gravel gardens, with jeff epping of olbrich botanical gardens

WE’RE GOING to do some gravel gardening—not merely applying a thin mulch-like topdressing of gravel to a garden bed, but planting right into a deliberate foundation of 4 or 5 inches of gravel. I talked about it with Jeff Epping, director of horticulture at Olbrich Botanical Gardens in Madison, Wisc., where he created his first gravel garden in 2009. We’ll learn what makes gravel gardens so appealing, and how to create one, too.

That first gravel garden at Olbrich Botanical Gardens that Jeff Epping and his team created wasn’t the last. There have been three more since, and gravel gardens created elsewhere for clients. Jeff, who lectures regularly to garden audiences around the country about his passion for gravel gardens, even transformed the front yard of his home to one in 2018, and he explained to me why and how.

Read along as you listen to the May 9, 2022 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).

gravel gardening, with jeff epping

Margaret Roach: Hi, Jeff, how is spring unfolding in beautiful Madison—which is the land of many gardens, as I remember having been there years ago.

Jeff Epping: Hello, Margaret, it’s great to be with you. It’s a little chilly as it’s been of late [laughter]. Sun shining for a change.

Margaret: Yay.

Jeff: So we’re happy about that. And all things are moving forward.

Margaret: So when you and I did a “New York Times” garden column earlier this year together about gravel gardens, what really made me laugh was you confessed early on in our conversations that you really didn’t like the term “gravel garden, anyhow, even though in this country you’re a leading proponent of planting into deep gravel. You don’t like the term because… and just tell us a little bit? [Laughter.]

Jeff: You bet. I don’t like it because it doesn’t conjure up beautiful flowery images of what these types of gardens can be, which are as beautiful as any other type of garden. I think when people think of gravel gardens, they may think of sort of a rocky alpine garden, it’s very hard and not so showy, but that’s not true. So anyway, I still call them gravel gardens since I haven’t come up with a better name [laughter].

Margaret: Right. So it’s like rock gardens aren’t about the rocks, right?

Jeff: Right.

Margaret: Yeah, same kind of thing. So the first gravel garden I ever saw, and actually it was two of them in the same trip to England many, many, many years ago. One was the seaside garden of the late artist, Derek Jarman. And the other was the car park, as they say, for parking lot in England, the gravel car park at Beth Chatto’s nursery and garden, a famous, famous place. What inspired you?

Jeff: I must admit, it too was Beth Chatto’s dry garden, as I think they call it. I was fascinated by how beautiful it was, and that it was a former parking lot. So I took lots of photographs and asked as many questions as I could.

Then it just kind of got parked in my memory until I saw a small gravel garden that Roy Diblik, who’s a good friend of mine and just down the road at Northwind Perennial Farms here in Wisconsin, he put in a very small garden and he was inspired by Cassian Schmidt’s gravel garden in Germany, in Hermannshof. He visited with Piet Oudolf, and Cassian told him all about it. He came back and started one himself.

And upon a visit, I saw it. I was like, “Roy, what the heck is this?” So he told me about it and I said, “Well, we’re going to have to do one of those at Olbrich.” And so we did, about a year later, and I actually had Roy involved in it a little bit because I wanted him to have a part of it. And so from that time, it just took off. So 2010, ‘12, ‘14, ‘16, all the gravel gardens went in at Olbrich and then mine at home in ’18.

And I created a very large garden with the Epic Systems staff out west of Madison, which is 3 acres in size. And it’s actually a rooftop garden. It’s over an underground parking structure that can hold thousands of cars. So it made perfect sense to put in a very drought-tolerant garden.

Margaret: Right. Well, to that point I’ve read… And Beth Chatto, she was a great garden writer as well and she even wrote a book in, I think 2000, the first edition of it came out, about gravel gardens and so forth. And so her garden, that former car park is even older than that. I’ve read that it has never required supplemental irrigation. So is this a water-wise approach? And what else does sort of gravel gardening have to recommend it? Kind of what’s the pitch when you tell people?

Jeff: Oh, absolutely. That’s a big part of it, right? Is that we need to do better, all gardeners, everybody in this country, in this world need to do better with their use of water. And when Doug Tallamy talks about our love affair in this country with bluegrass lawns and the amount of water and other nasty things that go into lawns, we just need to do better.

So I just think gravel gardens are just one more way that we can garden without the huge inputs of water and energy through fertilizers, pesticide, all those things. So the basis of the garden is, like you mentioned, 4 to 5 inches of gravel, which really is serving as a weed barrier. For a seed to land on top of that amount of gravel, which is a washed gravel, which is very important. It maintains the air space in between the particles of gravel holds very little water, no free water at all. So for a seed to penetrate, the root to penetrate that and grow and become a problem, so to speak is very, very rare.

And so it makes it very easy for us as gardeners to grow this type of garden in what I always say, it’s a system, it’s a concept of gardening. And it really needs to have very drought-tolerant plants in it. And the great thing is our native prairie plants are among the best performers in a gravel garden.

So we’re getting the great qualities of their disease resistance and such, and water-wise needs, but we’re also getting all of the wonderful animals, the insects, the birds, the mammals that eat the fruit from a lot of these plants and such. So yeah, it’s a good thing, for sure. [Above, a section of seed-filled gravel garden at Olbrich in fall.]

Margaret: Yeah. So, let’s sort of visualize, let’s pretend I have a bed, an area, and we’re not talking about if one wants to get started in this and give it a try for its water-wise qualities and its weed-thwarting qualities and so forth… We’re not talking about, you did your whole front yard, but we’re not talking about doing that as a first project. Let’s say we have a bed and right, right, like “Always starts small, Margaret.” [Laughter.]

And so what do I need to do? I don’t pile a bunch of gravel on top and stick plants. What do we do? Or maybe I do that? What do we do and how do we retain the gravel within it and so forth, just sort of describe the process?

Jeff: Right. So we can create these gardens in an open space if we want, or near a building—south side of a building, west, any side, really. Full sun is probably the biggest requirement. It’s not absolutely essential, but the palette of plants is much larger if you do it in full sun. So that’s what we do most often.

Anyway, so we want that gravel to be that depth, that 4 to 5 inches from the middle of the garden to the very edge. So what that means is we need to create some type of border that will hold the gravel in on the edges. If we just let it kind of go on its own, it’ll thin right down to an inch and down to nothing, and then of course, that’s where we’re going to get all sorts of weeds coming in.

So we typically use some type of stone. It could even be a landscape paver, a larger, bigger concrete paver, if you want, we’ve done that on a couple projects, but that needs to be at least 6 inches above the existing soil so that you have an inch of space at the top to hold the gravel in.

Now, if you’re doing it up against an existing building, or even a sidewalk—with a building, you have the foundation. So there’s your border right there-

Margaret: On one side at least, right?

Jeff: Yeah. Right, right. And then your sidewalk or driveway, if you will, there, obviously, it’s set. So on the edge and say in the first, at least 18 inches to 2 feet, you dig it down to 6 inches at the very edge and then just push that soil back farther in the bed and taper it off. And you could you could have a slight slope, 2, 3, even 5 percent slope. So that’s no problem.

I think one of the misconceptions people have is that you have to take away all of the soil, 5 inches or 6 inches deep. That’s not true. That’s just on the edges. You need to make sure you have that, but you can gently slope that. And what we’ve done with all of our gardens. We just keep the soil there.

Obviously get rid of any weedy plants, any vegetation that’s there. Get rid of any really bad guys like quackgrass or Canada thistle or something that’s going to come back to haunt you.

Margaret: Oh, I’ve never had a weed. Have you ever had a weed?

Jeff: [Laughter.] Never.

Margaret: No.

Jeff: Well, once you get that border in, then you bring the gravel in, and we use it’s about a quarter-inch, three-sixteens, quarter-inch size. Then we get a very hard gravel, something that won’t break down over time. So sandstone, limestone, typically not so good. And that can change the pH as well.

Margaret: Oh, O.K. So is this like a granite-y kind of a thing or?

Jeff: Yeah, granite, we actually, it’s a quartzite, which again is hard inner gravel. I use pea gravel, typical sort of pea gravel that’s rounded. So those things all work. And in fact, in England, of course, Beth Chatto’s garden is the first and foremost, but Hyde Hall, which is another Royal Horticultural Society garden, has made a beautiful gravel garden there atop of hill overlooking the garden. And they used much larger gravel, even up to half-inch in size. And so all sorts of different types.

But no fines in it, none of the real fine material that will become like a soil, right? Because then you have the potential for lots of reseeding, which is what we want to avoid.

Margaret: Right now to that point though, there are “gravel gardens” that encourage some reseeding, but this is a different style than what we’re talking about. In the United States, there’s a gravel garden at Chanticleer for instance, in Pennsylvania, right?

Jeff: Yes.

Margaret: Yeah. Do they have some self-seeding there? Is some of the gravel a little thinner? I’m….

Jeff: Yes, no, that’s good. That’s a very good point. And the gravel garden at Chanticleer is absolutely gorgeous. I know you…

Margaret: It’s spectacular, yeah.

Jeff: Yeah. It’s all over Instagram and it’s just beautiful. And I visited a number of times. There, yes, they are encouraging or allowing lots of receding, but of course they have a gardener there tending to it every day.

Margaret: Yes.

Jeff: And so you can do that, but if you do that style, the amount of maintenance will greatly increase.

And so I feel that the value of these gardens for the average homeowner—and to get them to do this rather than grow grass and mow and all those things—is that we are making it less maintenance-intensive than a lawn for one, and even other types of perennial borders and such. And in my home garden, most of my garden is not gravel garden, it’s just a small space. But I am always amazed at how little time I spend in it, which I love about it.

And then I just love talking about it, all my neighbors walking by and such. And when I first did it, they thought I was absolutely nuts, like many of the things I do at home. But now they’re like, “Wow, this is cool.” And I tell them about how little effort it takes to have something as beautiful as I have there, their ears perk up and, “How might I do this?” So it’s good.

Margaret: So we have this deep bed of gravel that we’ve created in the way that you’ve described, and it has this kind of curb edge all the way around so that the gravel doesn’t thin out at the edges, but stays consistently deep. And how in the world do I plant into that? So it’s a little counterintuitive to the way we usually plant. And what kind of plants? I’m assuming I don’t want to get like a big, giant multi -gallon perennial and try to wedge that into all that gravel.  How does this work? The planting?

Jeff: Yeah, no, that’s a great question. And actually planting is the fun part because after you do all the edges with the border and haul in the gravel and get it to the right depth, that’s kind of a chore. But the planting, you don’t use even any tools, you just get yourself a good pair of leather or rubber gloves, and you kind of dig like a dog and you put the plug, if you will, into that hole.

Now we typically plant 3-1/2-, 4-1/2- inch pots, quart pots, pint pots, what they’re often called. Gallons, only if we have to, because they’re deeper than we want. So there we have to like reduce the depth by peeling off some soil and such and get them to about 4 to 5 inches. But once we do get whatever it is we’re going to plant, we dig down, we see the soil below, we put the plug in, and then we just put the gravel around it.

And so the roots may touch the soil below or they may not. I often tease them in my hand, because you’re getting rid of any loose soil on the root ball. I always peel off the top inch or so of any potted plant because that’s where dormant weed seeds are hiding.

Margaret: Oh, it sure is. It sure is. Yes.

Jeff: Yeah. So once we do that and then we plug them in and boom, we push the gravel back. It’s not muddy at all. In fact, you never want to bring any of that soil below up into the gravel while you’re planting, because that will have the potential weed seeds in it.

Margaret: Right. So, and then I assume that even though this is a water-wise garden in the long run that initially, because these guys are kind of at first sitting in mostly gravel and aren’t rooted down into the underlying soil yet that we need to water carefully for a while, don’t we?

Jeff: Yeah, absolutely. And that’s always the funny part. And Roy mentioned that when he put his gravel garden in at Northwind, because people were like, “You just told us this was the drought tolerant garden, but you’re watering it every other day.”

Margaret: Right.

Jeff: Well, initially, yes. Of course, you have to give the plants a chance to root down into the soil below. And as we know, prairie plants develop very deep root systems over time, but you’ve got to get them there. And once you do, even in the second year, you’re very limited amount of water. And often during just droughty periods, extended drought, and then year three, probably nothing, unless you have some super drought. And then boom, you’re off and running, after that.

Margaret: So the way you plant these gardens, your intention and you’re talking about Prairie plants, and we’ll talk a little bit in a minute about some favorite plants of yours that have done well in these settings. But your intention is that they’re going to grow together. It’s not like we’re going to see miles of gravel in between once things grow in. And so what happens at cleanup time?

As gardeners, we’re used to a regimen of spring cleanup or fall cleanup. And I’m imagining that all that debris, again, might be the future home, if left in place, the future home for some seedlings and so forth. So what about cleanup? What’s the regimen there?

Jeff: Yeah. No, that’s, that’s a great point. And your cleanup is… And that’s something that we don’t even do much anymore. At least those of us who are trying to garden more ecologically.

We’re leaving the debris, we’re maybe mulching it a little, we’re keeping stems up for bees and other insects and such. But that is the one thing that is the most important maintenance task that you have is a very thorough cleanup in the spring of that gravel, because if that organic matter, those leaves and all that stuff, breaks down and enters the gravel, then you’re sort of starting to create a soil, right? [Above, a gravel gardern at Olbrich after spring cleanup.]

Margaret: Right.

Jeff: And then we have the right conditions for weed seeds to be able to become established. So I do leave stems up, hollow stems up to about 6 to 8 inches, but the rest of the material comes out and I just cut back everything by hand. Even in our larger gravel gardens here, we do it all by hand with pruners, because if we use some type of a string trimmer or whatever, it’s going to make more pieces that are going to be harder to remove. And you got gravel flying all over.

Margaret: Well, and I was going to say, that’s definitely a safety issue, yeah, for sure.

Jeff: Right. So I can cut it back. I just kind of tossed it on a tarp as I go. And then when I’m completely done, I wait a couple of days—because we’re doing this in early April, maybe even late March, get in there—and so there might be still snow for us underneath some of that material. So we leave it a few days, it all dries. And then I go over and lightly rake and/or use a blower. And I am not a big fan of blowers, but I have a little battery-powered one and that’s with everything here at Olbrich now, all our small equipment is battery-powered, including mowers.

And so I just use that, go through it, clean it up. And then all around my gravel garden at home I have other beds, I have perennial beds, and I just take that material and then just blow it into that and use all that material as a mulch in my typical beds. So I’m not throwing any on the curb and having it all fall down.

And as I do it, I try to be aware of… A lot of times tree leaves from my oaks and such around are in that gravel garden. So I try to be ginger with that when I take it out, because there might be cocoons of moths or butterflies or other insects in there and I’m hopefully I’m helping to preserve those.

Margaret: Right. So you’re trying to gently relocate this stuff rather than destroy this stuff.

Jeff: Exactly.

Margaret: Yeah. So, I want to talk in the last three, four minutes about just a couple or a few plants, you were mentioning Prairie plants and you’re obviously in the prairie region of the country and so forth, and Madison’s a famous place for the… I think one of the most outstanding, or one of the first prairie restorations is at the university there that we ever saw and all learned about and so forth.

And so prairie plants, what are some stars kind of that you can’t imagine a gravel garden without? Some that really have been standouts for you, that are signatures or whatever, at this point?

Jeff: Yeah. You bet. Well, I always start out any of my plantings with grasses, because there’s such of base for the garden. And so things like prairie dropseed, Sporobolus, are great. Bouteloua, or sideoats grama grass, which is a super drought-tolerant grass, little bluestem, Schizachyrium. Even big bluestem, if you have a big enough garden, if you have a bigger space and you can take that height, big bluestem or switchgrass, Panicum virgatum, those are the base grasses for the system.

And then I think probably my favorite perennial in the gravel gardens are pale purple coneflower, Echinacea pallida [above], that is truly a prairie plant and will last for years. Whereas Echinacea purpurea really isn’t a prairie plant. It’s more of a wood wind edge.

Margaret: Isn’t it funny that we all have always thought of it as like a meadow or prairie wildflower, but in fact, when you look at the range map for Echinacea purpurea, or purple coneflower, it’s not there [laughter].

Jeff: Right. Right. And we’ve tried it and it just… It’s around for a while, but it really sticks around because it reseeds a lot.

And that’s true of one of my favorite perennials that doesn’t do well in a gravel garden and that’s rattlesnake master.

Margaret: Oh, Eryngium, is that Eryngium?

Jeff: Yeah, Eryngium yuccifolium. And I was perplexed as why I couldn’t get it to stick around. And I spoke to my good friend, Neil Diboll of Prairie Nursery, and he was like, “Well, duh, Jeff, it always is in a prairie, but that’s because it seeds regularly and one individual plant does not last any length of time. And you’re not allowing that to happen.” And I said, “Oh, you’re absolutely right.” [Laughter.] So I actually plugged them in every few years because I loved it.

Margaret: You replenish it. O.K.

Jeff. Yeah. So I do some of that.

So there’s, there’s a whole list, like Euphorbia corollata, the prairie baby’s breath, is a fantastic plant in the gravel garden. The penstemons, Penstemon digitalis, for sure. Cup plant or compass plant.

Margaret: Silphium, yeah those are big guys.

Jeff: Yeah, they are. They are. Rudbeckia maxima. The coreopsis, Coreopsis palmata is a good one and it produces lots of great seeds, so I often see goldfinches munching on the seeds as they come through. Baptisia do great….

Margaret: Lots of good possibilities.

Jeff: Asters, goldenrods, all those.

Margaret: Well, it’s fascinating. And I’m tempted and I keep thinking about, “Hmm, is there a bed here that I’m going to try this in?” And so Jeff Epping of Olbrich Botanical Gardens in Madison, Wisconsin, the proponent of gravel gardening, thank you for making the time today to sort of teach us the 101 and I’ll give people more information on your other work and on Olbrich and the link to the Times story that we did in more depth and things like that so they can study up.

Jeff: Thank you. Thanks for having me and sharing the good word about gravel gardens.

(Photos courtesy of Jeff Epping.)

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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 May 9, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify