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Podcasts Human/Nature
The Tree That Won’t Die
Episode 8
The Tree That Won’t Die
When it comes to invasive plants, tree of heaven is public enemy number one. This week on the show, we get to the bottom of its bad reputation. We’ll discover which parts are science, and which parts are straight up racism. Human Nature is sponsored by BetterHelp and our listeners get 10% off their first month of online therapy at Support for this podcast is made possible by Gordon and Dona Crawford, who believe that quality journalism makes Los Angeles a better place to live. This program is made possible in part by the Corporation for Public Broadcasting, a private corporation funded by the American people.

Marcos Trinidad 0:00

[theme music] Hey, what's up? I'm Marcos Trinidad and this is Human/Nature. Every week we'll get out into the nature of your neighborhood with the help of people who see [ambient outdoor sounds and birds chirping] the world a little differently.

Raquel Falco 0:13

Let's go down this way.

Marcos Trinidad 0:15

Today I'm out in the San Gabriel Mountains with Raquel Falco.

Raquel Falco 0:18

We're on the Big Dalton Canyon Trail. [music out] It goes right along this stream. And it's not that big of a stream, but you know, you see lots of life, uh plant life and, and just the sound of the water's super soothing.

Marcos Trinidad 0:33

There's water flowing down from the hill and we're under this huge California Sycamore. It is absolutely beautiful here. [a bird caws continuously in background] Raquel is an arborist and park supervisor for the city of Glendora. And believe it or not, the reason why we're out here on this beautiful spring day is to kill some trees.

Raquel Falco 0:53

Let me get my drill bit here and put it in my drill. Okay. [sound of drilling]

Marcos Trinidad 1:02

Actually, just one kind of tree [bird cawing] specifically, a non-native tree called Ailanthus Altissima, also known as the Tree of Heaven. Sounds nice, right? But according to Raquel, it's a tree from hell.

Raquel Falco 1:17

[sounds of hiking through thick foliage] There's lot of different like woody shrubs and, and trees, but you can distinguish Tree of Heaven, because the bark sort of looks like a melon.

Marcos Trinidad 1:26

Her mission today? Find Tree of Heaven and destroy them.

Raquel Falco 1:31

[sounds of leaves rustling] I'm just gonna pull it in different directions to see if I can get to that root system.

Raquel Falco 1:39

[sounds of footsteps and a slow stream of water] They're very shallow rooted, and this soil is pretty moist, so that makes it extra easy.

Marcos Trinidad 1:51

When they're small enough, she rips 'em out of the ground with her bare hands. Others, she cuts in half with the handsaw she keeps hanging on her belt.

Raquel Falco 1:59

[water trickling] And in order to, you know, uh just sort of mess with the root system, I'll just cut them at this height. [sounds of her sawing] At the very least, I just cut them to try to slow down photosynthesis. [out of breath]

Marcos Trinidad 2:15

But sometimes even literally sawing them in half doesn't work. That's when the big guns come out.

Raquel Falco 2:22

This is called [sounds of bugs flying around] Triclopyr.

Marcos Trinidad 2:26

It's an herbicide that she injects straight into the tree.

Raquel Falco 2:30

I've got my little uh single injector here, and I'm plugging that into the hole that I've made. And so now that that's pretty secure, [sounds of her moving around] um I'm going to press on my gun, and I'm going to be very careful 'cause sometimes the pressure um, can be pretty uh great- great enough that it'll spew out. There it is, you see that? So I'll pull it out slowly. And then I'll go into the other hole I made, and I'll do the same thing.

Marcos Trinidad 3:02

In a matter of weeks the tree will start to lose leaves and die. And yeah, it's a pretty extreme method, but Raquel says it's necessary. For a lot of conservationists, Tree of Heaven is public enemy number one.

Raquel Falco 3:16

It's just a problem.

Marcos Trinidad 3:17

Tree of Heaven is almost impossible to kill. When Raquel saws down one tree, four or five are gonna come back in its place. It's super invasive, meaning it grows and reproduces really fast and it can crowd out native plants. It even releases a chemical that suppresses growth in surrounding plants. Like the native ones that Raquel wants to protect.

Raquel Falco 3:39

Some Laurel Sumac which is native, we're definitely leaving that. We've got some Mule Fat, which is native. That stays and then some Willow. Um, anything that's that's endemic or native to this region, we leave.

Marcos Trinidad 3:51

She's been working on removing Tree of Heaven from this trail for a couple of years now. And she's made some progress. But no matter what she tries, the work will never be done. [original music]

Raquel Falco 4:02

It's one of those things where I, I, I don't have hate for it, but I know what has to get done. I guess I can sort of get my emotions out of it and really just say, This is what I gotta do.

Marcos Trinidad 4:15

Today on the show, the most hated tree in the world. We'll discover how Tree of Heaven got here in the first place and get to the bottom of its bad reputation. Which parts are science? And which parts are quite frankly pretty f----d up? [music out]

Marcos Trinidad 4:43

For someone who doesn't know what the Tree of Heaven looks like, it doesn't really stand out from other trees. You know, tall, leafy, but to conservationists, it's unmistakable. Everyone has something negative to say about it. I recognize that can be a bit of an echo chamber. So I wanted to talk to someone who has another take on this tree, someone who actually kind of likes it.

Marcos Trinidad 5:08

[to Peter Del Tredici] Can you please introduce yourself?

Peter Del Tredici 5:11

Okay, my name is Peter Del Tredici. I've been working with trees for um, pretty much most of my adult life.

Marcos Trinidad 5:19

Peter has been an arborist with the Harvard Botanical Garden for more than 30 years. And he says he first encountered the Tree of Heaven when he moved from California, where he grew up, to Boston.

Peter Del Tredici 5:31

Well, obviously, the Tree of Heaven grows in California, and I must have seen it. It didn't make an impression on me until I moved east. And you see, not only in Boston, but New York City, this tree is growing everywhere, and it's growing in places where nobody obviously planted it. Coming out of the, you know, where the sidewalk meets the foundation of a house, or out of sewer grates. And uh, you know, I have to admit, I was sort of fascinated by this tree. And I guess I have used the word admiring of it, that it could grow under such adverse conditions and flourish.

Marcos Trinidad 6:09

Can you describe to me what the Tree of Heaven looks like?

Peter Del Tredici 6:14

Well, the Tree of Heaven is, I think the one word I would use to describe it is gawky. [Marcos and Peter laugh] It's very sparsely branched. It has very large twigs, and you see it in the winter landscape. It's like a stick figure of a tree. But right now, actually here in the Boston area, it's beginning to leaf out. And it happens very quickly. It goes from being a a twig to you know, fully leafed out.

Marcos Trinidad 6:43

Right? It it goes from like, Is this thing alive, to like, Oh, my God, I can't believe how much it's grown. So what's the history of how Tree of Heaven came to the United States?

Peter Del Tredici 6:54

Well, you know, it was a novelty in, you know, the late 1700s, I believe, early 1800s. [original music] It does exist as a wild plant in uh central and eastern China. And basically, you know, this would be after the American Revolution, America started to grow and expand and there were actually people with some wealth started to appear and people started wanting to grow gardens that contained, you know, ornamentals, not just food plants. And they uh began importing trees directly from Europe. And these were all um, you know, expensive ornamentals, and Ailanthus was one of the first trees to come over from Europe as an ornamental plant.

Marcos Trinidad 7:43

Just to clarify, you mention Ailanthus. Can you tell me the the botanic name for for the Tree of Heaven that we are referring to?

Peter Del Tredici 7:52

That's Ailanthus Altissima, and that just means, you know, very tall. One of the, not only was it fast growing and you know, nursery men like trees that grow fast. And remember, at this time, growing trees in the city was not an ordinary thing. The cities were for people and everything was paved over and you know, we're trying to keep nature out of our cities, but the Ailanthus was tolerant of these sort of difficult urban conditions. And then the other thing is that nursery men liked it because it was easy to propagate. It uh sprouted from what are called root suckers. In other words, if you dig a plant up, and you leave a little piece of root behind, that'll produce a new shoot. So the fact that it was easy to propagate uh meant that nursery men were able to increase it rapidly. By the 1860s, um, so within a period of about 40 years, it was the most common street tree in New York City.

Marcos Trinidad 8:46

That is shocking that that history of it being a desirable tree. What changed?

Peter Del Tredici 8:54

Several things happened. One is that the the tree is a little bit stinky. And the pollen, they thought that the pollen was getting into the water, because people had a lot of open wells in those days, and polluting the water and causing uh, yellow fever.

Marcos Trinidad 9:09


Peter Del Tredici 9:10

So th- there was a pa-, of course it's not true, but this was an easy thing to blame the tree for this. [laughing] And then it started, what happened is, the trees that they planted 20 years earlier started to sprout. Sprouts started coming up everywhere outside of the area had been planted. And uh [laughing] this is where uh people began to see what this tree can actually do once you plant 1000s of them all over the city. And so there was a movement, uh you know, beginning around 18-, you know, probably after the Civil War, that you know, we can do better than the Ailanthus. Let's get rid of it. But when you try to dig it up, as I said, every piece of root you leave behind, or you cut it down, it produces a new shoot. So if you go after the Ailanthus with a chainsaw or something, [laughs] and you cut it down, you get you know, maybe 20 new shoots coming where you had one tree before. [original music] [laughs] So all of the efforts to get rid of it simply propagated it.

Marcos Trinidad 10:07

This tree calls for backup. [Peter laughing]

Peter Del Tredici 10:11


Marcos Trinidad 10:12

When we come back, Peter and I talk about how America's intense relationship with Ailanthus was never just about the trees. [music out] [break]

Marcos Trinidad 10:29

So I can remember the first time that I had an interaction with Tree of Heaven. So I was in charge of a group of, at the time, what was considered at risk youth, and we were out weed whacking and removing invasive plants, and Tree of Heaven was everywhere. And when it was identified, for me, it was like, Oh, this is Ai- Ailanthus, Tree of Heaven. And it sucks. But I remember the actual moment when my attitude shifted. [original music] This was years later, and I'm sitting in a workshop about California Oaks. This workshop was taught by a person that is well respected in the field, written a few books and just speaks poetry when it comes to these Oaks. And then the topic of non-native plants, invasive plants, came up and one example was Tree of Heaven. How useless and how horrible this other tree is. It's from China. It doesn't belong here and you need to rip it out. And I thought, like, wait a minute, like, like, that's not actually cool. I'm not saying that I love Tree of Heaven. And to be honest, I will take it out when I find it. But the way we talk about Tree of Heaven really started rubbing me the wrong way. Because that hate, that language sounds familiar. It sounds a lot like the way some Americans talk about people who are not quote unquote, from here. And it turns out, racism towards people and prejudice towards Tree of Heaven have always been related.

Peter Del Tredici 12:23

Well, what's really interesting is that in the 1840s, 1850s, there's a famous landscape professional, his name was Andrew Jackson Downing who had been, you know, a promoter of trees, and it was his idea to build Central Park. He designed the Mall in Washington, DC. He wrote this [small laugh] amazingly racist essay called, Down with the Ailanthus. He used the Ailanthus as you know, this oriental, let's put it that way, that has you know, wormed its way into our gardens, you know, so sort of seduced gardeners with its beauty and its rapid growth. And now we know it's true character, and we've got to get rid of it. And we should only plant native species, because this plant is untrustworthy.

Marcos Trinidad 13:11

Wow. So there was some serious anti-Asian racism going on here historically, with the Tree of Heaven. I've got to imagine that didn't go away all the way. Can you tell us a little bit about what these opinions are today of Ailanthus, and and how would you summarize that?

Peter Del Tredici 13:31

[laughing] They're not good. They're definitely not good. Um, if you go into, you know, any of the major cities on the East Coast, Ailanthus, it's the most common tree in in the cities of the Northeast. But, you know, nobody counts it, nobody gives any credit for it, because it's not planted. So, you know, it's relatively easy to recognize, and in a lot of um, low income neighborhoods where this tree is quite common, uh people who live in those neighborhoods typically don't like the Ailanthus because it's seen as a indicator of neglect. You know, in other words, nobody is taking care of this land. You know, why doesn't anybody care about this neighborhood, you know. And that tree is Exhibit A.

Marcos Trinidad 14:15

So clearly Tree of Heaven is extremely disruptive to our native ecosystems, but it's kind of wrapped up in all of this racism and classism and-- What does all this mean for how we interact with Tree of Heaven in our neighborhoods? Like what are we supposed to do with Tree of Heaven?

Peter Del Tredici 14:37

Well, that depends on who you talk to and since you're talking to me, I'm gonna give you my answer. The thing is, is all trees produce shade. And the thing about the Ailanthus, it grows where no one planted it. [original music] So it provides ecological services. We have to call it that- in terms of, you know, managing stormwater runoff, uh producing shade, sequestering carbon, at no cost to the taxpayer, so nobody has to plant it, nobody has to take care of it or anything. So that is, you know, my definition of sustainability. Um, and the other place where, here in East anyway, where Ailanthus is really common is along interstate highways, where we use a lot of road salt in the wintertime and Ailanthus, being uh incredibly tough tree is totally tolerant of road salt. And a lot of our native species can't tolerate that road salt. So the highway bankings uh along the interstate are often covered with [laughs] Ailanthus trees, because they can tolerate those conditions. And they, in those situations, they're providing erosion control, and they're growing where nothing else will grow.

Marcos Trinidad 15:48

I can definitely see see the argument. And in fact, I'll be honest with you, you're the first person I've talked to, that speaks with, you know, that speaks so passionately about Tree of Heaven. It's remarkable. I'm I'm I'm listening. [music out] So I want to talk about climate change. Why is this tree going to matter as the climate changes?

Peter Del Tredici 16:13

Well, the thing is, is that, you know, climate change, uh you know, has changed absolutely everything. And one of the things is that, you know, here in the East, everybody talks about planting native species and restoring, you know, ecological habitats. And the fact of the matter is that there's no going back to the past. What we can do is move forward. And why I'm interested in this plant, and actually a lot of invasive species is these plants are going to do some heavy lifting in the future. And we actually need these plants because they're able to tolerate conditions that you know, most plants can't deal with at all. Longer periods of drought, like you're having in California, and we're having heavy rain. And so uh as the climate shifts, Ailanthus should be able to track those changes better than a lot of other species are able to.

Marcos Trinidad 17:06

Should we be ripping this tree out from our landscape?

Peter Del Tredici 17:11

Well, you know, if it's growing somewhere, just ripping it out, is not actually going to do very much. So I think declaring it uh, evil incarnate and saying, We've got to get rid of this tree. First of all, it's not going to happen, because people have been trying to get rid of Ailanthus on the East Coast, [laughs] you know, for a very long time without any success whatsoever. So my advice is to learn how to live with it, learn how to manage it in the landscape, so you know, get rid of it in those areas where you really don't want it, where it's interfering with infrastructure and stuff like that, or ruining your foundation or lifting the sidewalk or whatever. But, you know, it's growing in a lot of areas where it really doesn't matter. You know, in those areas where nobody is taking care of the landscape, and the Tree of Heaven is growing, we're getting services out of this tree uh, without doing anything to it. And so that's a good thing. You know, tell me again, what the problem is here. So, you know, I think that sure, if you, you know, if you've got the money to put in a formal park, great, go ahead and do that and get rid of the Ailanthus. But in the absence of those kinds of resources, and you know, you've got the Tree of Heaven growing there, particularly along, say, a roadside interstate highway or something like that. I don't know what the problem is.

Marcos Trinidad 18:30

If you had a Tree of Heaven in your backyard, [Peter laughs] would you rip it out?

Peter Del Tredici 18:35

Yes. [Marcos laughs] No question about it. It's because I want to grow other plants, you know, and so it's just gonna take over. And uh, you know, I- that's not what I want in my garden. But another way of phrasing that question is, you know, would the world be a better place if we eradicated all of the Trees of Heaven? And I would say no. Now in the countryside, that's a little bit different issue. And I can see in those areas, you may not want the Tree of Heaven, and it's probably a good idea to get rid of it because it's going to compete with the native vegetation, but in an urban context, I personally don't think we need to eradicate it.

Marcos Trinidad 19:13

We need all the trees we can get.

Peter Del Tredici 19:15

I would agree with you 100%. [theme music]

Marcos Trinidad 19:18

Well, thank you so much for sharing a wealth of knowledge about the Tree of Heaven, and it was great to just see your admiration for this tree. I, I really appreciate you taking the time and sharing this with us.

Peter Del Tredici 19:33

You're welcome, Marcos.

Caroline Champlin 19:39

Human/Nature is hosted by Marcos Trinidad. This episode was produced by me, Caroline Champlin with help from Carla Javier. Kelly Prime is our story editor. Fiona Ng is our acting supervising producer. Mixing and engineering by Parker McDaniels and Shawn Corey Campbell. Ex Manana composed our music and Doris Anahi Munoz is the music supervisor. Human/Nature is a production of LAist Studios. The marketing team created our branding with art by Christine Tyler Hill. Special thanks to Taylor Coffman, Sabir Brara, Kristen Hayford, Kristen Muller, Andy Orozco, Michael Cosentino and Neha Shaida. Antonia Cereijido and Leo G are the executive producers for LAist Studios. Our time in the field was recorded on Gabrieleno Tongva Territory. Support for this podcast is made possible by Gordon and Dona Crawford, who believe that quality journalism makes Los Angeles a better place to live. This program is made possible in part by the Corporation for Public Broadcasting, a private corporation funded by the American people. That's all for this episode of Human/Nature. We'll see you next time. [music out]

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