Invasive plants reconsidered

by Caroline Brown

I’ve been thinking a lot about invasive plants lately, because earlier this month I attended the Ecological Landscape Association’s winter conference where they were quite the hot topic, and I’m also preparing to write about them for one of my clients.

Let me preface by saying that at the ELA conference, which was fabulous, I attended all four of the permaculture talks that were offered by Dave Jacke and Jono Neiger. Dave is the primary author of a Edible Forest Gardens, a hefty and expensive 2-volume guide to “the ecology and design of home scale food forests” and the owner of an ecological design firm; Jono is the owner of a permaculture design and consultation firm.

Dave has an interesting perspective on invasive plants–frankly it takes cojones to get up in front of a crowd of green-minded, native-lovin’, invasive-hatin’ gardeners and landscapers and say some of the things that he did. But he had some good points, and I agree with him.

I prefer to use the term opportunist instead of invasive. Let me explain that. The word invasive, if you look up the word invade or invasion in the dictionary, it means a threat or attack. An army. If we call a plant or animal invasive, isn’t that anthropomorphizing? Do plants threaten or attack? [italics mine]

I understand, primarily because the piece of property I own is loaded with invasive plants and frankly is quite beautiful in the summer. The only mature tree on our property is a Norway maple that’s at least 50 years old. Most of it was already there when we bought the place, though I have previously confessed to planting English ivy and vinca minor (myrtle/periwinkle), before I knew much about invasive plants. We also have multiflora rose and Japanese barberry, and we used to have a giant Oriental bittersweet, which is the only invasive species that I’ve actually removed.

Plus, we are separated from a giant condo complex and old folks home by a large vacant lot that’s covered in Norway maples–they keep our yard very private. These plants are a major part of the architecture of our small (~7500 sf) lot. We aren’t rich, and since we can’t afford to replace mature trees and shrubs that serve an important purpose for us (privacy)–they’re not going anywhere.

Also, I don’t like it when I hear people talk about “trash birds” or “junk birds,” like house sparrows or starlings. I know that they’re hogs and they’re squeezing out bluebirds. I love bluebirds, OK? But as Hamlet said, “There’s a special providence in the fall of a sparrow.” And Hamlet was really quoting Jesus, who said “Are not two sparrows sold for a penny? Yet not one of them will fall to the ground apart from the will of your Father.” It’s not their fault that they’re sparrows, they’re not DOING anything. They just are what they are, doing what they do. It’s our fault they’re here anyway–they came to this continent on OUR ships.

Of course I realize that invasive species threaten the biodiversity of our ecosystem, but I have to think twice about spending so much money on removing invasive species and restoring native landscapes. Is it….wasteful? I don’t know. On a small property I’m aware of, it cost $20K to remove knotweed and restore native grasses and other plants. Maybe instead we should give it to say, India? I don’t know…it just gives me pause, that’s all.

Back to Dave:

If you understand succession ecology, you will understand that there’s no way a plant or animal alone can be responsible for the way it behaves. Invasion is only possible in the context of a certain kind of ecosystem situation. The first cause of succession is the availability of a site or niche. If there’s no site or niche available, no invasion can occur…. If invasion is not succession then what the hell is it? [italics mine]


The main thing is that the paradigm that we’re using to describe invasive species has many faulty aspects. The thinking is being muddled by framing the issues incorrectly. If we don’t see invasion as part of succession ecology then we are on the wrong track, folks. Because most plants that are considered invasive are disturbance adapted species.

I could go on and on about this. But I’ll skip to the solution. Dave has one:

The cropping principle is the corollary to competitive exclusion. When you have high competition and competitive exclusion occurring, the way to prevent competitive exclusion is by cropping the biggest competitor. If we can find uses for these plants..Kudzu grows very prolifically. It can be used for biodiesel, animal fodder, all kinds of food products, the list goes on. It’s an incredibly useful plant-that’s why it was brought here.

In other words, why can’t we figure out how to eat this stuff? Or use if for fuel, for cryin’ out loud?!

In the meantime, gardeners and others should not buy and plant them, and we should make our voices heard when we see them on sale in retail nurseries. (Frankly this is despicable. They KNOW BETTER.) And another thing that we can do is to stop the important of invasive species through better legislation. We as gardeners and nature lovers need to learn about these efforts and support them. I admit that I don’t know much about this, but I’m going to be learning about it soon for a client, and I’ll pass on what I learn.

Stay tuned…..

Photo courtesy of Wikipedia.


15 Responses to “Invasive plants reconsidered”

  1. Caroline:

    Thank you for all that information on invasive species and the thought surrounding them. Do you know of a website which lists invasive species for RI? I noticed your comment on the sale of invasives at retail nurseries and I am sure that reputable garden centers do not sell those plants which are regulated but there is a lag between when a law is passed and when the growers’ crop cycle is finished. The growers are suffering as they have a big investment in such plants such as barberry of which there are many ornamental cultivars which produce little seed and which are still on the invasive list. Perhaps there should be, and perhaps there is, compensation to the grower for unfinished crops to remove them from production. Just a thought. One other would be that out of the thousands of ornamental trees, shrubs and perennials imported into this country a small proportion are invasive. I am not saying that we should not be on the lookout for invasives but the landscape is so much richer. What would spring be like in New England if not for the lilac to name one! I am happy to hear that Dave is bringing new conversation into a somewhat hysterical topic. I agree with you, let’s find a way to use these plants in a positive way! While kudzu doesn’t winter over here, I have seen it in GA and it has a beauty all it’s own. Thanks for the post, keep up all thinking!

  2. Happy Spring C!!! Nice to see a new post on EFG. Great photo too. I am also back (sorta) over at Veggies…do stop by when you can.

    Huggs, G 🙂

  3. PS: Your header is AMAZING!!!!

  4. This is good — thank you for posting some of the transcript. It dovetails with the same sort of thinking currently ongoing about insects as “pests” in the garden, so I can see where he is coming from.

    Context is a big part of it, as he pointed out; as an example, butterfly bush isn’t invasive here in Maine, but I understand it is considered a nuisance in the Pacific Northwest. A responsible grower/nursery would do well to steer customers away from plants considered locally invasive, but the kind of “all-or-nothing” merchandise palette offered by a big-box store like Home Depot is really where pressure should be applied. If they can offer eco-forested lumber, they should also be able to cope with the idea that some plants shouldn’t be offered in certain locales.

  5. Another aspect of invasiveness that should be considered is adaptation to ecosystems that have been so changed, that return to the original condition is not possible. This may be the case for suburbanized areas, and areas that have been transformed by agriculture. This may be also be the case for all ecosystems if global climate change is a reality. While it may be preferable to maintain the original condition of forests and prairies, and the biodiversity that they maintain, that may not be possible in a transformed planet.

    With change of climate, every place may need exotic species in order to develop green cover and biodiversity. The plants that previously thrived in a particular location, may become too stressed to maintain their prior distribution.

    All of this is speculation, but if I have to choose between fragile, original plant species that can barely hold on, vs. some other vigorous, imported species (from a neighboring region, or elsewhere across the globe), I hope that I can be flexible enough to recognize the need for adaptation.

    That being said, I am no fan of Scotch broom, English ivy or the blackberries that have invaded the local forests. I do understand the desire to hold them back.

  6. In New England we suffer from many years of civilization and farming from suburbanization and urbanization. Our land is not natural in many respects. Some of the invasives where brought to us by horticulturalists and some hitch hiked. We don’t like them (sometimes we do sometimes we don’t) when they squeeze out other plant life. But in many cases ‘we’ introduced them. Let’s be careful about how we go about controlling them. Remember the fable of the town that had too many mice — cats to deal with mice, then dogs, then lions, then elephants —- back to mice!!

  7. Ginger, good point about growers–I had not thought much about them and how their businesses would be hurt by this. I’d like to find out what the “green industry’s” position on this is.

    there is a list at the website for the RI Natural History Survey’s initiative called the Rhode Island Invasive Species Council:
    It classifies plants in different ways, like widespread & invasive, restricted & invasive, invasive in other areas but not RI yet, etc. They stress the list has no legal merit–just informational.

    FF — agree with you about the problem at the national big box nurseries–I suppose they can’t (or don’t want to) have regional strategies. Maybe it’s just too much science for them to have to figure out what’s invasive in every ecosystem where they have stores. That being said, what’s up with the local nurseries with good reputations that sell euonymus by the boatload every year?

    I think I’ve run out of space, I’ll continue in a second comment.

  8. Hi Daniel — I read that poison ivy spreads more as the climate warms, so that’s a good example of what you;re talking about. I hope that some of the natives can evolve to be more hardy as the climate inevitably changes so the world isn’t covered in poison ivy and other such invasives.

    Hi Frank, agreed–I think we’re the culprit for most our invasive species problems. The perils of globalism, global capitalism, whatever you want to call it, I guess…..

  9. Hello Caroline,

    If you look up the words “anthropomorphic” and “opportunist,” you will see that calling a plant an “opportunist” is as much an example of anthropomorphism as is calling it “invasive.”

    David got it wrong, most invasive pest plants are not particularly disturbance adapted. The association of invasive pest plants with disturbed areas is closely tied to propagule pressure. In the early stages of ecological invasion, pest plant propagules are more commonly found in disturbed areas because it is to such areas that they can most easily spread from our gardens. As the population increases and massive numbers of propagules are produced, many pest plants can quite readily invade pristine, undisturbed natural habitats. Indeed, many pest plants are pest plants specifically because they are NOT disturbance adapted and because they indeterminately persist long after any traces of disturbance are gone.

    You can take your yard back from the Norway maples, multiflora roses, and Japanese barberries without compromising privacy and costing a small fortune. Just do it slowly and a square foot at a time…that’s how Rome was built and how an “endless and inexhaustible” prairie was turned into fields of corn and soybeans.

    And finally, I must ask, do you *really* love bluebirds?

  10. Thank you. Thank you. Thank you. Once again we are war with weeds. Never do we fully appreciate those plants which spread beyond our gardens or fall out of our pant cuffs. To the ecologist today there is no biological integration and certainly nature has made a huge mistake by making them part of the whole. And of course humans can save the day by using herbicides and biocontrols. Look now ecologists have a new job-exterminator. The sand bar is now “infested with weeds.” The herbicide is called Habitat. It sounds so good. As we busy managing the world of vegetation like its 1491 we don’t really want to know how nature benefits. We just know its invasive.

  11. Thank you for this article and sharing your thoughts regarding these invasive species. They were interesting.

  12. TO Rufino Osorio – the only sane mind here. All good points.


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