Physical Control (Methods to Control Invasive Plants)

Physical Control (Methods to Control Invasive Plants)

Part of Ep. 703 Invaders

Visit the Olbrich Botanical Gardens where Jeff Epping, director of horticulture, compares different physical methods for controlling aggressive plants.

Premiere date: Jul 10, 1999

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
We're at Olbrich Botanical Gardens in Madison. And I'm with the director of horticulture here, Jeff Epping. Jeff, when I think of Olbrich Gardens, I think of lovely flowers. I don't think of asphalt. Why are we starting in your parking lot?

Jeff:
Well, this isn't the first place I'd show you, let's put it that way. But we're talking about aggressive plants. I think you've looked at cultural controls, we want to look at physical control. And what better way to control an aggressive plant than with asphalt, concrete, curbing. So, that's what we're looking at.

Shelley:
This must be a pretty scary plant if you have to have it surrounded by concrete. Can we take a look at it?

Jeff:
Sure. It's pretty aggressive. It's called Lyme Grass or Elymus Glaucus. And we had it in the perennial garden, a short time-- about two months-- and it raced three feet in all directions. So, we got it out of there in a hurry, to say the least.

Shelley:
And you planted it in here. How does it spread, if it's going so fast?

Jeff:
It spreads by rhizomes or the roots, actually. And if you look here, here's the main body of the plant. And already, this early in the season, it's starting to spread out.

Shelley:
It's really a nice, blue grass, too. You've got maybe ten planted in this whole bed. How long do you expect these few plants to fill in the bed, then?

Jeff:
Oh, I hope by the end of the season it will pretty much take over. It's pretty quick to spread.

Shelley:
That's very quick.

Jeff:
Yes.

Shelley:
With something like this, is the only way you recommend planting it is in the middle of a parking lot? Or, is there a way we might want to use it in a small garden?

Jeff:
If I put it in my garden, I'd definitely have some type of physical barrier. So, you could plant it in a pot that was bigger or use a metal hoop, maybe eight to ten inches deep. And then, divide it every spring to lessen the size of it.

Shelley:
You've actually got some containers that you made for a real common aggressive perennial here. Can we go take a look at those?

Jeff:
Yeah.

Shelley, here we are in our mint garden at Olbrich. Mints are great to use in cooking and for other herbal uses, of course.

Shelley:
I love them in teas. I don't love them in my garden anymore, though, because they went under the sidewalk and took off.

Jeff:
Well, they're pretty aggressive. And what we've tried to do here to keep them in check, is we built these steel rings. They're about ten inches deep and 8 inches in diameter. And they work out pretty well.

Shelley:
What could I use instead of a specially-made steel ring?

Jeff:
You could use a chimney tile flue or a plastic pot, just cut the bottom out so it has good drainage, something that just creates a good, physical barrier.

Shelley:
Of course, how good of a barrier is it? This is mint here. This is mint-- I mean, it jumped the ring.

Jeff:
It has jumped the ring. And that was a mistake we made last year, is that we didn't divide the plants every spring. And what you can see in the mint here, and it happens in a lot of perennials, the center dies out and all the live new growth is around the outside. And so, then they jump over the metal ring. So, what you get to do is take out a good section here and plant it right back in the middle, like what we've done over here.

Shelley:
So, to keep it looking nice and in control like that, we'd do that every spring and still plant it in the ring.

Jeff:
Exactly. That still has the ring around it. We just covered it with mulch to hide it.

Shelley:
Do you have any other methods of physical control that are working real well here at Olbrich?

Jeff:
We've tried a couple others, but with mixed results. We can take a look at those right now.

Shelley:
Okay. Jeff, I recognize this plant. This is Plume Poppy.

Jeff:
That's right. It's a pretty aggressive plant. It's spread by roots to this point, even though it's surrounded by rock on all sides.

Shelley:
So, you didn't plant this here?

Jeff:
No, we don't want it there.

Shelley:
Well, where is the parent plant? Where did this start?

Jeff:
The parent plant is right here.

Shelley:
That thing spread, what, ten feet?

Jeff:
At least ten feet. And we planted it here because it was surrounded by a stone wall-- brick on two sides-- We had one way it could go, but obviously, it's gone every which way.

Shelley:
Why plant something then, if it's that much of a hassle?

Jeff:
It's really a beautiful plant. It gets up to six, even eight feet tall, with very frothy blossoms on it. It's a very architectural plant. So, we're going to put up with it in this situation.

Shelley:
You know, I have a confession to make. I know how beautiful it is. I've got it at home. I've had it for about seven years. It is not aggressive in my yard and I've finally figured out why. It's because it's so close to my black walnut tree.

Jeff:
That makes sense. Black walnuts produce a toxin that actually kills some plants. So, it's probably keeping this one in check a little bit.

Shelley:
Maybe we discovered a new way to control aggressive perennials. You said that you had one more that we needed to be careful about?

Jeff:
Definitely. This is a plant called Houttuynia, a cultivar called Chameleon, which I would not put in the ground, ever. It's got very, very aggressive roots. You can see them here. They're all out at the edge of the pot. And they'll just go forever. Keep it in a pot. You can even put it in a pot in water and it still is happy.

Shelley:
So, we really need to know our plants before we plant them.

Jeff:
Definitely.

Shelley:
Thanks, Jeff. Next up, we're going to look at some trees and shrubs that can also be aggressive.

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