WHAT THE WORD “groundcover” means has really changed in the years Ken Druse and I have been gardening. And I’ll admit right here, some of the choices that I made to do the job of covering the ground under shrubs and trees at my place are now plants I want to be rid of.
Last time Ken Druse, author of “The New Shade Garden” and 19 other books, was here with us, we promised to talk when he visited again about my groundcover eradication program, targeted at one rampant perennial and what might go there instead.
And that’s our topic today: groundcovers, out with the old, in with the new. Ken got me to detail what I am up to, and what I think are the next steps in turning large areas of too-aggressive mostly Asian plants into more desirable (and hopefully better-behaved) native ones. (I’m not getting rid of painted fern and autumn fern, above; though both species originated in Japan they are well-behaved here for decades.)
Plus: Enter to win a copy of his book “The New Shade Garden” by commenting in the box at the very bottom of the page.
Read along as you listen to the October 19, 2020 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).
rethinking groundcovers, with ken druse
Margaret Roach: And he’s laughing already, though I haven’t even finished speaking the introduction. Hello there.
Ken: Well, when you tell me what I promised, it’s like, “Uh-oh, O.K.” I can’t even remember what I promised. Hi, Margaret.
Margaret: Hi, Ken. So we should say before we get started, we’re going to have a giveaway of the “The New Shade Garden” book, which is one of your most popular topics and includes a lot of, of course, groundcovers. Because shade is often made by woody plants that need someone at their feet, right?
Ken: Well, I don’t want to… Well, I can plug the book, but it has an entire chapter on groundcovers and it has a whole page on sedges. I thought, “What’s the name of that sedge?” and I looked in the book, and there it is. And that’s pretty exciting.
Margaret: Yeah. So, last time we were speaking on the show. Of course, I guess I suppose I should ask you, did you have any frost in September?
Ken: Well, it was funny because, it was like shorts one day, long pants the next day, coat the next day, shorts the next day. [Laughter.] So, I guess there were three nights of light, very light frost and the plants looked O.K., but the car was covered with what looked like ice. So, it continues to be strange, doesn’t it?
Margaret: Very strange. And so, so dry. I know you’re not as dry as I am though you’re only a couple of hours apart, but you are, but you’ve technically had more precipitation than I have a couple of hours, few hours away, but still Northeast is dry.
Ken: I put all the hoses away, I took all the hoses out. [Laughter.]
Margaret: I see the revolving door theory of gardening. Yeah. All right. So last time we spoke, I confessed to being on a war against one groundcover that I used to love for its variegated sort of silvery and green leaves. Almost looks like an ivy-ish vining, but low, prostrate thing. Lamiastrum galeobdolon, yellow archangel [above], which 30 or more years ago when I planted it, it was like a coveted thing. And now it’s on the invasive list in the Northwest, and it’s invading into woodlands as the climate warms in the Northeast. And you’re starting to see it on the invasive list in new areas and so forth. And I have suddenly 40 miles of it in my garden, because it no longer stays within a reasonable range.
So, I mean, maybe we should first say what’s a groundcover and what do we want to use them for anyway? Right?
Ken: Me? O.K. I think a groundcover is a plant that increases in numbers over time, but does not run away or spread too fast. It’s usually weed-suppressing; that’s what we hope. And we have a couple of those.
And you think of a groundcover is something you can walk on, but there’s not a whole lot of plants that will tolerate being walked on besides grass lawn, but a groundcover is anything that could do what I suggested first: spread a bit and suppress weeds. And it could be 7 feet tall. It can be a big shrub. And I’ve seen that, but I guess, what do you think? Is that just about it?
Margaret: Yeah! And like what you said, we think when we hear, if you hear the phrase groundcover, you would think, oh, like turf I can walk on it, but there really ain’t no such things. I mean, there’s so few things that can tolerate that. I mean maybe creeping time in a lawn you could technically walk on, but it really almost none of them. So, yeah. And it can be any height, I completely agree.
It’s maybe a living mulch is the… Claudia West, a landscape designer of Phyto Studios, she says, “Plants are the mulch.” That’s one of her key phrases that we need to remember. And I think in a way, I have a lot of masses of groundcover, like Geranium macrorrhizum, the big root geranium.
Ken: Oh, the best.
Margaret: Yeah. And doesn’t seed around. It is rhizomatous, but the rhizomes don’t spread sideways underground. It’s kind of, like it sounds, “big root,” on the surface. So I find that easy—you can just edit, you can pull out a bunch and throw it away and so forth, but it gives you that weed suppression that you were talking about, right. It’s a living mulch. It shades the ground under the trees and shrubs helps keeps moisture and etc., etc.
But it’s not so rambunctious that it’s a troublemaker. It won’t jump out of where it was, where you intended it to be. Does that make sense?
Ken: Yes. There was one plant here 26 years ago that I guess the people before I bought this place planted, and I’m still eradicating it, and it was a groundcover this year. I think it almost ate the house, and it’s a Houttuynia?
Margaret: Oh, yeah. Houttuynia, the chameleon plant [detail below], that’s a nightmare. That’s actually one of the most popular stories on my website ever, one of the most-visited from Google searches is about “How can I kill this plant?”
Ken: And it is still sold.
Margaret: Nightmare plant. Yeah. We’ve mentioned it before. It is a nightmare plant, but the Geranium macrorrhizum, by comparison, it only exists in the places I’ve put it in, though I started with a few plants and I now have large expanses of it. It means that I don’t have to weed those beds as often. It’s nearly evergreen even here in Zone 5B and it just does a really good weed-suppressing kind of a job.
But then there’s like the Lamiastrum, which wants to take over the earth and so forth. So-
Ken: And you participated in its takeover…
Margaret: And I did. And so there’s lots of things, and we should say, of course, the disclaimer as ever: What is invasive in one place or becoming invasive is, again, the temperature shift, the weather or the climate shifts, is not the same as in another place. Something may self-sow in Georgia that doesn’t self sow in Michigan and so on.
Ken: Or even in the neighborhood.
Margaret: Yeah, yeah. Depending on soil types and so on.
Ken: …yes, exactly. Because there’s so many things that you can grow, like your Angelica gigas, I cannot grow that at all.
Margaret: Right. Right, right.
Ken: And for you, that comes up from seed, self-sown seed.
Margaret: So, I mean, the classic things that, I have to say that 150 years ago I wrote a book about groundcovers for some series, gardening series, I remember. A small book about groundcovers, and probably most of the plants that are in it, I would never grow today. And in those days and long before, as you can see remnants of all over the country, vinca, pachysandra, English ivy: they were the groundcovers.
Ken: Oh, yikes.
Margaret: And now miles of those, we’re seeing climb up trees like the ivy does and smother trees and be a disaster. But I think there’s a whole other generation of our plants from 20 and 30 and even 10 years ago that are going to do that, too. Do you know what I mean? So how do we pick a good one, and what do we do about the ones we have?
And I’ve just felt… and I’ve been doing this, I started last year in fall. And I think the spring and fall when the soil is generally moister right. And also when a big job of digging, digging, digging, isn’t such… it’s not like 95 degrees out.
It’s a good time to do it when the soil is generally moister, it’s easier to work out the roots. But the process takes… Like you can’t just dig up a bunch of stuff and then replant the area. So you have to have the long view. And it’s hard for me creating these big blank spaces and just kind of looking at them like, do you know what I mean? Like, it’s been pillaged. [Laughter.] Did you know that the spots just been… It looked nice with the stuff it looked knit together, right?
Ken: So what are you going to do?
Margaret: [Laughter.] So, I started last fall in one area; I did one area. This spring I did the second pass on that area pieces that re-sprouted. And depending on when I stopped seeing a robust reoccurrence, I’m going to replant the areas, but I acknowledge that it may be a year. In other words, like a fall, a spring and a fall clean up before I replant the second fall or something.
Ken: Oh, goodness.
Margaret: I know. And I guess you could do it sooner and then weed from among where the Lamiastrum or whatever it is comes up. I guess you could do that. But I it’s such hard work going in among everything and untangling the roots of your desired new plants and the old ones, do you know what I mean? It’s… Yeah. So I just decided that since we have the pandemic and we don’t have garden open days and all these things, I was just going to give myself the time to do it right.
If these were sunnier areas, which of course they’re not because they’re in the shade because they’re underplantings [laughter], I would probably have done the first pass and then put down plastic.
Ken: Right, solarized it.
Margaret: Exactly. But I didn’t think that would really do much in this situations that they’re in.
Ken: Well, you have an opportunity to do some experimentation try some horticultural white vinegar maybe, or some other quote unquote organic solutions, maybe get one of those blow torches? [Laughter.]
Margaret: Yeah, flame-weeders.
Ken: Yeah. That’s not going to help, I don’t think. I wonder-
Margaret: I don’t think they call it a blow torch.
Ken: …if you planted some of your Geranium macrorrhizum [above], I wonder if the Lamiastrum would come up through it. I suspect it would, but it stops just about everything.
Margaret: Hmm. Yeah. And what I’m planning to do, and I don’t know if—I think you’re doing this too—is where I have an opportunity where something dies or where I’ve decided to get rid of something, I’m going with native choices for the replacement.
And so the Geranium macrorrhizum is not a native, and I’ve got lots of it. And so that’s the other part of the puzzle, is doing the homework to find a good groundcover for the future that doesn’t have these characteristics of Vinca, Pachysandra, ivy or in the case Lamiastrum, or there’s lots of others. You said the Houttuynia, there’s many others that have this tendency to be overly enthusiastic and move sideways too fast, and too ambitiously and become a monoculture. That’s what they are, right? The groundcovers we don’t like are the ones that don’t allow anyone else to cohabitate with them.
Ken: Well, except we want to cover an area.
Margaret: Right. But we don’t want it to completely eradicate-
Ken: Well to go where it’s not wanted. And some things you might be able to mow the edge, and stop it that way, but you really want something that fills in. But maybe we have to think of it as something that clumps versus something that runs something that just increases in volume by getting larger, by the plant getting larger. I mean, I love ostrich fern, and I planted them. And after a few years they looked so incredible. But then I saw the rhizomes were across the path and coming up in the bed across the path. So, that’s a native plant here.
Margaret: Right. And it’s a great plant, and I have it here and I love it. But it should never, it can never be combined into a mixed planting with the hope that it will behave. So, for instance, at the edge of the woods here, I could put that and let it go into the woods where there’s nothing because of over the years, the deer, and so forth have browsed, and let it have its way. Because again, it’s a native fern, so it’s appropriate, but also, its rambunctious habit is desirable in a place that’s been decimated and deer don’t really like ferns. So, hello, that would be a good one. Bbut it’s not a good companion for other perennials in a bed.
Ken: No, I guess it would be a good one to plant next to the asphalt driveway. Something that could stop it. [Laughter.]
Margaret: Do you have other groundcovers besides the Geranium macrorrhizum, or do you have mostly sort of mixed plantings?
Ken: Oh, my gosh. When you said, “Let’s talk about groundcovers,” I started making a list of just the things that are here and it’s about, I don’t know, 25 plants that I’m using, and I’m surprised. When you asked me, I thought, “I don’t have any groundcovers.” And then I walked around, took some pictures. I have a lot of groundcovers.
And I thought also about things that I planted that I regret, because that you got me thinking about that too. And a plant that I was told wouldn’t spread Pinellia, I got two different Pinellia species. They’re almost like Jack-in-the-pulpits. And I was told, “Oh, no, there’s no problem with them.” And they even hybridized. And then they got into the compost. And that’s my future, is digging out Pinellia.
Margaret: So, and for those who are listening, really what we’re both acknowledging, and we theoretically have a lot of knowledge or some expertise or whatever. And so we’re informed, and we get information from other experts and blah, blah, blah. And yet we make mistakes. And I think that’s what we’re trying to say out loud.
And also things have changed as the climate changes. Things have changed even in the same location, and things that are listed in catalogs that say, this is good for this. Well, that may be for, again, for Georgia or for Chicago, but not the opposite. And you learnl you live and learn. And I think it’s a great time, the fall, and again, and then again, in the early spring: We’ve got to acknowledge some of the things that aren’t working, not just aesthetically, but ecologically that aren’t working and that need to be dealt with, and it’s going to make a mass, it’s going to make a big empty hole. But I want to say, let’s go ahead and do it, right? Let’s go ahead and finally face some of these things, not just let them march another mile.
Ken: Definitely. And you are doing that. And I’m wondering how can we know what will be a good groundcover that will behave? And I suppose we can look at a local public garden and see what’s happening there. We can read up whatever we can. We can look to friends.
We can think about how plants behave in their native habitats, if they’re not indigenous plants. Check something out, see if it’s something that eats a woodland or covers a hillside in China and think, “Well, maybe that’s not the plant for me.”
And think about how the plant spreads, we mentioned running. So if a plant has stolons or runners or like Lamiastrum, which is like strings, almost like a strawberry—it runs. And we realized that may not be the best choice, let’s look to something like native ginger [Asarum canadense, below at Ken’s] or something that just casually spreads. And if you buy enough plants and if you divide them, it will fill in, it’ll fill in like that Lamiastrum. And it won’t even take that long. Maybe three, third year, it’ll look pretty good.
Margaret: Right. Yeah. And there’s so many, like you said, the native ginger, and that can be a robust grower, but it’s pretty easy to take out where you don’t want it, just dig it out, and it is appropriate. And again, we’re both in the Northeast. So the adjustment has to be made to another species maybe than native Asarum, native ginger, or depending on where you live or another plant.
You mentioned Carex, the sedges, before. And there’s a lot of them that are appropriate to different situations that are different sizes and textures. Many of them native—the ferns, we were talking about the ostrich fern, but there’s many, many, many ferns. And in each region there’s appropriate ones for different conditions. These are some of the great plants that we need to, I think, investigate. So, yeah.
Ken: There’s the native geranium, Geranium maculatum.
Ken: Do you grow that?
Margaret: I do. And it was here when I got here. So it is a native plant in my area and it’s sows in here and there in shady areas, it doesn’t make a thick groundcover. It’s more of a… It’s a perennial, but it doesn’t make a mass like the Geranium macrorrhizum does. Yeah. So, many other, I mean, Epimedium, for instance.
Ken: I can tell you some of the plants around in my garden, I’ve got even Ajuga can be O.K., and you can mow that, too. You could probably walk on the smaller ajugas, but I liked that ‘Catlin’s Giant,’ and that’s so easy to get rid of; you just pull it up.
But we’ve talked about Brunnera here in dry shade before, which you didn’t have as much luck with as I do. I have it in the driest shade of all, and it’s just, it’s a completely weed-suppressing groundcover for me. And the Carex as you talked about, and I’m going to say something, Fargesia, do you what Fargesia is?
Margaret: It’s a clumping bamboo, yes?
Ken: You are right. It’s the only winter-hardy, cold-hardy to Zone 5 non-running bamboo. And the one I grow is about 3 feet tall and it’s very beautiful. And as you said, it’s a clump, and I’ve planted it where I have erosion issues. So, it’s a groundcover, 3 feet tall, and it’s fighting erosion. And Heuchera villosa—that’s a native plant.
Margaret: I love that plant. And that will self-sow around, so you’ll get more plants and not in a nasty way—very easy to just pick up and move. So that’s one that will give you, you can start with a couple of plants and you’ll soon have plenty, I think. You can move them around and make a nice big planting.
I think Tiarella, the foamflowers, speaking of other native things, another one that I plan to use in one of the areas that I’ve begun this eradication thing—that and some Christmas fern and some other ferns. I got a certain number of each one and I thought, “You know what? I’m going to put them in one spot, and let the little young plants grow a little bit,” so that when I’m ready to move them into the eventual cleaned-up spots, that will be good. [Below, Tiarella cordifolia.]
Ken: Your splinter nursery.
Margaret: Yeah. It kind of is; yeah, it kind of is. But I am definitely looking more and more for inspiration at the natives, because these are big areas. These are big areas, and I don’t want to introduce another alien plant into the big areas that could potentially in 10 more years or whatever, be a problem. And one of the things to do about “is it a problem or not?” that you were talking about before, it’s pretty eye-opening. If you put in the name of like “Lamiastrum invasive,” if you just do a two-word Google search or in the case of woody plants like “doublefile Viburnum invasive.”
If you put in, and you get so much information from all of the invasive plant societies and the science research projects around the country, and you get maps that show you where the plants proving to be a problem if it is, or if not, Missouri Botanical Garden, their plant finder database always tells about whether plants invasive or not, and where. You can do the homework before you buy 50 of something, or even five of something.
So, we just have a couple more minutes and I want to hear a couple more plants that you do you find. The Epimedium are not native, but I do find that some of them are spreaders in a good way, not super-invasive. And others are more tight. They don’t move as fast.
Ken: I have some, I grow some Xanthorhiza, yellowroot, which is like a sub-shrub. Polygonatum, there are native Polygonatum [Solomon’s seal], and there are ones that are not native, but in time they will fill in. And usually they’re, well, they’re between 2 feet and 4 feet, depending on which kind you get.
I’d love to say the native pachysandra can be a good groundcover, but it’s a little wimpy. It’s not like the Asian pachysandra, but I have a variegated version of the Asian pachysandra, and it’s so slow. And it’s beautiful. I don’t think it’s quite the same as the army green plastic one you can drive over [laughter], not quite. I grow some Liriope, and Microbiota—do you remember that shrub that was popular-
Margaret: Microbiota decussata? Yes, yes, yes [above].
Ken: Yeah, a while back, it’s sort of low-growing, I guess it’s called Siberian cypress. It’s slow, but that’s kind of a nice one. Nepeta and lavender-if you have sun, just picture Provence. You can grow lavender as a groundcover.
Margaret: Not here. [Laughter.]
Ken: Not here, either. Too cold for you.
Margaret: A lot of people had junipers as groundcovers. And one of the ones that, as a final thought, one of the ones, there’s a cultivar of the Eastern red cedar, Juniperus virginiana, called ‘Grey Owl.’ Have you ever seen it?
Margaret: It’s not super-low, but boy, it’s a beautiful blue-silver color, ‘Grey Ghost.’ So that’s when to look for, if you want a medium height groundcover, and it derives from a native Eastern conifer. Anyway, we’re out of time. Of course, of course, of course, there’s a million more to talk about.
But let’s look for some opportunities to do some cleanup. Let’s go ahead, and sort of bite the bullet, right? And maybe replace with something better.
Ken: And no Roundup.
Margaret: And no Roundup in the process. Right? Some digging folks, lots of digging. [Laughter.] You heard it here first. All right, Ken, I’ll talk to you soon. Thank you.
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Is there a groundcover (or other ambitious plant) that you are fighting to eradicate, that is taking over too much of your garden?
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the October 19, 2020 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).