE: Yeah. Kind of even like, could there be a brain, or could there be ears or, you know, just sort of like going off the deep end there. But maybe it makes her sort of more open-minded than -- than someone who's just looking at a notebook.


LINCOLN TAIZ: I think you can be open-minded but still objective. I mean, I think there's something to that. I think there are some cases where romanticizing something could possibly lead you to some interesting results.


ROBERT: So you're like a metaphor cop with a melty heart.




LARRY UBELL: That -- that would be an interesting ...


ALVIN UBELL: Don't interrupt. They have to -- have to edit in this together. Let him talk.


ANNIE: Yeah.


ALVIN UBELL: How much longer? Because I have an appointment.


ROBERT: All right, that's it, I think. Well, I have one thing just out of curiosity ...


ROBERT: As we were winding up with our home inspectors, Alvin and Larry Ubell, we thought maybe we should run this metaphor idea by them.


ROBERT: There's -- on the science side, there's a real suspicion of anything that's anthropomorphizing a plant. They just don't like to hear words like "mind" or "hear" or "see" or "taste" for a plant, because it's too animal and too human.




ROBERT: And the classic case of this is if you go back a few centuries ago, someone noticed that plants have sex.




ROBERT: That there was a kind of a moral objection to thinking this way. And I'm wondering whether Monica is gonna run into, as she tries to make plants more animal-like, whether she's just going to run into this malice from the scientific -- I'm just wondering, do you share any of that?


LARRY UBELL: No, I don't because she may come up against it, people who think that intelligence is unique to humans. And so I don't have a problem with that. I've been looking around lately, and I know that intelligence is not unique to humans. Okay? So I don't have an issue with that. And every day that goes by, I have less of an issue from the day before. So I don't have a problem. The problem is is with plants. They may have this intelligence, maybe we're just not smart enough yet to figure it out.


JAD: Well, okay. That's a parade I'll show up for.


ROBERT: Okay. let's do it!


JAD: Coming up on the Plant Parade, we get to the heart -- or better yet, the root -- of a very specific type of plant. And the -- I'm gonna mix metaphors here, the webs it weaves.


ROBERT: It won't be a metaphor in just a moment.


JAD: Yes. Radiolab will continue in a moment.


[ENRIQUE: This is Enrique Romero from the bordertown of Laredo, Texas. Radiolab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at]


JAD: Hey, I'm Jad Abumrad.


ROBERT: I'm Robert Krulwich.


JAD: This is Radiolab.


ROBERT: For this part of our broadcast, I'd like to begin by imagining a tall, dark, dense, green forest. Imagine towering trees to your left and to your right. And I need a bird, a lot of birds, actually. And a little wind. So just give me some birds.


JAD: You mean like sound?


ROBERT: Sounds, yeah. Birds, please. Birds.


JAD: Why?


ROBERT: Isn't that what you do? You give me -- like, I want wind, birds, chipmunks ...


JAD: Like, I'm not, like, your sound puppet here.


ROBERT: All right, never mind. This story ...


JAD: You'll get your sound at some point.


ROBERT: Begins with a woman. Or at the time actually, she was a very little girl who loved the outdoors. And I mean, like, really loved the outdoors.


SUZANNE SIMARD: When I was a little kid, I would be in the forest and I'd just eat the forest floor. And I know lots of kids do that, but I was especially ...


ROBERT: I'm sorry? You mean you got down on all fours and just ...


SUZANNE SIMARD: Yeah, I would just eat the dirt.


ROBERT: This is Suzanne Simard.


SUZANNE SIMARD: And so my mom always talks about how she had to constantly be giving me worm medicine because I was -- I always had worms.


ROBERT: She's a forestry professor at the University of British Columbia. And might as well start the story back when she was a little girl.


SUZANNE SIMARD: Well, when I was a kid, my family spent every summer in the forest.


ROBERT: And her family included a dog named Jigs.


SUZANNE SIMARD: And so in this particular summer when the event with Jigs happened ...


ROBERT: What kind of dog is Jigs, by the way?


SUZANNE SIMARD: He was a, not a wiener dog. He was a -- what was he?


ROBERT: You don't know what your dog was?


SUZANNE SIMARD: Not a basset hound, but he was a beagle.


ROBERT: Beagle.


SUZANNE SIMARD: Yeah, he was a curious dog.


ROBERT: And on this particular day, she's with the whole family. They're all out in the forest. It was summertime. And Jigs at some point just runs off into the woods, just maybe to chase a rabbit. Whatever. Couple minutes go by ...


SUZANNE SIMARD: And all of a sudden we could hear this barking and yelping. And we were all like, "Oh, my goodness! Jigs is in trouble!" And so the whole family and uncles and aunts and cousins, we all rush up there.


ROBERT: So they followed the sound of the barking and it leads them to an outhouse. And when they go in ...


SUZANNE SIMARD: There is Jigs at the bottom of the outhouse, probably six feet down at the bottom of the outhouse pit.


ROBERT: Oh, dear!


SUZANNE SIMARD: Where we've all been, you know, doing our daily business.




SUZANNE SIMARD: He'd fallen in. He's looking up at us quite scared and very unhappy that he was covered in ...




SUZANNE SIMARD: And toilet paper. And of course we had to get Jigs out. I mean, Jigs was part of the family. And ...


ROBERT: Since he was so deep down in there.


SUZANNE SIMARD: We had to dig from the sides.


ROBERT: To sort of like widen the hole.


SUZANNE SIMARD: Basically expanding it from a kind of a column of a pit to something that's -- we could actually grab onto his front legs and pull him out. And so we're digging away, and Jigs was, you know, looking up with his paws, you know, and looking at us, waiting.


ROBERT: And they're digging and digging and digging. And then all of a sudden, she says she looks down into the ground and she notices all around them where the soil has been cleared away there are roots upon roots upon roots in this thick, crazy tangle.


SUZANNE SIMARD: We're sitting on the exposed root system, which is like -- it is like a mat. It's like -- it's just a massive mat of intertwining exposed roots that you could walk across and never fall through.


ROBERT: She says it was like this moment where she realizes, "Oh, my God! There's this whole other world right beneath my feet.


SUZANNE SIMARD: Jigs had provided this incredible window for me, you know, in this digging escapade to see how many different colors they were, how many different shapes there were, that they were so intertwined. As abundant as what was going on above ground. It was magic for me.


ROBERT: Well, so what's the end of the story? Did Jigs emerge?


SUZANNE SIMARD: Jigs emerged. We pulled Jigs out and we threw him in the lake with a great deal of yelping and cursing and swearing, and Jigs was cleaned off.


ROBERT: But that day with the roots is the day that she began thinking about the forest that exists underneath the forest. And now, if you fast-forward roughly 30 years, she then makes a discovery that I find kind of amazing. She's working in the timber industry at the time. This is by the way, what her entire family had done, her dad and her grandparents.


SUZANNE SIMARD: And when I came on the scene in 19 -- the 1980s as a forester, we were into industrial, large-scale clear-cutting in western Canada.


ROBERT: She says a timber company would move in and clear cut an entire patch of forest, and then plant some new trees.


SUZANNE SIMARD: And, you know, my job was to track how these new plantations would grow.


ROBERT: And she says she began to notice things that, you know, one wouldn't really expect. Like trees of different species are supposed to fight each other for sunshine, right? I mean, you've heard that.


JAD: Yeah, absolutely. They shade each other out.


ROBERT: They shade each other. And they, you know, they push each other away so they can get to the sky. But she was noticing that in a little patch of forest that she was studying, if she had, say, a birch tree next to a fir tree, and if she took out the birch ...


SUZANNE SIMARD: The Douglas fir became diseased and -- and died. There was some kind of benefit from the birch to the fur. There was a healthier community when they were mixed and I wanted to figure out why.


ROBERT: Well of course, there could be a whole -- any number of reasons why, you know, one tree's affected by another. But she had a kind of, maybe call it a Jigs-ian recollection.


JAD: A flashback.


ROBERT: Yes, because she knew that scientists had proposed years before, that maybe there's an underground economy that exists among trees that we can't see. And she wondered whether that was true.


SUZANNE SIMARD: And so I designed this experiment to figure that out. It was a simple little experiment.


ROBERT: So here's what she did. She went into the forest, got some trees.


SUZANNE SIMARD: Douglas fir, birch and cedar. And then I would cover them in plastic bags. So I'd seal the plant, the tree in a plastic bag, and then I would inject gas, so tagged with a -- with an isotope, which is radioactive.


ROBERT: So these trees were basically covered with bags that were then filled with radioactive gas.




ROBERT: Which the trees ...


SUZANNE SIMARD: Would just suck up through photosynthesis.


ROBERT: So now, they had the radioactive particles inside their trunks and their branches.


SUZANNE SIMARD: We had a Geiger counter out there. As soon as we labeled them, we used the Geiger counter to -- and ran it up and down the trees, and we could tell that they were hot, they were boo boo boo boo boo, right?


ROBERT: And the idea was, she wanted to know like, once the radioactive particles were in the tree, what happens next? Would they stay in the tree, or would they go down to the roots? And then what happens? And what she discovered is that all these trees, all these trees that were of totally different species were sharing their food underground. Like, if you put food into one tree over here, it would end up in another tree maybe 30 feet away over there, and then a third tree over here, and then a fourth tree over there, and a fifth tree over there. Sixth, seventh, eighth, ninth, tenth, eleventh. All in all, turns out one tree was connected to 47 other trees all around it. It was like -- it was like a huge network.


SUZANNE SIMARD: And we were able to map the network. And what we found was that the trees that were the biggest and the oldest were the most highly connected. And so we, you know, we've identified these as kind of like hubs in the network.


ROBERT: And when you look at the map, what you see are circles sprouting lines and then connecting to other circles also sprouting lines. And it begins to look a lot like an airline flight map, but even more dense.


SUZANNE SIMARD: It's just this incredible communications network that, you know, people had no idea about in the past, because we couldn't -- didn't know how to look.


JENNIFER FRAZER: It's definitely crazy. I mean, you're out there in the forest and you see all these trees, and you think they're individuals just like animals, right?


ROBERT: Mm-hmm.


JENNIFER FRAZER: But no, they're all linked to each other!


ROBERT: Again, science writer Jennifer Frazer. I spoke to her with our producer Latif Nasser, and she told us that this -- this network has developed a kind of -- a nice, punny sort of name.




ROBERT: The what?




ROBERT: [laughs] You mean, like the World Wide Web? It's now the Wood Wide Web?




JAD: So this Wood Wide Web, is this just, like, the roots? Like what she saw in the outhouse?


ROBERT: No, no, no, no, no. No, it's far more exciting than that. It involves a completely separate organism I haven't mentioned yet. I mean, this is going places.


JAD: What creature? where we going?


ROBERT: I'm not gonna tell you. I'm gonna just go there. We went and looked for ourselves. I don't know where you were that day. Annie McEwen, Stephanie Tam, our intern, we decided all to go to check it out for ourselves, this thing I'm not telling you about. We went to the Bronx, and when we went up there, we -- there was this tall man waiting for us. An expert.


ANNIE: Is that Roy?




ROBERT: His name is Roy Halling. And Roy by the way, comes out with this strange -- it's like a rake.


ANNIE: He's got a trowel.


ROBERT: But it has, like, an expandable ...


ROY HALLING: It's a truffle rake.


ROBERT: Oh, it's an -- oh, listen to that!


JAD: Oh, that sounds dangerous.


ROBERT: And so we're up there in this -- in this old forest with this guy.


ROY HALLING: So there's an oak tree right there. It should have some.


ROBERT: And he starts digging with his rake at the base of this tree. He shoves away the leaves, he shoves away the topsoil.


STEPHANIE TAM: Can the tree feel you ripping the roots out like that?


ROY HALLING: I hope not.


ROBERT: And so now we're down there. Pulled out a that a root of some sort?


ROY HALLING: It's just getting started. They're called feeder roots.


ROBERT: We're carefully examining the roots of this oak tree. On our knees with our noses in the ground, and we can't see anything. I mean, I see the dirt.


ROBERT: Do you see anything white yet?


ROY HALLING: Like, I say, it's early in the season. So ...


ROBERT: He says something about that's the wrong season. I thought okay, so this is just stupid. But then ...


ROY HALLING: Finally! Do you have the lens?


ROBERT: He gives us a magnifying glass. You know, one of those little jeweler's glasses? Handheld?


ROY HALLING: Have a look there.


ROBERT: And he hands it to Annie.




ROY HALLING: You see it there?


ANNIE: Oh, yeah!


ROY HALLING: The white ...


ROBERT: Let me -- can I see?


ANNIE: Yeah, go for it.


ROBERT: Oh, my gosh, I do see them!


JAD: What do you see?


ROBERT: Little white threads attached to the roots.


ROBERT: Smaller than an eyelash. Maybe just a tenth the width of your eyelash. But white, translucent and hairy, sort of.


ROBERT: And while it took us a while to see it, apparently these little threads in the soil.


JENNIFER FRAZER: They're everywhere.


ROBERT: And when you measure them, like one study we saw found up to seven miles of this little threading ...


JENNIFER FRAZER: In a pinch of dirt.


JAD: What?


LATIF: A pinch?




JAD: What is this thing? Is it, like -- is it a plant? What is it?


ROBERT: What kind of creature is this thing?


JAD: Yes! What is it?


ROBERT: This is the fungus. Which by the way, is definitely not a plant.


JENNIFER FRAZER: They're some other kind of category. And for a long time, they were thought of as plants. But now we know, after having looked at their DNA, that fungi are actually very closely related to animals. They're one of our closest relatives, actually.


ROBERT: Now back in the day ...


JENNIFER FRAZER: This all has a history, of course.


ROBERT: When people first began thinking about these things, and we're talking in the late 1800s, they had no idea what they were or what they did, but ultimately they figured out that these things were very ancient, because if you look at 400-million-year-old fossils of some of the very first plants ...


JENNIFER FRAZER: You can see, even in the roots of these earliest land plants ...


ROBERT: You can see those threads.


JENNIFER FRAZER: This is a really ancient association.


ROBERT: And then later, scientists finally looked at these things under much more powerful microscopes, and realized the threads weren't threads, really. They were actually ...




ROBERT: Hollow.


JENNIFER FRAZER: These little tubes.


LATIF: Tubes?


JENNIFER FRAZER: Tubes. And the tubes branch and sometimes they reconnect.


ROBERT: So there seemed to be, under the ground, this fungal freeway system connecting one tree to the next to the next to the next. People speculated about this, but no one had actually proved it in nature in the woods until Suzanne shows up.


SUZANNE SIMARD: And there was a lot of skepticism at the time. But over the next two decades, we did experiment after experiment after experiment that verified that story.


JAD: Wait a second. Wait a second. Why is this network even there? Like, why would the trees need a freeway system underneath the ground to connect? And why would -- why would the fungi want to make this network?


JENNFER FRAZER: Well, they do it because the tree has something the fungus needs, and the fungus has something the tree needs.


ROBERT: Let me just back up for a second so that you can -- to set the scene for you.


JAD: Yeah.


ROBERT: When you go into a forest, you see a tree, a tall tree. So what does the tree do?


JAD: What's its job?


ROBERT: What's its job? It's soaks in sunshine, and it takes CO2, carbon dioxide, and it's splits it in half. It spits out the O2.


JAD: The oxygen?


ROBERT: Yeah. And it keeps the C.


JENNIFER FRAZER: Carbon, which is science speak for food.


ROBERT: It turns that carbon into sugar, which it uses to make its trunk and its branches, anything thick you see on a tree is just basically air made into stuff. However, if that's all they had was carbon ...


ROY HALLING: It will only be this tall.


ROBERT: That's Roy again. He's holding his hand maybe a foot off the ground.


ROBERT: It would be a teeny tree?


ROY HALLING: It would be smaller.


ROBERT: So if all a tree could do was split air to get carbon, you'd have a tree the size of a tulip.


JAD: Huh.


ROBERT: A tree needs something else. And what a tree needs are minerals.


JENNIFER FRAZER: Minerals from the soil. Very similar to the sorts of vitamins and minerals that humans need.


ROBERT: What kind of minerals does a tree need?


SUZANNE SIMARD: Like, nitrogen and phosphorus.




SUZANNE SIMARD: Potassium and calcium and ...




JAD: Why? What do these do for the tree?


ROBERT: Like, can a tree stand up straight without minerals?




ROBERT: It can't?


SUZANNE SIMARD: No, so for example, lignin is important for making a tree stand up straight. And lignin is full of nitrogen, but also compounds like nitrogen is important in DNA, right? It's an integral part of DNA.


ROBERT: Oh, so this is, like, crucial. If I want to be a healthy tree and reach for the sky, then I need -- I need rocks in me somehow. Liquid rocks.


SUZANNE SIMARD: You do. You need the nutrients that are in the soil.


ROBERT: And that's where the fungus comes in.


JENNIFER FRAZER: The fungus has this incredible network of tubes that it's able to send out through the soil, and draw up water and mineral nutrients that the tree needs.


LATIF: Wait. I thought -- I thought tree roots just sort of did -- like, I thought -- I always imagined tree roots were kind of like straws. Like, the tree was, like, already doing that stuff by itself, but it's the fungus that's doing that stuff?


JENNIFER FRAZER: Yes, in a lot of cases it is the fungus. Because tree roots and a lot of plant roots are not actually very good at doing what you think they're doing.


ROBERT: She says the tree can only suck up what it needs through these -- mostly through the teeny tips of its roots, and that's not enough bandwidth.


JAD: Wait. So, okay. So the fungus is giving the tree the minerals.




JAD: What is the tree giving back to the fungus?


ROBERT: Remember I told you how trees make sugar?


JAD: Yeah.


ROBERT: So that's what the tree gives the fungus. Sugar.


JENNIFER FRAZER: The fungi needs sugar to build their bodies, the same way that we use our food to build our bodies.


SUZANNE SIMARD: They can't photosynthesize. They can't take up CO2. And so they have this trading system with trees.


ROBERT: She says what will happen under the ground is that the fungal tubes will stretch up toward the tree roots, and then they'll tell the tree ...


SUZANNE SIMARD: With their chemical language. "I'm in the neighborhood. Can you -- will you soften your roots so that I can invade your root system?" And the tree gets the message, and it sends a message back and says, "Yeah, I can do that."


ROBERT: And then those little tubes will wrap themselves into place.


ROY HALLING: Well, you can see the white stuff is the fungus.


ROBERT: And we saw this in the Bronx. The little threads just wrapping themselves around the tree roots.


ROY HALLING: The last kind of part of the root gets tangled just around the edge.


ROBERT: And it's in that little space between them that they make the exchange.


JAD: What exchange would that be, Robert?


ROBERT: That would be sugar-minerals-sugar-minerals-sugar-minerals-sugar-minerals-sugar-minerals-sugar-minerals-sugar-minerals-sugar-minerals. And so on.


JAD: What -- I forgot to ask you something important.




JAD: If the -- if the tube system is giving the trees the minerals, how is it getting it, the minerals?


ROBERT: How's it getting the minerals?


JAD: Is it just pulling it from the soil?


ROBERT: Oh, well that's a miracle. I gotta say, doing this story, this is the part that knocked me silly. It's a -- it's a three-pronged answer. What a fungus does is it -- it hunts, it mines, it fishes, and it strangles.


JAD: What? How the hell ...


ROBERT: I'm not making this up. In 1997, a couple of scientists wrote a paper which describes how fungi ...


JENNIFER FRAZER: Have developed a system for mining.


ROBERT: Jennifer says that what the tubes do is they worm their way back and forth through the soil until they bump into some pebbles.


JENNIFER FRAZER: These little soil particles.


ROBERT: Packets of minerals. And then ...


JENNIFER FRAZER: They secrete acid. And these acids come out and they start to dissolve the rocks.


ROBERT: It's like they're drilling.


JENNIFER FRAZER: And the fungus actually builds a tunnel inside the rock. And it can reach these little packets of minerals and mine them.


LATIF: What?


JENNIFER FRAZER: If you look at these particles under the microscope, you can see the little tunnels. They curve, sometimes they branch. They look just like mining tunnels.


ROBERT: This is very like if you had a little helmet with a light on it. Like a human would.


JENNIFER FRAZER: Yeah. Maybe not with the helmet, but yeah.


LATIF: It's like Snow White and The Seven Tubes or something.


JAD: Wow!


ROBERT: And that's just the beginning. Jennifer told Latif and I about another role that these fungi play.


JENNIFER FRAZER: And that's hunter.


LATIF: Hunter.




ROBERT: What do you mean? Like, the plant is hunting?




ROBERT: Oh, hunting for water. I mean the fungus is ...


JENNIFER FRAZER: No, no, no. The fungus is hunting.


LATIF: The Fungus Hunter!


ROBERT: How do you mean? How do you mean?


JENNIFER FRAZER: So there's these little insects that lives in the soil, these just adorable little creatures called springtails.


ROBERT: They're sort of flea-sized and they spend lots of time munching leaves on the forest floor.


JENNIFER FRAZER: They're called springtails, because a lot of them have a little organ on the back that they actually can kind of like deploy and suddenly -- boing! -- they spring way up high in the air.


ROBERT: In the Richard Attenborough version, if you want to look on YouTube, he actually takes a nail ...


RICHARD ATTENBOROUGH: This pin will give you an idea.


ROBERT: And he pokes it at this little springtail, and the springtail goes boing! And you don't see it anywhere. It's gone.




ROBERT: Then of course because it's the BBC, they take a picture of it. It's doing like a triple double axel backflip or something into the sky.


RICHARD ATTENBOROUGH: It's the equivalent of a human being jumping over the Eiffel Tower.


ROBERT: Anyhow ...


JENNIFER FRAZER: One of the things they eat is fungus.


ROBERT: But then, scientists did an experiment where they gave some springtails some fungus to eat. They sort of put them all together in a dish, and then they walked away. And then they came back ...


JENNIFER FRAZER: And they found that most of the springtails were dead.


ROBERT: Instead of eating the fungus, it turns out the fungus ate them.


JENNIFER FRAZER: In the little springtail bodies there were little tubes growing inside them.


LATIF: What?




JENNIFER FRAZER: And this is what makes it even more gruesome. They somehow have a dye, and don't ask me how they know this or how they figured it out, but they have a little stain that they can put on the springtails to tell if they're alive or dead. When they did this, they saw that a lot of the springtails that had the tubes inside them were still alive.


LATIF: Oh, that's cruel!




ROBERT: The fungus were literally sucking the nitrogen out of the springtails, and it was too late to get away. No boink anymore.


JENNIFER FRAZER: And then they did experiments with the same fungus that I'm telling you about that was capturing the springtails, and they hooked it up to a tree.


ROBERT: To try to calculate how much springtail nitrogen is traveling back to the tree.


JENNIFER FRAZER: Well, 25 percent of it ended up in the tree.


ROBERT: Oh! So they figured out who paid for the murder.


LATIF: Right!


ROBERT: The trees did.


JENNIFER FRAZER: Mm-hmm. Yes. [laughs]


LATIF: Yeah. Is there anyone whose job it is to draw a little chalk outlines around the springtails?




ROBERT: Inspector Tail is his name. He's the only springtail with a trench coat and a fedora.


ROBERT: I have even -- I can go better than even that.


JAD: Huh.


ROBERT: There's -- they have found salmon in tree rings. Like, as in the fish.


JAD: In the tree?


ROBERT: In the tree. Well, in a way.


JAD: How in the hell?


ROBERT: Apparently, bears park themselves in places and grab fish out of the water, and then, you know, take a bite and then throw the carcass down on the ground. The fungi, you know, after it's rained and snowed and the carcass has seeped down into the soil a bit, the fungi then go and they drink the salmon carcass down and then send it off to the tree.


JAD: Oh, **** off!


ROBERT: The tree ...


JAD: That's **** bananas!


ROBERT: Salmon consumption. I was, like, floored.


JAD: Wow, that's insane!


ROBERT: Salmon rings in trees.


JAD: That's insane!


ROBERT: And look, and beyond that there are forests, there are trees that the scientists have found where up to 75 percent of the nitrogen in the tree turns out to be fish food.


JAD: From just bears throwing fish on the ground?


ROBERT: Yeah. So you -- if you would take away the fish, the trees would be, like, blitzed. Hobbled, really.


JAD: And is it as dramatic in the opposite direction? Like, from the trees perspective, how much of their sugar are they giving to the fungus?


ROBERT: Oh. Well, I asked Suzanne about that. Like, two percent or 0.00000001 percent? Or ...


SUZANNE SIMARD: No. Well, people have been measuring this in different forests and ecosystems around the world, and the estimate is anywhere from 20 to 80 percent will go into the ground.


ROBERT: Wait, wait, wait. What?


SUZANNE SIMARD: Yeah. 20 to 80 percent.


ROBERT: Of the tree's sugar goes down to the mushroom team?


SUZANNE SIMARD: Into the roots, and then into the microbial community, which includes the mushroom team, yeah.


ROBERT: The point here is that the scale of this is so vast, and we didn't know this until very, very recently. You have a forest, you have mushrooms. Now, it turns out that they're networked, and together they're capable of doing things, of behaviors, forestrial behaviors, that are deeply new. We're just learning about them now, and they're so interesting. Just for example ...


JENNIFER FRAZER: Let's say it's -- times are good. The tree has a lot of sugar. I don't really need it all right now. I'll put it down in my fungi. And then when times are hard, that fungi will give me my sugar back and I can start growing again.


ROBERT: What do mean, the fungi will give me my sugar back?


LATIF: It's like a bank? It's like a savings account?


JENNIFER FRAZER: It is! It is like a bank!


ROBERT: She says we now know that trees give each other loans.


JENNIFER FRAZER: Oh, yeah. Back and forth. Seasonally. They can also send warning signals through the fungus.


SUZANNE SIMARD: Yeah. So we've done experiments, and other people in different labs around the world, they've been able to figure out that if a tree's injured ...


ROBERT: It'll cry out in a kind of chemical way.


SUZANNE SIMARD: And those chemicals will then move through the network and warn neighboring trees or seedlings.


JENNIFER FRAZER: That something bad is happening. "I'm under attack!"


SUZANNE SIMARD: There's an enemy in the midst.


ROBERT: So if a beetle were to invade the forest, the trees tell the next tree over, "Here come the --" like Paul Revere, sort of?


SUZANNE SIMARD: Yes, that seems to be what happens.


ROBERT: So you can -- you can see this is like a game of telephone. One tree goes "Uh-oh." The next one goes, "Uh-oh." And then they do stuff.


SUZANNE SIMARD: They start producing chemicals that taste really bad.


ROBERT: So the beetles don't want to eat them.


SUZANNE SIMARD: It'll go, "Ick. I don't want that."


ROBERT: One of the spookiest examples of this Suzanne mentioned, is an experiment that she and her team did where they discovered that if a forest is warming up, which is happening all over the world, temperatures are rising, you have trees in this forest that are hurting. They don't do well in warm temperatures and their needles turn all sickly yellow. They will send out a "Oh, no! This is not so good" signal through the network. But also ...


SUZANNE SIMARD: The other important thing we figured out is that, as those trees are injured and dying, they'll dump their carbon into their neighbors. So -- so carbon will move from that dying tree. So its resources, its legacy will move into the mycorrhizal network into neighboring trees.


ROBERT: Oh, so it says to the newer, the healthier trees, "Here's my food. Take it. It's yours." Thud.


JENNIFER FRAZER: Or it could be like, "Okay, I'm not doing so well, so I'm gonna hide this down here in my ceiling."


ROBERT: Okay. I don't know if you're a bank or if you're an -- so it's not necessarily saying, "Give it to the new guy." Thud.


JENNIFER FRAZER: But we don't know. I mean again, it's a tree. It doesn't ...


ROBERT: I know, I know. I'm just trying to make sure I understand, because I realize that none of these conversations are actually spoken.


LATIF: Give it to the new guy?


ROBERT: Give it to the new -- well, that's what she saying.




ROBERT: Suzanne says she's not sure if the tree is running the show and saying like, you know, "Give it to the new guy." Or maybe it's the fungus under the ground is kind of like a broker and decides who gets what.


SUZANNE SIMARD: You know, I don't completely understand.


ROBERT: She says one of the weirdest parts of this though, is when sick trees give up their food, the food doesn't usually go to their kids or even to trees of the same species. What the team found is the food ends up very often with trees that are new in the forest and better at surviving global warming. It's as if the individual trees were somehow thinking ahead to the needs of the whole forest.


SUZANNE SIMARD: So we know that Douglas fir will take -- a dying Douglas fir will send carbon to a neighboring Ponderosa pine. And so why is that? Like so -- and I think that, you know, the whole forest then, there's an intelligence there that's beyond just the species.


ROBERT: Wait a second. Wait a second. You just used a very interesting word.


SUZANNE SIMARD: I know. Robert, I have -- you know what? It's 10 o'clock and I have to go.


ROBERT: Oh, all right.


SUZANNE SIMARD: This is getting so interesting, but I have ...


ROBERT: Unfortunately, right at that point Suzanne basically ran off to another meeting. But ...


SUZANNE SIMARD: Hello, Suzanne speaking.


ROBERT: Oh, there you are. Hey.




ROBERT: We did catch up with her a few weeks later.


ROBERT: When we last left off, I'm just saying you just said intelligence. Isn't -- doesn't -- don't professors begin to start falling out of chairs when that word gets used regarding plants?


SUZANNE SIMARD: Yes, we don't normally ascribe intelligence to plants, and plants are not thought to have brains. But when we look at the below ground structure, it looks so much like a brain physically, and now that we're starting to understand how it works, we're going, wow, there's so many parallels.


JENNIFER FRAZER: I do find it magical. I think there is something like a nervous system in the forest, because it's the same sort of large network of nodes sending signals to one another. It's almost as if the forest is acting as an organism itself. You know, they talk about how honeybee colonies are sort of superorganisms, because each individual bee is sort of acting like it's a cell in a larger body. Once you understand that the trees are all connected to each other, they're all signaling each other, sending food and resources to each other, it has the feel, the flavor, of something very similar.


ROBERT: Special thanks to Dr. Teresa Ryan of the University of British Columbia, Faculty of Forestry, to our intern Stephanie Tam, to Roy Halling and the Bronx Botanical Garden, and to Stephenson Swanson there.


JAD: And to Annie McEwen and Brenna Farrow who both produced this piece.


ROBERT: Thank you.


JAD: All right, Krulwich.


ROBERT: Okay. It's time -- time for us to go and lie down on the soft forest floor.


JAD: Yeah, and hopefully not be liquefied by the fungus beneath us.


ROBERT: This final thought. Bye everybody.


JAD: Bye.


ROBERT: I'm Robert Krulwich.


JAD: I'm Jad Abumrad.


ROBERT: For Radiolab.


JAD: Thanks for listening.


[ANSWERING MACHINE: Start of message.]


[ROY HALLING: This is Roy Halling, researcher specializing in fungi at the New York Botanical Garden.]


[JENNIFER FRAZER: This is Jennifer Frazer, and I'm a freelance science writer and blogger of The Artful Amoeba at Scientific American.]


[ROY HALLING: Radiolab is produced by Jad Abumrad.]




[ROY HALLING: Dylan Keefe is our Director of Sound Design.]


[JENNIFER FRAZER: Soren Wheeler is Senior Editor.]


[ROY HALLING: Jamie York is our Senior Producer.]


[JENNIFER FRAZER: Our staff includes Simon Adler, Brenna Farrow, David Gebel.]


[ROY HALLING: Matt Kielty, Robert Krulwich, Annie McEwen, Andy Mills, Latif Nasser, Malissa O'Donnell.]


[JENNIFER FRAZER: Kelsey Padgett.]


[ROY HALLING: Arianne Wack.]


[JENNIFER FRAZER: And Molly Webster.]


[ROY HALLING: With help from Alexandra Leigh Young, Jackson Roach and Charu Sinha.]


[JENNIFER FRAZER: Our fact-checkers are Eva Dasher and Michelle Harris. And remember, if you're a springtail, don't talk to strange mushrooms. Actually that's good advice for anyone.]


[ROY HALLING: Thank you. Bye.]


[ANSWERING MACHINE: End of message.]