Invasive Trees and Shrubs: Which Species Make the List?

Pat Etherington from Davey's Lake Bluff office talks with host Doug Oster about several invasive trees, including why they're problematic, what trees to choose instead and how he chose a career in arboriculture.  

To find your local Davey office, check out our find a local office page to search by zip code.

To learn more about invasives and smart planting, please read our blogs Trees with Non-Invasive Root Systems, The Best and Worst Trees to Plant Near a House (By Zone) and Tree Roots: Trees with Invasive & Non-Invasive Roots.

Connect with Davey Tree on social media:
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Connect with Doug Oster at www.dougoster.com. 

Connect with us: podcasts@davey.com. 

Transcript

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SPEAKER_00 0:00

Welcome to the Deby Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oyster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more because here at the Talking Trees Podcast, we know trees are the answer. I'm joined today by Pat Etherington. He is a sales arborist in Lake Bluff, Illinois, north of Chicago, for the Debut Tree Expert Company. And Pat, today we're talking all about invasive trees. How are you? I'm very good, Doug. How are you doing? I'm doing great. You had a storm come through today, though, right?

SPEAKER_01 0:44

We did. A lot of big broken branches and trees split in half, so it was kind of tough to see. But yeah, came through uh the Chicago suburbs here.

SPEAKER_00 0:53

Did you know it was coming? Did they warn you or did it just pop up?

SPEAKER_01 0:57

It was kind of a pop-up. I mean, they let us know about an hour ahead of time, but you never know where it's gonna hit. It hit our whole area, but it was only parts of the area that had the wind damage.

SPEAKER_00 1:06

So you're gonna be busy the next few days.

SPEAKER_01 1:09

Yes. A lot of drop by to do and things to look at. So yes.

SPEAKER_00 1:14

So we're

Bradford pear

SPEAKER_00 1:15

talking about invasive trees, and we'll gotta start with the granddaddy, the calorie pear, or you know, some people call it the Bradford pear. And what are the regulations in your state for this tree? Because there's many states where they just they do not want you to sell it, to plant it, or use it in any way.

SPEAKER_01 1:35

So Illinois finally uh stepped up and it's illegal to plant starting in 2028.

SPEAKER_00 1:42

Okay. So let's talk about even before we get to the invasive nature, the reason that every arborist I've ever talked to in my life does not want you to plant one of those pear trees.

SPEAKER_01 1:57

Well, they take over real fast. We thought they were good because they were supposed to be sterile, and it turned out we planted so many different cultivars that they began to cross-pollinate. And then, like I said, it kind of snuck up on us because we thought for a long time they were good trees and they tolerated a lot of lousy conditions. But now we're starting to see them take over really nice areas and fill in like crazy. So uh we know that they're not good.

SPEAKER_00 2:24

You know, I never knew that it was started off thinking it was sterile. I didn't know that part. And so you're saying that they just crossed with other cultivars and then they dropped seeds? Is that how it works?

SPEAKER_01 2:38

Yeah, they made enough cultivars that they got enough genetic variation. If you've ever seen the movie Jurassic Park, and they go, How do you know the dinosaurs aren't gonna take over? And they said, We made them all female. Well, that's what we thought we did too, and um no, that didn't work.

SPEAKER_00 2:55

Wow, and then there's problems with that tree as far as structure, too, right?

SPEAKER_01 2:59

Yeah, they have a real weak structure, it's very tight. Um, the newer, the Bradford pair is one that they grew because it was supposedly had a better, more open structure, but all of them are invasive, so what do we do if we already have them?

SPEAKER_00 3:16

Um well planted it plant planted in a development uh along of an alley of uh entryways into this uh beautiful McMansion.

SPEAKER_01 3:29

Right. Well, I suppose you're gonna keep them up there until they start to fall apart. But if you're right across from a forest preserve or something undisturbed, you're gonna start to see them take over there. So uh, but the ones that are already in place, it's kind of tough.

SPEAKER_00 3:46

Yeah. Uh but something we don't want to plant, and I guess uh if they're already there, you want to get rid of the little ones if you can. I don't know what I would don't know what to do.

SPEAKER_01 3:58

Yeah, if the little ones are coming up, cut them down. But like I said, they only last about 25-30 years, and then you get a good ice storm come through your area, and two or three of them will break in half. So it solves it solves itself there. But I've been down in Oklahoma and seen complete fields full of them. And they're starting to take over some of our forest preserves here in northern Illinois, so it's a problem.

SPEAKER_00 4:22

Is there

Buckthorn

SPEAKER_00 4:23

anything that can really be done to stop an invasive this uh rampant?

SPEAKER_01 4:30

Uh well, we've got a lot of experience out here with buckthorn, and European buckthorn, especially, is nasty, and it's very hard to kill, and it was filling up fields and native woodlots, and so it's a big education campaign. Um, you know, it's a lot of our county forest reserves do a good job of educating people, but then they also spent hundreds of thousands of dollars cutting them down, herbiciding the stumps, treating them so they didn't come back. So it's costly and long, but we can do it.

SPEAKER_00 5:03

Tell me about the buckthorn because I don't know anything about it.

SPEAKER_01 5:06

Oh my goodness. So that was my first thought when they were talking about pears was wow, we've already got buckthorn. And literally, when I was down in Oklahoma and I'm looking at this field full of green trees, I'm like, that looks a lot like buckthorn, and but it was in bloom, and buckthorn doesn't bloom. So I was like, oh my god, those are pears, they rival the buckthorns. So it literally just takes over everything, and buckthorn is even nastier than pears because it has a lilopathy, so it produces chemicals to inhibit other plant growth. So when homeowners get it in their yard, it'll kill their grass, not just from shade, but it you get a big uh woodlot full of it, and your diversity goes down to about three species that'll grow underneath it, uh, where you normally want hundreds or thousands of different things. So it's pretty nasty.

SPEAKER_00 5:56

It sounds absolutely awful. Insidious, yes. Yeah, oh, insidious, that's even a better term. Uh what else is on your list of invasives? Things that we shouldn't plant. I guess that's the is that the number one thing we can do. Do not plant one of these invasive species.

SPEAKER_01 6:14

Yeah, it's best if you can avoid certainly obviously buckthorn and uh pears for sure. Pears are sexier, so that's a little harder to stay away from uh because of the flowers. Uh but we also tell people around here try not

Barberry trees

SPEAKER_01 6:27

to plant barberries, which is a it's a little bush that comes in either purple or green or yellow. They're real cute and pretty. Um, but they'll get out into the woodlots and they're invasive too. Uh tree lilacs will also kind of spread. And I love tree lilacs, they're a pretty tree. But we start to see them running around, not as bad as the pears. Um uh burning bushes, which I think are very attractive. Um can also not nearly as bad, but they'll get invasive too. So those are kind of the big ones around here.

SPEAKER_00 7:01

Well, let's go back to Barberry because it's so funny that you mentioned that because they have come out with some sterile ones, but after what I just heard about uh pear trees, I would never plant a barberry. Also, it uh actually here, a tick magnet for us here in Pennsylvania. You know, we we we're always uh worried about ticks. Anyone who's outside is worried about ticks. And uh a barberry is uh uh, like you said, a terrible invasive. Are we still able to plant barberries? I know we're not supposed to, but I don't even know. I guess you do see them in the nurseries, right?

SPEAKER_01 7:45

You do. They're in the nurseries out here, and they're not as bad here. I would imagine they're far worse in Pennsylvania, but I've seen fields in Wisconsin where they're starting to take over. And I don't know if they're on the invasive list up there or not. So again, it's an education campaign.

SPEAKER_00 8:03

You know, one time I was doing a radio show and somebody called in and they needed a plant uh in this place they never go to, but it was going to be on a uh like a cemetery plot. And for some reason, I stupidly blurted out Barberry, and I'll tell you what, it it took about two years till that that uh fell away. Every every Master Gardener conference I went to said, Were you the guy that said Barberry? So it it can happen. Now I know better, but I was you know, I was it was right right while it was live on the radio. I'm thinking in my in my head, like, what what can she put in there that that would be indestructible? She's not gonna be able to water it, and it's it's gonna be a memorial plant, you know. And uh I again blurted out Barberry, and that was that was the wrong thing to say, Pat.

SPEAKER_01 8:58

Well, at one point, my colleague David Horvath, who I think you spoke with, um interviewed. He was the one, he's like, it was probably 12 years ago when I was planting a pear tree, and he said, You can't do that. And I said, Why not? And he said, They're invasive, and I said, I haven't seen that. He's like, Don't plant any more of those. So, all right. It was the last pear I ever planted. Um, but like I said, then driving around, I'm like, Oh, he wasn't kidding, it's pretty bad. So everybody's gotta learn at some point, and you know, it's trial and error a little bit, so yeah.

SPEAKER_00 9:34

And that was the last time I ever mentioned Barberry.

SPEAKER_01 9:37

Well, good. So that worked then.

SPEAKER_00 9:40

Uh burning

Burning bush

SPEAKER_00 9:41

bush, we know. Uh, again, not as invasive as some of these other plants, but still something that you see it everywhere, you know. You see it in the forest where it shouldn't be. Uh, and then what what else were you talking

Tree lilacs

SPEAKER_00 9:56

about was on your list?

SPEAKER_01 9:57

Oh, I think tree lilacs I've seen escape. I haven't seen them take over like the others do, but I've seen them escape and grow where they weren't planted, which is a starting sign, you know. So it's tough because it's like you said, we want a plant that's indestructible. Well, if it's indestructible, what keeps it in line?

SPEAKER_00 10:17

Yeah, yeah. So when you are out with a client and they sort of they don't know any better, they they just see this tree, this pear tree that that blooms so beautifully in the spring, and they ask you, hey, can we put one of those in? How do you how do you break it to them?

SPEAKER_01 10:35

Oh, I quickly tell them, hey, that's you know not a good tree, it's uh it's invasive, and offer them. Uh, there's plenty of crab apples that bloom just as nicely. We get a few cherries that do okay out here. There's uh alternatives to the pear out here, so that's usually what we're happy to recommend.

SPEAKER_00 10:54

Well, let's talk crab

Crabapples

SPEAKER_00 10:55

apples because I need your help there because I've had this crab apple outside my kitchen window for 30 years, and it's gone through everything Davy can do to help it. Trees have fallen on it. There's only one little stem left. I really want to replace it with a modern crab apple. The crab apple is a perfect tree for that spot, but you know, this old-fashioned one, it was been here since who knows when, the 70s. Uh it just gets apple scab no matter what. And I'm I'm just assuming actually that maybe a newer variety will be a little bit more resistant to the fungal disease.

SPEAKER_01 11:36

They're not, they are, they're not impervious, but there are much better varieties. Um, Jeff Lite is a wonderful upright white. Was this a white flowering crab apple you said? This one was pink, almost pink. Um uh firebirds, uh, royal raindrops are pink pink. Um Selkirk's a little bit older variety, but still fairly disease resistant. So uh Donald Wymans are still out there, and those are they get really big if you've got a lot of space there. So, but those Jeff Lifes are just they're upright. They it's a good pear replacement, so it's a good one.

SPEAKER_00 12:12

All right, those are great ideas. Uh, when uh the Davy Arborist I work with here comes back for his six-month visit. Okay, uh, I'm gonna suggest uh what you said there and see what he thinks and see if we can put one in there because you know us and our trees, um there's a million other trees I could put there, but there's just something about it. I've seen it every spring, and I know it's I know it's on its last legs. I actually it it had a little like kind of sport or something, and somehow I was able to move it and it's it's growing fine. This is like this was like 10 years ago. Yeah, I don't even I didn't know what I was doing, but at least it's a it's a nice tree and it blooms nice, but not where I can see it right from the kitchen window. So I what about that? Do you think I should consider something different than that crab apple? Uh I'm I'm I'm only sticking with the crab apple because that's what I've always seen there. But I wonder if there's a better choice, something cooler. I don't know.

SPEAKER_01 13:15

Crab apples are one of my favorites around here in Chicago. They're usually right on time for Mother's Day and prom. Uh, it's usually everybody goes off and gets a picture in front of the flowering crabs, you know. Um, so tough to replace for that. And you can get them in all shapes upright or spreading. I mean, it sounds like you may need a more spreading one if it's you're trying to keep it in the window view there. That's what we had in my house in Michigan where I grew up, was uh right outside the kitchen window. So my mom did dishes and saw the crab apple, and she loved it. So uh other examples though, um, flowering cherries,

Nurseries on Lake Michigan and Lake Erie

SPEAKER_01 13:50

uh a little tougher here in Illinois, but if you got a good spot, they're certainly gorgeous and about the same shape. Um, you guys are probably a little more mild there in Pennsylvania, so they would probably do better there.

SPEAKER_00 14:02

Well, I'm actually wondering because I was gonna ask you, Lake Bluff, I mean, you're right on Lake Michigan.

SPEAKER_01 14:07

Yes.

SPEAKER_00 14:08

Do you get is that an advantage or a disadvantage? Like if for Lake Erie, like north of us, Lake Erie, all the nurseries are up there. It's an advantage for them. It stays warmer longer.

SPEAKER_01 14:17

100%. So that's what it is for you too. On the west side of the lake, we get about a half a mile where it definitely makes a difference. Um, much further inland than that. You got the west winds out of here bringing in the the weather, and so um, but you can get a few things to grow along the lake here that don't grow elsewhere, it's a microclimate.

SPEAKER_00 14:39

Interesting. Uh, one thing I want to point out to people that are listening, we do

Pat's crosscut saw

SPEAKER_00 14:44

this via video, and so we can see each other, and you have the coolest thing hanging up on your wall back there. What is that saw? How big is it? That's like an old forester's saw, or what is it?

SPEAKER_01 14:58

It's it's an old cross-cut saw, and I used it and went to college, uh, Michigan State, and we used to go to what we called Conclave, which was a forestry, it was a logging competition. And uh, you had to take a cross-cut saw and you had to pump that, you know. That was how they used to cut the logs into boards, not just you know, sections, but they would cut the whole oh my. It was and it's oh my gosh, is it a lot of work? So uh I I had a client give that to me, and I I really like I want to get it cleaned up and maybe painted at some point.

SPEAKER_00 15:31

So how long is that blade? I can't tell from where it's at.

SPEAKER_01 15:36

It's probably about four feet long. So it takes a pretty good set of arms to push it through a log for sure.

SPEAKER_00 15:42

I don't think my old arms could push it through a log, and I'm I'm not sure if my arms could have ever pushed that thing through a log.

SPEAKER_01 15:50

When we were young, it was really hard. So I I we watch these guys at the log. Of course, they use the you know the chainsaws that are powered by snowmobile engines, but uh they still do the cross-cutting, and those guys, they're bodybuilders, have they're huge, so and they get the momentum going. And if the thing's sharp, it's pretty amazing. They they'll laser cut them now, and it'll really slice through quite a bit as it goes. So wow.

SPEAKER_00 16:16

Uh anything else on the invasive list? Was there a maple that we we talked about?

SPEAKER_01 16:21

Oh, I mentioned Amur

Hohner maple

SPEAKER_01 16:22

maples. Oh, that's it. A cute little I don't see them as much as I used to. Um, they got the small leaves. Uh, it's it's an Asian maple tree, and um they're not as popular as say flowering pears, but I still see them planted, and we don't like them.

SPEAKER_00 16:39

So, in general, just

Don't plant the wrong plant

SPEAKER_00 16:43

just give us a rundown real quick, just like what it's about choosing the right plant and not choosing the wrong plant. Do I have that right? Don't plant, don't plant the wrong plant.

SPEAKER_01 16:57

Don't plant the wrong plant and don't plant the right plant in the wrong spot. So we got into planting trees here. I've been planting trees for a long time, but one of the reasons we got into planting them was because most of tree problems, many of the tree problems we were seeing happened when they were put in. Uh, too tall a tree underneath wires, uh, light-loving tree in the shade, or vice versa. Um, planted too low, planted next to other plants that wanted to be wet or dry. So getting the right tree, getting some advice, you know, talking to an arborist or a good landscape architect, or if you've got a botanic gardens in your area, um, you know, get some advice before you invest all the money into buying the plant and effort into planting it.

SPEAKER_00 17:46

Now, before I let you go, I want to ask you how you got

Pat's career

SPEAKER_00 17:49

into this, why the job's right for you. Oh.

SPEAKER_01 17:52

So I was studying forestry, and uh um I my there weren't a lot of forestry type jobs when I was getting ready to graduate. And my late in my junior year, I went to see my advisor and he said, Well, arborculture. And I said, Well, what's arborture? And he said, Well, it's tree care in urban areas. And I said, That sounds counterproductive. They've got trees in urban areas, and he says, Oh my gosh, yes. And he says, one tree in somebody's backyard is worth more than half a forest of trees in the middle of nowhere. And so he recommended actually, he said, there's a suburb in the Highland Park in the Chicago area that has a wonderful forestry program. In fact, if you're familiar with the Mr. T story, he was the suburb north of us where he went in and clear-cut a bunch of trees, and so they started creating tree ordinances around here to help protect the trees. And um, so the foresters there help enforce that. And I came out here to Chicago and I they helped out, and it's beautiful. And I thought, this is really neat. So I'm still learning new trees every day, and I get on some really cool properties, and I work with some really cool people and really cool trees. So it's a lot of fun and I love it.

SPEAKER_00 19:11

Well, Pat, I'm glad that you're never going to plant a pear tree, and I'm I'm glad that I will never mention Barberries. So thank you very much for all the information and uh the good content. It was fun to talk to you.

SPEAKER_01 19:24

You too, Doug. Keep spreading the good word. Alrighty. Talk to you later.

SPEAKER_00 19:28

One of the reasons I love hosting this podcast is how these conversations with the guests evolve. That was that was so much fun, and I appreciate it. Thanks, Pat. Now, do me a favor, subscribe to the podcast so you'll never miss an episode. Do it every Thursday called the Talking Trees Podcast from the Davy Tree Expert Company. And I'm your host, Doug Oester, and I want to know what we should be covering. Let us know. There's a couple different ways to do it. You can send us an email to podcast at Davey.com. That's P-O-D-C-A-S-T-S at D-A-V-E-Y.com. You can also click the link at the end of our show notes to text us a fan mail message. Your ideas could be on a future show. And as always, we like to remind you on the Talking Trees podcast trees are the answer.