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WE GARDENERS want to do the right things: to attract pollinators, for instance, or grow more natives, and be environmentally conscious. We also want to create gardens that work for us, that are manageable—and resilient—even in tough situations and changing times. But goals like “sustainable landscaping” or “ecological landscape design” can sound a bit lofty and theoretical to those of us without a landscape-architecture degree.

Landscape architect Thomas Rainer is co-author with Claudia West of a new book called “Planting in a Post-Wild World” that inspires us to design plantings that function like naturally occurring plant communities. It also instructs how to manage them, not doing painstaking and often impractical garden maintenance, plant by plant, as in traditional horticulture. (Enter to win a copy of the book in the comments box below.)

Washington-based Thomas Rainer teaches planting design at George Washington University, and has designed landscapes for the U.S. Capitol grounds; the Martin Luther King, Jr. Memorial; and The New York Botanical Garden, as well as more than 100 private gardens. He is also a keen—and daring–home gardener.

I welcomed him back to my public-radio show and podcast. Read along as you listen to the Sept. 21, 2015 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).

my q&a on ecological design, with thomas rainer

Q. Can you distill for us the idea of “Planting in a Post-Wild World,” which is also kind of your design philosophy?

A. I had been in a practice for many, many years where we were doing a lot of high-end residential garden design. It was great—I loved the immediacy of that. But I always had large maintenance crews to follow up on my planting designs. When you have clients with large budgets and really good gardeners, I think your understanding of how well you design plantings can be a little bit inflated—which I think happens.

I swapped; I kind of had my Olmsted-ian itch and wanted to get into a firm that does much more large-scale public parks, public landscapes, embassies—I love that scale, love projects that affect a larger group of people. But they are the types of projects that sometimes have budgets to plant once, but not to maintain them.

And Claudia was dealing with the same thing—a lot of municipal designs, a lot of rain gardens. People with the very best intentions, but not always the kind of budgets or the kind of knowledgeable maintenance crews that I’d had previously. It left us in a place where we had a lot of projects that looked great for the first year, and then really fell apart.

Both of us were really wanting to be sustainable, we wanted to be beautiful–we had all the goals that I think a lot of home gardeners have. But we really wanted to understand how to put plants together in a way that actually was a little more resilient–in ecological terms, but also just in maintenance terms for crews like that.

For us, the post-wild world is the fact that we don’t have as much wildness in nature as we once had, and that trend doesn’t look like it’s changing. But there is a lot of space around us—in cities and in suburbs. The landscape architect Gilles Clement calls it the “third territory,” all the little remnants of green you have in cities—the medians, the roundabouts, the backyards, the public-library spaces. The sum total of all that space is fairly large, even though it’s a confetti of isolated green spaces.

I think our attention is turning more to those areas—what is planting design, and how can we make it really functional for those types of landscapes, and not only for high-maintenance ones?

Q. Last time we spoke on the show, Thomas, we focused a lot on the native vs. exotic debate, which can become very contentious. This new book doesn’t get into arguing, arguing, arguing but is very positive. It’s a very optimistic view about designed plant communities that are inspired by naturally occurring ones. You get your inspiration from nature, even in the post-wild world.

A. That’s right. And the inspiration isn’t only the beautiful native-plant communities you see hiking in the Shenandoah Valley or these great National Parks. There is a neighbor across the street, kind of a hippie, who doesn’t do much with his yard, and has this sort of “hell strip” along his sidewalks, filled with weeds [above]. I remember at one point going over—and it’s probably 2 feet wide within a 10-foot segment, so 20 square feet—and I counted 26 different species of weeds growing in there.

I started thinking about that density and diversity of plants growing in there, in something that just spontaneously emerged. It wasn’t beautiful at all—it looked like a weed patch. But I had nothing like that in my own garden, in terms of density and diversity, in any 20 square feet I had.

It was really remarkable to see how many species were interweaving together. So whether it’s these pristine, beautiful native inspirations or just how weeds really grow together, we started thinking there is a difference between the ways plants grow in our garden and the ways plants grow in the wild—whether it’s urban wild, or wild wild.

We wanted to really understand if there are some principles on how plants grow together that could inform garden planting—inform landscape planting, design planting, in a way that would be very practical.

There is a lot of ideology around native plants and we’re strong proponents and heavy users of native plants. But at the end of the day we really wanted just some practical solutions to some of the problems that we faced on a daily basis.

Q. In nature, whether in the post-wild world or in the Shenandoah, what you don’t see is something like a 3-inch-tall mown lawn and 100-foot trees as the only two elements. You see layers, staggered layers, like that hell strip across the street from you. You see different plants of different sizes and purposes and root system structures fitting together and making a community.

A. That’s right. All the plants are adapted—what we mean by “community” is that all the plants are roughly adapted to that environment. You can’t have an Agave next to a wetland iris; they’re not compatible in terms of the habitat.

The other element is that all these communities—whether a meadow or a forest or woodland edge—is that they’re layered vertically. The shorthand:

There are lots of different layers, and I think one of the things we worked hard on—because every community has different layering systems—was really trying to translate layers in ways that were applicable horticulturally, not just ecologically.

The big takeaway was that in almost all these naturally occurring plant communities, they had kind of a ground-holding matrix of plants. A meadow: Everyone can see the taller grasses, or the flowering forbs. But when you really get down to what’s at the base of some of these taller species, there are lower grasses, there are horizontally spreading rhizomatous plants—a number of different species actually hold the ground underneath.

Or in the forest floor, the same thing happens with sometimes low woody species, or spring ephemerals or ferns and sedges. There is always this layer, unless you’re in the desert or Antarctica or something—in most temperate climates, nature abhors bare soil. [Above, from the book: mayapple under an oak in early spring.]

Nature will fill bare soil, usually with plants. That was a big takeaway for us. The idea of mulch, in the American sense. We use a whole lot of bark mulch, that essentially forms the groundcover layer, because we know if we leave nothing there the weeds will come in or the soil starts drying out. We really think it’s possible—not only possible but possibly lower maintenance—if you replace this layer or the dependence on this layer with low, shade-tolerant plants that are compatible with more upright species. Not that mulch is not valuable.

Q. In the book you call this layer “green mulch.” Living mulch.



A. Yes, green mulch—plants. There are a lot of functional benefits from it. It does keep the soil from drying out and releasing carbon dioxide. The sunlight hitting the soil will degrade the organic matter much quicker than if it’s covered. Functional benefits: I’m a big perennial gardener, but we all know that perennials change so much in the course of a year. If it’s a warmer-season perennial, there are early times from March to May when the ground’s pretty bare. So balancing cool- and warm-season growers so you are always covering the ground.

In the groundcover layer, diversity becomes very important in terms of having many different root structures and competitive strategies : clumping plants, creeping plants. And as many different textures. It’s really a plant’s shape—its morphology—is how it really forms a reaction to other plants in the wild.

You know a massive Echinacea in the wild might flop over or look funny, but the whole shape of an Echinacea, for example, is meant to grow out of grasses. The whole stretching form, the low basal foliage—it’s all an adaptation to the community it’s supposed to be around.

Q. To its neighbors.

A. The more different shapes you have—it’s like a jigsaw puzzle in a lot of ways on the groundcover layer. The more different shapes you have, the more that can interlock. In a lot of ways, because these plants are so low, diversity doesn’t always mean chaotic plantings. In the upper design layers, you can still have some levels of massing, or some patterns. If you can cover the ground in the lower layers, you have a lot of flexibility to what you do design-wise in the upper layers.

So for formal gardens, maybe you do want to mass those upper layers more cleanly, so there is more intentionality and pattern to it. In a more naturalistic garden, maybe you’re expressing the ground-plane layer more heavily and the upper levels just get dotted in, some low grasses.

That’s what I really like about this idea: You don’t have to become a naturalistic gardener to have better vertically layered plantings.

We have one image in the book [above] of this fantastic mix of plantings in Germany, in a very formal, 300-year-old Greek Revival-looking house. I think a mix of maybe 20 species of perennials are in the middle of these garden beds, that are meant to have different waves of color from May all the way to November. It’s fairly mixed, but they had this beautiful boxwood parterre around the edge of it. They put an orderly frame around the mixed planting. All of a sudden, what might have been without that frame a very messy, wild, naturalistic piece looks totally appropriate with this very formal, historic garden.

We’re excited about the adaptability of this idea of layering, because it’s not so much about a style—we’re not advocates of a style. It’s really about some better functional ways of creating ecological combinations instead of just color combinations.

Q. There’s one diagram in the book [above] that has the three primary layers that you highlight and tell us to think about. You’ve mentioned the “green mulch.” Can you tell me about the others?

A. The other two are kind of more the design layers, the things you see at the top. One category we really like is kind of a mid-height layer. You have the groundcover layer, and then next is what we call a “seasonal theme layer,” and this would be masses or drifts of plants that have a long season of bloom, and really carry a seasonal moment. So maybe irises in the spring, or asters in the fall, or Asclepias (the butterfly weed) in the summer. Different mid-height clumping plants that become part of the groundcover layer part of the year—become part of the background green—but when they bloom they really light up the whole garden.

Q. Right.

A. There are some really exciting designers in Europe. Heiner Luz, and I think the work of Cassian Schmidt does a lot with this layer. They’ve designed these mixes of 20 to 40 species for public parks, and even though it’s really highly mixed and the plant list looks chaotic, there is only one or two things blooming at one time. You have these high moments—one high moment rolling into the next high moment. The stuff that goes green isn’t visually dominant; these other things come up.

That’s really the seasonal theme layer: mid-height plants, clumping plants—but you’re really trying to think about the big seasonal swell stuff, like asters in the fall or iris in the spring.

And then the uppermost final layer would be the structural layer. In a mixed planting even those these are your trees or shrubs, in a meadow planting these could be things like your taller grasses—your Panicum, Miscanthus, the bigger Andropogon. Some of those really tall Rudbeckia maxima. Those really become structural in a meadow planting.

These are not necessarily numerically dominant, but they are visually dominant. So in a forest the trees and shrubs are some of the bigger elements that give it its boom. In a lot of ways you want this to be very simple; a lot of repetition in this layer can help calm down the diversity in the lower layers. The repetition of a tree creates the feeling of a grove even though you might have a dozen woodland ephemerals and sedges and ferns on the ground plane.

Or the repetition in a woodland setting of rhododendron or azaleas, in key places, gives the sense of calmness, even though at the lower levels there is a lot of diversity. I think what’s fun in this idea is that playing with proportions of the different layers can create very different effects—from very calm effects to much more vivacious, highly mixed looks.

Q. Fireworks. [Laughter.]

A. Fireworks—exactly.

Q. You mentioned Germany in one breath. This approach in the new book is rooted in various sort of ornamental-horticulture adventures in Germany starting in what, the 1980s?[Above, planting at Hermannshof garden in Germany.]

A. One of the great things about teaming with Claudia, who is from Germany originally, is that she is able to translate some of these great resources—mostly German, and some Swiss. Really since the 1980s on they have been trialing what they called these mixed perennial plantings, and the whole idea is that they have come up with entirely novel plant communities.

These are not groups of plants that grow together anywhere in the world, but they have taken the most ornamental selections of say, a Mediterranean-type climate. So the best Mediterranean ones might be some of the California annuals mixed with some of the western Australia perennials, and they’re recombined them into these perennial mixes.

The other thing I love about the German approach is that they’ve trialed these mixes for 10 years or more. For designers it’s a little scary, because the whole purpose is to eliminate the need of a designer whatsoever. They really want to democratize perennial planting. They’re intended for roundabouts or public parks—the kind of sites I deal with on a regular basis in which people want perennial planting, color, diversity for pollinators—but they don’t really have the know-how to make it happen.

So they give people the list, and the plants are already assorted into the different layers. You put them out totally at random, and it doesn’t really matter where you place the stuff because there’s a proportion and you kind of randomly plant them. They’ve had really remarkable results; some of the published photos of these medians and roundabouts where the maintenance level is very low is really impressive.

Q. And the drama, the ornamentality, is really high.

A. They have a high bar for color, yes. A lot of the mixes have color themes.

Q. There is sort of this mantra in the book, and your work in general, about management, not maintenance–quite different from the stuff I end up crawling around on my hands and knees doing all day in my horticulturally motivated garden. But maybe more like what I do where I manage my upper meadow. What the difference between maintenance and management?

A. A maintenance approach focuses on a different set of prescribed activities for different plants. I have a perennial border that’s not at all a designed plant community, and I know which plants need to be staked, or which ones are water hogs, or which need to be trimmed off the path. That’s a lot of my activities—a different set for different plants.

When you move from an individualistic approach to horticulture to this community approach, you’re really thinking about managing—the task is for the entire mix of plantings. You’re not doing something different for one plant (though you can always do a little bit of that).

Generally the activities are based on once-a-year cutbacks; it’s based on making some adjustments yearly to your seasonal theme layers that may be pooping out and you need to add more of that. It’s really looking at moving maintenance away from an individualistic approach to doing coarse actions aimed at the whole mix.

That can really decrease the amount of maintenance on a planting, particularly with lowered water use. I just have a small perennial border, but I spend a ton of time staking in some types of years, and a good bit of time pruning things away because it’s next to some paths. So if you have the mix designed for the space and for the site, a lot of those individualistic actions almost become irrelevant.

I was talking to the director of the Lurie Garden in Chicago. One of the things they’ve gone to for their annual cutbacks of perennials is to use a mulching mower once a year. That big annual cutback was a huge task for them, and they’re moving more toward broad-scale ecological approaches to managing these mixed plantings.

Q. More like I would do with my meadow, where once a year I mow it, the first week in May, and mulch up and rake the debris, and then go in twice in the growing season and rogue out or cut down to the base any Rubus—any raspberry or blackberry or other woody invaders I see. And that’s it.

enter to win ‘planting in a post-wild world’ I’LL BUY A COPY of “Planting in a Post-Wild World,” by Thomas Rainer and Claudia West for a lucky reader. All you have to do to enter: Comment in the box at the very bottom of the page, after the last reader comment, answering this question: Are any ares of your garden based more on the idea of a plant community than a traditional horticultural design? Are you “managing” rather than “maintaining” any of your landscape (the way I am with my upper meadow compared to beds near the house)? No answer, or feeling shy? Just say something like, “Count me in,” and I will, but an answer is better. I’ll select a random winner after entries close at midnight on Sunday, September 27. Good luck to all.

(Photo credits: Images from “Planting in a Post-Wild World,” by Thomas Rainer and Claudia West, except mayapple photo by Mark Baldwin; German boxwood planting by Christa Brand; Hermannshof meadow by Adam Woodruff.)

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 Sept. 21, 2015 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).