Roger: 0:02

Talking Trees with Lily and Jad. Welcome to Talking Trees. In today's episode, we delve into the fascinating yet troubling story of Ailanthus altissima, commonly known as the Tree of Heaven. We begin with a detailed overview, exploring its biology and journey from its native China to becoming an invasive species across the globe. And journey from its native China to becoming an invasive species across the globe. Next, we dive into a study which unravels the reproductive biology of A altissima, examining the factors that drive its seed germination and vegetative spread. Finally, we turn to insights focusing on strategies for controlling this species, including chemical and biological methods and the importance of collaboration with public authorities. Stay with us as we uncover the challenges and implications of managing one of the world's most notorious invasive trees.

Jad: 0:59

Welcome back everyone. Today we're taking a deep dive into a tree that's well a little bit infamous. It's Ailanthus altissima. You might know it as the tree of heaven.

Lilly: 1:08

Oh yeah, that name's a bit ironic, isn't it? Given its reputation?

Jad: 1:12

That's exactly what we're going to explore. We had a listener reach out, actually someone who works in Europe, and they're dealing with this tree professionally. So we thought, why not? Let's get into all the nitty gritty details of Ailanthus?

Lilly: 1:23

It's become a real headache, especially over in Europe. You know it's actually the only tree species officially listed as invasive by the EU. Pretty serious stuff.

Jad: 1:36

So no pressure on us, right? Well, for this deep dive, we've got our trusty Wikipedia open and we've also dug up a research paper from 2024, all about managing this tree. So let's start with the basics. What exactly is Ailanthus? For those who might not be familiar, All right, so Ailanthus altissima.

Lilly: 1:49

It's a deciduous tree and it originally hails from China. It's a fast grower too. Shoots up pretty quick, can reach up to 30 meters tall. But here's the thing doesn't live all that long. Not a long lifespan, nope. Usually less than 50 years. Might hit 100 in some cases, but that's rare.

Jad: 2:05

So it's a sprinter, not a marathon runner, huh, but there's got to be something else, besides its invasive nature, that makes it stand out.

Lilly: 2:13

Well, the smell is something else, that's for sure.

Jad: 2:15

Ah yes, the Infus Elansus aroma.

Lilly: 2:19

Some people say it's like peanuts or cashews.

Jad: 2:21

I've heard that.

Lilly: 2:21

But others they're like, nah, more like rotting cashews. It's definitely not winning any popularity contests for fragrance.

Jad: 2:29

Yeah, I can imagine Not exactly something you want wafting through your garden, right, but let's backtrack a bit. How did this tree from China end up becoming such a problem in Europe?

Lilly: 2:38

It's a classic invasive species tale. Really. Ailanthus was brought over to Europe in the 1740s as an ornamental tree, believe it or not.

Jad: 2:46

Really, people actually wanted this in their gardens.

Lilly: 2:48

Oh yeah, back then anything Chinese was all the rage. And this tree, well, it looked exotic, grew fast. Gardeners loved it.

Jad: 2:56

So it was like the trendy houseplant of the 18th century.

Lilly: 2:59

Exactly, but you know how trends are. The shine wore off pretty quickly once people realized this tree had a knack for how do I put it? Overstaying its welcome.

Jad: 3:10

You mean spreading like wildfire.

Lilly: 3:12

That's putting it mildly. Ailanthus is incredibly good at making more of itself. One female tree can pump out a mind-boggling number of seeds we're talking up to 300,000 per year and of course, the wind carries those seeds everywhere.

Jad: 3:28

Wow, no wonder it's so hard to control. But it's not just the seeds right, Doesn't it also spread through its roots?

Lilly: 3:33

You're right on the money. It can reproduce through its roots as well. Basically, it sends out these root sprouts, so even if you cut the tree down, it can just pop right back up from its root system. It's like fighting a hydra, honestly.

Jad: 3:43

A never-ending battle.

Lilly: 3:44

Exactly Chop off one head and two more grow back. It's a real nightmare for folks, especially professionals like our listener in Europe, who are trying to manage this tree.

Jad: 3:53

So let me get this straight. We've got a fast-growing tree, smells a bit funky and spreads aggressively, both through seeds and roots.

Lilly: 4:02

Okay, yeah, I'm starting to see why it's considered invasive, but let's dig a little deeper. What kind of impact does Ailanthus have on, you know, the environment itself and even on human health?

Jad: 4:11

Oh, the impacts are pretty significant. They touch on a lot of different areas. One major concern is its allelopathic nature.

Lilly: 4:20

Allelopathic. Now there's a word you don't hear every day. What does that even mean?

Jad: 4:24

In simple terms, Ailanthus releases chemicals into the soil and these chemicals, they actually inhibit the growth of other plants. It's like chemical warfare in the plant world.

Lilly: 4:34

So it's not just taking up space, it's actively trying to sabotage the competition.

Jad: 4:39

Exactly, and this gives it a big advantage allows it to form these dense thickets where native plants just can't survive.

Lilly: 4:46

And what about the effects on us, on humans? You mentioned the smell isn't exactly pleasant. But are there other health concerns? Oh yeah, for some people the smell's more than just unpleasant. It can actually trigger nausea and headaches. Then there's the skin irritation Contact with the plant can cause dermatitis, which is a pretty nasty rash, and we haven't even gotten to the roots yet.

Jad: 5:06

Roots what's the deal with the roots?

Lilly: 5:09

They're poisonous Straight up. If you ingest any part of the root system, you're in for a bad time. It can cause serious health problems. So yeah, it's a real worry, especially in places where kids play or where there's livestock around.

Jad: 5:23

Wow, this is starting to sound pretty bleak. We've got a tree that's bad for the environment, bad for our health and spreads faster than rumors in a small town. Is there any hope of controlling this botanical bully?

Lilly: 5:34

Well, it's definitely not an easy fight, but there are strategies being used to manage a Lamthis. We can start by talking about the more I guess traditional methods of control.

Jad: 5:44

Like just chopping it down.

Lilly: 5:46

It's a bit more complicated than that. Mechanical control, which includes cutting, mowing or girdling, can work for seedlings or small trees, but remember those root sprouts. They make it really tough to completely get rid of a mature tree.

Jad: 5:58

Right back to the Hydra analogy. You get rid of one part and another pops up. What other options are out there?

Lilly: 6:04

Well, herbicides are another tool we can use and they can be quite effective, especially when they're applied properly. But of course there are downsides. For starters, you've got to be extremely careful using herbicides near water sources. You don't want to contaminate those. And, just like with the mechanical methods, ailanthus' ability to re-sprout from its roots makes it really hard to completely wipe it out. To re -sprout from its roots makes it really hard to completely wipe it out, often takes multiple applications, which gets time consuming and expensive.

Jad: 6:33

Sounds like we need a more targeted approach, something that can take out Ailanthus without causing a ton of collateral damage to the surrounding environment.

Lilly: 6:40

That's where biological control comes into play and that's what we'll dive into next. So yeah, biological control, it's kind of a game changer when it comes to managing invasive species and with Ailanthus there's some really promising research happening.

Jad: 6:52

So we're fighting fire with fire, huh, or I guess, in this case, tree with fungus.

Lilly: 6:58

You got it. We're basically using Ailanthus' natural enemies against it. Think of it like recruiting a double agent from within the enemy's ranks.

Jad: 7:07

Okay, I'm liking the spy thriller analogy. So, who's our double agent in this case?

Lilly: 7:12

It's a fungus called Verticillium nonalfalfa.

Jad: 7:15

Verticillium nonalfalfa. Okay, not gonna lie, that's a mouthful. But what makes this fungus so special? What's it?

Lilly: 7:23

gonna do to our Ailanthus problem? Well, it's a soil-borne fungus and it causes a wilt disease specifically in Ailanthus.

Jad: 7:34

Think of it like a botanical version of a targeted virus A targeted virus, so it's like a sniper taking out Ailanthus while leaving other plants safe.

Lilly: 7:38

Exactly. It's pretty remarkable. The fungus gets into the tree usually through wounds in the roots or the trunk, and then it spreads through the xylem.

Jad: 7:46

Now refresh my memory. What was the xylem again?

Lilly: 7:49

Right, it's the system of vessels in a plant that carries water and nutrients, you know, from the roots up to the rest of the tree. It's basically the plant's circulatory system.

Jad: 7:58

Ah right, so this fungus basically clogs up those vessels, like cutting off the tree's supply lines.

Lilly: 8:04

Precisely that's exactly what it does Disrupts the flow of water and nutrients, and then the tree starts to wilt, eventually dies. And here's the best part Phytocillium non-ulphalfate seems to really have it out for Ailanthus.

Jad: 8:19

That's great news. We definitely don't want it going rogue and attacking other trees. But how do scientists actually use this fungus? Are they just spraying it all over the place?

Lilly: 8:27

Not quite. It's a little more sophisticated than that. Researchers are testing out different ways to introduce the fungus to a lamppost in a controlled way, Like they might inject the fungus directly into the trunk of the tree or they might introduce it to the soil around the roots.

Jad: 8:42

So it's more like a targeted injection than a widespread spraying.

Lilly: 8:45

Exactly that way. There's less risk of harming other plants that aren't our target. And there's another interesting twist to this whole biocontrol thing there's this little helper that actually helps spread the fungus.

Jad: 8:56

A helper. Okay, now I'm really intrigued. Who is this mysterious accomplice?

Lilly: 9:01

It's a type of weevil. Eucryptorhynchus brantii is its name.

Jad: 9:05

A weevil. I usually think of those as pests that get into grain or flour. What's so special about this one?

Lilly: 9:11

This particular weevil has a very particular taste. It loves to munch on Ailanthus wood.

Jad: 9:18

Ah, I see where this is going. So they're like tiny little lumberjacks, weakening the tree and making it easier for the fungus to take hold.

Lilly: 9:26

You got it the adult weevils and their larvae. They bore into the tree, making all these wounds and tunnels.

Jad: 9:32

And that gives the fungus easy access right. Yep exactly.

Lilly: 9:35

And here's the really clever part as the weevils move from tree to tree, they actually carry the verticillium non-alfalfa spores with them, so they're spreading the infection as they go.

Jad: 9:46

So it's like they're a botanical special ops team infiltrating the Ailanthus ranks and delivering a deadly payload. That's pretty awesome, but this all sounds very high tech. Can our listener in Europe you know the one dealing with Ailanthus professionally? Can they just go out and buy some of these biocontrol agents?

Lilly: 10:02

Unfortunately, it's not that simple the use of biocontrol agents. It's very strictly regulated.

Jad: 10:07

That makes sense, I guess.

Lilly: 10:08

Right, we want to make absolutely sure that introducing a new species, even if it's targeting an invasive one, we've got to make sure it doesn't end up causing even more problems in the ecosystem, unintended consequences and all that.

Jad: 10:21

Yeah, no. Rogue weevil releases.

Lilly: 10:23

Got it. So what advice would you give to our listener then? They're obviously eager to tackle this Ailanthus issue.

Jad: 10:29

Yeah, the first thing I'd say is get familiar with the local regulations on Ailanthus management, because it's officially classified as invasive by the EU. They've probably got specific guidelines, maybe even eradication programs in place, so work within the system. Exactly, no going rogue. It's really important to work within the established framework and talk to the local authorities or environmental agencies. They might even be able to connect our listener with some ongoing research projects or biocontrol efforts that are happening in their region. In the meantime, there are still some practical things they can do to manage Ailanthus on their own, you know, while they're waiting for those more advanced solutions.

Lilly: 11:08

Like what? What kind of things can they do? Well, prevention is key, like with most things. So identifying and removing Ailanthus seedlings as early as possible, that's huge. Remember, those seeds can travel really far, so it's an ongoing battle, but that early intervention can make a big difference.

Jad: 11:25

So it's all about being vigilant, making sure those little Ailanthus invaders don't get a chance to establish themselves. But what about the bigger trees, the ones that are already well established?

Lilly: 11:35

For those, mechanical and chemical control methods are still options, but again, always, always following local regulations, and while biocontrol agents might not be readily available just yet, it's encouraging to know that research is moving forward. Hopefully these more targeted approaches will be more widely available in the future. It's an exciting area of research, that's for sure. You know. It's funny when you think about it. This tree Elampus. It's public enemy number one in a lot of places, but it actually has a pretty long history, especially in China, where it's native.

Jad: 12:06

Oh really. So before it was the bad boy of European forests, it had a more I don't know respectable role.

Lilly: 12:13

Exactly. For centuries it's been used for all sorts of things in China the wood, for example. It's really strong and durable. I never would have guessed. Yeah, it's been used in construction, making furniture, even as fuel and for making paper.

Jad: 12:28

So it's not all bad then.

Lilly: 12:30

Not at all, and there's more. It even has a history of medicinal use in fina, different parts of the tree. They've been used to treat all sorts of things Dysentery, skin conditions, you name it.

Jad: 12:41

So it's like a botanical Jekyll and Hyde, capable of both harm and healing.

Lilly: 12:46

That's a great way to put it. I guess it's a good reminder that even species we label, as you know, invasive, they can still have valuable properties and their relationship with humans can be pretty complex.

Jad: 12:56

That's a really good point. It's easy to just slap a label on something and call it a day, but nature is rarely that simple.

Lilly: 13:02

Exactly. Speaking of nuances, I stumbled across something interesting in the Wikipedia article. Remember how Ailanthus is notorious for, you know, sprouting back even after you cut it down.

Jad: 13:13

Oh yeah, the botanical hydra. Hard to forget that.

Lilly: 13:16

Well, there's this Taoist metaphor that compares a spoiled child to get this a stump sprout of Ailanthus.

Jad: 13:23

Because they're both stubborn and refuse to be controlled.

Lilly: 13:26

You got. It Seems like even in ancient Chinese culture people recognize Ailanthus' tenacity, its ability to just bounce back no matter what, which, I guess, makes it both fascinating and a pain in the neck.

Jad: 13:38

It's like nature's giving us a little life lesson there.

Lilly: 13:40

Yeah.

Jad: 13:41

But let's get back to those challenges of managing Ailanthus. The research paper mentioned some pretty detailed germination experiments. What was that all about?

Lilly: 13:48

Right. So researchers have been studying how Ailanthus seeds germinate under all sorts of different conditions, trying to figure out, you know, what makes them so successful at spreading.

Jad: 13:58

So they're basically trying to crack the enemy's code.

Lilly: 14:00

Exactly, and what they found is that Ailanthus seeds are incredibly adaptable. They can germinate in a huge range of temperatures. They don't even need much light.

Jad: 14:09

So they're not picky at all about where they set up shop.

Lilly: 14:12

Nope, not even a little bit. They're not picky at all about where they set up shop. Nope, not even a little bit. And to make things even tougher, the research suggests these seeds can stay viable for years, even in harsh conditions.

Jad: 14:21

Wow. So even if you clear out an area, there's a good chance. Those seeds are just hanging out in the soil waiting to make a comeback.

Lilly: 14:27

Yep, that's the problem. It's a constant battle. It just shows how important long-term monitoring and management are. Getting rid of Ailanthus it's not a one-time fix, you know. It takes a lot of effort and you got to be persistent, especially with those super adaptable seeds.

Jad: 14:44

Well, I think it's safe to say we've done a pretty thorough, deep dive into the world of Ailanthus today. We've covered its biology, its history, its ecological impact and of course, the ongoing efforts to keep it under control.

Lilly: 14:57

It's been quite a journey, but I think the biggest takeaway especially for a listener who's working with this tree professionally knowledge is power. The more you understand about Ailanthus, the better equipped you'll be to manage it. You know, understanding its strengths, its weaknesses, even its cultural significance.

Jad: 15:12

I totally agree. So to our listener out there in Europe, go forth and tackle that Ailanthus problem head on and remember you're not alone. There's a whole community of researchers and experts working towards a future where Ailanthus is no longer such a threat.

Lilly: 15:27

And who knows, maybe one day we'll look back on all this and be amazed at how much progress we've made. Maybe we'll even figure out how to use Ailanthus to our advantage, you know, while keeping its invasive tendencies in check.

Jad: 15:38

Now that would be a real victory, turning a botanical foe into a valuable resource. Well, thanks for joining us for this deep dive into the world of Ailanthus. Until next time, keep exploring, keep learning and keep diving. Deep learning and keep diving deep.

Roger: 15:55

Today, we uncovered the complex story of Ailanthus altissima, the tree of heaven. From its biological traits and reproductive strategies to the challenges of controlling its invasive spread, understanding this species is crucial in managing its impact on ecosystems worldwide. Thank you for joining us. If you enjoyed this episode, be sure to subscribe and let us know what topics you'd like us to cover next. Together, let's keep exploring the fascinating world of trees, one story at a time. Until next time, take care and stay rooted, thank you.