Garden Rant – Conservation Sense and Nonsense

Garden Rant recently published an article by garden-writer, Marianne Willburn, defending gardeners who prefer a diverse garden over an exclusively native garden. This issue has been hotly debated for several decades, generating conflict in gardens and garden societies. These are places where people seek refuge from life’s many challenges. Some mourn the loss of peace in the garden and wish for a return to peaceful co-existence between gardeners regardless of which plants they prefer. As American politics have become increasingly polarized, all the more reason to foster peace in our gardens.

Conflicting Goals in the Garden

The primary goal of home gardeners was beauty prior to the advent of the native plant movement. As the saying goes, beauty is in the eye of the beholder, which is a way of saying everyone has their personal definition of beauty. In the garden, some prefer order and symmetry while others prefer naturalistic chaos and abundance.

The native plant movement brought an entirely different goal to the garden about 30 years ago. Native plant advocates want a garden that they believe will best serve the wildlife that lives in it, from the insects at the bottom of the food web, to the birds that eat insects and beyond, to the top of the food web. Beauty is not their goal. In fact, a beautiful garden is considered by some the antithesis of a native garden, judging by the gardens of some of my neighbors whose gardens look dead half the year in our Mediterranean climate that is without rain half the year.

Dictators in the Garden

Such different viewpoints about the purpose of our gardens could have lived peacefully side-by-side if native plant advocates had respected the opinions of cosmopolitan gardeners, but they didn’t.

To quote the Garden Rant article, the native plant movement “saddles everyman gardeners (whether they wished to grow Hemerocallis [daylilies] or fill a raised bed with herbs) with the burdens of past and present ecological damage to our planet, the saving of species from extinction, and the reversal of climate change.”

Source: Garden Rant image of media article

If you haven’t been on the receiving end of such a moralistic lecture from a native plant advocate, you may think that’s an exaggeration. Here are a few examples of such condescending lectures from native plant advocates about the obligations of gardeners to save the planet:

Gardens planted with non-native plants are “blooming wastelands where the flowers feed nobody at all.”
“The typical suburban yard is actually worse than a wasteland. It’s a death trap.”
Margaret Renkle, NY Times, March 28, 2021

“It turns out I’ve been filling my yard with a mix of ecological junk food and horticultural terrorists.”
“I’m sorry to say that if you have a typical urban or suburban landscape, your lawn and garden are also dooming the Earth.”
Dana Milbank becomes a native plant gardener, Washington Post, April 7, 2023

“’I think of it as chemotherapy,’ said Doug Tallamy, a University of Delaware entomologist and guru of the native-plant movement. ‘We have ecological tumors out there. If we don’t control them, we have ecological collapse. We have the collapse of the food web.’”
Doug Tallamy, Washington Post, June 30, 2023

“…no other “don’t” has been shouted more loudly lately than the list of plants to avoid, the various nonnative, longtime nursery-industry standards that are now understood to cause environmental harm.”
Margaret Roach, NY Times, March 17, 2026

Such dire predictions of ecological collapse are overheard among neighbors, over garden fences, in garden society meetings, and in conferences of the California Invasive Plant Council and the California Native Plant Society. Articles with similar themes are found in garden magazines and in the publications of environmental organizations such as the Sierra Club and the Xerces Society.

If the extravagant claims of advocates about the superiority of native plants received the scrutiny and analysis they need, the native plant movement would not have the power and influence that it presently has. Now let’s turn a bright light on the claims of nativism in the natural world.

Debunking Nativist Myths

Nathan Lambstrom is a botanist and professional landscape designer who has given us an example of how nativist myths persist. He reports that Doug Tallamy supports his claim that insects require native plants by obscuring the many contributions non-native plants make to moths and butterflies. He manipulates his data set to hide the documented contributions of non-native plants, including plants considered “invasive.”

I was introduced to the nativist myth that native plants store more carbon than non-native plants nearly 20 years ago in an undergraduate ecology class at UC Berkeley. The University’s land manager who was responsible for destroying non-native trees on the University’s open space told the class that “carbon storage in non-native trees doesn’t count.” I was horrified that the class as well as the professor teaching the class accepted this nonsensical statement without comment. The truth is that both native and non-native plants and trees store carbon while they are alive that would otherwise be released into the atmosphere, contributing to climate change. As long as native plant advocates continue to demand the destruction of non-native plants and trees, they cannot claim that their projects reduce greenhouse gases that cause climate change.

Academic Ecologists Retreat from Invasion Biology

Recently, Thomas Christopher (one of Doug Tallamy’s co-authors and allies) interviewed James Hitchmough, a British ecologist on his Growing Greener podcast. The title of the podcast suggests that Mr. Hitchmough’s viewpoint “challenges the US Consensus” regarding the relative value to insects of natives compared to non-natives. Mr. Hitchmough’s response was that the claimed preference of insects for native plants was conventional wisdom among ecologists in the past, but that “when they did the [field] work, they changed their view.” He also said that the singular focus on the needs of lepidoptera skews the issues because lepidoptera are only 15% of all insects. Other taxa of insects have less restricted host plant preferences than lepidoptera.

That change in viewpoint has occurred among academic ecologists in the US, but continues to be resisted by many gardeners, such as Thomas Christopher. Professor Emeritus Juliet Stromberg recently published a book about her journey from her graduate education, which was deeply steeped in invasion biology, to her present viewpoint, based on decades of fieldwork and as expressed by the title of her book: The Unruly Wild: Embracing Ecological Change in the Southwest.

Stromberg’s book is representative of the opinions of many academic ecologists today. Change in nature is inevitable and it is usually both good and bad, from the perspective of other members of the ecological community and no matter the geographic origins of plants and animals. When judging the impact of new members of an ecological community, the most likely answer is “it depends.”

Endorsements of Stromberg’s book suggest that she is not alone in her realization of the value of introduced plants, which are adapted to the conditions humans have imposed on them:

“An erudite love story of nature in the American Southwest.”
Fred Pearce, author of The New Wild

“Stromberg has written a masterful treatise on why a knee-jerk response to eradicating nonnative plants is not just misguided but counterproductive.”
Dov F. Sax, co-editor of Species Invasions

“Julie Stromberg articulates, with personal knowledge and deep love, a new way to understand and care for a changing world.”
Erick Lundgren, University of Alberta, Canada

Climate change, human activities, and evolution force us to embrace ecological change. Juliet Stromberg helps us to face this reality without fear, but with hope that nature can continue to cope with the demands that humans have made of it. Our efforts to prevent change are futile and they often cause more damage than the environmental changes themselves.

Restoring Peace to Our Gardens

We encourage gardeners to restore peace to our gardens by respecting our cosmopolitan preferences in our gardens, as we respect the preference of others for native plants.

We are republishing an article from the Garden Rant blog with permission of the author, Susan Harris. Susan is a professional garden writer who lives in the Washington DC area. Garden Rant is an award-winning garden blog with a huge readership of garden writers, landscape professionals, and home gardeners. They report over 80,000 readers per day.

In this article, Garden Rant enters the controversial debate about the arbitrary use of the word “invasive.” We agree that this word is both over-used and misused. However, this is more than a semantic debate. It’s an important debate because the word is being used to justify huge destructive projects that are damaging the environment by needlessly attempting to eradicate non-native plants, using polluting methods such as herbicides and prescribed burns.

If you have never debated with native plant advocates, you might find the comments posted to this article of interest. They are typical of the many dialogues we have had with native plant advocates in the past.

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This is a long-simmering rant about the many ways the term “invasive” causes confusion, and more. DO weigh in with alternatives, pushback, and rants of your own.

“Invasive” as synonym for “nonnative”

Google “native versus invasive” and the 5.6 million hits confirms my observation that this is a common usage, and it’s led to a common misperception in the public that the opposite of native is indeed invasive. QED: nonnatives ARE invasive. Even regular garden writers sometimes use this juxtaposition, which should more accurately be “native versus nonnative” or I guess, “exotic.”

That great leveler, Wikipedia, confirms this problem about the term “invasive”: “The first definition, the most used, applies to introduced species (also called “non-indigenous” or “non-native”) that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically.” At least their second definition is more accurate and even includes native species like deer. No argument there.

Defining away the invasive behavior by natives

Can native plants be invasive? Sure, as evidenced by the above-mentioned deer or in the plant world, wild grape. But when native plants are termed invasive someone invariably pipes up to correct the writer because by definition, they’re nonnatives only. And sure enough, legally, by the official U.S. government definition, only nonnative plants can be deemed invasive – for purposes of qualifying for money to remove them. The 1999 Federal Executive Order on Invasive Species defines an invasive species as a “species that is not native to a particular ecosystem…”

Invasive plant lists covering large regions – even continents!

We all know that plant behavior depends on the exact conditions the plant is growing in, as well as more broadly, the region. So some plants that behave well in the North are overly vigorous in the South. Or some, like the infamous purple loosestrife, are vigorous in wet spots, not in dry ones. Examples abound.

Spirea and Doublefile Viburnum (L), Lespedeza (R)

Yet this site by the U. Georgia and many other sources, including the National Park Service, don’t distinguish by region, and the resulting list of “invasives” includes these surprises to gardeners near me: several viburnums, two verbascums, several veronicas, red and white clo0ver, Japanese yew, 3 spireas (MOST on the market), various salvias, willows, nandina, grape hyacinth, Miscanthus sinensis (without specifying that it’s only the early-bloomers that spread), Lespedeza thumbergii, Pee Gee Hydrangea, cotoneaster, and strangely, littlestem bluegrass (Andropogon virginicus). Yet native thugs like trumpet creeper are encouraged and they’re not invasive?

That designation of Spirea really bothers me because it’s such a self-sustaining, easy, low-maintenance and well behaved shrub, one I’ve grown for 30+ years with no signs of trouble. And yet another source – the USDA National Invasive Species Information Center – also targets Spirea Japonica and says this about it: “Spreads rapidly and forms dense stands that crowd out native species.” This and other contradictions between official reports and in-garden experiences growing targeted plants is puzzling to me.

Adding to the overly broad regionality of invasive-plant designations, there’s a new book on invasive plants, written for a national audience.

Shouldn’t invasiveness be designated locally? And sometimes, for certain conditions?

“Invasive” used instead of “spreading”

I’ve heard garden-club members describing their passalong plants at plant swaps as “invasive” if they spread at all. Which leads to said garden club being accused of encouraging the use of “invasives,” among other things.

Methods of “invasion” all lumped together

The USDA lists these characteristics of invasive plants: “produce large numbers of new plants each season; tolerate many soil types and weather conditions; spread easily and efficiently, usually by wind, water, or animals; grow rapidly, allowing them to displace slower growing plants; spread rampantly when they are free of the natural checks and balances found in their native range.”

Yet some of those qualities are valued in the garden – especially tolerance of many conditions. And for the gardener on a budget, especially one trying to replace their lawn with another groundcover, spreading is a good thing and it’s usually described more positively as “fills in quickly.”

What if the standard were: Does the plant spread in a way that causes harm to natural areas? For example, plants that are spread by birds, like English ivy, so that the seeds can go everywhere and harm natural areas. Unlike Spirea and Nandina that spread by rhizome and produce a couple of offspring every year, if that – just like Itea does? Or if it’s simply spreading in the garden, is it impossible to control, like running bamboo?

For example, “Invasive Species of Concern” in Maryland includes mostly plants we’d all agree are thugs and not even considered garden plants, but daylily? As a sun-lover, it won’t spread into the woods and even out in the sun, how hard is it to dig up?

Or a plant could be harmless in a townhouse garden on Capitol Hill but potentially harmful if planted on the edge of a forest.

I wish there were several terms used to describe spreading behavior by plants, rather than the single term “invasive.” How’s a gardener to choose between groundcovers like pachysandra, periwinkle and English ivy, when they’re lumped together as equally thuggish when only one of them will grow virtually to strangle trees, set seed and spread indiscriminately?

More science-based info, please

In researching the topic of “native versus exotic” I came across one example of the type of reporting on invasive species I’d like to see more of – based on research, not scare tactics. Just one quote from this article by Cornell will piss off some readers, but here goes: “A small percentage of plants exhibit invasive tendencies, while the majority of plant introductions are benign or beneficial.”

Solutions for “invasiveness” coming?

Plant breeders are hard at work breeding out invasiveness in popular garden plants, as reported on the Native Plants and Wildlife Gardens blog. Though controversial, especially among native-plant advocates, this type of breeding is recognized by pragmatists as a step in the right direction.

Daylily photo credit.

Tag: Garden Rant

Seeking Peace in Our Gardens