Is Ecological Restoration Just Gardening?

Lagoon Park in Santa Barbara by Van Atta Associates.  Photo by Saxon Holt

I recently read a wonderful and thought-provoking article by Peter Del Tredici, Senior Research Scientist at the Arnold Arboretum of Harvard University. Del Tredici has been on my radar since he published a subtly subversive book called Wild Urban Plants that I reviewed earlier this spring. This new article posits the question: “Is ‘landscape restoration’ really just gardening dressed up with jargon to simulate ecology?’. Here is a bit more context:

“Implicit in the proposals that call for the control and/or eradication of invasive species is the assumption that the native vegetation will return to dominance once the invasive is removed, thereby restoring the “balance of nature.” That’s the theory. The reality is something else. Land managers and others who have to deal with the invasive problem on a daily basis know that often as not the old invasive comes back following eradication (reproducing from root sprouts or seeds), or else a new invader moves in to replace the old one. The only thing that seems to turn this dynamic around is cutting down the invasives, treating them with herbicides, and planting native species in the gaps where the invasives once were. After this, the sites require weeding of invasives for an indefinite number of years, at least until the natives are big enough to hold their ground without human assistance.

What’s striking about this so-called restoration process is that it looks an awful lot like gardening, with its ongoing need for planting and weeding. Call it what you will, but anyone who has ever worked in the garden knows that planting and weeding are endless. So the question becomes: Is “landscape restoration” really just gardening dressed up with jargon to simulate ecology, or is it based on scientific theories with testable hypotheses? To put it another way: Can we put the invasive species genie back in the bottle, or are we looking at a future in which nature itself becomes a cultivated entity?”  Peter Del Tredici from "Neocreationism and the Illusion of Ecological Restoration," Harvard Design Magazine.

I’ll confess: I am not an ecologist or an expert at ecological restoration. I have, however, worked with ecological restoration experts like Rutger’s Steven Handel. Consider my recent experience on a two thousand-acre agricultural site that we intended to convert into a mosaic of different native habitats. After going through the process of analyzing the site and preparing a restoration concept, my impression was that restoration was really not that different from the design process I use for any ornamental landscape. Obviously, the goals were different and our application of native habitats was based in a much more thorough site analysis. But the end result was the same: we imposed a human concept of what “nature” should be on the site. The end result would be entirely artificial and constructed.

Vernal Pool created in an area that once wasa parking. Van Atta Associates. Photo by Saxon Holt

In addition, our constructed “native” landscape would require years of intensive maintenance to get it established, and decades of ongoing management to keep it native. After this experience, Del Tredici’s analogy to gardening resonated with me.

Del Tredici’s conclusion for designers and gardeners is to “not to limit themselves to a palette of native species that might once have grown on the site.” He argues for using plants that will tolerate the conditions of the site, native or not, particularly in the tough urban conditions.

I have two responses to the article. The first is to agree with Del Tredici’s claim that ecological restoration creates “entirely artificial and constructed” landscapes. It’s absolutely true. It bursts the romantic notion that we can bring back plant and animal communities as they existed before Columbus arrived. It also challenges the myth that native plants are natural, good, low maintenance, and self-sustaining. They aren’t. They require human intervention. The sooner we can lose the mythology that “nature” will come back one day, the sooner we can get to the real work of creating entirely artificial, native landscapes that perform essential ecological services.  See my posting here for more on this.

Boardwalk at Lagoon Park in Santa Barbara by Van Atta Associates. Photo by Saxon Holt

Secondly, I disagree somewhat with Del Tredici’s direction that designers abandon the native only approach. I certainly don’t mind using some non-natives. But implicit in Del Tredici’s assumption is that natives are somehow weaker or less adaptive to the tough conditions of an urban site than some non-natives. I entirely disagree with this point.

Of course, some natives—many of which are ubiquitous in the nursery trade—are not tough enough for urban sites. The natives that are widely available in the nursery trade are mostly selected for their ornamental value. We’ve hardly explored the full potential of native systems to address the environmental challenges of the day. To judge the adaptability of native plants based on the scant selection of natives that are currently available in the trade is preposterous. Mark Simmons, a researcher at The Lady Bird Johnson Center, is doing research that proves that many native plants are much tougher than non-natives and capable of solving many of our environmental problems. I will feature an article on his research later this month.

I love articles like Del Tredici’s. The debate over natives vs. exotic plants is really a debate about what is natural. I look forward to the day when we drop our romantic notions about nature existing somewhere “out there,” and can start to focus improving the ecology of the human-impacted landscapes that we encounter every day.

What do you think?  I would love to hear other reactions to Del Tredici's article, especially any who have some experience or thoughts about ecological restoration.

Plant Local: Provenance Matters

The dramatic shift toward native and sustainable gardening in the last decade is remarkable. As images of giant plumes of oil spilling into the Gulf gave us all reason to despair, I drew deep comfort from seeing so many fellow gardeners join the green revolution by converting their plots into islands of biodiversity, or by plowing up their lawns and planting vegetable gardens. These small acts of resistance are reasons to hope.

Plants being propagated by tissue culture in a lab.

As the use of native plants in gardens has moved from fringe activity to mainstream practice, gardeners need to pay attention to where their native plants come from. Here’s the problem: the vast majority of plants in the nursery trade, natives included, are being mass propagated from a relatively small gene pool. For example, consider the meteoric rise of the use of tissue cultures to propagate plant. Nurseries select unique or beautiful cultivars of a plant, say for example, Itea virginica ‘Henry’s Garnet’—a truly vigorous and ornamental native shrub. They want to reproduce the ornamental characteristics of this exact plant and at the same time eliminate the possibility of genetic variation or aberrations. So they take samples of the plants tissues (such as a stem tip, node, or meristem), place it in a sterile nutrient medium and allow it to multiply. In this artificial environment, propagators can develop roots, multiply the number of plantlets, or create new embryos for artificial seed.

Now as weird science as all of this sounds, it’s not terribly different than taking a cutting of your favorite plant to share with a friend. The great advantage of tissue culture—and other asexual propagation techniques—is that it creates predictable plants. Gardeners can be guaranteed that the Itea virginica they purchased will have the deep crimson fall color, the prolific blooms, and the cascading stems of the ‘Henry’s Garnet’ cultivar. It also offers a much-needed alternative to native plants that were taken from the wild, a once prevalent practice.

The great problem with asexual propagation is that as we lose native habitats to development, the natives we are replacing them with represent a much narrower genetic pool than what existed. More often than not, the native plant you buy at your local retail nursery was probably populated by tissue culture from a native population somewhere far away. For example, how native is a plant that was derived from a source in Tennessee, propagated in a petri dish in Oregon, shipped as a liner plant to Michigan, and then delivered to a retail nursery in Massachusetts? By the time that plant hits your garden, its passport is full.

On the left, an unplanted Panicum in Texas (photo by Rick Darke); on the right, the Panicum cultivar 'Cloud Nine'

Why should you care if your Itea virginica ‘Henry’s Garnet’ came from a tissue culture that originated from a plant in Swarthmore College in Pennsylvania when you live in Alabama?  Because it could affect the performance of your plant. Plants have phenotypic variation associated with geographic sources that allow plants to adapt to the stresses of a particular locality. Local populations have adapted over thousands of years to the particular region, developing what biologists call alleles, or alternative forms of gene. An Itea from Alabama may have alleles that allow it to adapt to high humidity, while the Pennsylvania Itea might be more cold-hardy.

Provenance matters. Right now the native plant movement still relies on horticultural approach to plants—one that focuses on ornamental characteristics of plants without concern for the plant’s provenance or community. By doing this, we lose not only the allelic diversity of local plants, but also the aesthetic appeal of plants that have been perfectly evolved to a specific region.

Left: Liatris scariosa var. novae angliae only exists on Martha's Vineyard and Nantucket; Right: Liatris spicata from the Midwest

Consider another example. I worked on a few projects on Nantucket and Martha’s Vineyard where we sold the clients on the concept of a mostly native landscape. We worked with a local meadow specialist who pointed out that several of the native species we were considering had unique varieties on the island. For example, we wanted to use Panicum virgatum, but learned that the Panicum native to the islands looked completely different than Panicum you see in the tall grass prairies of the Midwest. The island Panicum was short and had this wonderful vase-like profile, whereas the Panicum evolved in the prairies was tall and upright. We also learned that the island had its own unique species of Liatris (Liatris scariosa var. novae angliae) that had evolved to stand up in the wind and salt of the islands much better than the Liatris spicata being sold on the main land. For one project, we ended up using a local propagator who grew all his plants from seeds collected on the island. Not only did we preserve the allelic diversity of the island’s plants, but our finished garden fit into the context much better than if we had used tissue-culture natives from Midwestern sources.

The copper tones of Little Bluestem collected from local seed sources have a deeper color than Little Bluestem from off island..

So how can you truly plant locally? Gardeners should support nurseries that propagate natives from local populations. If you’re not sure, ask your local nursery owner where he or she gets her plants. This strategy has been remarkably successful in supermarkets; it can work for the nursery trade as well. Choose seed sources that you know are harvested from local populations. Or even better, learn how to sustainably collect seed from wild populations. There’s nothing quite as grounding or satisfying as going into a wild landscape, gathering seed, and then raising that plant in your garden. Go local with your garden. I promise, you will love it.

The End of Groundcovers

If I could banish one word from the English language, it would be "groundcover."  The era of the groundcover must end.  While this age of American landscape design has its roots in the Victorian garden, it has been the dominant landscape ethos since the post WWII housing boom.  The primary idea of this era is that non-lawn planting beds need to be covered in a low maintenance, evergreen groundcovers such as English ivy, periwinkle, or pachysandra.  The results of this philosophy on our landscapes are nothing short of catastrophic: millions of acres of meadow and forest have been decimated by these invasives, and we've forsaken the spiritually enriching act of gardening for the environmentally impoverishing act of landscaping.

The Rise of the Groundcover

It's easy to understand how groundcovers became so popular.  As American suburbs sprawled away from city centers, individual homeowners quickly became absorbed in the enormous labor of maintaining huge expanses of lawn.  With so much lawn to maintain, the rest of the yard needed to be relatively maintenance free.  Planting beds were established where lawn wouldn't grow--typically in the shady areas under trees or at the edge of the lot.  How to fill these leftover beds became a problem.  Next to a manicured lawn, bare earth or mulch looks empty and unfinished, but filling these large areas with plants could be expensive. 

The groundcover became the magic cure.  Tolerant of sun or shade, wet or dry, these low, creeping plants could be sparsely planted in a bed and left alone.  Within a year or two, the bed was covered in lush carpet of glossy green ivy, the bright blue flowers of periwinkle, or the happy white spires of pachysandra. When maintained, the long flowing curves of planting beds created sinuous lines against the lawn, a declaration of the well-tended yard.

But the problem was that these yards were inevitably not well-tended.  The very quality that initially drew homeowners and landscapers to these plants--their ability to spread--became the beginning of an aesthetic and ecological disaster. 

Ecological Disaster

The honeymoon period (two or three years after the installation) yielded to the invasive period, and homeowners quickly realized that these low maintenance darlings actually required maintenance--lots of maintenance.  The plants began to move and destroy: the ivies grew up trees and down slopes; pachysandra crept into a wet area and down stream channels; periwinkle moved across slopes choking all other vegetation in its path.  Not even structures were safe.  The clinging roots of ivies invaded mortar, the muscular branching of wisteria damaged buildings, and the thick impenetrable roots of periwinkle altered the hydrology of yards. [Image to left shows Vinca major, periwinkle, smothering a forest floor].

Often in suburban neighborhoods, the developer backs lots right up against undevelopable land like forested streams or adjacent woodlots.  The groundcovers, unaware of property lines, spread into forests, streams, and meadows.  Vines climb into the canopy, covering leaves and blocking photosynthesis.  The additional weight of the vines often break branches and canopies particularly during snow.  The understory invasives smother the ground-plane, preventing native plants from seeding and regenerating the canopy.  Ecologists call the zones dominated by invasive groundcovers "ecological dead zones." [Image on right shows English ivy decimating forest floor and smothering trees.]

The U.S. Forest Service now estimates that invasive plants like groundcovers strangle 3.6 million acres of national forests, an area the size of Connecticut.  And that's just national forests.  Invasive plants are thought to cover 133 million acres of federal, state, or private land, an area the size of California and New York combined.  Each year invasives march across 1.7 million acres, almost double the size of Delaware. 

An Alternative Concept

The concept behind groundcovers is as pernicious as the plants themselves.  It is based on the mythology of the quick and easy, low maintenance yard.  Groundcovers signal a disconnect between the owner and the land, a message saying "I don't want to deal with you".  The professionals who use these plants, both designers and contractors alike, automatically assume the lowest possible expectations for that piece of land.  Groundcovers are chosen based on the assumption that the area will be ignored, abused, or abandoned. 

Groundcovers represent a failure of the imagination.  Americans understand trees, shrubs, and groundcovers, but beyond these categories, we're pretty much lost.  We lack England's rich garden history and thus fail to understand how to use herbaceous plants like perennials, grasses, annuals, or vines to enrich our planting beds.  Native plant enthusiasts have long recommended native alternatives to invasive groundcovers, but their suggestions typically replace one type of plant with a less invasive counterpart (a vine for a vine, a creeper for a creeper).  What these lists fail to do is to challenge the aesthetic that prompts the homeowner to use a groundcover in the first place. 

The alternative to groundcovers is not slightly less invasive groundcovers, but planting beds filled with native biomass.  We need to re-imagine our beds filled with a rich tapestry of perennials, grasses, shrubs, and low trees.  While our unfamiliarity with these materials make them intimidating, we should rely on the toughest and most resilient native perennials and grasses to fill our borders.  The demand for evergreen should be replaced with plants that provide winter interest: dried grasses, seed heads, and structural deciduous shrubs.  We should transform our ecological dead zones into ecological hotspots by creating connected areas of native biomass.  When we do this, we invite pollinators and birds back into our landscapes. 

[Native biomass: Goldenrod and Echinacea fill a planting bed.  These plants are low maintenance, provide nectar for birds and butterflies, and beautiful as they change through the seasons.]

A Model Project

Ten Eyck Landscape Architects in Phoenix recently completed an award winning project for a labratory building for the University of Arizona.  The landscape around the building functions both as an outdoor classroom and a high performing native landscape.  The project harvests water and provides and interface between students and nature.  The former grayfield is now a thriving habitat for birds such as the roadrunner and hawks searching for ground mammals.  The ASLA awards jury said of the project, "This project shows us everything that we should find in a university landscape.  Not a blurred interpretation of "native" but rather a commitment to accuracy." 

[Students enjoy a break at an outdoor classroom surrounded by vegetation native to the Upland Sonoran.  Photo by Bill Timmerman.]

[The pond is home for endangered fish and is listed by the U.S. Fish and Wildlife Service as a "Safe Harbor" urban site.]

And I'm including one additional image to show how native grasses can be used as a groundcover alternative.  This photo taken at Chanticleer Garden in Pensylvania by Rick Darke. 

[Native grasses such as Prairie Dropseed, Sporobolus heterolepsis, make an ideal alternative to invasive groundcovers.  Photo by Rick Darke.]

Modern Naturalism: Artifice in the Natural Garden

For several weeks now, I have been extolling wildness and naturalism as a virtue in the design of landscapes. My claim is that man-made landscapes need to embrace “nature” in a more intentional and expressive way. In making those claims, I have been perhaps too dismissive of the importance of artifice in designed landscapes. A few thoughts about that here.
First, any designer that calls his or her work “naturalistic,” “sustainable,” or “ecological” cites nature as an authority to justify their designs. Obviously, many landscapes claim to be natural that are entirely different from each other. What is abundantly clear in the age of greenwashing is that terms like “natural,” “sustainable,” and “green” are human constructs, loose signifiers that can be applied to almost anything--particularly anything in a landscape. Ideas about nature ultimately reveal more about us than it does about the landscapes they describe.

“Nature is an abstraction,” writes Anne Whiston Spirn, professor of landscape architecture at MIT, “a set of ideas for which many cultures have no one name, ‘a singular name for the real multiplicity of things and living processes.’” In landscape design today, naturalism is a science (ecology), a moral calling, and an aesthetic. Designers sling these terms around without much thought or discussion about what they mean.

So in all my eager advocacy for naturalism, I too have been a bit loose with the terms. Anne Whiston Spirn writes that “nature is both given and constructed.” I believe in both of those realities: nature as outside of me and nature that is inside of me. The line between those two is a fuzzy one. This is not reason to despair; instead, we should celebrate this fuzziness.

For me, the myriad of meanings for what is natural is no reason to reject naturalistic design. Instead, it is an invitation to explore this conceptually fertile ground. The medium of our art is living, ever-changing elements of plants, water, light, and soil. Designers get the rare privilege of working with an ephemeral palette, of asserting our control and then losing it. Lately, I’ve gotten much more joy out of losing it.

That is why I am drawn to designed landscapes that celebrate the evanescent with bold artifice. Trying to erase the evidence of human intervention feels inauthentic to me, as flat and unconvincing as a trompe l’oeil. All true naturalism must first be a humanism. The landscapes that captivate me both intellectually and spiritually are those that blur the lines between natural and cultivated, between nature as other and nature as me. Artifice is not only acceptable in naturalistic designs, but necessary. It prevents plagiarism by forcing the designer to show her hand. The benefit of artifice is that is grants the designer sweet catharsis: it reveals to the world that this design, like all good landscape design, is a blessed forgery.

Are Gardens Natural?

The natural and sustainable gardening movement is all the rage the days, and for good reason. Gardens represent a golden opportunity to create ecologically productive areas in a time of great environmental decline. But all the talk about sustainability raises the question: are gardens ever really natural? And if not, what does that mean for gardeners trying to be sustainable?

The very idea of a garden implies human intrusion. No garden is natural in the pure sense of the word, because no garden is permanently self-sustaining. Even Beth Chatto’s revolutionary Gravel Garden—which has never been artificially watered —would disappear in 30 or even 100 years from now without human input (pictured above). Nature changes constantly. Left alone, most gardens in temperate zones would end up as woodland.

Gardens are time arrested. The very acts we perform while gardening—watering, pruning, weeding, replanting—are acts against time. All gardening is an attempt to halt ecological succession and freeze it at a point that pleases us aesthetically. Gardeners are like referees, preventing plants from engaging in the warfare they would wage if left alone. Our obsession with benign happy flowers has blinded us to the barbarous combat taking place outside our doors. Plants smother, steal, poison, and invade their neighbors. While we may be oblivious to this conflict, we are nonetheless a part of it: gardeners ultimately pick which side wins.

If gardens are not natural, should we despair? Martha Schwartz, the celebrated and controversial American landscape architect said at a recent lecture, “We view the landscape much as the Victorians viewed women: as either saints or whores.” In an essay called “I HATE NATURE,” Schwartz goes on to say that Americans still exalt a mythical wilderness out there somewhere (the saint) and denigrate any man-made landscape (the whore). This mythology means we don’t see the potential of man-made landscapes to create ecologically productive landscapes. Schwartz writes:

“Our American wilderness paradigm keeps us from developing a clear idea about how to resolve our human activity upon our landscape and how to develop an attitude that can resolve this dilemma constructively. The Dutch, possessing a culture that is clear-eyed about the fact that their native landscape is a man-made artifact, have a much more pragmatic approach to building and development, resulting in healthier and more sustainable environments.”

So what should we do? My suggestions are simple. First, we drop the mythology that nature exists “out there” in some national park and understand that the human landscapes we inhabit everyday—the parking lots, streets, cities, and suburbs—are really all the nature we have left. Once that dirty little truth sinks in, we can stop treating the man-made landscapes as something to hold our nose and pass by, and start repairing the natural systems within it. The same industrial drive that conquered and obliterated the wilderness can lay the groundwork for recreating it within human landscapes.

Second, we make peace with time. Gardening is ultimately a conversation with time. All of our pruning, mowing, weeding, and planting are acts of defiance against the march of time. My suggestion is not to stop gardening, but rather engage with the natural processes working within our garden. Loosen up that landscape. Allow a little self-seeding to happen. Connect with the seasons. Use plants that channel the ephemeral such as light catching grasses or perennials that emerge and die. Understanding the beauty of the ephemeral opens us to see ourselves in time rather than against it.

China Sweeps American Landscape Architecture Awards

Rising Star Yu Kongjian’s Radical Vision

Design firm Turenscape in concert with Peking University Graduate School of Landscape Architecture virtually swept this year’s ASLA awards, winning an unprecedented three of the twelve design awards, including the prestigious Award of Excellence and two Honor Awards. The group beat out the hugely popular Highline, New York’s elevated rail park, anticipated by many to win this year’s top award.

All three of the winning projects were large scale, regenerative landscapes that transformed formerly degraded sites into lush, public parks. “This is very powerful,” wrote the Awards jury for the Shanghai Houtain Park, built on a former brownfield. “It’s full of the right messages of our profession. The scope is exquisite. The presentation is excellence. Shanghai never has a blue sky, and recognizing this kind of sustainable project in that context is important.”

Lead designer and professor of landscape architecture Yu Kongjian has long worked to bring attention to China’s impending environmental crisis. Yu views landscape architecture as “the art of survival, not an art of entertaining and gardening.” Awarded ASLA awards eight times since 2002, Yu is a rising star in the world of landscape architecture. In 2007, Yu won an Honor Award for The Red Ribbon in Tanghe River Park, a project that Conde Nast Traveler named as one of the seven modern architectural wonders in the world.

A Different Kind of Park

Yu has long advocated for a different kind of public park: “Why can’t we use agricultural plants, crops, wild grasses, and fruit trees to decorate cities and parks? They are equally beautiful but yield fruits and demand little attention."  Yu's love for wildness is balanced by an appreciation for the agricultural and industrial heritage of a site.  The winning projects frequently use the concept of agricultural terraces and rice fields to create ecologically productive landscapes.


Shanghai’s Houtan Park uses wild grasses and crops as a water-filtering machine, cleaning 2,400 cubic meters of water a day. “There is a beauty in wild grasses,” says Yu. “We don’t see it because we have a twisted aesthetic, taking natural things to be lower class. We are addicted to city beautification: uprooting agricultural crops and trees on the land, building cities, and importing expensive and fruitless garden plants.”

Yu goes on to make an analogy: “It’s kind of ludicrous and harmful feudalistic aristocratic aesthetic. Like when we bound women’s feet and still viewed it as beautiful and elegant. We now are binding the feet of nature.”

To view more about the winning projects click the links below:

Shanghai Houtan Park: Landscape as a Living System

The Qinhuangdao Beach Restoration: An Ecological Surgery

Tianjin Qiaoyuan Park: The Adaptation Palettes

Five Best Plants to Attract Wildlife

Never thought of your garden as a wildlife preserve?  Well, it may be time.  The statistics about human impact on nature are grim.  Consider a few: America grows by 8640 people per day, and we sprawl across an additional two million acres per year (the size of Yellowstone Park).  The total paved surface of the country is the size of Missouri, and our non-paved surfaces are mostly lawn and sterile plantings.  What's left of our woodlots and forests are invaded with 3400 species of alien plants like bittersweet, honeysuckle and privet that have consumed 100 million acres of land (the size of Texas).  In the lower 48 states, humans have converted 54% of the total land into cities and suburbs, and 41% into various forms of agriculture.  That's an astounding 95% of total land dedicated to man-made use.*

Nature no longer happens somewhere else. Gardeners represent the last best chance to reclaim some of our lost biodiversity.  Our local animals need native plants--preferably lots of them in contiguous and connected areas--to survive and reproduce.  While I love many Asian or European ornamentals, they support only a tiny fraction of the wildlife that natives do.  For example, a Kousa dogwood (Cornus kousa) supports no insect herbivores while our native flowering dogwood (Cornus florida) supports 117 different species of moths and butterflies.

So what should you plant?  Turns out, not all native species are equal.  Some plants sustain much more diversity than others.  University of Delaware professor Douglas Tallamy has studied eastern native plants and documented the different species they host.  Check out this list of five SUPERPLANTS that support wildlife. 

1. Oak Trees (Quercus)

Oak trees top the list for the total number of species they host.  They support an astounding 534 species of butterflies and moths, nearly five time the amount of a Beech tree.  In addition, their acorns provide an abundant food source for small mammals and birds.  Oaks have been diminishing in forests as a result of fire suppression, all the more reason to add one to your yard.  Plus, oaks are a beautiful and elegant, providing shade in the summer and allowing light in the winter (great for energy efficiency).  Try an underused oak like the stunning Scarlet Oak (Quercus coccinea) for fall color, or the Nuttall Oak (Quercus nuttalli) for vigor and ease of transplant. 

2.  Goldenrods (Solidago)

Goldenrods support the highest number of moths and butterflies of any herbaceous species in the study, a whopping 115 different species.  They are also an important nectar source for native bees and insect pollinators.  Wait, don't Goldenrods cause hay fever?  No.  It gets blamed for it because it blooms at the same time as Ragweed.  Most goldenrod species are drought tolerant, low maintenance, and have a long season of bloom.  Try a Goldenrod cultivar like 'Fireworks'  or 'Little Lemon' for a late summer show.

3.  Black Cherry (Prunus serotina) image from mobot.org

Black cherries are rare in the nursery trade, mostly because they are considered a weed for so many years.  But Black Cherries are among the most ecologically productive plants in the U.S., supporting an astounding 456 different species of moths and butterflies.  This tree is a veritable food court for wildlife: their beautiful white blooms in April provide nectar for bees and other pollinating insects, their fruit provides food for birds and small mammals, and their trunks are favorite foraging ground for woodpeckers.  Plant Black Cherries along the border of your property, preferably contiguous with other trees and shrubs to maximize the wildlife impact.  If you can't find tree sizes in the nursery, don't fret.  Plant denser groups of smaller saplings for a lush and informal hedge row.  Here is a link where you can get seeds.

4.  Asters

Asters are second only to Goldenrods in terms of the number of moths and butterflies they support (112 different species!).  American asters are among the most colorful and showy of all native perennials.  Don't even bother with Asian varieties; the American natives are every bit as intense, drought tolerant, and easy to grow.  Plus, we are spoiled for choice.  The New England Aster (Aster novae angliae) are great for massing, the Wood Asters (Aster divaricatus & cordifolius) are good in the shade, and Smooth Aster (Aster laevis) are great for interplanting among grasses.  My personal favorite are the Aromatic Asters (Aster oblongifolius) like 'October Skies' (pictured) and 'Raydon's Favorite.'  Compact (18-24"), vigorous, and an explosion of mid-autumn color. 

5. Willows

One of the most under appreciated shrubs in America turns out to be one of the most ecologically beneficial ones.  Willows form large shrubs or small trees that stabilize streambanks, remove pollution from water, and provide food for as many as 455 different moths and butterflies.  Our colonial forbears used willows for baskets, building construction, and fencing, but  we've all but forgotten this amazing shrub.  It's not only practical, but beautiful.  Bluestem Nursery is the authority on the many different uses and varieties of willows.  Consider a willow for its steely blue leaf color, or for its outstanding stem color that rivals Red Stem Dogwoods.  Bluestem Nursery has catalogued just a few of the many uses for these plants. They're incredibly fast growing, too.  If you want an instant hedgerow, or a living fence (see picture) this is your plant.

(Statistics from Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens by Douglas W. Tallamy.)

Loosen Up that Landscape!

An Earth Day Challenge to Gardeners and Designers

"Do gardens have to be so tame, so harnessed, so unfree? What's new about our New American Garden is what's new about America itself: it is vigorous and audacious, and it vividly blends the natural and the cultivated." James van Sweden

My former boss and mentor, James van Sweden was always quotably evangelistic about the need for American gardens to loosen up. Founder of the New American Garden style, James van Sweden and Wolfgang Oehme created a legacy of projects that presented a beautiful and lush alternative to the typical American garden scene: a sea of lawn with overgrown evergreens stuffed under foundations.

James van Sweden is hardly the first or only voice advocating for an alternative to the typical American yard. Organizations like Lawn Reform, writers like Rick Darke, and landscape architecture firms like Andropogon have all offered compelling alternatives to the typical American landscape. But forty years after the first Earth Day, I have to ask: has the American garden style really progressed?

For home gardens, there are small signs of progress. In the last two years, there has been an increase in vegetable gardening, a renewed interest in native plants, and the occasional person getting rid of their lawn. Despite these glimmers of hope, there is little indication that the style of gardening has actually changed. The basic ratio of lawn (~90%) to planting bed (~10%) remains the same. And what makes up the paltry planting beds are mostly stiff evergreens.

What’s worse is how many professional landscape architects or garden designers still perpetuate stiff and formulaic designs. In the name of modernism, how many urban plazas or institutional sites arrange evergreens in rigid stripes? Or how many self-trained garden designers fill backyards with uber-wavy lawns (because curves are natural!) only to dot in twelve perennials and four shrubs?

Instead, let me present a case for a radically different landscape, a departure from the traditional obsession with fixed forms. My humble advice to gardeners and designers for Earth Day is:

1. Invert the Relationship of Lawn to Planting Bed: Think of your lawn as an area rug, not as wall to wall carpeting. Lawns are best when they are defined on all sides by hardscape or planting beds. This gives them legibility and definition and gives you an opportunity to show off loose perennials, grasses, and shrubs around it. If you’re lawn is more than 50% of your yard, it’s probably too big.

2. Use a Majority of Plants that Change Seasonally: There’s nothing more satisfying in gardening than watching a landscape change through the seasons. Watching plants emerge out of the ground in spring, fill up in volume and color in summer, and then dry in winter connects you with the cycles of the seasons. Dedicate a large percentage of your yard (at least 1/3) to perennials, grasses, and deciduous shrubs—mostly native—and enjoy the drama of the seasons.

3. Think Winter Interest, not Just Evergreens: While every garden or landscape needs some evergreens, most American landscapes use far too many. Most ornamental and native grasses dry beautifully in the winter, and many perennials yield stately seedheads that look stunning in the snow. Include native deciduous shrubs like Itea virginica, Cornus alba, or Ilex verticillata for colorful stems and berries in the winter.

4. Bulk up that Biomass, especially for Pollinators: The amount of native biomass (the total mass of living matter in an area) is in severe decline thanks to development. But gardens represent one of the best opportunities to reclaim it. Carve out areas dedicated to wildness in your yard. Plant your borders with a loose mix of native shrubs; allow part of your lawn to convert to meadow; or let that low area become a rain garden or biofiltration zone. University of Delware professor Doug Tallamy has proven that native plants support an exponential number of more pollinators than do exotic plants. Plants that support butterflies, bees, and other insects invite birds and other wildlife into the garden. Check out Doug’s list of the most effective plants for Lepidoptera.

5. Have fun: One of the first reactions I get when I tell people I’m a landscape architect is an immediate moan about how terrible their yard is. People don’t know what to do and are overwhelmed by the maintenance required of mowing lawn and clipping shrubs. While I believe in principles of design, and in the need for landscape professionals, I believe more strongly in people having a joyous engagement with their garden. No matter what that looks like. So get out there, start with a manageable project, and create the change that loosens up your yard. Be daring, be bold, and have some fun, for crying out loud.

Seeds of Change: How to get Tasty Veggies, Preserve Biodiversity, and Sock it to the Man

For the last two years, seed sales have hit record highs due in large part to the recession, the long winter, and a general increase in home gardening. The internet has made access to seeds cheap, easy, and fast. But how do you know which seed companies to buy from? And what are the environmental implications of your seed selection?

Want to know how to sock it to the agricultural conglomerates? Or how to save seeds from the fate of biotech companies and patent lawyers? Here’s a quick guide that explains what you should look for when buying seeds.

1. Support Small, Established Family-Owned Seed Distributors
Last year rumors spread across the internet that mega-seed company Burpee was bought by Monsanto, a massive agricultural conglomerate know for their genetically modified seeds. This rumor was not exactly true, as Monsanto actually acquired Seminis, a company that sells seeds to Burpee. Seminis sells not only to Burpee, but also to other large seed companies like Jung Seed, Johnny’s Selected Seeds, and Park seed. The big boys are indeed getting bigger.

While the ownership hierarchy and propagation ethics of large seed companies are murky, there are plenty of small, family-owned seed companies that offer a diverse selection. Select companies such as family-owned Baker Creek Heirloom Seeds. This husband and wife team are taking on corporate agriculture with their grassroots “Pure Food” movement. Their charming populism is even more seductive when combined with pictures of their adorable daughter holding baskets of heirloom fruit. Just try and resist their free catalogue—it’s pure garden porn. In addition to Baker Creek, I’ve listed a few other notable seed companies at the bottom of this blog that are worth looking into.

2. Buy Open-Pollinated Seeds
Open pollination is the oldest method of developing seeds, predating agriculture itself. Open pollination means seeds either pollinate themselves (self-pollinating) or are pollinated by insects or bees. Why does this matter? Open pollinated seeds are dynamic, that is they change and adapt to local sites. The plant’s genetic material is often crossed with the genetic material of another plant of the same species, resulting in hardier strains adapted to the local microclimate. The great diversity of heirloom apples that once populated colonial America was a result of new strains of apples that were open pollinated. Supporting open pollination means you are creating more genetic diversity in our food and plant supply.

Most seeds on the market are hybrid seeds. These are the offspring of two distant and distinct parental lines. ‘Better Boy’ and ‘Early Girl’ tomatoes, for example, are hybrids of a couple different lines of the same species. The problem with hybrids is that breeders limit the genetic diversity to guarantee a certain trait—say size or a color. Even more insidious than hybrids are GMOs or genetically modified organisms. Much of mass food production—like the Idaho potato—are now propagated with GMO. This means a plant of one species has its genetic material spliced with plants of another species. These are crosses that would have never happened in nature. Eighty percent of all corn, ninety percent of all soybean, and almost ninety percent of all cotton comes from genetically modified plants. While the jury is out on whether GMO are actually harmful to us or the environment, one thing is for sure: the world food supply is genetically narrower than at any point in history. Using open pollinated seeds preserves genetic diversity.

3. Collect Your Own Seed; Trade with Others

Nothing makes you feel more grounded with the cycles of nature than harvesting, drying, and storing your own seeds. Want to connect on a spiritual level with the botanical universe? Or achieve gardening self-actualization? Collect seeds. Seed collection requires you to watch the reproductive cycle of plants, to notice pollination, and understand how and when flowers turn to seedheads. Plants will no longer be your blooming indentured servants, but free ecological beings capable of self-seeding and adapting.

Last year, I noticed a Heuchera cultivar of mine had self-seeded in the garden. It was remarkable to notice the slight variations this new plant had from its parent, a result of the miracle of open pollination. My very own cultivar. Collecting seeds can be easy or difficult depending on the species. Start with annuals, then progress to perennials and shrubs.

Once you’ve achieved a small level of proficiency with seed collecting, you’re ready to embark on the next frontier: the black market seed trade. Ok, so maybe it’s not a “black” market, but there’s something downright exhilarating about arranging a backroom trade on the internet, then getting a shipment in a blank envelope. GardenWeb offers an a great starting place for seed exchanges. Become a bartering expert. Where your obsession takes you from there is up to you.

Check out these Family Owned Seed Companies:

www.sustainableseedco.com/pages/  A California company that sells untreated, open pollinated, heirloom seeds.

www.mariseeds.com/ A Tennessee company selling over 500 varieties of tomatoes and peppers.  The Italian love oozes from this site. 

http://www.rareseeds.com/ The Baker Creek Seed Company mentioned above.

www.dianeseeds.com/ Diane's sells high quality seeds.  Her selections are minimal but good.

www.seedsavers.org/Content.aspx?src=buyonline.htm A seed exchange and vault dedicated to preserving biodiversity.

http://nativeseeds.org/catalog/index.php?cPath=1 Specializing in seeds of the southwest desert and native cultures.

www.selectseeds.com/cgi-bin/htmlos.cgi/2010/catalog.htm  Specializing in open pollinated annual flowers and other antique varietals.

www.victoryseeds.com/  Rare, Open-pollinated & Heirloom Garden Seeds

The Wild Garden

What in your garden is truly wild?

At its heart, the sustainable gardening movement is about creating gardens that look and act more like nature.  Or at least an interpreted form of it.  But how many of our gardens actually let wildness in?  Do we allow plants to self-seed and roam freely?  Are happy accidents permitted, or do we quickly correct them and steer the garden back on course?

The concept of wildness in gardens is not new.  But the topic is hotter than ever these days.  Author, lecturer, photographer, and designer Rick Darke has recently revived William Robinson's classic tome The Wild Garden.  William Robinson (1838-1935) introduced a revolutionary book in 1870 that advocated an authentically natural approach to planting design.  Now Rick Darke has republished this timeless work, complete with Darke's own photographs and preface.

No one in America has Rick Darke’s eye for plants in their natural habitat. Darke is one of the few planting photographers today to get beyond the horticultural close up and show plants living and growing in their natural habitats. The result is dramatic. Darke’s books are literally changing planting design in America, as his photographs serve as powerful inspiration to landscape architects and gardeners. Now those photographs come together with Robinson’s timeless text.

The Idea of Wildness

The concept of wilderness has inspired literature throughout the centuries. But Robinson dispenses with this mythic “wilderness” and offers a concept of wildness that is entirely relevant for creating a modern, ecological landscape ethic. The wild garden, “has nothing to do with the old idea of ‘Wilderness,’” writes Robinson in his preface. Robinson’s wild garden is not a pristine sanctuary untouched by human hands, but a place where human activity and natural ecology intersect. “Some have thought of it as a garden run wild,” Robinson says.

A New Aesthetic

That Robinson’s wild garden does not preclude human intervention, but welcomes it, makes it the starting point for any gardener serious about sustainable design. Chapter by chapter, Robinson richly describes strategies for arranging plants to work within naturally occurring plant communities. Robinson is a plantsman’s plantsman. Each chapter focuses on solid techniques for combining plants into various natural habitats, creating a hybrid space that is at once wild and man-made.

His combinations are poetic: double crimson peonies dotted through a field of native grasses; clumps of yellow alliums growing along a forgotten fenceline; or drifts of Lily of the Valley gathered in a sunny copse in the woods. His work describes a new aesthetic: a third nature where cherished cultivated plants intermingle freely with effervescent native vegetation.

In addition to the text, the book has almost a hundred exquisite drawings and engravings by British artist Alfred Parsons. The drawings bring to life Robinson’s vision, adding a moody richness that conceals as much as it reveals.

The Wild Garden is essential reading for any plant designer, landscape architect, or gardener. This textbook provides layers of inspiration and depth not offered by today’s coffee table books on planting. Since reading this book, my planting designs have been liberated, and I owe a debt to Robinson and Darke for expanding my imagination.

Spontaneous Gardens: The Next Frontier in Green Design?

Is the ultimate strategy in green garden planting not to plant at all? The concept of spontaneous gardens--gardens that emerge without human intervention--is a relatively new concept in America, but one that has potential to change the way we garden.

Most gardeners spend quite a bit of energy combating "spontaneous vegetation." Unless it happens in a forest or a meadow, spontaneously occuring vegetation in human landscapes is not welcome. I spent an hour last weekend mercilessly attacking Henbit (Lamium amplexicaule) and Yellow Woodsorrel (Oxalis stricta) in one of my gardens. But earlier this morning, I was blown away by the most beautiful drifts of purple-blooming Henbit and Ground Ivy along the George Washington Parkway. In the urban setting it was a pest; in a more pastoral setting, it was a wildflower.

When you strip away the cultural baggage and consider these plants purely from their ecological function, a new picture emerges. Spontaneously occuring vegetation reduces urban temperatures, provides food and habitat for wildlife, prevents erosion, builds soil, and often performs phytoremediation. In addition, the act of creating and maintaining a spontaneous garden is a completely sustainable process. It requires almost no soil preparation, allows the plant to pick the site, needs no fertilizers or other inputs, and is ridiculously low maintenance.

While the concept of spontaneous gardening resides at the fringes of the American gardening scene, Europeans have worked at the concept for decades. The book The Dynamic Landscape, edited by Nigel Dunnett and James Hitchmough, is a collection of essays that teach strategies for manipulating spontaneous vegetation to create more pleasing human landscapes. A central theme of the book is allowing spontaneous to flourish, but selectively adding or subtracting species to create desired effects. Very similar to the maintenance strategies of meadows (River Farm meadow pictured below). The planting strategies are based on strong ecological research into meadow and grassland maintenance.



When it comes to planting design and gardening, I am a control freak. The idea of waiting for weeds to take over my prized lot, and then only doing minor tweaks to it makes me insane. But two recent revelations have started to change my mind. First, I used to pass an abandoned yard in Capitol Hill on my way to work every morning. It was a lawn that had gone fallow. Left alone, it was by far the most interesting and beautiful yard I passed. The drifts of clover and buckhorn plantain floated gracefully among the inflorescences of grasses. Pollinators swarmed. I spent more time staring at that dumb lot than any of the other skillfully maintained gardens.

Second, as a planting designer, I spend several hours a day meticulously designing planting plans to look natural. It's hard. In fact, it's damn hard to pull that off without looking contrived or ridiculous. It takes thoughtfully developing strong gestures, then carefully creating layers of interest, balancing grasses with forbs and woodies, creating texture and contrast, then thinking through the seasons of bloom. And to be completely honest, the end result fails as often as it succeeds.

One of the more inspiring landscapes I've seen recently is Piet Oudolf's design for the Highline. He uses a highly designed planting to mimic the quality of the spontaneous vegetation that dominated the abandoned rail track. It is remarkable precisely because it is so reminiscent of the abandoned rail tracks.

It's the realization that all of my efforts at planting design--even the most inspiring planting I've seen--are all aimed at having that certain quality, the je ne sais quoi, of naturalness. Not an imitation of nature, mind you, but an effervescent interpretation of it. The great irony is that creating easy, loose-looking landscapes requires working a design to death.
So maybe there's something to this spontaneous garden thing. Maybe my great crusade to get American gardens to loosen up should start with me. Let those weeds go. Create a "Freedom Lawn." Or a spontaneous green roof. Or throw some seed bombs and see what happens. The lessons from the mean and gritty world of urban ecology might just teach us how to flourish in the future.

In Praise of our Weedy Urban Misfits

I'll admit it: I'm a plant geek. If I have a car wreck, it will not be because I was playing with my Blackberry, but because I was wrenching my neck to see some grass on the side of the road. I secretly love the days at work when someone brings in an unidentified plant into the office--I can identify faster than anyone else. I even remember the street address of interesting plants I see in my neighborhood. "Remember that spectacular Chaenomeles on 12th and Maryland?" I'll ask my wife, who usually rolls her eyes.

But underneath my I-dare-you-to-find-a-plant-I-don't-know bravado, I have a weak spot. My horticultural Achilles heel. I don't really know weeds. Yes, I can write a dissertation on the differences of South African restios. And I can see differences between indistinguishable Heuchera cultivars. But I can't tell you the names of the seven or eight wild urban plants growing in the cracks in my sidewalk. The most ubiquitious of all plants remain anonymous to me.

Until now. Thanks to a book that Rick Darke suggested to one of my colleagues, my weedy dementia will soon be over. The book, Wild Urban Plants of the Northeast: A Field Guide, written by Arnold Arboretum's Peter Del Tredici is a must own book by every horticultural enthusiast. Del Tredici has elegantly and simply catalogued all of the "weeds" that surround us. Yes, yes, I can already hear your objections. I admit, a book about weeds may not be the sexiest horticultural topic. However, what Del Tredici has done is nothing short of revolutionary.

Almost every other book on weed identification assumes the following: you must be able to identify the weed in order to kill it. But Del Tredici unveils the hidden complexity and value of wild urban plants. In addition to the standard field guide identification, Del Tredici catalogues the ecological functions the plant contributes to the urban environment.

For example, many of the common lawn weeds such as clover (Trifolium repens) or Birdsfoot Trefoil (Lotus corniculatus) actually improve the soil by fixing nitrogen in its roots. I spent an entire summer in high school pulling up Lambsquarters (Chenopodium album) from the parking lot of a nursery. Now I find out that this European alien provides food and habitat for wildlife, helps to build soil on degraded land, and actually performs phytoremediation by absorbing heavy metals (zinc, copper, and lead) out of the soil.

Del Tredici's book accomplishes two remarkable feats for a field guide. First, he draws attention to a group of plants the entire horticultural universe has ignored, and in so doing, opens a new world for discovery. Turns out, the misfits on the margins of plant society turn out to be some of the more interesting characters. Second, Del Tredici's book upends the traditional categories of natives vs. aliens or "good" vs. "bad" plants. In the mean and brutal world of urban ecology, the good guys and bad guys may not be that far apart. The pioneers of our denuded and abused urban environments may just turn out to be the plants of the future.