MOST OF US may automatically think “monarch” after hearing the word “milkweed,” or vice versa. And that’s in fact a critical and intimate relationship, the one between monarch butterflies and native milkweed plants.
But the genus Asclepias offers sustenance to a wide diversity of animal species beyond just that one beloved insect.
I spoke about that diversity recently with Eric Lee-Mäder, author of the recent book “The Milkweed Lands: An Epic Story of One Plant: Its Nature and Ecology” (affiliate link). Eric is an ecologist at the invertebrate-focused Xerces Society, where he is the pollinator and agricultural biodiversity co-director. He and his wife also operate Northwest Meadowscapes in Port Townsend, Wash., providing regional native seeds and consultation services for meadow-makers.
Plus: Enter to win a copy of the new book by commenting in the box near the bottom of the page.
Read along as you listen to the Nov. 13, 2023 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).
the world of native milkweeds, with eric lee-mäder
Margaret Roach: Eric, I’m so glad to talk again and I so have been enjoying your book and loved working on the “New York Times” story with you together. How are you?
Eric Lee-Mäder: I’m good, Margaret. Thank you so much. This is indeed a really interesting topic and I’m excited to dig in more.
Margaret: Yeah, you did. And the book’s illustrations are just charming, and they just are so engaging. So your collaborator also is to be thanked for bringing this book to life.
Eric: Yeah, Beverly Duncan, I think, is exceptional in the botanical art sector because she not only can capture the plants, but also really, I think, does a beautiful job of telling the story of intersection of the plants with the animals and how these plants really have sort of persisted in very human-altered landscapes as well.
Margaret: Yes. Well, until we did the recent “New York Times” garden column together, I had no idea what a diversity of native milkweeds there were in North America. I mean, it’s staggering. I only know a handful here where I am in the Northeast, and so I would’ve said, oh, how many are there in North America? I don’t know, 10 or 15, but it’s how many?
Eric: Boy, it depends sort of a little bit on where we draw the boundaries between North America and Latin America. But here in the United States, the continental United States, there’s easily six or seven dozen that you could, with a lot of looking, go out and find. But a lot of these are fairly uncommon in most of North America, most of the United States. A lot of these are odd little desert plants, or little plants that are tucked away in the pine barrens of the southern states. There are species like the aquatic milkweed [Asclepias perennis], which literally hangs out in cypress swamps. So tracking down a lot of these is a kind of Herculean effort.
Margaret: Yeah, I mean, again, you’re saying dozens and dozens and dozens, and I would’ve thought a little more than a dozen maybe. I had no idea. I also had no idea how much of their territory had been erased. And you start the book by saying, “The milkweed is a displaced citizen in its own land. Where it once owned the continent, it’s now a kind of vagrant, occupying the botanical equivalent of homeless encampments.” So tell us a little bit about what happened since we arrived to the milkweed. What happened to the milkweed?
Eric: Yeah. The story of the milkweed is in many ways the story of so many of our native plants, particularly our native prairie and grassland plants. And prairies and grasslands are in many places very dependent upon on human management and human stewardship of the land. If we think about the tall-grass prairie ecosystem, east of the 100th meridian [where the Great Plains begin], so much of that landscape was managed by Native people conducting burning to maintain open areas for hunting or farming. And those conditions kept the forest at bay. They provided expansive, sunny habitats for plants like milkweed to grow.
Now, what has happened since then, of course, is that we immediately settled upon those grasslands. We turned places like Iowa into essentially industrial-scale corn and soybean fields.
And most of those prairie plants, not just the milkweed, but most of those prairie plants are largely absent from most of the landscape. The interesting thing to me about milkweeds both in the East and the West, however, is that among all of those prairie-meadow-grassland plants, milkweeds have interestingly stuck around in their own way. And that way is oftentimes as roadside ditches. It’s oftentimes as the sole native plant that springs up in a vacant lot in Detroit, or in an irrigated, irrigation canal in eastern Washington State.
So they have remarkably sustained themselves in their own sort of way, but it’s a far cry from what those original grassland ecosystems must have looked like.
Margaret: And it’s not exactly a reception or accommodations fit for a god. And if I’m remembering correctly from the book, I think the Latin name of Asclepias, the genus, harks back to a Greek god or something? Is that true?
Eric: It does. The Greek god of medicine, Asclepius, who is often represented with the staff that has the snake coiled around it, which of course is the symbol of medicine.
It’s interesting, because the milkweed has had these different representations to us as humans, as Native people, and early European botanists discovering the plant. They were really quite interested and intrigued by the healing properties of milkweeds. But then we’ve also gone through these other periods where we’ve treated it as a cropland weed that needs to be eradicated.
We’ve treated it as a source of industrial materials like latex and seed fluff, and now we’re beginning to revisit it, I think, as an important conservation plant and a plant that’s really interesting, actually, really quite deeply fascinating, to include in home gardens and in more visually driven landscapes. Whether that’s… I’ve seen them on green roofs in Des Moines, Iowa. I’ve seen them planted in really interesting corporate campus plantings. I’ve seen them in amusement parks [laughter], in ornamental garden beds. They’re kind of showing up. They’re having a moment.
Margaret: Yeah. Well, you mentioned about how we changed whole states, what became states, to… We plowed up the sod and we changed whole ecosystems. And then lately in recent decades, we’ve also taken another tack in our sort of nonstop warfare against milkweed and many other native plants, as you pointed out, which is these very advanced herbicides. Because these are plants that would’ve been in grassland communities that became crop fields, and then we started managing our crops with these very sophisticated chemicals, yeah?
Eric: Yeah. It’s funny, if you talk to people of a certain generation in the Midwest, in essentially the major soybean-producing states, the now adults who were farm kids of a certain era will talk about “walking the beans,” and it has a particular meaning. They would walk the beans before the age of genetically modified crop technology that imparted herbicide resistance to soybeans. So to get weeds out of soybeans, you would have to walk up and down the rows. And milkweeds were, in many places, sort of the principle weed that these farm kids were trying to pull out of the soybeans.
And then in the late eighties and early nineties, there was this extensive work to unlock the genetic-modification potential of corn and soy. And the major crop interests, the big seed companies and pesticide companies were able to develop these lines of soybeans and corn that now you can spray with herbicides like glyphosate, and all of the weeds in those fields die, leaving the crop unharmed.
And this has been a major change in the abundance of milkweeds in particularly the Midwest, the core breeding area of the monarch butterfly, where these plants were once able to subsist a little bit within those crop systems.
Margaret: Right, right. Yeah. Well, speaking of strong medicine, and you talked about medicine and Asclepius and so forth, but they have their own strong medicine, these plants, the milkweeds, which is deadly to some animals, but other animals can utilize it. I want to talk about that in a minute.
But the herbicides are even stronger “medicine,” and I use medicine in quotes in that case. But as far as their chemistry, these plants, it’s often spoken about as like some kind of chemical warfare. They have these natural… the chemicals within the plants that help them resist herbivory, predation, etc., how strong they are and how fierce and all that.
But you don’t really talk about it in the book as warfare or whatever. You talk about it as a partnership or sort of a two-way relationship with the other creatures. And I wanted to talk about that, because I think that’s so much of a better way to think of it, even though they are strong and they are tough.
Eric: Yeah. It’s a particular irony of milkweeds that they do produce these cardenolides, these chemicals that can affect the cardiovascular function of animals that consume them. But these chemicals are actually quite variable in concentration depending upon the milkweed species in question, depending upon the part of the plant in question, depending upon the growth stage of the plant in question. And there are anecdotal instances of mammalian toxicity, livestock eating these plants and then keeling over dead.
In terms of the specific documentation of that, things start to get murky very quickly, and we see that it’s probably a few milkweed species that are the most highly toxic to things like cows or horses eating them. And then we see these odd instances of other mammals like jackrabbits that seemingly quite happily eat milkweeds with some regularity. And we see these traditions of people eating these plants as well. There is sort of a forager tradition, probably beginning with indigenous people and continuing with folks like George Washington Carver, and then more modern foragers who actually cook and eat the young shoots or green pods of common milkweed [Asclepias syriaca].
All of that said, of course, people are immediately drawn to the stories of things like the monarch butterfly, which are consuming milkweed foliage as caterpillars to absorb these cardenolides into their body and use them as a chemical defense against predators.
But as I describe in the book, and as my colleague, Beverly, so beautifully illustrated, if milkweeds developed this strategy to prevent herbivory, it’s been a losing strategy [laughter], because I can think of very few other prairie plants or grassland plants, sunflowers maybe, but very few other grassland prairie plants attract so many and such diverse herbivores as milkweeds do.
Margaret: Right. And I think you call it “the hungry throng” in the book, right? Or something, is it the hungry throng? And there’s a great illustration: It’s like, this milkweed plant and it’s got everybody and their mother nibbling on it, all different species [laughter].
Eric: It’s true, it’s true. And in the case of monarchs in particular, which is of course the most famous relationship or partnership that milkweeds have with an animal, there is this common perception that it’s a one-way relationship; that the monarchs are feeding on the milkweeds, defoliating the milkweeds, and then fluttering off to do what monarchs do.
But there is an open question about the role of monarchs as milkweed pollinators in my mind. And milkweeds have very complex, interesting floral morphology. The complexity of milkweed flowers is easily comparable to the complexity of orchid flowers. They’re remarkably intricate. They function a little bit like a mousetrap, where the pollen is packed into structures, little packets called pollinia, and those pollinia attach themselves literally like clothespins to the legs of insects.
And then insects become, in some cases, quickly burdened by many of these little clothespins attached to them, sometimes even entrapping the insect to the flower. And bees get the most credit for that work.
Now, what’s interesting is that monarchs probably don’t get a lot of pollinia attached to them. They have long, slender legs, not the kind of legs or hairy bodies that these little pollinia clothespin can easily attach to. But the thing that monarchs do have is a long-distance migration. And because of that, even a few of these little pollinia clothespins attached to a monarch may result in very, very long-distance gene flow between milkweed populations.
And as we’ve talked about, the fragmentation of habitat, the loss of habitat, the rise of herbicides and crop lands, these milkweed populations are really, really isolated now across many, many regions. And so having an animal that can carry pollen many miles from one plant to another may be really significant in the ongoing survival of milkweeds. So I think this is really a true partnership in many ways, and one that we really don’t understand beyond a surface level.
Margaret: So there’s this diversity of milkweeds, dozens; I think in the book you say 90 or something like that, at least species. And you talk about this hungry throng in the book, also at least 40 insect species that you could think of off the top of your head almost that feed, as you say, “often or exclusively on North American milkweeds in the summer.” And then there’s all these bees and wasps, besides butterflies and moths, that come to the flowers to get nectar. It’s quite amazing.
So then let’s transition to sort of which ones, because that’s a lot of different milkweed species, and most of them are not in seed or plant catalogs or let alone at the garden center. In fact, one of the only ones I ever see at the garden center is A. tuberosa, the butterfly weed.
So what are some that… You’ve met a lot of them, you know or you’ve read about and studied a lot of them. What are some of the ones that you want to sort of shout out for us here, because there’s gardeners listening, and for different applications: for a meadow or for a border or for different applications, which ones are you most excited to share?
Eric: Yeah, and Margaret, we’ve spoken a few times. You probably have a sense that I have a particular fondness for the kind of rangy, ruderal, weedy… [laughter].
Margaret: I heard that your wife teases you a little bit about the front yard, Eric [laughter].
Eric: Yes, yes. I am really, really partial to common milkweed. Largely, for very nostalgic reasons, it’s a plant I grew up in close proximity to, and it was my first exposure to milkweeds, and consistently attracts the full spectrum of really interesting milkweed partners.
Margaret: It will spread.
Eric: It will spread. But it is a survivor plant and I think it does have, I think it’s got great utility in a lot of landscapes. So I do want to start there briefly for a moment, and I would compare it to showy milkweed. So if you’re west of the 100th meridian, basically the line that bisects the Great Plains extending all the way to Oregon and California from the Dakotas and Nebraska and Kansas, showy milkweed [A. speciosa] is the Western equivalent of common milkweed. And both of those plants I think are underutilized in applications like bioswales and in roadsides.
And recently there was even a very interesting article in the Times about common milkweed along freeways in New York, and people finding really high monarch butterfly value from those plants, right adjacent to very busy roads.
So I do think those plants are worthy of respect, worthy of attention, and worthy of planting in those kinds of functional landscape settings where you need a sturdy, tough native plant that can withstand some difficult conditions.
As we move more into, let’s say a slightly more manicured home landscape or maybe more manicured public green space, Asclepias tuberosa [below], as you mentioned, the butterfly milkweed is I think worthy of its common, increasingly common use in those sorts of settings. It’s compact in nature, it’s not weedy, it doesn’t spread around into areas where you don’t really want it. It also has such interesting dense orange flowers that to me it is on par with any sort of cultivated variety of garden plants that you might find.
The butterfly milkweed is probably best in well-drained soils, but for rain gardens or wetter soils, there’s swamp milkweed [A. incarnata]. And then again, in the West there are species like woollypod milkweed [A. eriocarpa].
Margaret: Oh, I’ve never heard of that [laughter].
Eric: The very hairy, interesting plant with kind of bluish-green foliage. There’s heartleaf milkweed [A. cordifolia], which is an amazing sort of alien purple-green. But narrowleaf milkweed [Asclepias fascicularis] would be my other top pick for the West for very, really kind of sometimes tough, well-drained, drier, hotter conditions. It’s a really, really important monarch butterfly plant in the Western U.S.
Margaret: So the narrowleaf milkweed as well. And that’s an important one for the Western monarchs then as well.
Eric: It is, yeah. It’s probably the most common summer milkweed in much of the Western U.S. So when the monarchs are inland in the Western states during the summertime breeding, it’s one of the really, really important plants.
Margaret: O.K. I just wanted to ask you about the seed company, Northwest Meadowscapes. It’s all Northwestern seed, is that correct? What you and your wife have built with the…
Eric: We have expanded quite a bit.
Margaret: Oh!
Eric: So we built our company around a very regional Pacific Northwest meadow-focus, and this region is very underrepresented for the expansive Camas meadows and wildflower meadows that used to exist here. So we’ve tried to fill that niche, but we’ve been expanding and now are growing seed for much of the Inland West. We’ve got some interesting garden plants and crop plants, and we are slowly sort of expanding our availability of edible garden plants and meadow plants for all kinds of places.
Margaret: Well, you’re a busy guy, Eric Lee-Mäder. Between that and the book and the work at Xerces, it’s a lot. I’m so glad to talk to you again, and I appreciate your making time. I know it’s the busy season still, so thank you so much for doing this. And I hope I’ll talk to you soon.
Eric: Thank you so much, Margaret, and happy gardening.
more on milkweeds
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 14th year in March 2023. 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 Nov. 13, 2023 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).
