Gardening to Save the Planet

Gardening to Save the Planet

  • By William Cocke
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  • August 2021-Vol.7, No.8
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  • 9 Comments

Editor’s Note: William Cocke is a longtime gardener and native plant enthusiast with an interest in the relationship between gardening and the natural world. For more than 10 years, he wrote a monthly natural history column, “Blue Yonder,” for Blue Ridge Outdoors. He also provided editorial assistance for the regional guide, Piedmont Native Plants: A Guide for Landscapes and Gardens.


In 2008, Douglas W. Tallamy, an unassuming professor of entomology and wildlife ecology at the University of Delaware, shook up the gardening community with a surprise hit, “Bringing Nature Home: How You Can Sustain Wildlife with Native Plants.” In it, he made the case that the relationship between native plants and the insects that have evolved with them is the essential link in maintaining healthy ecosystems. Incorporating native plants into basic garden design is not only desirable, but also imperative, to reverse declining populations of insects and restore balance to an otherwise broken system.  

More recently, in his 2019 book “Nature’s Best Hope: A New Approach to Conservation That Starts in Your Yard,” Tallamy builds upon this idea, but he takes on a more activist tone. He wants to change the way we interact with and perceive the landscape around our homes. It’s no longer enough to select a plant that is pleasing to the human eye, every choice we make must also support a complex web of life. He’s now on a mission to save the world—one garden at a time. 

Doug Tallamy. Photo: Rob Cardillo, courtesy of Workman Publishing Co.

Tallamy is an unlikely revolutionary. In person, his genial science guy demeanor has made him a favorite on the garden club speaking circuit. His writing style leans toward the professorial—a gently persuasive Socratic method punctuated by the occasional exclamatory statement. It’s as if he can barely suppress his enthusiasm. As the book’s title suggests, Tallamy maintains a generally sunny outlook, which is a welcome corrective to the book’s dark underlying theme: the natural world is in big trouble, with many ecosystems in steep, possibly irreversible, decline. In the Anthropocene, humans are not part of the problem, they are the problem. Fortunately, in Tallamy’s view, they can also be a part of the solution. 

In “Nature’s Best Hope,” he aims to inspire a nationwide, grass roots movement he calls “Homegrown National Park.” By awakening those of us who are disconnected from the natural world and changing the ingrained habits and practices of those who are already gardeners, Tallamy believes that, collectively, we can create a homeowner-driven patchwork of personal parks that could blanket the country. In doing so, each of us can play a role in mitigating the effects of habitat loss, fragmentation, and even climate change. If every landowner pledged to convert just half of his or her lawn into a functioning native plant community, Homegrown National Park could cover 20 million acres, weaving the fabric of a vast park system into every ecosystem in the continent.

 It’s a beguiling concept. But there is a lot of information to digest. The book devotes entire chapters to wildlife ecology concepts such as carrying capacity, ecosystem function, keystone genera, and interaction diversity. Fortunately, Tallamy is adept at explaining complex scientific concepts in lay terms. And as an entomologist by training, he devotes one of the lengthiest chapters in the book to how gardeners can become stewards of what E. O Wilson calls “the little things that run the world”—insects. In doing so, he makes a compelling argument for what might be described as insect-driven garden design.

A recent study of native bee populations conducted at Delaware’s Mt. Cuba Center, a public garden and conservation center dedicated to native plants, appears to support Tallamy’s argument for a garden-centric approach to conservation. In conducting a survey of native bee populations on the 1,000-acre property, in both the natural areas and the cultivated gardens, its researchers found that bee diversity was highest in the gardens. So human-designed spaces acted as vital links to the larger landscape—providing oases of diversity that sustain the wild areas surrounding them. 

Gardening for insects sounds a bit creepy. What about gardening for our own benefit, for the sake of a beautiful outdoor space we can call our own? Tallamy wants to upend our whole notion of what’s considered beautiful to include a vision that transcends what looks good to humans and encompasses what sustains the other creatures we share the world with. 

Yellowwood blossom. Photo: William Cocke

Yet, as a scientist, Tallamy can’t help creating hierarchies—much of his and his students’ research involves ranking various native plants and the insect species they support—and I quibble a bit over his preference for certain native plant species over others. While I certainly can’t argue with the praise he lavishes on the oak tree (the subject of his latest book) nor with his point that including just one species of oak in the garden can support hundreds of beneficial insects, he risks giving short shrift to other native trees, such as the yellowwood, because they support fewer insects. We have two mature yellowwoods in our yard and they are unparalleled shade trees, bedecked with stunning displays of fragrant white flowers, aswarm with pollinators, in the years they choose to bloom. He also neglects to mention the several species of mountain mint that, in my observation, are late summer magnets for a diverse set of native bees and wasps. 

Yellowwood tree (Cladrastis kentukea). Photo: William Cocke.

Paradigm shifts rarely happen without controversy. Tallamy has taken some heat for his insistence on the superiority of gardening with native plants and, particularly, his insistence that we make a point of eradicating invasive plants in the landscape. A mostly laudatory April 2020 article in Smithsonian magazine devoted space for a rebuttal to Tallamy’s research from Arthur Shapiro, a professor of entomology at UC Davis. In the Smithsonian story and a later follow-up, Shapiro noted that non-native eucalyptus trees in California support overwintering monarch butterflies and that other introduced plant species do support insects that, in some cases, have found them to be acceptable and even superior food sources. He also presents evidence that some insect species can exhibit evolutionary adaptations to non-native plants in hundreds of generations, rather than the thousands posited by Tallamy. In other words, some insects, even so-called specialists, may adapt to feeding on plants that they haven’t co-evolved with in something approaching a human lifetime. 

This latter point is especially important when considering climate change, another ecological crisis—and perhaps the most pressing one—that Shapiro and his supporters believe Tallamy largely ignores. If native plants cannot compete in a changing climate and are displaced by more aggressive or better adapted invasives, then the wildlife associated with them either adapts or dies, Shapiro argues. Invasives are the consequence of climate change, not the cause of associated plant or animal extinctions. 

That argument, though, seems to me to reinforce Tallamy’s plea for a new conservation approach to gardening, one that gives native species a fighting chance to survive climate change. Leaving large-scale native plant restorations aside, Tallamy’s one-garden-at-a-time approach to maintaining the habitats we’ve constructed, either on purpose or unintentionally, as productive for wildlife as possible, is eminently doable. Controlling invasives on a backyard basis can be achieved with a little sweat equity. Not planting them at all is even better. Placing a non-native azalea in the yard or allowing a monoculture of autumn olive to overtake your landscape may support a few insect species at certain times of the year, but it’s a bit like asking a starving person to go on a diet in the middle of a famine. A healthy, balanced landscape is better able to sustain a greater variety of species in what is certain to be many challenging decades to come.

In an extensive Q&A section, Tallamy attempts to address questions and criticisms of his approach. After reading his book, my preferred habitat is somewhere out in the squishy middle ground. Trying to return the landscape to a misty prelapsarian paradise is an undertaking that would make Sisyphus despair. So it’s okay to incorporate some non-native, noninvasive plants into your garden design. My personal preference is to incorporate about 80% natives into the garden with the rest of the space reserved for exotics. Planting early-blooming bulbs, for example, is a relatively benign way to bring in a welcome burst of color to the spring landscape. I love the structure, height, and heady purple of Tatarian asters in the late fall, so I’ve mixed them in with native asters and goldenrods, the superstars of the late season garden. 

In Nature’s Best Hope, one of Tallamy’s aha moments comes when he observes three monarch butterflies flitting from milkweed to milkweed along the narrow strip of native plants on New York City’s High Line. If these highly specialized insects could find their host plants in the middle of one of the world’s most urban settings, then why not work with nature’s resilience to create a matrix of life that begins with a humble backyard? The Homegrown National Park could incorporate window boxes overlooking Central Park, a postage stamp prairie in a Milwaukee yard, or a desert garden in the exurbs of Los Angeles. It’s a vision—and a challenge—that Tallamy presents the home gardener, and one well worth considering. 

Little things add up to big things, but in the end it’s the little things that may save the world. 

References:

“New survey offers a glimmer of hope for declining native bee populations,” Washington Post  (4/28/2021)

“Meet the Ecologist Who Wants You to Unleash the Wild on Your Backyard,” Smithsonianmag.com (April 2020)

“Doug Tallamy speaks . . . Art Shapiro responds … Million Trees fills in the gaps,” milliontrees.me (March 2020)

 

9 Comments

  1. Million Trees

    Thank you for providing a link to my blog, Conservation Sense and Nonsense (conservsense.org) in this excellent article. You have accurately identified the central questions in the debate about Doug Tallamy’s publications and you have presented them in an informed and even-handed manner.

    To clarify my viewpoint on this debate, I reiterate that everyone should be encouraged to plant what they want in their gardens. If you prefer native plants, by all means plant them. The crown jewel in my small garden is my native oak tree that has damaged the foundation of our home, but will remain regardless of the consequences.

    As your article points out, the issue only becomes contentious when harmless non-native plants are killed with herbicides that are far more harmful to wildlife than any non-native plant. If serving insects are the motive for an exclusively native garden, using herbicides defeats the purpose.

    If your readers are interested in this debate, I suggest that they take a look at this article published by Bay Journal (Chesapeake Bay): https://www.bayjournal.com/opinion/forum/let-invasive-plants-do-their-job-so-the-natives-can-take-over/article_7387fc70-93c6-11eb-a929-03fb0e9b107b.html?fbclid=IwAR0OI6q3D2jYpTLyWPeXZgf0kGY7KYJEaCB0a96c21nfZSWK3k4AJp5DKKg The many comments on that article are an excellent example of the interest in these issues.

    1. William Cocke

      Thanks for your comments. I don’t think the herbicide issue is that difficult to address from the homeowner’s standpoint — don’t use them! If you have to use an herbicide, then be very selective and employ best practices such as painting cut stumps and otherwise minimizing damage to surrounding vegetation. Large-scale application is another issue altogether and one I’m reluctant to jump into.
      — William Cocke

  2. Fern G Campbell

    William,
    A great summary of the challenges that we as individual gardeners have, particularly in our current climate crisis. I agree that the invasive plants and vines are loving this climate! I love your reminder for us to consider planting the beautiful native Yellowwood tree, Cladrastis kentukea. This article serves as a great reminder to me that every plant we choose to plant should support the complex web of life…my new slogan to live by: “Plant Choice Matters”
    So much to do….so little time!

  3. Dominic Carpin

    Excellent piece of writing. I’ve been developing some theories of farm as ecosystem here in Beaverdam. I have a large stand of Tanacetum vulgare. I plant buckwheat and cowpeas in the summertime. Phacelia tanacetifolia. I leave as much native meadow standing as possible. Quite a lot of milkweed, Queen Anne’s Lace and Goldenrod everywhere. A large grove of elder. Wild blackberries. My cool season cover crop is a mix of crimson clover and spring oats. It’s amazing the amount of activity that generates as forage for bumblebees, indigo buntings and blue grosbeaks. Red dock is a ridiculously noxious weed on a vegetable farm, yet it supports the buntings and grosbeaks with its seeds.

  4. Marlene A Condon

    Autumn Olive takes such a bashing from people who obviously know little, if anything, about this SUPERB wildlife plant!

    (1) When full-grown, shrubs bloom in spring, providing an abundance of nectar to a vast number of insects, from bees of many kinds to wasps and butterflies. Predators, such as many spider species, are also able to find food because of all the pollinators visiting the plants. (2) Autumn Olive produces an abundance of fruits in mid-late summer to provide food for mammals, including Black Bears (!), as well as birds of many species. NOTE: Although it’s been suggested that these fruits are not good food for migrating birds, you don’t need to worry. Autumn Olive fruits are so quickly eaten that they are usually long gone when migrating songbirds come through. However, there is absolutely nothing wrong with an animal eating this fruit, which provides a source of quick energy for immediate everyday activities, such as foraging and even breathing! To suggest there is “junk food” in the natural world goes against evolutionary adaptation. It also suggests that somehow the birds of Asia (where Autumn Olive is native) are biologically different from our native birds, which is nonsense. (3) Sapsuckers, which visit Virginia for the winter, obtain much sap from Autumn Olive shrubs. Their sap wells provide a source of nourishment for other species of birds and mammals, and even insects out on warm days (which is critical to their survival). (4) In late winter, when natural foods are becoming scarce, Autumn Olive provides buds readily eaten by Gray Squirrels, Dark-eyed Juncos, American Goldfinches, and White-throated Sparrows. What native plant supports as much wildlife as Autumn Olive? And this is not to mention “structure” that is important for providing protection from predators from spring to fall and cover from weather.

    I might add that the loss of caterpillars, the main insect Doug Tallamy is concerned with, is hardly due to a dearth of native plants; the wider world is full of trees. Caterpillars, being the larvae of moths, are undoubtedly in short supply because MOTHS are in short supply, thanks to the ubiquitous lighting in human society, much of which is often not even necessary. The suggestion that people can save the natural world simply by growing native plants is not to be taken seriously. Folks need to do a whole lot more than that to save our wildlife, and therein lies the problem. Everything else is much more difficult for people to do than just growing some new plants.

    Sincerely,
    Marlene A Condon, Author/Photographer, The Nature-friendly Garden

    1. William Cocke

      Autumn olive is identified as an invasive species by the Va. Cooperative Extension, and is labeled as highly invasive by the Virginia Dept. of Conservation and Recreation. A plant acquires the “highly invasive” label when it spreads easily, alters ecosystem processes, and can cause substantial impacts on undisturbed natural plant communities.

      Virginia is far from alone in this regard; a number of states, including Tennessee and Kentucky treat autumn olive as a “severe threat” due to its ability to spread easily and displace native vegetation, and it is identified as an invasive by most states in the eastern half of the U.S. as well as by numerous national organizations, including the USDA’s National Invasive Species list and by the US Forest Service.

      Birds may eat the berries of autumn olive, but this factor simply cannot outweigh the harm it can cause. As it spreads, autumn olive creates a dense shrub layer that prevents the growth of other plants. The fact that it can transform large areas into a monoculture is the problem. A monoculture of any plant–native or not–is rarely a good thing.

      From a purely observational perspective, I’d encourage folks to notice the landscape the next time they drive down I-81 in the Shenandoah Valley. Autumn olive has taken over vast swaths of territory to the exclusion of everything else. The thing about invasive plants is that they exploit openings in native landscapes. Another example that comes to mind: With the demise of most of our native hemlocks to the wooly adelgid, thickets of autumn olive have overtaken entire stretches of riparian habitat in the Appalachians, to the detriment of native plant communities and trout fisheries that have existed for tens of thousands of years. To a brook trout expiring from high water temperatures, I seriously doubt that autumn olive is a superior riparian alternative to a mature hemlock.

      I DO agree with you about lighting issues — but so does Tallamy! He devotes a good chunk of his book to this very real problem. After reading his book, my wife and I no longer leave our porch lights on at night — we only use them as needed.

      You ask “what native plant supports as much wildlife as autumn olive?” I can think of an obvious one — the many oak species that Tallamy devotes much of his writing to. One of the most useful pieces of advice I took away from Tallamy’s books, and it’s one of the highlights of his presentations, is for homeowners to let an oak grow in the yard if there is room for it. It really is amazing to me how quickly an acorn-grown oak can develop into a large tree in the home landscape. My advice — Grow an oak, cut down the autumn olive!

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