making the switch to native groundcovers, with duncan himmelman of mt. cuba

I’VE SPOKEN recently on the show about my personal war on certain groundcovers I planted years ago that have turned out to be hideous thugs. Many other gardeners I hear from have likewise come to lament their overly cooperative, spreading plant choices, like rambunctious vinca or pachysandra.

We all want groundcovers to do weed-suppressing duty and tie the garden together aesthetically, but the wrong choices can definitely backfire. Native groundcovers are a smarter alternative that will provide those and other benefits and they’re today’s topic.

I talked about making the change is Duncan Himmelman of Mt. Cuba Center, the noted native plant garden and research center in Delaware, where he’s the education manager. A course on native groundcovers taught by Duncan—from low perennials like heucheras or tiarella (above) or sedges to shrubby possibilities like ‘Grow-Low’ sumac—is one of the half-dozen on-demand recorded online courses that Mt. Cuba is currently offering.

Plus: At the bottom of the page, I’ve put together a list of links to help you research the plants native to your area to identify some good possibilities.



And:
I’ll buy tickets to the Mt. Cuba virtual class of your choice for two lucky readers; enter in the comments box at the bottom of the page.

Read along as you listen to the December 21, 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).

native groundcovers, with duncan himmelman

 

 

Margaret: Before we get started, we’ll say we’ll have another giveaway like we did, I don’t know, a month or so ago when you visited to talk weeds, one of the other courses that you’ve been doing at Mt. Cuba, that’s available virtually. And I’ll buy a ticket or two for people to attend the classes as the giveaway.

But as I mentioned in the introduction, I’m now eradicating some naughty plants. [Laughter.] Sound familiar?

Duncan: Very much familiar, and I agree with you in terms of plants like vinca and Japanese pachysandra. Back 40 years ago, people were saying, “Hey, here are some great options for you.” And now, fast-forward, we’re regretting every moment of having planted any of those in our yards.

Absolutely, my interest in native groundcovers of course comes from switching out those particular groundcover options to have native plants that can provide ecosystem benefits and provide alternatives to the lawn.

Margaret: Yes. The naughty, un-environmental lawn that doesn’t do much for wildlife and we mow, mow, mow and use all kinds of non-sustainable things in the process of doing so and feeding it and whatever.

Duncan: The carbon footprint is amazing. Avoid it at all costs.

Margaret: So you’ve been thinking about groundcovers for a long time, as I recall. I think you even did maybe part of your doctoral work or some graduate work at Cornell years ago on groundcovers, didn’t you? This has been a long interest.

Duncan: Yeah, it has. I was in the Urban Horticulture Institute at Cornell, and we were looking for a groundcovers that would survive urban conditions. The premise of the research was to use woody plants instead of herbaceous plants. And the reason being that, woody plants have year-round structure. If you’re in a city like urban environment, you can appreciate the fact that herbaceous groundcovers lose their foliage over winter, and people could step on them and compact the soil.

We were looking for shrubs, in point the fact, that would be up to 3 feet in height and have some opportunity to spread and cover the ground fairly quickly. It was an interest of mine at that time. And in terms of recommending shrubs as groundcovers, people have kind of shied away from that, because they think of the groundcover as traditionally being something that’s low to the ground, 6 or so inches, and spreads. But there are a number of fronts that can fill that role.

Margaret: Yes. In some spots especially, you want that extra dimension. Plus I’m on a very steep site, and there’s a small flat backyard area and then a water garden, and then there’s a steep incline again, where the property rises again. I have a lot of woody groundcovers on that area. It’s a tough spot to get in there and work in all the time. It’s precarious so it’s great to have things that are kind of permanent and solid and been there for a very long time and I don’t have to get in there all the time and deadhead or tweak things. Do you know what I mean?

Duncan: [Laughter.] Yeah, exactly. Yeah. There’s a lot of maintenance that goes into herbaceous groundcovers. One of the primary shrubby plants that I like to recommend for that exact situation, a hillside that’s full sun-facing and well-drained is ‘Gro-Low’ fragrant sumac [Rhus aromatica, above and below]. It’s the best choice for so many situations because it roots in quite easily, it spreads slowly but steadily. And it has a lot of beautiful features such as the green foliage during the spring and summer. And they turn beautiful, beautiful crimson and a wine red in the fall.

It’s a plant that we were recommending of course in our graduate research at Cornell. I see it more and more being used out in the landscape, whether it’s urban, commercial or even residential. Great choice for that kind of situation. They love full sun, well-drained soils, and they’ll knit your hillside together. [Below, ‘Gro-Low’ sumac in fall color.]

Margaret: It’s funny you mentioned that right off the bat because a friend of mine, she’s been calling me. She used to be the Vice President of Horticulture at the New York Botanical Garden. She’s since changed her life and become a physician. [Laughter.] Made a life change and she lives near me in this rural area. With the pandemic and everything we talk on the phone once a week and on Sunday, she said in the weekly call, she said, “Oh, I’m just loving what’s going on with my ‘Gro-Low’ sumac, my new planting.” So there you go. Yeah.

Duncan: Well, that’s good to hear.

Margaret: I guess it had like you said, different colors. It had some good color. She’s been pleased with it.

Duncan: The fruit of it, the red fuzzy fruit that it produces late in the season, is again, food for robins, goldfinches, chickadees. That late fall, early winter, or when birds are looking for something nutritious. I think it’s a great plant. I really do. I love it.

Margaret: As we’ve just inadvertently said, groundcover can be many things that have different statures. It’s not just flat to the ground, herbaceous. But I do find that a lot of us with gardens, especially… Mine’s an older garden, I have a lot of groups of shrubs and so forth, a lot of area that I used to mow and I want to stop mowing maybe. Sometimes the herbaceous stuff is good, especially under groups of shrubs. I feel like we all have spaces where we could use that rather than dare I say, the heinous bagged wood-chip bark mulch. [Laughter.]

Duncan: Are we going to talk about mulch today, Margaret?

Margaret: No. We’re just going to say “ick.” I’m a lover of mulch, don’t get me wrong. I believe in using a good-quality mulch as a passive soil amendment and improvement, a material that breaks down.

Duncan: Right. Yeah. I agree with you.

There’s a lot of different opportunities to use groundcovers on any kind of scale. That was one of the realizations I came to recently, when I was teaching the class, and a woman from New Jersey said that she had combined three or four groundcovers at the entrance of her house in an area that was formerly just devoted to mulch, as you just said. She basically combined, I think it was Tiarella [above] and some Heuchera and a third groundcover, just there at the entrance to her house.

And it wasn’t an extensive area. I think another thing that people think about with groundcover is that it has to cover acres. When I think of the groundcovers that we’re suggesting, the native plants here at Mt. Cuba Center, the amount of ground that they’re covering can be relatively small. As you said, beneath your shrub bed, for example, that may only be 10 feet by 6 feet. You can put a groundcover under there, like some of the tiarellas or even some of the sedges, and it’s covering the ground. It really is fulfilling a role, even though it’s not what people may think of in terms of a vast expanse of something.

Margaret: Which really comes from our connection and association with lawn as groundcover, because that’s big. The garden designer I admire a lot called Claudia West of Phyto Design, she famously has said that “plants are the mulch”—in another anti-bagged-mulch statement [laughter]. Plants are the mulch and I think that’s true. I call what you were just talking about, that your student from New Jersey did, where you don’t have to make one mass of a monochrome of one plant the way that the ubiquitous pachysandra, vinca, Hedera helix or English ivy… You don’t have to do that kind of giant stretch of it. I think of when you combine a few in a smaller or larger area—I think of it as “making mosaics.” Do you know what I mean? It’s like living mosaics. I love that.

Duncan: When I was talking about it in my groundcovers class, I use the term like a tapestry of living plants. And living mulch is exactly what we should think of groundcovers as. Taking the place of the mulch that people traditionally see in a garden.

When you mentioned the idea of combining a couple of different plants, today as I came into work, there’s plantain-leaf sedge out here in the garden. It’s also called seersucker sedge because it has a great puckered leaf surface, really neat. And there are many, many sedges out there that can be used for groundcovers or other ornamental uses. Plantain-leaf sedge out in the garden is green today. It’s not looking super June green, but it’s still green, and providing some visual interests out there in the way that we’ve used it. It’s one of the groundcovers that I recommend people use, because it can take dry to moist soil and part sun to shade. I’m sure Margaret, you have people emailing you constantly, asking “What can I grow in the shade?”

Margaret: Have you been reading my mailbox? Are you a hacker? [Laughter.]

Duncan: Yeah, really. People say, “What can I grow in the shade? What can I grow in the shade?” There are a number of sedges. The plantain-leaf one I like because of its texture. And I was recently looking over some of the photos that we have here at Mt. Cuba, and there’s one in which we have plantain-leaved sedge coupled with Tiarella, another spring groundcover with pretty little dainty flowers early on in the season. The combination of the two textures is quite nice. The linear texture of plantain-leaf sedge, and the more heart-shaped or three-lobed shape of the Tiarella, the foamflower, beneath that. A great example of saying, O.K., rather than, as you said earlier, having a vast expanse of plant X, why not put two or three together that suit the same kind of conditions. Shade: Tiarella. Shade: sedge. [Above, C. plantaginea and Tiarella together at Mt. Cuba.]

Margaret: Right. The sedges, the Carex—I have been noticing in areas of my property where I’ve stopped mowing out to the perimeter, out to the fence line, and I’ve sort of let the areas go a little wilder gradually. I’m doing these multi-year experiments to see what comes up and how that could be managed instead for more diversity and so forth. I’ve noticed that some Carex, some sedges, have appeared. I think the one that’s appeared the most is finer-textured than the one you just mentioned, the plantaginea, is that right, Carex plantaginea? is that what you just were talking about?

Duncan: Yeah, Carex plantaginea.

Margaret: I think the pensylvanica maybe, the Pennsylvania sedge, I think that may be what I’m seeing a lot of; it’s finer-textured.

Duncan: It is. When we were talking about lawn, people think of that very fine, narrow leaved grass that’s out there being mowed and Carex pensylvanica has that same kind of thin, narrow foliage that comes up from a central crown, if you wish—I guess crown is the only word I can use. And it grows up and then the tall, thin foliage cascades over on itself. It gets about a foot tall. When you plant them as a series of plants together, it gives you a very fine-textured and sweet look in the landscape, a very relaxed and informal look.

It looks like grass, but people shouldn’t be mowing it. I think that the beauty of the plant is in the fact that its structure is so visually attractive. People have planted it very closely together to give the impression of lawn, if you wish. It will do that. It will grow as a uniform mass, but people then have to remember to leave it looking as it does in its sort of lax form until late winter, when they can mow it down and then it comes back and it looks great. It’s a beautiful plant. Maybe that’s what you have coming in, but it does give the impression of grass.

Margaret: Yes. But it’s very beautiful, because as you said, it’s a little arching and it’s not as stiff as mown grass. Very beautiful. We should say when we were talking, I forgot to sort of disclaim this, but obviously you’re in Delaware, I’m in New York State. The cast of characters—though in our case, some do overlap, and there are some native plants that would be good groundcovers that are even wider-spread around the country. But each person in each area who’s listening, we’re talking inspiration here, but we can’t tell you the plants for every place of everyone listening.

Duncan: No, no.

Margaret: People have to go to a place like the website or educational courses at somewhere like Mt. Cuba, or their local wildflower center or native plant society or regional native plants society. There may even be an Audubon center or something like that in your area. One thing I’ve been doing is, the flora, F-L-O-R-A—as in a survey of all the plants in an area. If you put into Google search, “the flora of,” and say, “Eastern Pennsylvania” or “XYZ County,” you may come up with someone, some scientists, some non-profit, whatever, or some academic institution who’s actually been studying that.

You may even be able to get nitty-gritty down to your local area and get some inspiration. It’s kind of fascinating and it’s kind of fun to do this sleuth thing, to find out what your native groundcovers are. I love that part, but I guess I’m a geek. [Some suggested resources for such a hunt are in a box lower down the page.]

Duncan: You’re right and people are listening in from God knows where here. That is one of the primary ways that they can find out about what it is in their specific region that is going to satisfy their groundcover needs. I echo your sentiments.

Get out there on the internet and find the flora of your region, and see what there is available. The plants that I generally talk about here at Mt. Cuba range from Zones 4ish down to Zone 8ish. Zones 4 to 8 in general, sometimes 9, a little South of us here into the Carolinas or Virginia. The plants that I generally talk about in my class are within that kind of a spectrum of hardiness. [Above, a fancy-leaf selection of Allegheny pachysandra called ‘Silver Streak.’]

Margaret: I want to just zoom through some more plants. I’m taking out Lamiastrum, horrible plant, I wish I’d never planted it. Oh my goodness. I’m taking out miles of it.

Duncan: [Laughter.] Good luck.

Margaret: I’m usually repeating three digs or three uprootings in each area to clear, and even then I get more re-sprouts. It’s taking me a year or something to prep, and then I’m starting to add some little baby plants, which I asked my nursery for—they buy them in normally and pot them up and sell them as big plants.

But I said, “Look, charge me whatever you want, but I don’t need them potted it up. I need trays of the little plants and they marked them up and sold them to me. They bought them wholesale and I got like Christmas fern and a couple of Dryopteris whose names I forget. Anyway, I looked up some ferns that were around my area and I’ve been plugging those in gradually to replace Lamiastrum. Ferns are a whole separate topic.

Maybe instead, I’d love to ask you about heucheras. You mentioned them before briefly. Even though the ones that do the best for me as groundcovers, aren’t native to here at all—it’s the Heuchera villosa types. Can you explain to me a little bit about which Heuchera make a good groundcover?

Duncan: Well Heuchera villosa is actually one of the ones that we recommend down here at Mt. Cuba Center, because it does it cover a large space of ground. It will spread to about 1-½ even 2 feet. In foliage it’ll get up to about a foot. And then in flower, it’ll get up to 2 feet. The cultivar ‘Autumn Bride’ of hairy alumroot is one that we use here on site. [Above, the plant during Trial Garden tests of the genus Heuchera at Mt. Cuba.]

It really is for us a relatively no-fail Heuchera. It’s hardy from Zones 4ish to 8, and it is a part-sun to part-shade plant. I’ve noticed it here where it’s in a sunnier location, the heucheras in general, in full-sun locations, aren’t at their best. I think that they’re really the kind of plant that does far better in a partial shade environment where the soil can remain a little bit more moist.

I think Heuchera in general is a woodland plant, and it grows in organic-y woodland soils with ample moisture around the roots. ‘Autumn Bride’ is one that we use because it blooms late in the season. People think of Heuchera as blooming early in the season, many of them do, but this is one that will come on in flower as I said, up to 2 feet, white flowers late in the season. That’s one we are using.

The other Heucheras that are available to people, and there’s a whole host of them ranging in color from green to silver to purple, etc.

When people plant them as groundcovers, I think they have to realize that they don’t spread in the sense of being rhizomatous. They basically remain in a clump that gets bigger and bigger every year. If I was to use a variety of Heuchera, I think that I would use them in a smaller application, not a huge swath of them necessarily, although ‘Autumn Bride’ is taking up a 15-by-6-foot area in one of our gardens. And just be careful to make sure that you’re paying attention to the moisture level in the soil. But there are lots of options there for people to choose from.

Margaret: Another thing I wanted to ask you about: native pachysandra—very different from the Japanese pachysandra. It’s not native where I garden, but I’ve had it for many years in my garden. It’s kind of a variegated leaf.

Duncan: Yeah. It doesn’t look at all like the Japanese pachysandra, you’re quite right. It doesn’t have that glossy dark green foliage. It has more of a silvery-gray to muted foliage. It’s very short to the ground like it’s Asian counterpart, 6 to 8 inches in height. It blooms early, early in the spring with very short little cylindrical flower stocks that are, if you’re way down there, you can get your nose in, you can smell them. They’re fragrant.

But the thing about Allegheny pachysandra, Pachysandra procumbens [above, leafing out in spring], is that it is very, very slow to spread. If you are getting it, you have to be patient with it because you’re going to spend a fair amount of money on a plant. If you’ve got three or four of them to put in an area where they will thrive—which is again part shade with a degree of moisture—they will spread over time, and again, it will be relatively slow.

Very beautiful plants and really a softer look than the Japanese pachysandra. We’ve planted it here in combination with one of our Christmas ferns. So we have Christmas ferns dotted in amongst it. In one part of the garden, we’ve also put in some of the variegated green-and-silver-leafed Heuchera. They all require the same kinds of conditions: cool, moist, semi-shade, and they make a nice textural composition.

Margaret: In the last minute or so, maybe one more shrub that you want to say that you’ve successfully used. You shared one for my back hillside [laughter] when I need to replace what’s there. Any other shrubs that you’re excited about or that you guys use as groundcover at Mt. Cuba?

Duncan: Yeah. We use drooping leucothoe, Leucothoe fontanesiana [above]. It’s a great plant for the shade, cool shade. It’s native to regions where it is on hillsides and banks and associated with waterways south of us here. It’s hardy from zones 5 to 9, but I saw a huge patch of it at Wellesley College years ago on a hillside—again, a hillside—in shade. Once it’s established, it’ll really do quite well in that kind of environment. It’s evergreen, it’s related to blueberries, it’s ericaceous, and so the white flowers in the spring are very, very attractive. So evergreen large shrub, 3 to 4 feet high by 3 to 4 feet spread again, in those cool shady environments. Kind of the opposite of the ‘Gro-Low’ sumac. Hot sun for sumac, and cool shade for drooping leucothoe. Do not plant drooping leucothoe in the sun. Please do not.

Margaret: [Laughter.] Don’t torture it. Just in closing, I want to say there are, about six classes now among the offerings? There’s weeds, there’s groundcovers…

Duncan: Plants for container gardening, butterfly garden. There’s one on the milkweeds for monarchs. We’re going to be changing some of them out in February-March. We’ll have a few new ones coming on board, one of which will be native evergreens. People can get wind of what’s out there in terms of evergreens for their property from short little groundcover evergreens, all the way up to tall pine trees.

Margaret: Oh, interesting. I was going to ask you about and we don’t even have time, but I was going to ask you about the Eastern Red Cedar, Juniperus virginiana, there’s these sort of gray-leafed cultivars. ‘Grey Owl,’ I think. And they’re not too short. They’re maybe knee-high or so, and those are looking very interesting to me for larger expanses. So many ideas to talk about. [Laughter.]

Duncan: Right. Exactly. Yeah. The ‘Grey Owl’ will do really well in sunny locations. That’s one for another conversation.

Margaret: Well good. Well, Duncan, we’re going to have a giveaway, as I said. I’m so glad to speak to you again and let’s keep in touch. I always learn so much when I talk to people from Mt. Cuba. So thank you.

Duncan: You’re quite welcome. Nice talking with you.

enter to win a mt. cuba virtual course ticket

I’LL BUY on-demand classes of their choice for two lucky readers, from among Mt. Cuba’s six current offerings: summer weeds, natives for containers, milkweed and monarchs, butterfly gardens, native groundcovers, and one on soil. All you have to do to enter is answer this question in the comments box farther down the page:

Are you facing down any thuggish groundcovers–or growing any native ones to recommend? (Tell is where you garden.)

No answer, or feeling shy? Just say something like “count me in” and I will, but a reply is even better. I’ll draw a random winner after entries close at midnight Tuesday, December 29, 2020. Good luck to all.

 

more from mt. cuba

(Photos from Mt. Cuba Center except where noted.)

which native plants match your site? some references

YOU WANT TO GET as local as you can in matching native plants to your place, as Duncan Himmelman and I talked about in the transcript above. Often simply a web search for “flora of —” (insert your state or even county and state) may yield great results. Virtually every state has a state flora, and a state native plant society (I’ve included where to browse a list of those), or both. I am starting with my local examples–specifically with New York, since I live there–and then adjacent regional ones and on up to national (and even Canadian). Like we said: some sleuthing required (but worth it)!

  • New York Flora Atlas: search for a list of plants recorded for a particular NY county. (The New Jersey one, as another example, is here.) You can then restrict that list to native plants or non-native plants. For other states try starting at…
  • a list of state wildflower societies, from American Horticultural Society. The state societies will probably provide a link to the state flora database on their websites. There are also wildflower societies and other nonprofits (including Mt. Cuba) to explore, like…
  • Go Botany (New England regional), from the New England Wild Flower Society
  • Native Plant Finder from National Wildlife Federation, University of Delaware and U.S. Forest Service (searchable by Zip Code; launched 2018).
  • Atlas of the Flora of New England by Ray Angelo and David Boufford of Harvard. Doesn’t specify native, but does mention if the species’ origin from other countries/continents is known.
  • Calflora (California), of native and non-native plants, including the ability to search by plant name or by location–so for instance to explore the plants of a park, or other area you might be visiting.
  • Native Plant Information Network (National, Ladybird Johnson Wildflower Garden): Get an alphabetized list of all the plants (8,593 species) on which they have data, then narrow your search to a particular state.
  • Vascan, a searchable online atlas of the vascular plants of Canada, will show a map along with nativity status, and allow you to create a province-based checklist.
  • The Biota of North America Program (BONAP) allows you to map species to county, for each state, and search on a particular species and understand what its distribution is, native and non-native. Coming: tools that allow you to create a checklist for your own county.
  • The USDA Plant database, including maps and the ability to search by state, for example.
  • You can also use Missouri Botanical Garden’s Plant Finder, which specifies native range in the results of each plant description (but doesn’t include maps).
  • NatureServe Explorer: Searchable database on 70,000 plant, animal, and fungi species, updated in 2016.

prefer the podcast version of the show?

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 December 21, 2020 show using the player near the top of this transcript. You can subscribe to all future editions on
iTunes/Apple Podcasts or
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podcasts here).

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