I’M THINKING about trilliums, prompted not just because these treasured spring ephemerals are coming into their season, but by the disturbing news in a report just published that found that 32 percent of all North American Trillium species or varieties are threatened with extinction.
My guest is Amy Highland, the Director of Collections and Conservation Lead at Mt. Cuba Center, a botanic garden and native plant conservation nonprofit in Delaware, one of three organizations behind the findings.
Amy, a graduate of Purdue’s Public Horticulture program, has traveled throughout the temperate forest of North America to find rare plants in need of conservation. We talked about trilliums and also how we as gardeners can be more involved in conservation of native plants over all. (That’s Trillium grandiflorum ‘Quicksilver,’ A Mt. Cuba introduction, above.)
Read along as you listen to the April 25, 2022 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).
trilliums in trouble, with amy highland
Margaret Roach: Happy spring, Amy. I bet it’s beautiful down there at Mt. Cuba right now.
Amy Highland: It is. Things are popping every day.
Margaret: I bet. I bet. So in the report that I’ve read and all of this information about trilliums that we’re going to get into, I was not surprised to see Mt. Cuba as one of the three conservation organizations behind this report on the endangered status of trillium. But one of the others, the New Mexico BioPark Society, or Albuquerque BioPark, it did surprise me because I don’t think there are any native trillium in New Mexico, are there? So tell us about them and about the third partner, NatureServe, and how you all did this.
Amy: That’s true. There are not any trillium species native to New Mexico, and that was not lost on the researchers from the BioPark either. And it is one of the reasons why we held our workshop time here at Mt. Cuba Center, where we could see some of these specimens as opposed to there in Albuquerque.
But the New Mexico BioPark has a commitment to these assessments of how plants are doing in the wild. And they work regularly with the International Union for the Conservation of Nature on medicinal plant species. And a little known fact is that trillium is actually a medicinal plant species. So they were asked to pursue trillium as one of the early assessments that they did. They reached out to us at Mt. Cuba because of our national collection of trillium. And we were able to pull together our third partner, NatureServe, because they also have an assessment process that they use, and worked with every trillium expert that we could find in North America.
Margaret: NatureServe also has the NatureServe Explorer, the sort of search tool… I mean, I’m just am a layperson, but that I use if I want to find out kind of the range of a plant, where it’s wild range is or whatever. Where you can type in a genus and species, and it kind of populates a map in real time of where that plant is occurring and so forth. Is that-
Amy: Yes. NatureServe is a fantastic resource. They not only create maps, but they regularly work with botanists, boots on the ground, looking at these plants in the wild to say how are they doing? Is this population under threat? Does this population need some external conservation? Or that kind of thing. Do we need to put a land easement together for this population?
So NatureServe actually consists of an entire network of botanists across the US and Canada, and also internationally to look at these plants and to evaluate how they’re doing. And then after they bring together all of these assessments, sometimes there are these kinds of workshops or events where we come together, and we say, “O.K., if you know that your trillium is doing well and you know that your trillium is doing well, well, how is the entire genus or the entire family doing in North America?”
And that’s what this study really allowed us to do, was to look for the first time holistically at all of these plants across North America and give a true assessment of their status, so that we can make conservation decisions in the future.
Margaret: So let’s just talk about how many trilliums are there in the world, how many species? And how many are where? Because I think North America has the lion’s chair of them, yes?
Amy: That’s correct. There are thought to be three areas in the world where trillium diversity kind of concentrates. The highest concentration of trillium species is going to be in the American Southeast. The second highest is in the American Northwest. And then the third is an Asian concentration. So there are three centers where a lot of evolution happened, and you’re going to find more species in those areas where there is a lot of diversity, because of that evolutionary history.
Margaret: Interesting that there are three centers, since everything in trilliums comes in threes [laughter]. [Above, Trillum cuneatum from Mt. Cuba’s collection.]
Amy: Oh, is it cute. Yes. I’ve never thought of it like that.
Margaret: Yeah, because right? I mean, all the parts are in threes, yes?
Amy: Yes they are. That’s where its name comes from. Trillium, parts of three, three petals, three settles, three leaves.
Margaret: Yeah. Interesting. I’m always fascinated by their intimate relationship with independence really on—or interdependence—with ants that are there kind of, that love that juicy bit on their seeds and move seeds around. And I just love all that kind of, those stories of interconnections between animals and plants.
Amy: Yeah, that’s a story that many spring ephemerals have. They produce the fatty packet that you’re talking about, the eliaosomes on their seed, that’s attractive to ants and other insects. And one of the best things about trillium is you see it in the wild, and you feel like you’ve stumbled across some sort of fairy magic, like who put this plant here? This is amazing.
Margaret: Right, right.
Amy: But because of the way they’re dispersed through ants or that kind of thing, you can sometimes see them in really interesting patterns, like a ring of trillium. And you think, oh my goodness, who planted this here [laughter]? Well, it was the ants. They were carrying their seed, and somewhere along the way it got heavy, and it just fell there. And it could create a little circle of trillium.
Margaret: Sweet. So with the research, with the report, what were the sort of major takeaways? I mean, if 32 percent of all North American trillium species or varieties are threatened with extinction, what are the drivers of that bleak news?
Amy: We did take the time to delineate certain threats that are affecting trillium all across the country. Some of them are no surprise to any of us: land-use change, human development, or even how water moves across the land, right? When we change that as humans, it has rippling effects throughout our ecosystems.
Another one is white-tailed deer. We have huge white-tailed deer populations, and trillium are particularly delicious [laughter]. So when a trillium is eaten by a deer, it kind of sets back the life cycle of that trillium plant for a few growing seasons, depending upon how much it already had stored in its root system. But if a deer comes along and takes a bite of the trillium, the next year it won’t produce all three leaves. It’ll go back to its juvenile days and produce maybe one leaf that year.
Amy: But it will take it several seasons before it’s capable of producing a flower again, and therefore reproducing at all. So the white-tailed deer really do harm trillium populations, and that’s something we saw over and over again in this study.
Margaret: And that’s not unique to trillium. I mean, white-tailed deer in these large herds and so forth, they have become predators, whatever you would use the word, of many native species of plants, yes? I mean-
Amy: Yes, that’s-
Margaret: Or implicated.
Amy: Very accurate. They’re hungry, and there’s a lot of them. And the natural areas where they used to find refuge are becoming smaller or disappearing altogether.
Margaret: Right, right, right. So animal predation by deer is one factor that was in the report. And there were others, of course.
Amy: Oh yes. The one that was maybe the most interesting for us, or at least got the most laughs around the table, was the feral hog situation in the South. [Above, Trillium stamineum from Mt. Cuba’s collection.]
Margaret: As in pigs [laughter]?
Amy: As in pigs. Yes.
These are pigs that either escaped domesticated pens or were seeded into forests by hunters or that kind of thing. And I think years ago, we used to hear about feral hogs on islands where they could just destroy the ecosystem of the island. Well, now they are widespread throughout the American South, and they are pushing their way north.
And as they do this, they are eating as they go. But the major difference between a feral hog and a deer is that a deer will come up and take a bite. A pig will root up the roots itself, and they can destroy a population overnight.
Margaret: Wow. I had no idea. I had no idea.
Amy: And they reproduce very quickly. They have large litters. And there’s a lot of food that’s required to sustain them. So we’re seeing the effects of feral hogs on our trillium plants as well.
Margaret: Wow. I really had no idea that was an issue. Well, what other good news was there for the plight of trillium in the wild?
Amy: [Laughter.] The good news is that people are interested in trillium. They’re that charismatic megaflora, the big, shiny flowers that people are interested in. And that gives us a little bit of a leg up when trying to preserve these plants in the wild. People can understand the need to preserve something so beautiful. So that was a bright spot. And we are finding that the threats we’ve identified are not insurmountable. There are absolutely ways to preserve these plants long term. We simply have to make a commitment to do it and allocate the funding that’s going to be necessary for the preservation.
Margaret: We know a lot and read a lot and hear a lot about invasive species—non-animal, I mean, plant invasive species. Is their competition for turfs, literally-
Margaret: …from invasive plants as well in the case of trilliums?
Amy: Yes, there absolutely are. The worst offenders, that I’m sure all of your listeners deal with, the kudzus, the multiflora roses. Those kinds of plants are taking up the resources that these trilliums need to thrive. However, we did note that it was sometimes a double-edged sword. So sometimes a patch of multiflora rose will actually protect a trillium population, because the deer don’t want to deal with the multiflora rose any more than we do. So it slows them down and makes it so that they can’t get easy access to that delicious trillium leaf.
Margaret: Interesting. Interesting. So, as I said in the introduction, you’ve traveled extensively in the temperate world, observing native plants in their natural habitats. You’ve undoubtedly seen trilliums in theirs. What kind of habitats do they occur in in nature? Who are their partners and so forth?
Amy: Oh, sure. Well, being ephemerals, early spring wildflowers, they have some companions that we try to mimic here at Mt. Cuba Center as well when you see them in the garden. So common plants like Virginia bluebells or barren strawberries or bloodroot are all things that I see with trillium usually.
Trillium like the Eastern temperate forest. Many of them evolved here. They’re very happy in these environments. They tend to like things a little bit more pristine than, say our common bluebells. Bluebells, they’re happy just about anywhere, but trillium require less soil disturbance. They need ready access to water. I’ll often find them growing along a stream or a little rivulet. Sometimes they need protection, so you’ll find them tucked up under a boulder on an embankment, or you’ll see them on the downward side of a giant tree, where they’re just looking to seek out a little bit of shelter from both predation and the elements.
Margaret: Interesting. When we spoke the other day on the phone, I told you that the first trilliums I ever met were about 35 or more years ago when I bought the upstate New York house that I live in now, full-time when I was a weekender. I was doing a repair on the front porch, and I saw under the deck of the porch, just tucked under the edge—speaking of protection—I saw these three little plants, and I didn’t know what they were.
And I dug them up because I thought why would a plant want to live under the porch, and put them in a garden bed that I was making. And they turned out to be the wakerobin or Trillium erectum, sort of a reddish-colored native trillium to my area, my region. And since they’ve multiplied and so on and so forth. So some of them are tough little guys, but not under the pressures that you were talking about before, obviously. [Above, some of the progeny at Margaret’s.]
Amy: That’s right. And probably there near your home, the deer were a little bit too timid to get to your porch.
You’ll actually see that effect happen in the wild too, specifically at like national parks or of that kind of thing. You can search an entire forest segment, and sometimes the greatest diversity in that forest segment is right along the roadside. The only reason for that is that the deer are intimidated by the road traffic. So about the 5 feet before that road, they won’t necessarily browse everything to death.
Margaret: Wow. So that’s our new direction in conservation, is that we’re going to populate highway edges with… Instead of the horrible things we’ve always put along them, we’re going to try this instead, I guess [laughter].
Amy: We should. We should. And absolutely we should work towards not using pesticides, herbicides on roadsides, because so many species need those roadside as refugia, a place to survive.
Margaret: Right, right. I never thought about that. That’s very interesting.
So sort of when you want to tell gardeners or other members of your audience that you reach through your work at Mt. Cuba, or the people we’re talking to today, kind of what we can do… I mean, so I can grow my trilliums here in the garden and so forth, and I can not use chemicals and I can grow a diversity of native plants and the things that we talk about a lot in gardening. But you have some messages, I think, for us about how we can participate in conservation and so forth as well.
Amy: Yes. The first one is simply what we’re doing today, which is learning more about biodiversity. It’s often shocking to people to learn that there’s more than one trillium, or more than one clematis, or that the European version of something that you’ve been growing actually has a counterpart here in North America that fits a little bit better in with the ecosystem.
So whatever possible, I encourage people to learn as much as they can about the environment, and to pass that knowledge on. We all have friends that we talk to or grandchildren or whomever it is. And sharing our love of nature is very infectious, and I think it’s going to do a lot for conservation in the future.
Amy: The other one I often say is conservation can be conservation by addition. We don’t need to get rid of everything that we’ve ever had before in favor of a native plant garden. Native plants play very well with non-native plants. And if you are growing your grandmother’s roses, you do not have to stop growing those grandmother’s roses. Just maybe put a native phlox in there as well so that we’re supporting the butterflies and the bees and the soil organisms and all of those things.
The last one would really be just if you want to participate in the conservation of these species, don’t go it alone. There are a lot of people studying these plants. There’s a lot of great conservation organizations in this part of the country that are looking into these things and need help. So certainly look into someone who’s interested in the species that you are interested in, and see how you could participate.
Margaret: Right. I mean, in your area, of course, in the Mid-Atlantic, I mean, Mt. Cuba’s such a place to do all those things really: to learn, to find out which plants, to become more involved. And there are great places in most or all regions of the country. So I often look on the North American Native Plant Society website.
It has state by state, and Canadian province by Canadian province, a whole list of all of the native plant societies and entities like Mt. Cuba. So you can actually zero in on your own, and find a place that you can meet like-minded people and learn more and so forth, and often even attend a plant sale and find locally appropriate native plants. So that’s, I think, positive, too. Yeah.
Amy: That’s fantastic. And I’m so glad that you mentioned local plant sales as well, because as gardeners, as horticulturists, one of the things that we can do very, very easily is make sure we know where our plants come from. We can always speak to nurserymen and make sure that the plants are legally and ethically obtained. These plants are grown in cultivation. You can absolutely get them from a nursery. It takes a really long time to produce one, but you can get them.
So make sure that if you are going to buy a trillium for your garden, that you’re going to a Plant Delights Nursery, or someone with a very good reputation, so that we’re making sure that these plants are not being poached from the wild.
Margaret: Right, right. You mentioned earlier medicinal use and that that had led to some of their poaching earlier on and so forth in the case of trillium. Did I read in the report that they’re used in the skincare industry, or something that I didn’t know about? What’s that sort of ethnobotanical, or whatever, aspect of trillium?
Amy: One of the common names of trillium is birthwort. And once upon a time, it was used to help women in childbirth and that kind of thing. Today they are primarily used in the skincare industry. It produces an astringent-like effect. So if you want a natural astringent, trillium is one of the plants that can provide that for you.
The problem is it’s really only one, maybe two, species, that provide that astringent quality. And unfortunately, we are seeing an uptick in poaching happening from trillium of all species, because the people poaching them can’t tell the difference—being taken from the wild and presumably being sold to the skincare industry.
Margaret: Oh. You also mentioned just in the last two minutes, but tell me in the beginning you mentioned the sort of national collection, so to speak, of trillium, and that you have this enormous collection there at Mt. Cuba. How diverse is it? And they’re profiled on the website, I think, as well. The Mt. Cuba website has great plant profiles and incredible pictures. And so people want to dig deeper. And again, How diverse is that collection?
Amy: We have roughly 84 taxa of trillium here at Mt. Cuba Center. That’s variety, species, types of trillium. We have horticultural forms. They are cultivars that are just grown to be beautiful. We have wild-sourced material that is meant to live here until it’s needed back out in the wild, and then we will be able to propagate and put it back. We have carpets of trillium at this time of year. It’s actually a great time to visit because our trillium garden is in full bloom, but it will be so until about the second week of May.
Margaret: Wow. That’s a long… That’s amazing; that must be just incredibly beautiful. Well, Amy Highland, I’m so glad that you and your colleagues did this work in collaboration with these other entities, again, but also that I’m always glad to talk to anyone at Mt. Cuba, because for me, over so many years, it’s been such an influence in my personal interest in native plants. And as I said, it has so many great resources on the website. Although it’s Mid-Atlantic focused, I think it’s very inspirational for people everywhere. So thank you for making the time today, and thanks for the work that went into this report, pigs and all, oh my goodness.
Amy: Well, thank you, Margaret. We hope to have you here again soon sometime.
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. 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 April 25, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify