Invasive Perennials

Invasive Perennials

Part of Ep. 703 Invaders

Visit the Flower Factory in southern Wisconsin.  Co-owner Nancy Nedveck discusses invasive perennials--plants that return year after year and spread by either re-seeding or by their roots.

Premiere date: Jul 10, 1999

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
We're at the Flower Factory in southern Wisconsin, where they grow and sell just an enormous variety of perennials. And we're in one of their demonstration gardens. I'm with one of the co- owners, Nancy Nedveck. Nancy, we're talking about invasive perennials, perennials that are weedy. Give me a definition of what that actually means.

Nancy:
An invasive perennial is a plant that will come back year after year and it will spread by either re-seeding or by roots.

Shelley:
And these can be really aggressive?

Nancy:
They can be a real problem if you don't site them very well, which is real critical.

Shelley:
So, there are times when we actually would want them in our garde n.

Nancy:
Right. Here at the Flower Factory, we have a re-seeding perennial here, the Stylophorum diphyllum, or golden poppy. The bloom is a real nice golden one in the spring. And you would deadhead it by breaking off the seed, like this.

Shelley:
So, once it's done blooming, if we want to control its spread, we have to take the seeds off.

Nancy:
Right.

Shelley:
And do we use this a ground cover? When is it at its peak?

Nancy:
Right. It's at its peak in the spring.

Shelley:
Okay.

Nancy:
In May. And then, what we also do, is we have hostas that are growing in amongst it. So, as the Stylophorum dies back, then hostas take over and will compete and keep it under control, also.

Shelley:
So, we were controlling this in two methods, by deadheading, getting rid of those seeds, and by letting other aggressive plants kind of duke it out together.

Nancy:
Right.

Shelley:
Can we look at another way we might use one of these aggressive perennials?

Nancy:
Sure, we have some grasses over here. Shelley, another reason to have an invasive plant is for screening, a quick screen. This is Miscanthus or maiden grass. This, by August, will be nine feet tall.

Shelley:
Wow. So, in one season, we'll be able to block out the road, the neighbors or anything. Now, do we have to worry about it getting carried away and spreading?

Nancy:
Yes, it can. Some Miscanthus varieties are very vigorous runners. Here, you would want to make a selection, where we've got ones that are just clump formers.

Shelley:
So, even invasive comes in varying degrees. Some are less invasive than others.

Nancy:
Right.

Shelley:
So, know what you're getting when you buy it.

Nancy:
Be sure and ask questions.

Shelley:
Okay. Now, you said you had another one that was a real hassle.

Nancy:
This is ribbon grass or Phalaris. We just love it because of the variegated foliage. But it is so vigorous that we do have to limit it by having a bottomless pot or by deadheading.

Shelley:
So, this spreads by seed and by roots, then?

Nancy:
Right.

Shelley:
But it's beautiful. I can see still wanting to try it.

Nancy:
Right. You really don't want to throw it away entirely.

Shelley:
Maybe not in a small, formal perennial garden.

Nancy:
No.

Shelley:
Now, you said you had another one that was a real good solution for a problem area. First, what's the problem?

Nancy:
Well, the problem is under the tree. It's really hard to mow. And then, also, a lot of the weeds come in. So, we like to use this Carex or sedge under it, because it limits the weeds. And also, you don't have to mow it.

Shelley:
What do you mean, it "limits" the weeds?

Nancy:
Well, you don't see any weeds in there, do you?

Shelley:
So, this is a case where it's actually weeding out the weeds, itself?

Nancy:
Yes.

Shelley:
Oh, my kind of perennial.

Nancy:
And then, we also like to limit the plants by either, one, we mow this here...

Shelley:
So, you mow around the outer edge?

Nancy:
Yes. But also, Carex loves sun and water.

Shelley:
It's a moisture-loving plant.

Nancy:
Right. So, where do we put it? In just the opposite, in a very bad situation for it, but yet it still does well.

Shelley:
So, we can control aggressive perennials by planting them in the wrong spot, basically.

Nancy:
Right.

Shelley:
That's an excellent idea. Let's take a look at a couple other examples.

Nancy:
Okay.

Shelley:
Here we've got another problem area: dry shade under a silver maple. And yet, it looks like you've come up with a great solution. What's happened here?

Nancy:
We picked two very aggressive plants and they compete with each other to control themselves.

Shelley:
So, they're duking it out and keeping each other behaved.

Nancy:
Right.

Shelley:
How many did you originally plant here?

Nancy:
We had ten plants of each variety.

Shelley:
So, maybe invasive perennials are an economical deal, too, because buy one and it'll spread. Now, with two different plants, I'm assuming you're getting more than one season of interest.

Nancy:
Right. The Lamiastrum galeobdolon here, or yellow arc angel, grows by runners and it's in a nice, fast, quick spring growth.

Shelley:
What do you mean by a runner?

Nancy:
Like this. This would grow. It would root along each leaf node.

Shelley:
So, as it rests on the ground, it basically just keeps rooting out and out and out.

Nancy:
Yes, and my common name for it is galloping overground.

Shelley:
I assume that means it really spreads.

Nancy:
Yes.

Shelley:
How do you control it from going into your lawn?

Nancy:
We just mow it.

Shelley:
Okay, that's easy enough. What about the taller plant with the purple leaves?

Nancy:
This one is Lysimachia ciliata purpurea, or Yellow Loosestrife.

Shelley:
Is this related to the purple loosestrife that's banned?

Nancy:
Not related. It's just a common name.

Shelley:
Okay, so this works fine. And you've got a nice combination of height and different colors, too.

Nancy:
Right. It really extends the season of interest.

Shelley:
I'm assuming they're also behaving, again, because they're planted in dry shade. Let's review how we can control plants using cultural control.

Nancy:
You'd want to limit the fertilizer, the sun and the water.

Shelley:
So, learn about the plant and maybe plant it deliberately in the wrong spot.

Nancy:
Right.

Shelley:
Okay, thanks Nancy.

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