thoughts on invasives, plant conservation–and connection, with michael piantedosi

SOMETIMES WHEN WEEDING in my own garden, I get a sense of overwhelm, a feeling that the unwanted plants are winning. If a gardener can be daunted, imagine how a conservationist with an expert eye must feel in the fight against invasive plants in the vast scale of the native landscape. Michael Piantedosi of Native Plant Trust, the nation’s oldest plant-conservation organization, acknowledges the weight of the task, but also calls himself “a hopeful optimist.” He shared some of his strategies and also how we as gardeners can each make an effort toward conservation–and the sense of deep connection that it, and gardening, can foster.

For the past four years, Michael has worked at Native Plant Trust (formerly known as New England Wild Flower Society) as manager of the New England Plant Conservation Program and seed-bank coordinator. Now he has been named Director of Conservation there, leading the internationally recognized team focused on documenting and saving imperiled plants and restoring habitat.

Native Plant Trust offers educational courses in-person and online on topics related to native plants and conservation; see all the offerings here.

Read along as you listen to the October 7, 2019 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Spotify or Stitcher (and browse my archive of podcasts here). (Photo of Michael, below, by Tara Shugrue.)

invasives, conservation & more, with michael piantedosi


Margaret Roach: I was very, very happy to see of your promotion. As I said in the introduction, “overwhelm,” you know?

Michael Piantedosi: Yes, that’s about right.

Margaret: I think of your job a little bit like a surgeon in the battlefield, do you know what I mean? You are there to help and you’re working really hard and you’re being optimistic, but it also feels a little bit like an onslaught, I suppose, conservation does, yes?

Michael: Yes, there’s a lot of fronts to take on at one time, whether we’re talking about, you know, issues of climate change or as you’ve talked about, invasive species and then the combination of several different affronts to conservation of native plants. You know, it’s a lot of diversity to tackle. It’s a lot of different issues to get into one at a time, but it often feels like, you know, I’m swinging my arms wildly trying to figure one of them out, but we’re working on it.

Margaret: Yes, yes, yes. You are, and as I said in the introduction also, you are at this organization that’s the nation’s oldest plant-conservation group, and there have also been victories … “victory” sounds too absolute, but there have been things that you’ve, like for instance, post-hurricane recently you have done some work that has shown progress. Can you tell us a little bit, for instance, about that as an example of one of your escapades? [Laughter.]

Michael: Sure. So, a few years ago we took on the Seeds of Success Program, focused on Hurricane Sandy restoration areas along specifically the New England coastline.

It was successful to the extent that we were able to procure and then provide over 800 collections of native species seed to restoration projects. It was everything from habitat restoration of salt marshes to river ways in riparian areas, all the way to areas that had been majorly impacted by invasive species as a result of major disturbance because of the storm. So, these seeds were really a critical resource to bring back some of the habitat or at least to bring it into some sort of balance.

Margaret: You were able to do that in part because of the sort of seed vault that you have, the collection of seeds that you have being preserved there?

Michael: In part, yes, I think that really informed a lot of our seed collection and then seed-storage abilities, and it has since. In particular with this project, it was focused on common species, so we were able to be able to basically look at an entire habitat, say a wetland, and pick out the individual species that occur there that are native to New England that were in abundance enough to be collected from without doing harm, and then provide them to restoration projects for planting and seeding. [Above, Michael collecting seed; photo by Matthew Charpentier.]

Margaret: I see. Just as a layperson, a sort of advanced beginner, nowhere am I more shocked–even more so than in my own garden–than driving along the roadsides recently. I had a new book come out, and I went and did a lot of events. I’m driving here and there and places that I’ve been before, but not for a number of years in some cases. Boy, oh boy, it just seemed like Japanese knotweed has taken over the planet. I’m in the Northeast, we should say that, but I know that extends in many areas of the country, for example. Seems like the roadsides are just full of invasive species. Am I imagining that or is that true?

Michael: Absolutely true, yes. You mentioned Japanese knotweed, which is actually on every continent except Antarctica at this point, so you’re right in that.

Margaret: Oh!

Michael: But yes, the roadways and major byways are often these channels that propagules travel on, whether that’s bits of seeds on the tires on your car or on your feet, or even, you know, moving from one construction site to the next through soil or through pieces of root or rhizome. That is absolutely a way that that invasive species travel throughout major areas that otherwise they would’ve been limited based on, you know, maybe a wild animal dispersing the seed. We certainly move at a much faster pace and at a much wider scale. Most wild animals in North America are not quickly going to Europe for a few weeks and coming back. It’s something we do explicitly.

Margaret: So many of our invasive plants, speaking of Japanese knotweed… I’m fighting a losing battle with Oriental bittersweet [Celastrus orbiculatus] in my area, for example, another one… but so many plants we call invasive seem to be from Asia if you look them up, and their range maps and their places of being native. Do we return the favor [laughter]? Have our plants moved elsewhere out of the United States, out of America?

Michael: Sure. Yes. There’s several good examples of that, but it should be said, too, before we go too far into this subject that there is a difference between invasive species and exotic species or non-native species.

Margaret: Right, and thank you for taking time to first tell us that. Yes, yes.

Michael: That difference is simply that an invasive species is something that has the tendency to invade, to dominate a given habitat, to not really have anything to keep its population in check, versus a non-native or exotic species, which is explicitly just not from a given region based on herbarium specimens and other historical data.

But often they are combined, as in Japanese knotweed [Fallopia japonica] or a lot of other species that tend to come from the Asian continent. It’s not anything specific about Asia or Europe or Eurasia or anywhere else in the world. It’s simply a matter of when you show up at a place, you will probably become a weed if you don’t have anything to keep your population in check. That’s usually because there’s no niche that’s evolved around the species that show up. Basically, there’s no insects that can eat the leaves or the fruits and destroy the plant, or slow it down at least, keep its population in numbers. There are birds that don’t prey on it and so on and so on. That’s the basic reason why anything becomes invasive.

Margaret: Right. So even though hostas are from Asia, the example I was giving you about Asia, they are not invasive in their nature. They haven’t seeded into our woodlands throughout Eastern North America, for instance, compared to the knotweed. Yes.

Michael: Right. That’s also true of native plants. I mean, you can consider in some instances poison ivy as an invasive plant. It can take over big habitat areas if there’s a major disturbance. It is native here, in New England at least. But you know, it also has those tendencies.

Margaret: Right. Black locust [Robinia pseudoacacia] is one that I’ve been reading about recently. I live in an area where there’s a lot of black locust in the woodlands, in the forests, and certainly a lot of seedlings that I have pulled out myself in many places. That’s another one where it’s native or near-native [native to North America but not my specific county], but very aggressive, yes?

Michael: Yes. You know, it’s interesting, too, because we look at these terms like native and non-native and invasive, and often we’re considering them as static terms, that they exist in a period of time and not in the obvious stochastic changes that happen in any ecological system. There are always changes in species makeup and species variety, and that’s always going to happen; that’s what evolution is all about.

At the same time there are individual species that show up that you know for the time being, throw that whole place out of balance. They do cause ecological harm and economic harm, social health concerns, like increases in Lyme disease tied with certain invasive species. But that could go on for a while, that whole subject.

You mentioned an interesting point that I want to comment on, too, which is that the native species to, say, North America or specifically my region of New England, they do occur elsewhere as invasive species. A good example would be smooth cordgrass, or Spartina alterniflora for those scientific Latin name people out there. [Photo above of cordgrass © 2019 by Marilee Lovit; from GoBotany plant finder database of Native Plant Trust.]

Margaret: [Laughter.]

Michael: That’s one that, you know, whether it’s on the West Coast of North America where it’s become invasive in some cases or major coastal areas of Asia, that’s a species that is one of the foundational species in our salt-marsh ecosystems in the Northeast. Yet when it’s brought to a place where, again, it doesn’t have any other plants or animals or competition to keep its populations in check, it explodes and it becomes completely out of balance.

Margaret: Now, you just used a little botanical Latin and frankly, whether common names or Latin names, and I prefer the Latin ones, especially when I’m talking about my weeds or invasive plants, I’m almost surprised how few people seem to know the names of unwanted plants. They may know their garden plants, “Oh, that’s my such and such. I just bought it at the local nursery. I’m so excited to have it …” You know what I mean? Some coveted plant, but with the weeds it’s like, “I don’t know, that’s a weed, that’s a weed, that’s a weed.”

I love learning their names and about their life cycles and where they came from and so forth, because I feel like it informs my strategy for living with them and working against their taking over the whole place. [Laughter.] Is that a first step for us either as gardeners or in conservation? Is at a first step to sort of know what the palette of your opponents is?

Michael: That’s a great point. Yes. I mean, that’s basically the first step to awareness and consciousness of what’s around you. I say that in part because the Latin or scientific names of a lot of our plants species do reveal more about the plant to us than otherwise if we didn’t know them, or if we used simply a common name that … Common names often are set in a kind of anthropological uses or in regional specifics. But the scientific name often breaks down the literal, morphological physical features of the plant or its tendency to grow hair or to produce certain colored fruits or leaves. So, I think that is a level of seeing that also reveals the plant world to us.

You know, we talk a lot about plant blindness and combating that. It’s certainly true I think in the general public in this country where very few plant species can be recognized or talked about. Most of them are things like “Christmas tree” or “grass,” you know?

Margaret: Yes. [Laughter.]

Michael: They’re these big generalized groups of plants that really are-

Margaret: “Rose bush, rose bush.”

Michael: Yes, roses in general. Or grasses in general, which we have hundreds of different species in each. But the first step is taking a bit of time to look a little closer at what’s around you outside, whether it’s in your garden or beyond it.

Margaret: Yes. Because what I think is wonderful, about the internet, for instance—even if you don’t have field guides … I’m a field-guide freak, I have a million field guides to everything and the more local, the better. Do you know what I mean? Because it’s so helpful. They’re my literal guides to what’s going on and I can always find the answer.

But the internet, if you were to search, if we were in California or Michigan—or wherever we were, even down sometimes to the county level—for “California invasive plants,” you will find today and for every state, and again even maybe every county, you will find a glossary pretty quickly of profiles of invasive species of your area, for instance. I mean, it’s out there. It’s not hard to get that information anymore.

Similar to weeds, a lot of the university extensions and so forth have incredible guides, searchable, that you can key out your weeds and so forth of garden weeds. So, I think those tools are really illuminating and a gardener’s best friend, and probably a conservationist’s or beginning conservationist’s good friend, too.

Michael: Absolutely.

Margaret: So, here we are as gardeners, and doing tasks, and I wanted some advice from you. So, for instance, I’ve been editing a little sort of meadow, an un-mown area above my house, again in the Northeast and it’s little bluestem, and lately the goldenrod seems to be wanting to march across the whole thing. It’s not Canada goldenrod; there’s five or six others, five or six species, but not Solidago canadensis. But anyway, so I want to edit because … And for me it’s a little bit of a contrivance, it’s not just a natural thing. I’m not mowing this area regularly. I’m mowing once maybe in the early spring, you know, to favor the little bluestem.

So, I’m editing, and I’m the other day taking out goldenrod. I think of course right away, “Oh, I can’t leave those bare disturbances, those open bits of soil, because who knows what’s going to pop up?” Maybe something worse. When we want to give an advantage to native plants but also do a little editing, tell me a little bit about what should a person like myself be doing in a situation like that? [Laughter.]

Michael: Yes. I think one of the … Nature abhors a vacuum, and giving the leeway of bare soil to anything often amounts with whatever’s in the air or whatever’s being blown in through seed—anything could land there and it very well could be something you don’t want. So it does make sense to select for things that maybe not only you want but also maybe the wildlife around you that values it for food or for shelter or something else. Those are the kind of decisions that I make at home as well, which I have almost 2 acres that’s basically meadow, and a lot of that is because I’ve put down specific species of seeds, collected wild, that I want to see in my yard as well.

But it’s not simply that I want it for beauty, though that is a major part, of course—aesthetics is part of your landscape, but it’s also for the fact that I know it will feed the insects that will crawl all over it, and then those will feed the birds, and the birds will be fed to the mammals. The whole food web benefits from this, never mind the fact that below ground the soil is being nourished by having really deep root systems that can hold water and create microbacterial communities.

You know, there’s really few disadvantages with using native species in your garden. I think outside of the fact that some of them, as we talked about, do really run all over the place and I think depending on what what kind of eye you have for it, it can look messy or disturbed, but I personally am way over that issue. [Laughter.] I see them as-

Margaret: You’ve let it go, let it go, let it go. But with editing, we never want to leave a place barren, a bare spot, right?

Michael: Yes.

Margaret: I mean, when we’re editing or starting something, we’ve got to … Otherwise it could be pandemonium what pops up, I think.

Michael: Right. It’s a good idea to put down seed. I think, you know, in general, too, the farther along in a plant’s life cycle you can put it in the ground at home, the more likely it is to survive. So, if you can grow small plugs from seed that you’ve got, that’s an excellent way to kind of ensure survival of the plant you’re putting in the ground, or at least to make it more likely.

Margaret: Yes. For instance, I wanted to increase the balance of the little bluestem. I think I’m going to maybe collect a little seed soon from some of my existing plants to have more plugs for next year when I do this editing again. Because this time what I did is I went to a native plant nursery near me, which from local seeds produces local plants, and I bought some plants. But I could kind of make my own, you’re saying, for next time.

Michael: Sure, yes. I mean, that’s been one of the joys of the position that I’ve occupied here at Native Plant Trust is knowing very intimately how to collect seeds of a wide variety of native species. It’s again a simply a matter of just paying attention and being conscious of a plant’s phenology. So, what time of year is it going to flower? What time of year does it produce fruit? When is that fruit ripe in the landscape?

This kind of thing, it’s not simply something that feeds into our garden, of course that’s very important, too, or into our meadow, or yard.

It also feeds our, I think, need for meaning in the world and in the natural world. I think truly having a deeper relationship with the plants and animals that occur around you, that fosters a love of conservation and an empathy for the land. So, you know, I think it’s a bigger exercise than simply going and collecting wild seed for use in your own yard, though I think really everyone is capable of doing this. It’s very simple. Of course, the difficult part is getting anything to grow in the manner you want it to. That’s more difficult.

Margaret: [Laughter.] As Margaret has been finding out with her goldenrod.

Michael: Sure, yes.

Margaret: I wanted to ask, I saw you gave a talk recently that was called something like “Conservation Through Use,” and I didn’t really know about that. When I read about it, I thought, “Oh, I do know about this. I just didn’t know the …” and then there was like a synonym, “reciprocal conservation.” Can we talk a little bit about conservation through use? Because in a way I feel like maybe gardening qualifies in certain ways. Native-plant gardening may be qualifies, at least, so tell me a little about that.

Michael: Sure, yes. A lot of that term in the first place, you know, I’ve been inspired certainly by the book “Braiding Sweetgrass” by Robin Wall Kimmerer, where she does talk about reciprocity a decent amount in that book. Really what I’m getting at with that topic is simply that humans don’t inherently have a damaging effect on their natural environment. So, wild places are not harmed inherently by humans. It’s just that we have a long track record of doing so, at least in the past 300 years.

I think we can foster a more personal relationship with individual plants and individual animals on the landscape simply by giving gratitude and by understanding that we are also part of that ecology, if we can take down these figurative walls and literal walls that keep us isolated from interacting with wild landscapes. Whether that is, as I mentioned before, collecting seed or simply being really appreciative that you are given a strawberry from the ground without doing anything for it, it’s that kind of thing that …

Sometimes the issue in conservation is certainly: Do we have the resources to tackle habitat restoration or save an imperiled species? That has to be based on scientific data, and of course the scientific method is paramount. At the same time, we have a bit of an issue I think in our relationship to nature in general, and that relationship also needs to get a hard look, whether it’s through kind of assuming that whatever we’re doing is harmful and that we have to stop humans from going into wild places and preserving them by putting a figurative glass dome over it, or totally exploiting a habitat.

I think those two things need to be addressed, and we need to understand that it’s more nuanced than that, that we can be vectors for dispersal of seeds. You know, check out your socks or your boots at the end of a hike.

Margaret: Yes, we can; we can accidentally.

Michael: We can accidentally do it. There’s certain plants that if we intentionally harvest them at the right time of year, knowing their phenology, knowing when they produce seeds, actually help them by letting them thrive on that disturbance that you know, digging up a small tuber or you know, like a potato or something—in a lot of wild plants that is really helpful.

Gardening is a great example of this. It’s a firsthand interaction with a living organism that is nonhuman. I think simply through understanding that you do a lot of work in the garden, but there’s a lot of it that’s outside of you, and a lot of it I think can be elaborated on with just your awareness of what you’re growing, what it seems to thrive on, how to propagate it in the future. All of these things are part of that. It doesn’t take as much, I guess, individual human interaction with wild plants because they often are doing their own thing all the time as it would in a garden setting.

But I think the same can be at practice there, which is simply being conscious and grateful for what has been given to you from the earth is the first step.

Margaret: Good, good thoughts, Michael; very good thoughts. It speaks to me, at least, and I hope to others listening. I’m so glad to meet you officially, and again, congratulations on taking on the new position. I hope we’ll talk again. There are even online courses besides in-person learning opportunities at Native Plant Trust, and lots and lots of information on the website to kind of take some of these ideas we’ve been talking about a little further. So, thank you so much for making time today. [Below, photo of Michael conducting a fern survey, by by Matthew Charpentier.]

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 10th year in March 2019. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the October 7, 2019 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).

  1. Mary says:

    Wonderful conversation — so helpful to learn a little about how we gardeners can work with all the plants whose seeds come our way. I’ve started deadheading Hostas as mine are seeding out into the beds and the woodland edge.

  2. Susan Meeker-Lowry says:

    Here in NY where I moved to last fall from Maine, wild parsnip is very quickly taking over the fields & roadsides. Pushing out milkweed, asters, goldenrod, etc. and it’s toxic! It only spreads by seed & generally it seems to be getting mowed after the seeds are viable rather than earlier in its lifecycle. This is so frustrating to me. I wonder what we can do about this plant. It doesn’t seem to have a useful purpose, like some of the others we can eat or use for medicine.

  3. Rebecca says:

    I am putting the cart before the horse here, reading the whole article a bit later. This morning I have been pulling and piling Japanese Stilt Grass and actually came inside to google if it had any redeeming qualities because it has simply taken over. If you ever find a bit in your yard, garden, woods…PULL IT! Or if this is a money maker crop, I’ll be rich!

    1. margaret says:

      It is a horrible thing, Rebecca. My friend Ken Druse has talked to me about his trials with it again and again! The key is to pull before it drops seed for next year’s crop (here that is maybe early September).

  4. Kyle says:

    I get your point, Margaret, but please stop picking on black locust. We inherited some in our backyard (southwestern PA) and I love them. So do nuthatches, wrens, woodpeckers, and squirrels. They are nitrogen fixers and produce the best firewood. Okay, they do sprout in colonies, clog gutters, and the limbs do fall (firewood.) And, it’s a good example for how a North American native can be “invasive” in different regions of the country. Just give them a break. Especially this time of year when you can admire the twisted stand of Appalachian witches whirling under an October sky.

    1. margaret says:

      Correct, a good example of how a “native” isn’t native everywhere. Where you are located R. pseudoacacia is close to or in its original range, where I am it has romped across woodlands formerly containing a balance of other trees. I have many big beautiful ones here and their flowers are amazing and I love the deep fissured bark…but they’re a bit too successful in my area, sadly. So the states around where I am consider it an invasive.

  5. Marie says:

    In my large pollinator garden (that happens to be in my front yard) I allowed several types of New England aster to seed. While they are gorgeous right now, they seed everywhere in my somewhat controlled (and sometimes out of control) garden. I’m inspired to cut the seed heads and try seeding it in my woods and margins of my side yards. It can’t hurt and hopefully I can control the seeding in the garden – I pulled out 100s of aster plants this spring and still have tons of it in the garden. I did this with golden rod – allowed it to seed in my garden but it just became too unruly so I ripped it out, but I do allow it to grow in the margins of my side yards. I need to find some better behaved late season natives.

  6. nancy nichols says:

    Best way to deal with stilt grass is to pull in spring and late summer before it goes to seed. And any other time you see it advancing into a bed. Redeeming quality is that it is easy to pull (think mugwort) and remains short. Pretty chartreuse ground cover if it weren’t so rampant. Pennsylvannia Smartweed, (Polygonum pennsylvania) is a taller delicately branching late summer invader that can overwhelm in no time if you’re near water. Also easy to pull, coming out in hand fulls with just a tug. It’s sticky and can cause a short-lived skin irritation so beware. Follow same routine to keep in check. A wild edible, member of the buckwheat and knotweed family and host to wildlife. Through observation, diligence and plan of action we can manage what species we don’t want taking over cultivated areas. In rural environments the outer, wilder edges sustain the ecosystem.

  7. Patricia Sechi says:

    I have become an avid seed saver. My question has to do with the right time and method for seeding. I read that poppies and coneflower for instance, can best be seeded in the fall by broadcasting and lightly covering with good soil. Some native perennials like Milkweed, I understand, can be heavily seeded in mulchy compost and soil in a plastic container like the ones you get leaf lettuces in with holes in the lid and placed for the winter where it will get sun. Is there a way to know which perennials need to overwinter and by what method, and which seeds you might save for early spring to either direct sow or start seedlings?

  8. Cindy says:

    Years ago, i saw black locust cut back to make a shrub, maybe fifteen feet high. It was floriferous and relatively easy to pick the flowers. The flowers were treated like elderflowers. It does sucker.

    All the orange and black bugs are supposed to be north american. I read about one recently, that laid its eggs in tree of heaven. This Chinese supposedly sold one particular cultivar back in the 1800s. Now who looks at stinkwood trees? I have seen different colored seedheads. Maybe the chartreuse turns brown.

  9. I enjoyed this program. I work with our county invasive management group. It often feels like we are fighting a losing battle. I feel like it is better to do something rather than nothing. Maybe other people will finally get the picture and the world will come to some sort of healthy place.

  10. Scarlet says:

    I hear you about weeding and how it can be overwhelming! And invasive species can be such a huge challenge. I love native plants because they are well suited to the conditions of the area but rarely do they get out of hand.

  11. Garry Root says:

    I am putting the cart before the horse here, reading the whole article a bit later. This morning I have been pulling and piling Japanese Stilt Grass and actually came inside to google if it had any redeeming qualities because it has simply taken over.

  12. Mike Z says:

    A couple year’s back, I read “Nature’s Garden: A Guide to Identifying, Harvesting and Preparing Edible Wild Plants.” There was an interesting anecdote about Native Americans cultivating patches of wild edibles wherever they grew. They would harvest a portion for sustenance and divide a portion to continue propagating the edible for future harvests. It was the first time I had considered humans having a positive relationship with the ecology of a place. Would Michael consider this kind of relationship as aiding the conservation of a place? Too often I feel we get stuck in the “put a glass dome over it” strategy of conservation for fear of doing harm when we could be actively improving a place.

  13. katie says:

    i used to be friends with michael online, years ago. its so interesting and amazing to see him on here. mikep, if you see this…hi!

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