So, Non-Native Plants are Good Now?

There’s a big tempest going on these days in the world of conservation biology. I suppose a certain amount of controversy among scientists isn’t too unusual, but this one directly affects us native plant advocates, so it has gotten my attention.

Should we learn to love this sort of landscape?

Here’s the thing: a few respected biologists have recently been proposing that we should stop worrying about the question of native vs. non-native plants. Basically, their message seems to be that invasive plants are no big deal, the world is changing, and we should just get over it. Move on. Embrace what they call “novel ecosystems.” Accept the new reality.

Maybe this debate isn’t even so big, in the scope of things. Imagine questioning whether the Earth is flat or round. Do human bodies consist of four humours or something else (like maybe a hundred trillion cells)? I’m pretty sure everybody now agrees that the Earth revolves around the sun, but in 1633 poor old Galileo was convicted of heresy and placed under house arrest (for the rest of his life!) for following that damned new Copernican doctrine. You get the point. Scientific argument goes on and on, while we regular folks listen in and try to make sense of it all, until some sort of truth comes into focus.

The ferns and spring wildflowers that once grew here may not be officially extinct, but Japanese Stiltgrass has effectively taken over the entire forest floor.

So, back to the current controversy. “Recent analyses suggest that invaders do not represent a major extinction threat to most species in most environments.” So writes Mark Davis, author of Invasion Biology and one of the leading voices for this new point of view. This particular statement is from his article “Don’t Judge Species on Their Origins,” in Nature (June 2011, Vol. 474). Some respected biologists do agree with his conclusions and many disagree with him, but more on that later.

I myself am troubled by this “non-natives are no big deal” message, for several reasons.

First, the authors of this literature frequently use the terms “non-native” and “invasive” interchangeably. In paraphrasing their message just above, I did it too. Did you notice? Well, we all know that this is wrong. So when Mark Davis begins his article by writing, “Over the past few decades, ‘non-native’ species have been vilified for driving beloved ‘native’ species to extinction,” he’s mis-stating the issue, right at the start. Worse, by implying that all non-native plants are necessarily invasive, he’s misinforming the public.

Here’s my second concern: why focus on extinction as the only evidence of harm? New data may well show that “extinctions due to competition” are rare, but, really, extinction isn’t the big problem for most of the world. The big issues are species displacement, loss of biological complexity and a weakened food web. Even without evidence of lots of extinctions (and I suspect that with further study we will discover more losses than are evident now), non-native species can powerfully diminish the vitality and resilience of any landscape.

Who's got the upper hand here... the native blue-flag or the European yellow iris?

They say invasive species help heal the planet. Did this riverbank ecosystem need any help before the multiflora rose thicket took over?

A third problem involves media coverage. This idea is getting a lot of attention in the form of reviews, op-eds and blogs that extract and condense their message from scientific literature that originally contained numerous caveats and exceptions. Unfortunately, much of this subtle detail is getting lost along the way. What most people hear, as a result, is that we really don’t need to be so concerned about non-natives. For some, especially those who are predisposed to automatically dismiss all environmental concerns, this message can so easily translate into not being concerned at all. The true message is increasingly getting blurred and lost to the public.

A little-known dispersal vector: holiday decorations.

I say this as a member of the public myself. For quite a while now, I’ve been hearing about these guys who preach that invasive plants are good. Whaat?! I suppose I’m as likely as the next person to cling to my cherished beliefs, but I’m chagrined to admit that, in my knee-jerk reaction against these “invasive-plant lovers,” I’ve waited until now to explore their facts. And, as it turns out, the message I’ve gotten is not accurate. Despite their sometimes rather extreme language, what I’ve discovered is that these scientists are trying to convey a more nuanced message: the native-alien story is more complex than we’ve thought, and in the face of new data we all ought to look at the situation objectively, without attachment to familiar dogma.

Now, I’m fairly well informed about plants and landscape design, but I know I’m not qualified to evaluate their data. So at times like this I look to other authorities to guide me. At a recent conference that I attended, Doug Tallamy (entomologist and author of Bringing Nature Home) helped me out: he listed the current arguments in favor of re-thinking non-native plants, and he then proceeded to discredit all of these points with his usual clarity and quiet certainty backed up by simple facts. When he spoke, I sat up and noticed. His is a voice I trust.

Purple Trillium at the base of a Musclewood tree: who needs 'em?

Which brings me to trouble number four: respected experts who dispute the conclusions reached by Mark Davis and his colleagues don’t get much media coverage. Is this just the media’s natural tendency to focus on the new and controversial? Perhaps.

Here’s Mr. Davis again, instructing us: “It is time for scientists, land managers and policy makers to ditch this preoccupation with the native-alien dichotomy and embrace more dynamic and pragmatic approaches to the conservation and management of species – approaches better-suited to our fast-changing planet.” With some trepidation, I wonder out loud: does this new, less-gentle and less kind point of view represent an attitude that’s becoming more prevalent in society as a whole? Maybe, maybe not.  But how different his tone is from Doug Tallamy’s: “You can be indifferent about non-natives only if you don’t understand, and even love, the complexity and necessity of the ecosystems being displaced.”

So, with due respect for those who propose a new way of thinking about non-native species, I’ll continue to believe as I have up until now: that we need to be careful of the Earth and protect it from our hubris and mistakes. To do this, I will still give preferential treatment to native plants, and avoid using non-natives if possible, in every situation. And, as an advocate for rich, diverse and healthy landscapes everywhere, I will also keep my eyes and mind open, to see what kind of truth eventually emerges from the current controversy.

Why keep growing Burning Bush (Euonymous alatus), which is clearly no longer a "harmless ornamental"....

.... when we could just as easily plant actually harmless and highly beneficial, native Highbush Blueberry?


© 2011, Sue Reed. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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  1. Kelly Bennett says

    I think hubris is an excellent word to use in this context. It seems that there are so many examples of humans taking a “dynamic and pragmatic” approach to some aspect of the natural world, and it is always a disaster for the ecosystem involved.

  2. Suzanne says

    I think the confusion begins with definitions that are not clear: what is a “native” plant and what is a “non-native” plant? What is an “invasive” (though, admittedly, this is more clear?) A number of plants I have been researching lately were introduced by Europeans in the 1700’s or early 1800’s and, yet, are included in texts like William Cullina’s “Native Tree, Shrubs and Vines” and Donald Leopold’s “Native Plants for the Northeast.” This is very confusing.

    Perhaps the “more nuanced” landscape is included in these resources or do we go back to “before the Pilgrims came” (one definition I read from a respected educational institution about the landscape we are trying to create here in the Northeast.)

    As much as I respect and agree with Doug Tallamy, there has to be more reference points out there. The resistance comes for me when one person is lionized while the rest of the scientific community is providing valid research and no one is talking about it.

    • says

      Suzanne, I’m surprised at your comment: I’ve never discovered any species in Cullina’s book or Leopold’s that were not truly native North American plants. Anyone can make an error, but those books are considered pretty authoritative by most people. Perhaps you can list a few examples of plants in those books that you think are not actually native to North America, so we can evaluate your claim?
      Vincent Vizachero recently posted..Olmsted-approved Native Shrubs

      • says

        Vince –

        big difference between “native to the Northeast” and “native to Stamford CT” – I also find plants all the time listed as having a “range” including all of CT but these plants don’t grow naturally any where near the coast where I live.

        I want the plants that my wildlife will recognize as food.


        • says

          Sue Sweeney, I love your point and think it would be good for all of it to think this way and adopt this as our criteria. “I want the plants that my wildlife will recognize as food” is perhaps the heart of the native plant movement. Why landscape plants that use valuable resources like water, soil and space while contributing little to wildlife habitat. Much to the disappointment of my wife I’ve let pokeweed and goldenrod grow on our 3/4 acreage. There’s nothing more beautiful than a fawn coming into the yard or squirrels playing in the line of trees. It would be nice if more people adopted your attitude. We should all want “plants that our wildlife will recognize as food”. I’m certainly going to use your phrase as my adopted new motto.
          Sovereign John recently posted..Health department raids community picnic and destroys all food with bleach |

    • says

      Suzanne, you raise good points. We do need more than just Doug Tallamy to validate the concern about non-native plants. I mentioned him mainly because his is a name many people recognize as an expert. There are thousands more scientists who question the idea of accepting non-natives as “inevitable and just a part of the new reality,” but most of them are unknown to the public and/or remaining fairly quiet in their opinions. Which is another part of the problem. But, fortunately, the more we all talk about it, the clearer the truth will become, in time.

      Regarding definitions: this confusion about terms can at times be a big nuisance, but it is also an indication of how profound and complex this whole issue is, and that’s what stimulates such interesting dialogue!

      • says

        To all the commentators: I can only speak for myself but when I refer to D Tallamy it is because he popularized the work of many professionals, making it accessible to the lay community. He is not the ultimate expert but we all owe him a debt for bringing the key theme into popular consciousnesses.

        To all the “let the best plant win” commentators: I, for one, don’t want to live in a homogenized world made up of only the few hundred toughest generalist species that can stand my City’s (warming) climate.

        May be I can’t get all the alien mugwort out of the alleyways in my City where it is aggravating our kids’ asthma, but I can save a few acres as a nature preserve where City dwellers can enjoy the plants and animals seldom seen in the inner city, and where at least some of of the non-generalist wildlife species can continue to exist for their own sake as well as ours. I can educate at least a few people to see the consequences of their actions on the environment so they can make informed choices.

        • Sue Sweeney says

          oops I was interrupted by an earthquake. To continue: by “so-called experts” I mean like the one recently published who counted the number of robins eating alien honeysuckle berries each fall and concluded that since she saw more robins doing this each year that the honeysuckle was good for the environment. Like if you saw more people shopping at Walmart, that has to mean… If you don’t understand why this is not good science, I think it would be good to figure it out – IMHO that is.

          BTW: I don’t know what you do for a living but I volunteer full time to take out the invasives, and preserve the local genotype natives so I think I’ve earned the right to speak.

          PS I am not Sue Reed’s “buddy” – I”ve never met her – but wish some day to be so honored.

  3. says

    There’s a great many non-native plants I cherish and make use of freely in the garden.

    What I dislike are thugs. And so far, practically everything in the yard that’s seriously thuggin’ has been a non-native, and when I’ve done the research, has usually been on the invasive species of serious concern list. (The sole exception there being hummingbird vine, which is a pretty thuggin’ native.)

    I think gardeners who have to garden amid the invasives and sit down to research the plants causing them headaches are likely to find that there’s something to all this invasive species stuff. I just don’t know why more people don’t DO that…
    UrsulaV recently posted..Io Moth Caterpillar

    • says

      I agree…. we all should be as informed as possible, and base our actions on careful thought about the most current data available. This is a lot to ask, I know, when we just want to buy a pretty flower or garden the way our grandparents did. But at least we can try! That’s the one thing I do agree with Mark Davis about: the world has changed, and we need to respond to that change. Where I differ from him is on HOW to respond.

  4. says

    Good article! I personally think that sometimes no one is looking at natural areas and seeing what clearly is happening due to invasives and to the home garden to see why so many chemicals are needed since Integrated Pest Management is no longer an option if the plants don’t support native insects to fight the fight. Where the heck are our lowest members of the food chain?

    There is always a tipping point for something that once was “uneventful” to become detrimental to life. Smoking is a prime example. 40 years ago we thought nothing about smoking…it hadn’t reached the “tipping point”. Then the surgeon general took a hard look at cancers and well, we all know where we are today. It clearly has a major bearing on health issues and is no longer acceptable.

    I thank the writers such as Sally and Andy Wasowski (Requiem for a Lawnmower) who got me thinking about what was happening around us and helped me make the decision of avoid non-native plants in my garden (moving forward) and Doug Tallamy for bringing the problem of damaged ecosystems and the food chain to the forefront of our conversations. And you, Sue Reed, for keeping the conversations going.
    Loret recently posted..Tribute to a Great Friend

    • says

      The more we talk and explore and probe and question and clarify, the better things will get. That’s my goal: to stimulate discussion. I want this topic to be brought forward into more people’s awareness. With enough knowledge and the judgment of many minds working together, humans eventually do get things right. (It’s that “eventually” part that’s so tricky, because we often have to get it wrong for a while before we get it right!)

  5. says

    I do believe we need to look at the thugs in the garden world…many know them but a book or good reference for gardeners would help..plants to avoid in your area or anywhere…these are the real problem plants…for me I try to use valued texts that show what are natives although that is still an issue as to what is truly native…still I replace the thugs I did not know about and cling to the belief that I am making my patch a better place…as far asnon-natives being OK…no they truly aren’t but again we need to continue to hear the other side loudly
    Donna recently posted..Garden Journal-Dog Days of August

    • says

      Yes, I agree. We need to hear both sides, and the more that both sides can continue to speak respectfully and without exaggeration or name-calling, the more effective the discussion will be. (I’m even a bit wary about calling plants “thugs.” After all, they’re just doing what they’re designed to do, and the word “thugs” makes them sound malevolent. I’m hoping we can soon come up with a better term for fast-spreading, fast-growing plants that are actually just being successful, from nature’s point of view.)

    • says

      The trouble with non-native plants goes beyond those that behave like “thugs”. Some may carry pests and pass them on to related native plants. The original hosts are resistant to the pests they have co-evolved with; but the native plants aren’t and become devastated. One example is the hemlock woolly adelgid, ( Another example I wrote about recently is the viburnum leaf beetle ( Worse yet some of these threats may lay dormant for many, many years and then explode and spread like wildfire through the native plants.
      Whether the hemlocks and viburnums become extinct is not the only issue; the profound alteration of the ecosystems is enough to take these problems seriously.
      I agree with Sue, I don’t call them thugs; they are doing what all living organisms are supposed to do, to grow and multiply. It is our meddling with nature that causes them to become problematic. Earlier botanists and horticulturists didn’t know these things and took pride in bringing new species from distant lands; but, by now, we should know better.
      It is true that many non-natives are here to stay, but that doesn’t mean that we should give up the struggle. We should try to contain their spread as well as prevent the arrival of additional non-natives.
      Thanks for an excellent and clear article.
      Beatriz Moisset recently posted..Utilities right of way. Native plants

  6. says

    Years ago when I began designing and creating wildlife habitat gardens I discovered that there were several plants that I was constantly doing battle with, plants that had a tendency to wipe out everything else in their path. That list has grown longer through the years, sadly. I began to research each of these plants and all of them were of foreign origin and all of them are now on the invasive species lists for many states. The worst thing is that I now see many of these plants spreading through natural areas. They’ve jumped the garden fence and are now happily blazing their path of destruction through my beloved woods. And yet, we continue to sell these plants. That is the root of this problem
    Carole Sevilla Brown recently posted..Lets Just Eat the Invasive Plants

  7. says

    If you have any doubts about the harm invasive plants do to an ecosystem then get out there and volunteer at a local restoration project in its early stages and stay with it through several years. Watch the recovery of a vital diverse ripairan or prairie project and you will never doubt again the necessity of working to slow invasive organisms into the landscape.

    As for what constitutes a native. The few hundred years we have been over populating this system in north america started at a point in time near enough that evidence as to what was here still exists. So that is a good starting point but not an absolute list. Humans are the invasive species doing the most damage on the earth everywhere and we must find a way to keep the changes we bring to every space we inhabit from wiping out so many other species. Just because we can purify our sewer water to be reused as drinking water does not mean I look forward to living that way.
    Gloria recently posted..Rattlesnake Master Pollinator Information

    • says

      I agree with you. One idea I point out in my book (Energy-Wise Landscape Design) is that a great way to save energy in our gardens and grounds is to monitor and remove invasive plants before they get established. The cost of invasive species control runs into the billions of dollars nationwide each year, and that accounting doesn’t even factor in the energy expense. Not to mention the energy wasted when an earlier gardening (or energy-saving) effort has been negated by invasives.

  8. says

    I have couple very brief questions and stay confused so maybe the experts here can help.

    1. Why is no one complaining about the hundreds of acres of mono-genus sedum and perennial peanut roofs going in across the US in the name of sustainability and conservation and green? Feral sedum is creeping everywhere.
    2. How do I justify my rooftop agriculture projects? Most food is non-native.
    3. Why is the native plant & wildflower community so passive and not shouting like this cool article everyday?

    Last point. Whenever I start talking exotic the other side slams me by saying ‘they behave’! Truly there is a difference between exotic and invasive. One comment I had sent to me was that I was ruining a fledgling industry by using the 10-20-30 rule for biodiversity on green roof design. A sedum roof is only one genus and lots of invasive list made species.

    So – I need your support on the roof too! :) And want to hear the take on food plants…..
    Kevin Songer recently posted..Green Roof Designs are different than ground level landscapes. Green Roofer Responsibility.

    • says

      Hi Kevin. I completely agree with your concern/alarm about the use of non-native plants on green roofs. I’ve been very slow to accept the whole notion of green roofs simply because they always seems to be loaded either with lawn grass that required extensive mowing and probably couldn’t be maintained organically, or with sedum and little else, and that always bothered me, and I hadn’t yet focused on the native possibilities as alternatives to sedum. So I applaud your efforts to bring this issue into our awareness.

      When it comes to food plants, my answer used to be simple: the discussion about natives vs. non-natives was not about food plants at all. Now, however, with permaculturists advocating the use of perennial food crops in our landscapes, things are getting a bit murkier. I mean, do we REALLY need to grow hardy kiwi in the Northeast, supposedly as a necessary source of vitamin C? I agree that it may be good and more sustainable to reduce our consumption of citrus fruit from the south, but wouldn’t it be better to grow kale for our C? Kale is guaranteed to stay in our gardens and not invade nearby woodlands, which kiwi has already started to do. It’s all so delightfully complex!

  9. James Hitz says

    I don’t suppose any of those scientists are fishermen trying to get to the water through the multiflora? We get a lot of unwanted animal species brought into this country as well. I guess African bees should be welcomed. Bring in elephants and lions and let them go where they want.

  10. says

    Great article, Sue! Most of my gardening is focused on providing habitat for pollinators, my darling animal group. Research has shown that the majority of pollinators get the greatest benefit from native plants- those that evolved in a location along with them. But, I’ve noticed that some non-natives like Lavender Chaste-tree can be the only thing around that feeds bumble bees in June where I live in Georgia! I think that’s primarily because too few folks have planted natives so that something is blooming all season long. I’m sort of on the fence with this one… I think I’ve decided that any of my own future garadening efforts or advice to others will be to plant natives, but allow beneficial non-natives to stay-put. If I moved into a house with a few chaste-trees in the yard, I couldn’t bring myself to chop them down just because they’re not native. Glad you brought up the topic so people think about it! :)
    Athena Rayne Anderson recently 3-month birthday celebration!

    • says

      Hi Athena. I hear the same line of thought about Japanese Knotweed here in the Northeast: the flowers provide great pollen for bees in August and September, so beekeepers love it. But wait… what were the bees eating before the knotweed swallowed up every other plant in sight? Yep, they were eating the pollen of asters and goldenrod. No problem. So I agree with you, it’s the absence of appropriate native plants that can make non-natives seem desirable. But comparing the effect of non-natives to what would happen if there was nothing growing there…this isn’t a fair comparison. We have to compare them to the thriving ecosystems they displace. And when we do that, non-natives always come up short. You might enjoy reading my earlier post: “You calling Me a Purist?” for more thoughts on this issue.

    • says

      Athena – I tend to think of the foreign super-sweet pollinator attracting plants the “pollinator stealers”; I have at least anecdotal evidence that they distract pollinators from the native plants. These garden plants may not be invasive but if what I think is so pans out in studies, they could be doing even more harm.

  11. Glenn says

    I enjoy the verbal jousting by the experts and those of you in the know. Everywhere I go to shop for plants (big boxes especially) non-native invasive plants are being sold. Education seems the only option still available to combat the use and propagation of invasive plants. In addition to harry home owners, a large part of the horticulture industry is at fault. I live in the Southeast. When one hikes in any wooded area near an established, landscaped subdivision, it is easy to find invasive non-natives which began their lives in a well manicured yard. And there is not enough Round-Up in the world to slash and spay all the C. privet. This is a lament coming from a guy who even appreciates May Apples!

  12. says

    Hi all. We (the authors of ‘Don’t judge species on their origins’) ARE paying attention to these discussions. One of the points we made was that the distinction between alien and invasive has never been consistently, carefully drawn in any literature, protests to the contrary notwithstanding. Some attempts have been made to standardize the terminology (beginning while Darwin was still on the HMS Beagle) but they haven’t gained much practical traction. ‘Alien-invasive-species’ has been run together into a single pejorative conception. That said, to suggest that any species is ‘invading’ gives it both undue credit (for having the motivation and awareness and capability to take and hold territory) and undue blame (for some unspecified malevolence arising from its association with humans). Still, we never suggested it would be fine to put everything everywhere. There are all kinds of perfectly good reasons not to do that. But the reasons we tend to think of as ‘ecological’ all ultimately reduce to preferences, and that makes the job of affecting them a sociopolitical exercise. So, unless you (yes, really, you personally) are willing to completely revolutionize the lives you lead, humans will continue to redistribute biota at a fantastic rate. Become a seed-saving natives-only locavore, make all your own shelter,clothes, tools and equipment from local materials, stop using imported power and don’t go anywhere except under your own power while carrying nothing. Failing any of that, you continue to support the ‘currents of commerce’ that are now an established fact of the planetary biogeography. As the spread of (e.g.,) quagga qnd zebra mussels shows very well, it only takes one person who doesn’t go along, or who forgets once, or just fails once, to break a blockade. Even the most committed, self-styled enemy of invasive species spreads them with one hand while ‘fighting’ them with the other. Another of our points concerned novel ecosystems. There is now, frankly, no place in the biosphere that stands wholly unaltered by direct or indirect human influence. Even ‘natural areas’ aren’t natural in that sense, and weeding to keep them unaffected by humans is just another way for humans to affect them. By the same token, habitat loss is just another way of saying “there is no ‘there’ there” for once-native species. But only in very, very rare cases does that mean there is no habitat for anything in those places. Sometimes it means that a species from halfway around the planet can do well under the newly prevailing conditions. In the real, actual world a reflexive bias in favor of natives can lead us to continually disrupt a newly configured landscape simply because it doesn’t match anything we’ve known (or heard about) before. That was the reason we brought up the tamarisk case. Tamarisk has been demonized at great fiscal and environmental cost for decades, for no good reason and to no good purpose. How all that got started will surprise you (see my website for access to my papers on tamarisk). Now, a word about honeybees. At least some of you know that honeybees aren’t native to the Americas; they have had an enormous effect on pollination rates that has certainly led to a new pattern of spatial dominance among ‘native’ plants. Any standard that allows honeybees to be considered native throws the whole concept of nativeness under the bus. Africanized honeybees are no less native than non-Africanized honeybees in the Americas. In one sense they are MORE native, because the genotype originated in South America and never existed anywhere but in the western hemisphere. But I tell you what, let’s do throw nativeness under the bus. As its actual originator pointed out in the 1860s, nativeness is “a purely negative conception” based on absence of recognizable evidence for human agency in a species’ distribution pattern. As I said before, humans now affect everything in the biosphere directly or indirectly, by choice or by accident, ‘subsidizing’ or ‘taxing’ evolutionary fitness. You will not find a single biotic distribution on the planet that hasn’t been somehow pushed or pulled, expanded or diminished or relocated by human agency. Native is no longer a meaningful idea, at least not in the sense of connoting purity or belongingness; and it hasn’t been for centuries. It’s not that kind of world, and no amount of nostalgic acting out will make it that kind of world, ever again. The fact that bumblebees will pollinate Vitex, and that robins will eat alien honeysuckle (and at my house, in the winter, even old, dry chinaberries) suggests that everything else operates pragmatically while we’re busy composing morality tales.

    • says

      Hi Matt. Thank you for taking the time to write such an extensive comment. I hope that many people will have the opportunity to review it and get better informed about your point of view. I’m pretty sure that labeling other peoples’ perspective “nostalgic acting out” and “morality tales” will not particularly help in clarifying the facts. I do agree with you, however, that humans affect everything on the planet. To me, that’s just further confirmation that we should be a lot more careful in our actions, not less careful.

      There’s a huge thunderstorm about to pass over my house, literally, so I have to sign off and shut down for now. More later, I hope.

    • says

      Hi again Matt. Okay, I’ve spent some more time reading your exposition. As best I can figure (a few paragraphs or logical transitions in your composition would have been helpful, but never mind), you’re saying:
      1. There’s no clear definition of the term “native,” so let’s just give up trying to figure it out. Should we also stop wrestling with all complex issues, just because they’re difficult?
      2. There’s no “ecological basis” for choosing natives, it’s all just personal preference, a “socio-political exercise.” So… the habitat diminishment that we all clearly see all around us, that has been documented by science, doesn’t actually matter at all, simply because other things can grow in place of the species that have been displaced? I disagree entirely with this point. Ecosystem health depends on a functioning food web, and not all species are equal contributors to that web.
      3. If we can’t act with perfect consistency, with every single one of our actions supporting our goal, then there’s not point in doing anything at all. This is the same argument used by people who say, well, if you’re going to drive a car or live in a house or breathe air, then you can’t say you’re trying to help the environment, because just by being alive you’re harming the environment. I’m no philosopher or debater, but I’ll bet there’s a term for this kind of pointlessly circular argument.
      4. If only one person doesn’t go along, there’s no point in trying. Hm. Doesn’t all of human history negate this argument?
      5. A “reflexive bias” in favor of native species causes us to disrupt “newly-configured” landscapes just because they’re unfamiliar. Your example of the tamarisk situation may be valid, or maybe not. I’m not qualified to evaluate it (and I confess I haven’t yet gone to your site to read more about it). But I do wonder whether a few mis-guided programs to remove invasive species invalidate the entire effort in every case.
      6. Honeybees aren’t native in North America, so the fact that a lot of people don’t realize this fact therefore nullifies the entire concept of nativeness. Well… no…to me this just means that a lot of people don’t realize honeybees are native to South America, and we need to continue our education efforts (and encourage people to provide habitat for native bees and pollinators).
      7. Native is no longer a meaningful idea, in terms of purity or belongingess. I’m pretty sure native never has meant “pure,” but the term does imply a sense of species “belonging” in certain ecosystems because of the role they play in the functioning of those systems. Is there some new evidence that these complex relationships are no longer valid or “meaningful?”
      8. The world has changed and people who care about native species (and ecosystem health) are just “nostalgically acting out.” This implies that the only reason we work to protect our landscapes from destruction is because we’re clinging to the past and blindly resisting change. Well…I acknowledge that there may be some current in our society right now that may be impelling some of us to protect things we cherish, as the world changes so swiftly and we fear losing our familiar touchstones. But that is not the whole reason. The whole reason would take a much longer paper to explore than I can do here. For me, however, and I believe for many others, the reason is simply a matter of advocating for the many invisible creatures who hold the planet together, and whose work we do not even come close to understanding, and who are so easily destroyed by our errors and carelessness.
      9. Nature is amoral (pragmatic), so humans should be amoral too. Why should humans have values? Um. If I were you, I wouldn’t end with this lame argument.

      • Tami says

        Wow, reading these comments has convinced me that you and your readers really do not have ‘open minds,’ nor do you believe in ‘education.’ In fact, there’s a real anti-scientific literature bias I see here (see the ‘so-called experts’ comment below) as well as lots of straw-man arguments used to advocate whatever it is you’re advocating. I especially find it disturbing how you insist on filtering all ecological understanding through the writings of Dr. Tallamy, whose guidebook is really only useful if you’re gardening in the midatlantic states. He seems like a great teacher who has the kernel of a great idea, but who is still far from having it fully fleshed out. I look forward to his new improved book as well as the books from other people who develop his ideas further based on solid science.

        Ecology is a complex subject to tackle and being in an MLA program, I can assure you that my education is woefully inadequate on this subject. You might feel the same way. One book I’ve come across to help me with my thesis research is ‘Ecology of Fragmented Landscapes‘ by Susan Collinge. It’s a broad and readable survey of current ecological research which highlights many of the areas of dissention like ‘native vs. non-native’ which exist in this field. I especially recommend reading the section discussing the whole ‘wildlife corridor’ concept: did you know that years of research have yet to prove they work? Yet in school and in ‘ecological gardening’ books it’s gospel.

        Another trend is the new subfield of Urban Ecology, which I believe you and your buddy seem to be ranting about above It is also little understood. Impassioned pleas on behalf of ‘invisible creatures’ might well ultimately work against their best interests in highly disturbed urban areas. Maybe it IS better to watch with a critical eye to see how nature rapidly adapts to our relentless moves on the earth and then act to support what has actually been documented to work to their advantage. Sneering at the work of curious scientists clearly isn’t.

        BTW, I’m a beekeeper too. Apis mellifera, the domesticated honeybee, is NOT native to South America as you assert above.

        • says

          Hi Tami, and thanks again for your comments. This whole subject is so deliciously complex, we can just keep learning about it forever! I can’t really speak for this blog’s readers’ attitude toward science, but my goal in the original article was to examine my own preconceptions and reactions, evaluate facts as I understand them and promote further inquiry and learning. Not sure who the “ranting buddy” is to whom you refer. I do regret mis-stating the origin of honeybees…. that was definitely an “oops” statement that I wanted to retract as soon as it went out, but… too late. Anyway, it’s too bad you’re leaving the conversation. We all do benefit from hearing a wide range of thoughtful perspectives. So far, I myself haven’t heard any convincing evidence that non-native plants should be welcomed, but I’ll definitely check out the book you recommend.

          • David Martin says

            Urban ecology, of sorts, has been around for a long time. I recall a University of Georgia ecologist critiquing the squares in Savannah for an undergraduate field trip.

            I live in Florida, where like it or not, we have lots of permanently established non-native plants, ranging from a large number of African legumes to the purple Phlox from Oklahoma that’s at home on roadsides. A lot of them are more or less innocuous, others wreck entire ecosystems (an Asian climbing fern would be one of those). There’s also the huge assortment of yard plants, some of which are bound to become pests. My yard has a lot of them. I don’t think the cycads will become problems, and probably few if any of the palms, heliconias, or bromeliads. The yard’s in an urbanized area, so there are no issues with feeding non-native pollinators that could affect native species. And there’s native species from laurel and young live oaks to shrubs, palms, and lots of beach sunflowers, which of course shouldn’t be living so far inland.

            An interesting model for landscaping in a natural area is on display at Archbold Biological Station south of Lake Placid, Fla. A new education building on a disturbed site needed low vegetation in case of wildfire. The grasses and herbs that were installed are all native to central Florida, though I think a few aren’t native to the Station. The flowery grassland isn’t like anything on the Station, but it makes a suitable setting for the building.

    • says

      Matt: you and your co-authors paint with too broad a brush. Not all those who try to minimize the flow and impact of non-natives are being sentimental. On the other hand some grow non-natives for sentimental reasons; for instance those who tried to re-create British gardens in America or India, or those who maintain rose gardens in this country.

      I am neither sentimental nor xenophobic (see my piece: I do not hate invasive species, and I know that many agree with me. I see abundant evidence that the movement of huge numbers of species by human beings is causing serious threats to healthy ecosystems. The trouble is not with the organisms, nor with their ability to be invasive.

      We don’t advocate going back to a pristine state because we don’t know what that is or there is no such thing. It is impossible to reassemble a community once it has been severely altered. Even if it was possible to restore a pristine state, it would be artificial because organisms evolve and ecosystems evolve and the reconstructed one would not be truly natural.

      All what we want is to restore, as much as possible, a functional healthy ecosystem that has been invaded by non-native non-coelvolved organisms. We know that it has taken many thousands or millions of years for ecosystems to develop the assemblages of organisms that seem to be working best in that particular location. The infusion of large numbers of aliens disrupts that balance. We should mitigate that impact as much as possible and prevent new invasions as much as possible. This is pragmatism, nor sentimentality.

      1. The Africanized bee is not native to South America. It was introduced to Brazil; it escaped and started moving north.
      2. I thought that the jury was still out on the tamarisk tree.
      3. Could you supply references on the Dendroctonus ponderosae beetle killing more trees than any other? I could make a list of 10 non-native insects that all combined destroy more plants than the tens of thousands of native herbivorous insects all together. An isolated example would prove nothing.
      4. “Robins eat honeysuckle and chinaberry”. Of course they do now that the natives they used to feed on are gone from that area. Now, can you prove that those alien plants are good for the ecosystem in other ways? Food for caterpillars, pollinators and many others, interactions with mycorrhizae and soil micro-organisms, etc. You must look at all the interactions, please.
      Beatriz Moisset recently posted..Utilities right of way. Native plants

  13. says

    Sue – you always say it best!

    In addition, when I read these so-called “studies” written” by so-called “experts” I can’t help wondering about the role here of the significant commercial interests in continuing to sell easily propagated non-natives which have a tendency to be only too hardy and spread only to fast. It doesn’t take a lot of money to commission a study and get the results published in an area where the press is not particularly well informed.

    Another driving factor simply may be the size the of the job — it’s always appealing to some to say “we don’t need to bother” or “we don’t need to be responsible for what we’ve done/are doing”. I can see some resource-pressed land managers quickly embracing the “I don’t have to anything” theory.

    The bottom line, though, is that the non-generalist native species, and their entire ecosystems, are worth saving and we need to do so as best we can.

    Further, well-meaning people deserve accurate information so that they are aware of the results of their buying and gardening choices.

  14. says

    Thanks Sue! And thanks for pointing out the commercial-interests angle. I also wonder whether it might be a good idea for all of us, when discussing this issue, to start using the terms “generalist” and “specialist” for plants, rather than native, alien, etc. Hmm. You’ve given me a new thought. Great way to start the day!

  15. says

    At times it seems a free-for-all with the horticultural industry bringing in whatever they want to the detriment of ecosystems. Here in Ontario, Canada, garden journalists are espousing the great benefits of a non-native species, sea buckthorn (Hippophae rhamnoides)

    Sea buckthorn has been identified as invasive in other parts of Canada and among other places, like Ireland. It was used extensively to stabilize slopes (much like invasive Russian & autumn olives). In 2004 at the Canadian Botanical Association’s second symposium on invasive alien plants, it was named the 15th most invasive plant in natural areas. “When it comes to questions about which are the most serious invasive plants of natural habitats in Canada, the situation can change relatively quickly. Five of the top ranking candidates for ‘worst’ nationally are not on the standard lists because their recognition, establishment and spread have been very recent.” (

    Slow and weak legislation, a complicit industry (horticultural industries) and ignorant gardeners make for a ripe takeover of green spaces (including home gardens) by waves of invasive species. Many of us are not complacent and are prepared to fight the good fight to help our local native plant species for the sake of our environment.

    • says

      Hi there, Local Scoop, whoever you are, and thanks for the informative links. I really agree that the hort industry folks have a big role to play in this situation, and so far they’re all mostly playing it in favor of the immediate bottom line. As more and more businesses make the switch to “greener” practices, however, I hope that what used to be called the “green industry” itself soon catches on.

  16. Cindy says

    Decided to comment, read the quite a philosophical education..but I still think the photographs in this post are worth a thousand we want a woodland floor covered in Japanese Stilt Grass or leaves, mosses & me the choice is obvious..

  17. says

    Hi Cindy, and thanks for commenting. We in the native plant movement are in the midst of a very exciting time, with lots of backlash coming our way as more and more people see the value of gardening and landscaping with native plants. This seems like an inevitable part of all social change: certain people or factions believe they just have to mount a charge against the forward progress. Remember when the value of innoculation was feared and rejected, and then it gradually became accepted by all, and now there’s a small group of people who insist that vaccines are bad, despite mountains of evidence to the contrary? This new crop of scientists and their evidence that denies the importance of being careful with non-natives… they’re so typical of all backlash movements. We just have to keep pushing for real objective clarity, not fear, and not kow-towing to the pressures of mainstream commerce.

  18. Brian Higgins says

    Sue – I think your post is a very well reasoned argument against the shortcomings of Mark Davis’ research – so much so that I hope it gets picked up as a counterpoint and gets further distribution. I haven’t read his book, but the following statement “Recent analyses suggest that invaders do not represent a major extinction threat to most species in most environments.” reads as if it was crafted so that not only is it true, but also the Truth. Extinction is the most extreme example of total loss of a species, but this extinction happens locally and at much smaller scales every day. To steal from another arena…plants don’t kill plants, people kill plants. We have to understand the intersection between the science of why native landscapes are shrinking and ecosystems of all scales are collapsing, with cultural behaviors.
    It seems as if Mark Davis was working backwards from his conclusion and this is a true problem in scientific research everywhere.

    • says

      Hey there Brian! Nice to hear from you, and thanks for the positive feedback. I’m so intrigued by this support of non-native species. It almost seems like there’s a group of professionals coming along who want to pioneer a new set of beliefs, to be the ones who toss out the old knowledge that we’ve been working for decades to convey to the public and that are just now beginning to be understood and accepted. And now, snap, it’s time to move on! I may be wrong about this, but the pattern is familiar. The development of trends – how they arise, swell, swerve, subside, revive, etc. – is fascinating! I wonder what Aldo Leopold would say about all this. Or Jens Jensen.

  19. says

    Oops, I meant to say “and that IS just now beginning to be…” and not “that ARE just now beginning to be…”
    Quickie last-minute edits will be my downfall.

  20. ruth rogers clausen says

    It is critical to remember that exotic means “comes from other places” It is NOT a synonym for invasive.
    Don’t we have invasive natives as well? The bulk of the garden plants that are cultivated are not invasive, native or non-native. Surely there is a chance that a plant such as Korean Campanula takesimana will take over . Indeed it is a thug. Other Campanulas such as European C. lactfolia are perfectly good garden plants that do not roam. Do not get wound up about some of the rhetoric out there. Much of it is over reaction and lack of plant knowledge.

  21. says

    Interesting discussion. I wanted to add an urban perspective to the discussion. I work in Chicago as a part time landscape designer. Since I’m in the middle of an urban area, I’m more concerned with avoiding invasives from a garden maintenance perspective and adding natives and plants that provide food to help support what wildlife we have. As a longtime member of MELA Audubon Society and Nature Conservancy, I am concerned with preservation and sustainable practices. I’m not a scientist or Botanist.

    I have trouble envisioning how something I’m growing in the city is going to get out of bounds (except in the neighbor’s garden-think Joe Pye Weed) unless I’m near a river, forrest preserve or other non urban area. In that case, I’m a lot more careful because the forest preserves have become infested with a Buckthorn and wild garlic that make hanging out there less interesting than it once was.

    Most of the businesses I work with are using sustainable products/practices and specialize in native plants. I rely on them to offer the best solutions. I’m not a purist, but if a native will work, I’ll use it over something else. If a product is more sustainable, I’ll recommend its use. It’s the best I can do and still please clients.

    Chicago is the home of green roof, including gardens where people sit and relax as well as the traditional green roofs. While green roof gardens are tricky because of wind, I see trees and all kinds of plants on roofs these days. As we get more experience with green roofs, I’m sure the industry will discover better plants to use. In the last ten years, there has been a lot of progress with removing weight in products to allow more green roofs. In a highly urbanized area of high rises, it’s wonderful to be able go to a garden to relax that doesn’t involve transportation.

  22. says

    Sue, you’ve really stirred up a good one here, well done!

    I have been listening to both sides of the discussion, here and in conferences and literature for a few years now, and I have to say that I see hubris, emotion, misstatements and misclassifications from both sides. I think there are also alterior motives behind some of the arguments on both sides (some monetary, some ego). It is extremely difficult to come to conclusion (let alone follow), both sides of the topic, and that is the major problem in the debate (especially for the layman). This past winter at the ELA conference the dinner keynote was on this same topic. The proposal was to stop wasting time and energy as we have been in the war on invasives, and take a deep breath and reexamine the problem and its solutions. Emotions took hold of the audience, and any chance that this could be a construction discussion were lost during the comments portion of the evening. That was a shame, because all discussion should be honored in order to move forward with a comprehensive plan.

    My thoughts: Invasives are here to stay, and they will increase in numbers and species. Constructive battles should continue to be waged to slow or stop this from happening. The inclusion of native plants in planted landscapes should be promoted. Non invasive alien plants should not be vilified. Native invasive plants should not be vilified, but should also be included in stewardship plans where appropriate. Garden “thugs” should not be considered invasive unless they meet defined criteria (please research the characteristics that deem a plant invasive). Our focus as scientists, horticulturists, architects, designers, naturalists, gardeners, landscapers and homeowers, should be on promoting high levels of diversity within each ecosystem, in a manner appropriate for each ecosystems needs (again, please perform due diligence). There are too many instances in our history, as example of “experts” getting the science wrong, and even more evidence of the masses adopting incorrect information.

    There is/will be a solution to the invasive problem. We have clearly not come to conclusion as to what it might be as of yet, and the final answer might not be to either sides liking, but I look forward to the discussion.
    Scott Hokunson recently posted..Nearly Wordless Wednesday – 8.31.2011

  23. says

    Hi Scott, and thanks for your thoughts. I agree with so much of what you say, especially that this is a very valuable, important discussion. I actually avoided the ELA conference last year because at that time I didn’t want to hear all three panelists spouting the same line. Now I wish I hadn’t skipped it, just to have heard the varied points of view. Finding that right balance between science and emotion is so tricky, and it’s an issue that’s always with us, in every part of our lives. I’m thinking that maybe the public ultimately absorbs more of the emotional message than the scientific one.

  24. Gov Pavlicek says

    “But how different his tone is from Doug Tallamy’s: “You can be indifferent about non-natives only if you don’t understand, and even love, the complexity and necessity of the ecosystems being displaced.”

    So what he says: ” If you undestand it, you wil agree with me. All of you.” Well, Mark Davis has been involved in restoration ecology. And he is not alone. Dov Sax did a lot of research that was peerreviewed and he notes the same things like Davis does. And so does James Brown, Steve Gaines and alot of others who have done peerreviewed research.
    Besides: it does not matter if one is knowledgable or not about anything. If some people like a newcomer for his or her reason, than that is his/her right in a democracy. No scientist, as I already said, can be more qualified to do so. In the end, if the ecologist likes change and dynamics he could still like the newcomers. And if another ecologist does not like the changes he sees, he may have another opinion.

    I love some nonnatives for what they brought here in The Netherlands. Like Picea sitchensis, a newcomer here dispersed by humans (why should humans not be allowed to disperse?). It has given way to forest of unprecedented richeness in ferns numbers and species. Picea abies, although marginally native or nonnative is FULL of redlist species, many of the fungi. These are chopped down routinely precisely because they are considered nonnative (only because humans stoped them form reentering after the last iceage and pollen record do not dismiss it as a native tree over here).
    and inspite of mycologists who beg organisations not to do it.
    Woods of Austrian Pine support exactly the same communities as the native Scots pine. So do larchforests: they also give a way to a lot of redlist species (funghi and birds).

    In so many articels over here (aswell as neighborouring Germany and Denmark) you can read that tforrests are removed solely because they somehow don’t belong here. Not because they are invasive or not.

    The general public is against this too, even after “explanations”. Various universities, like Wageningen, have researched the stance of the public. Out of 150 woodlandscenes those with clearly visible immigrant conifers (Douglas Fir especially) were BY FAR prefered. They were the number one and number two and this was asked to visitors of the natural parks. other research has shown that the public highly values those conifers of the US/Canada over here and again, are strongly against cutting them down because of invasiveness, nationality etc.

    I also can show you a lot of pictures of native species wreaking havoc ( in the view of local anagers) in forests, on heaths etc. Like Scots Pine, Larch and birch. Like the Pine Beetle in the Pacific NW. Should we eradicate them too?

    The problem with nativists and restoration ecologists in general, in my view, is that they have a big problem with change. With accepting that mankind is just another natural factor that has big a big impact on this planet and that you just cannot seperate this animal from nature. As you see, we are of course part of this planet. We will influence. Whether this is good or bad is a personal choice, not a sceintific fact.

  25. Edward says

    I’ve taken to trying to propagate native plants on my parent’s yard. It’s actually hard!
    It’s difficult to find out what is and isn’t native at Home Depot. I would like to take cuttings of some plants I like and spread them around, but I’m not sure if they are native. I’m not sure if the stand of wild roses is Rugosa Rose (invasive) or Virginia Rose (native) I’m not sure if the Honesuckle is Americam Honeusuckle or the Japanese invasive variety.

    Also, what is Native and what is Invasive is really a product of where you live, so information you get off the web can be misleading.

  26. says

    I have been following this debate over the past few years too, and it has always bewildered me that academics (at least one from Harvard no less) would be dismissing invasive plant eradication as ‘romantic’ and pointless. Do those same sceptics not agree that what humanity needs right now is to protect and maintain more than 7 billion people on earth from increasing environmental instability and severe weather events caused by global climate change? It’s been proven that areas with healthy numbers of native plants contain more species biodiversity than areas populated with the usual exotic natives, so surely the protection of current biodiversity and fully-functioning ecosystems makes sense for our own sake? Biodiversity supports resilience and a site’s ability to adapt to rapid changes — monocultures are the opposite especially in an urban setting where most of the world’s population now lives. I find it very disheartening to hear the fight against invasive plants being dismissed. A lot of work is being done at local levels everywhere to restore disturbed areas with regionally native plants – with real, visible successes in the form of increased levels of wildlife from the micro level on up. To encourage scepticism towards the value of keeping our natural areas free of the pollution of invasive plants, then you must also dismiss the value of biodiversity to the continuation of human life on Earth at a time when major environmental upheaval already threaten our way of life. NOT helpful, and as you say Sue, is already being touted as ‘gospel’ (a convenient excuse) by those looking for reasons to carry on with our full-earth-destructive-suicidal trajectory.
    Ellen Sousa recently posted..Use Your Leaves – Making Leaf Mold and Leaf Compost

    • says

      Thanks Ellen, for your thoughts. One tricky piece of this mystery is that we’re not dealing only with facts here. You and I and our like-minded colleagues keep trying to be rational and make common sense points, but there are deeper currents, flowing below everyone’s consciousness, which are pushing the discussion in directions that seem inexplicable and bewildering to many of us. I’m not sure what to call these currents… Socio-cultural movements? Academic pendulum-swings? People’s need to reject a way of thinking simply because it is becoming mainstream? Blind resistance to changing one’s attitude? If I were a social psychologist or cultural anthropologist I might have the right language to describe this phenomenon, and if I understand it better myself I might be able to do a better job of getting through to the naysayers.

      What seems especially sad to me is that the general public’s appreciation for and acceptance of native plants is just STARTING to get off the ground (“native plants” at Lowe’s!), after nearly 100 years of educational effort, starting with pioneers like landscape architect Jens Jenssen in the 1920’s, and Edith Roberts and Elsa Rehmann, the authors of the delightfully informative book, “American Plants for American Gardens,” and continuing right through to this wonderful present-day blog (which a client of mine excitedly told me to go check out!). And now our efforts have to be directed in two opposite directions: reaching out on one side to bring along the uninformed and untrained, while simultaneously reaching out the opposite way to appeal to people who think they already understand the facts but have rejected them in favor of a new, more tradition-busting philosophy. It’s hard to know what to say and write. But I appreciate your words, and all efforts!

  27. Chris says

    I agree that nonnatives are bad but a few have “naturalized”. I think people like Mark Davis confuse these plants as being representative of all nonnative species, however the only reason these plants “naturalized” was because they filled a void in ecosystem caused by us (Dandelions *cough* *cough*). More still the number of “naturalized” plants is actually quite small, are an exception not the rule as Mark Davis Advocates, and many are unappealing themselves with little commercial value.


  1. […] Sue is not afraid to dive right into controversial topics, bringing thoughtfulness and wisdom to every discussion, and having the ability to answer critics with objective insight. Check skill out in action in her post So Non-Native Plants are Good Now? […]

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