dreaded norway maples, good groundcovers (including sedges): shade-garden q&a with ken druse

TO MARK A YEAR of monthly Q&A podcasts together, Ken Druse and I themed our latest conversation to a topic that many listeners ask about in one way or another a lot of the time: gardening in the shade, a particular expertise of Ken’s, who has written two books on the subject.

This is the 12th of our monthly Urgent Garden Question Q&A shows, and we thank you for your support—and for your questions most of all. You can keep them coming any time in comments or by email, using the contact form, or at Facebook.

Read along as you listen to the Jan. 1, 2018 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

Plus: Enter to win a copy of Ken’s newer shade book, “The New Shade Garden,” using the comment box at the very bottom of the page.

ken lecturing jan. 13 in the berkshires, plus talks in jersey and michigan, too

KEN DRUSE is the featured speaker at the Berkshire Botanical Garden’s annual winter lecture, Saturday Jan. 13 at 2 PM at Lenox (MA) Memorial High School. I can’t wait (it’s near me; I’m going). His topic, from his latest book: “The New Shade Garden: Creating a Lush Oasis in the Age of Climate Change.” We hope to see you there: ticket information is at this link. Ken’s other upcoming dates, from New Jersey to Michigan, are listed here.

shade-garden q&a with ken druse




Q. As a backdrop for people, you’ve done two shade-gardening books, “The Natural Shade Garden” in 1907, or what year?

A. [Laughter.] That’s right.

Q. Yes, that’s right.

A. 20th century.

Q. No, see I can’t remember the year of “The Natural Shade Garden,” the first one.

A. Is it like ’92? [Laughter.]

Q. Yes, something like that. Then “The New Shade Garden,” which was what, just a year or so ago?

A. Yes, and that’s a totally different book.

Q. Yes, which really takes into account how much has changed on a more global scale, climate-wise and the reality of how we’re gardening today. Just quickly, what got you started on this as sort of a specialty? Did you grow up in a forest or something?

A. No. People think that I’m an expert, and I guess after I finish writing a book, I kind of am an expert; but I think of myself as a journalist, because I usually want to know about a subject, and then I discover a lot about it and write about it. I don’t always know about it beforehand. But I had a house in Brooklyn, which I’ve sold subsequently, and it was in a shady backyard so I needed to know more about shade, and that’s how that happened.

Q. O.K., so necessity was the mother again of invention.

A. Right. I thought laziness was the mother of invention. [Laughter.]

Q. As I said in the introduction, there are always questions about dry shade, and especially the trickiest trees to grow things under, conifers being one.

A. Right.

planting under a norway maple

Q. And we can talk about that later maybe, but a couple of questions this week were about the dreaded Norway Maple tree, a non-native, invasive species of maple. It has proven invasive in many areas, especially the East. It was brought over in like the 1700s from Europe, and it kind of backfired eventually, as it became a popular street tree and yard tree. [Acer platanoides foliage, above, by Martin Bobka from Wikimedia.]

We have a couple questions today, as I said, one from another Margaret, a Margaret on Facebook, and one from Valerie, in an email. And basically one of them just says:

“What to plant under the dreaded Norway Maple?” And Valerie gives us some ideas about some of the things she’s tried: hostas, sedums, a smokebush she says that should be twice the size by now.

“Everything is sort of stunted if it grows at all” is what she’s saying, and she’s really almost at the point, she says, where she’s ready to just plant thugs—herbaceous thugs, like things that are practically invasive or invasive themselves to compete with it. Obviously, we don’t want to recommend that, so Norway Maple: is this something that comes up a lot when you lecture and so forth?

A. Yes it does, and they’re terrible plants and had been banned in some states, and in New York City they can’t plant them anymore. People ask me about that a lot, and I don’t know where this person lives. Did she mention that?

Q. She’s in Zone 6, I think. Well, there’s two different people and they’re both in Zone 6, but in different spots. But Eastern.

A. Well, when people ask me about that, because the roots are so shallow of the Norway Maple, and the shade that it produces—they’re almost like overlapping black shingles, the leaves. The shade is so dense, the soil is so dry, and as you know, Norway Maple has an allelopathic … is that the right word?

Q. Yes. Sort of exudes a chemical that would …

A. …inhibit the growth of other plants.

Q. Well you know, the interesting thing about that though is that in the papers lately and the journals there are some scientists who say yea and some who say nay on that. They’re saying, “the studies don’t really bear it out,” but yes, it seems allelopathic in the sense that it’s this wasteland under there, “but we’re thinking maybe not.” Maybe it’s just what you just said, the dense shade and these surface roots. Then of course it’s a rampant producer of seeds, right?

A. Oh, terrible.

Q. Yes. So those themselves are another form of competition. The allelopathic thing I think is under dispute, but who knows?

A. Well, and also they drop their leaves later than the native trees. You can drive on Route 95 in Connecticut [laughter] and you can see all these yellow-leafed maple trees, and long gone are the sugar maples. That’s another bad thing that happens.

What I say to people in this kind of situation, and what I’ve done, especially under maples, is plant containers. You get containers, you elevate them on a couple of bricks so they’re not directly on the roots of the trees, and there are a lot of things that you can plant.

I usually choose plants from a zone that’s one zone colder than the one that I’m in [for containers], so if you have hostas that are cold-tolerant, although they need a little more light, so you really need some shade-tolerant plants, but they can be annuals if you can find them, perennials, I don’t think there’s a whole lot of woody plants that are going to like that too much, but you can try it. I would say planting containers. Just think about an elevated garden in that terrible situation.

Q. So staging pots. And these have to be large containers, because if you’re in a cold winter zone, and they have to be weatherproof…

A. Right. [Photo above by Ken Druse.]

Q. …if they’re going to stay out. You’re saying staging like a vignette or a number of vignettes sort of in that area, like you might on a patio or something.

A. If you want to make a whole garden, but maybe start by a half whiskey barrel or some big plastic tubs.

Q. Right. I keep wondering if, going back to sort of what Valerie and her question, she was saying she’s ready to go for the invasives, and I think I read, and I can’t really even remember where, I read one gardener who was experimenting with this. His thinking was, “Well, O.K.. If this is an invasive tree from Europe…” Well it wasn’t invasive in Europe, but when it came here it became invasive. What grew around it successfully in the old country?” And kind of looking that up.

It was hard for him to be exactly precise, but I remember that of course it turned out [laughter], as Valerie was inclined to do, it was like … oh, what’s the worst goutweed and lamium and stuff that once you’ve got it, forget about it; you’re never getting rid of it. It was stuff that has also become … herbaceous stuff that in some cases has become invasive here. So we don’t want to go that way, just to be clear.

But I keep wondering: I live surrounded by a state park. A lot of woodland. Big trees, not Norways thankfully. But there’s a lot of that old trees with big roots, surface roots, and a lot of shade and dry and so forth, and I see that certain plants seem to just tough it out there, like certain asters, for instance, if you’re in the East.

A. Oh yes, that’s true.

Q. Like the big leaf aster—is that macrophyllus I think? And divaricata, the white wood aster. Do you know what I mean? They seem to sometimes just make their way in tough spots, and I wondered if you watered—if you put in small plants and watered carefully as they were getting acclimated, would they maybe take hold like they seem to do with the edge. I’m just extrapolating from the edge of my woods, you know?

A. I think it’s something very important that you said, which was “watering.” A lot of people want to grow native plants, and they don’t do that well, and they think, “They’re native plants; they should get along by themselves, because they do in nature.”  But really you have to establish them. In the beginning, you have to really water them.

When I started my woodland garden, which is under a white pine, a moisture-sucking white pine, I covered about a quarter of the soil—

Q. [Laughter.] Is that a special species of white pine, moisture-sucking?

A. Moisture-sucking white pine. So I added some compost to about one-quarter of the area under the tree and planted in that, but really watered that first year. Things to try maybe: wild ginger, Asarum canadense. Uvularia, Polygonatum, maybe Maianthemum, the mayflower would probably do it. You know Maianthemum, the mayflower? But maybe even false Solomon’s seal. I know that Christmas fern would do O.K., but it would take a long time to look like anything. They’re very slow. [Above, Polygonatum by Ken Druse.]

Q. Right, so you’re mentioning some Eastern natives—and they’re in various areas native. But you’re mentioning things that would, again, like my wondering about those two asters that I see doing their thing at the edge of the woods in tough spots, that would be competing in their native environment. They would be competing frequently with big trees.

A. Or getting along with. [Laughter.]

Q. Getting along with. O.K., sorry. Didn’t mean to sound like it was confrontational. I was thinking about the American ginger, Asarum canadense also. That seems to me to be a real doer. It’s like a robust kind of groundcover. It’s herbaceous. It’s not going to give you evergreen cover, but … Did you say Virginia creeper, Parthenocissus quinquefolia? [Photo above of A. canadense by Ken Druse.]

A. No, but …

Q. To me, that would go anywhere. It seems like it-

A. Yes, but it’ll go up the tree and … I don’t know.

Q. But you know what?

A. That kind of gets out of control.

Q. Yes, but it’s a super high-value wildlife plant.

A. That’s true. Well, it’s funny, because I was thinking “poison ivy,” but we don’t want to get into that or talk about—

Q. Right.

A. It’s a super high-value wildlife plant that would probably do O.K..

Q. Well, and with the Parthenocissus, with the Virginia Creeper, and then there is one, I think it’s Parthenocissus inserta, the Western one [also in some of the Eastern U.S.]. It used to be all one species throughout the whole country, and now it’s been subdivided or some crazy thing. But it’s super high-value; it has gorgeous fall color; it has fruit. So actually, again, it’s not like either of these people is loving this tree. Even if it did climb up the tree, birds will nest in it and that’d be O.K. Do you know what I mean? If all else fails…

A. Would you think it’s O.K. to grow Boston ivy [P. tricuspidata]? Do you think that’s acceptable to grow a non-native Parthenocissus?

Q. Ah, I don’t know. I guess if all else fails. But in these types of woodsy edge kind of environments, I always like to think: well maybe we should put some of the natives. Because there’s so much action going on with our wildlife, our birds and our insects at that sort of “edge” of the habitat, that’s sort of where lower vegetation transitions to bigger. There’s so much life usually. Anyhow.

A. You know, you’re talking about plants that can compete and maybe even “thugs.” Under a spruce tree here, I planted ostrich fern, which can really take over, but it’s completely naturalized. A dangerous word.

It’s a native plant but it’s like a 3-foot tall green lawn, and it’s just gorgeous under the spruce. It goes right up to the trunk of the spruce and it’s very beautiful. It’s in a place where I can’t really grow anything else and where I don’t need to get—and I sort of keep the edge clear. Every year I’ll pull up some and either transplant them or throw them out. Or mow them. I don’t mow them, but if I had a lawn there…

shade groundcover on a sloping site

Q. Linda on Facebook asked about sugar maples. She has a sugar maple—which is not an alien maple species—and she’d be interested in the best groundcover plant to try on a steep piece of hillside.

I get a lot of questions about steep spots. And this one is shaded by the sugar maple. The grass is dead, she says. Maybe there’s some moss around, but she’s down to kind of bare dirt and it’s in this kind of wild part of her yard, so she’s most interested in natives. Do you have some sort of favorites for a steep spot like that, groundcover-y kind of natives that she’d want to use?

A. You know, your description of it sounds pretty. [Laughter.] More moss and rocks and maybe some snowdrops and leave it at that, but I know that’s not the question.

Q. Those snowdrops are not natives. But something to hold the steep site.

A. I’d say to try Pachysandra procumbens. [Photo above of leaf detail and bloom.]

Q. The native pachysandra would be nice, yes.

A. Native pachysandra. And again, the Polygonatums, and they’re deciduous, but that’s something. And I think that Christmas fern even though it takes a while; maybe you can buy a larger plant. Some other ferns too, but Christmas fern’s great, because it is sort of evergreen, it  looks O.K. until February, and then it pushes the new growth in the spring anyway. But that’s a good drought-tolerant, tough plant once established, and I think that would look pretty good under a sugar maple.

sedges for dry shade

Q. Jai on Facebook is asking about dry shade and wants to know about have we grown any Carex, the genus Carex, the sedges. Grassy looking but not grasses. She is wondering natives, non-natives? Are they invasive? How to get started? You probably have grown more of them. I have a lot of native ones around the edge of my property. Any thoughts there? I have some thoughts, but do you have any thoughts

A. I love the Carex, and it’s sort of like … You know in the movie “The Graduate” when they said “One word: plastics”? Well, I have one word for you: sedges. Because there are so many new ones coming out, and they’re so beautiful. Now, I’ve heard that Carex flacca … I think that’s what it is … can be invasive, and I’ve heard that C. kobomugi, which is a Japanese one, can be invasive too. But I have a Carex flacca … maybe you’ve seen it … called “Blue Zinger.” It’s about, I don’t know, 8 inches across. Five years it’s 8 inches across, so I don’t know how this thing would become invasive. It doesn’t really move.

Q. Right, so some do, some don’t. Some spread more than others, you’re saying.

A. Well, Carex pensylvanica, which is a native for us, it sort of spreads gently like a grass might. It’s certainly not difficult to control, although you wouldn’t want to.

Q. Right. It’s lovely.

A. It’s like if you have an area where you would like something that waves in the breeze, and it’s almost like a lawn and you don’t want to have to even mow it, it’s beautiful and green, Carex pensylvanica is great. But I think there’s a lot of Carex. There’s Carex appalachica. I don’t know if you’ve seen it. It looks like a little dwarf Cousin It, a little mophead. And I have some of those planted under a maple and also at the base of an ash tree—we still have ash trees here—and they’re just doing fine. They really don’t move that much. I should probably divide them if they want to get more. But they’re just swell.

Q. The suggestion I would have is that some of the wholesalers that specialize in either natives or in grasses and sedges—there are two of them that I love to look at their lists, and they actually note which ones are native and which ones aren’t.

A. North Creek Nurseries.

Q. North Creek Nurseries is one, and you can’t buy from these—these are wholesalers, but they have great lists. And then Hoffman Nursery as well, and they even have like a whole PDF that you can download a comparison chart of all the natives and non-natives and their growth habits and so forth. I think that looking at those kinds of big sellers of them and then finding out what local nurseries in your area they sell to, if they do, but sort of getting some clues from lists like that might be a way to begin.

A. And you’ll see pictures of everything, and North Creek also has where you can click on retail sources.

Q. That’s what I mean. Exactly.

A. And it shows you where you can get them.

are there any vegetables for shade?

Q. So vegetables:  Rosa on Facebook wants to know:

“Are there any vegetables and herbs that will grow in the full shade or in part shade” and what type of light?

And Marty, also on Facebook, was thinking about “growing broccoli on the northwest side of the garage” and worrying about this:

“In the shade, are slugs going to have a better chance of causing havoc?”

So a couple of vegetable-garden questions.

I always think, you know, if you have less than full sun, you don’t want to really struggle with eggplants and tomatoes and peppers and so forth, the things that are trying to make a big fruit. But you want to do more of your sort of leafy and root things like your leafy greens, kale and chard, and salads and spinach. Then things that are, again, roots like beets and radishes. Rhubarb I don’t think needs a ton of light. I’ve grown parsley in the shade of other things, but not the dark. I don’t think stuff is going to grow in the dark.

A. No. Maybe mushrooms.

Q. Yes. Well, one could do that indeed. One could do that.

A. Maybe. I don’t even know that. You asked those questions and the answers are “No, no, no, maybe and no.”

Q. Oh, thank you very much. I’ll just check that off. [Laughter.] But seriously, morning sun is generally less intense than afternoon sun, and how many hours and so forth, but if you don’t have six hours of full sun, I wouldn’t do the sort of heat-loving, the real intense…again, the ones that are trying to make the big fruits, like the tomatoes and the eggplants and the peppers and so forth.

A. Well, it’s funny that you’re saying that, because in six hours of sun or of even a little bit less, I have grown winter squash. ‘Butternut’ squash. But you get three fruits, you could go to the store and buy three fruits.

Q. Right, and I have a squash patch that’s maybe 10 x 10, and I got 35 giant ‘Butternut’ out of it. Do you know, because it was in the sun. It’s in full sun.

A. Right.

Q. And I had four hills or three hills, and I got 100-something pounds of ‘Butternut’ for the whole year.

A. You know, I do grow Fragaria vesca [above photo by Ken Druse], the Alpine strawberries. I’ve been growing them in pots just because it’s easy and they’re hardy, but I grow those in some shade, and that’s something you can’t get at the market. Of course, they yield like a tablespoon full of strawberries.

Q. [Laughter.] I know, it’s funny.

A. But that’s enough for cereal though. And they’re pretty.

plants we’re getting rid of

Q. I just want to ask a question on my own, Ken. Are there shade plants that when you did that first book that we were talking about at the beginning of the program, that you coveted and you cultivated that you’re now sort of excommunicating from your garden? Because I know that is one of the big changes in my garden, is that some of my earliest shade plants that were sort of connoisseur or gorgeous then, are now thugs. I know them to be thugs. A lot has changed in that time. Is there anything you’re getting rid of?

A. Well, you’re putting me on the spot.

Q. I was just curious if there was anything that you wish you hadn’t planted or … Look. Houttuynia, the chameleon plant … [photo above]

A. I didn’t plant it. [Laughter.]

Q. It’s the worst weed ever, and everyone wanted it. It was beautiful looking then, right? It’s hard to get rid of. I mentioned them before, the yellow archangels or whatever they’re called. Lamium galeobdolon?

A. Lamiastrum.

Q. Lamiastrum galeobdolon, right. You know, terrible thug. I wish I hadn’t planted those. I was just curious if you had any. Last two seconds. Just tell me. [Laughter.]

A. I can’t think of anything offhand, and it’s funny that you’re saying this, because we really were sticking with native plants, but for dry shade and shade-tolerant and even blooming: hellebores.

Q. True.

A. And we didn’t mention it, but it’s funny that you’re asking me about regrets. I’m O.K. so far, but when I first got Helleborus, and they were so expensive. I would work so hard to grow them from seed, and it was a lot of work. You had to do warm and cold, and cold and warm and wet, and then after about three or four years I was looking under the leaves, and there’s babies everywhere.

Q. Exactly. Very productive.

A. So that’s actually maybe a problem for the future. It breaks your heart to pull ’em out and throw ’em away, but I’ve been pulling them out and throwing them away, and I think if I wasn’t careful, that could be a problem.

more about shade gardening

  • Ken’s list of shade recommended shade plants
  • My most-used groundcovers: 10 I use,  and a few toughies for dry shade
  • Browse past A Way to Garden shade-garden stories

enter to win ‘the new shade garden’

I’LL BUY A COPY of “The New Shade Garden” by Ken Druse for one lucky reader. All you have to do to enter is comment in the box at the very bottom of the page, answering this two-part question:

Is there a shade plant you cherish most, and also one you wish you’d never planted (like my Houttuynia and Lamiastrum)?

(My most cherished might be the beautiful native blue cohosh, Caulophyllum thalictroides–not rare, but lovely.)

No answer, or feeling shy? Just say “count me in” or something like that, and I will, but an answer is even better. A random winner will be selected after entries close at midnight Tuesday, January 8, 2018. Good luck to all; US and Canada only.

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 seventh year in March 2016. 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 Jan. 1, 2018 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

(Disclosure: Purchases from Amazon affiliate links yield a small commission.)

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