IT’S TRILLIUM WEEK the first week of May at Garden in the Woods, the headquarters of Native Plant Trust in Framingham, Massachusetts, the nation’s oldest plant conservation organization with more than a century of history. Well, with a little help from today’s guest, it can be Trillium Week in your garden, too, around this time each year.
Uli Lorimer has made a career of working with native plants, including a diversity of trillium species (like T. cernuum, above, with Phlox stolonifera at Garden in the Woods). He was longtime curator of the Native Flora Garden at Brooklyn Botanic Garden, and in 2019, became director of horticulture at Native Plant Trust, the former New England Wild Flower Society, which was founded in 1900.
Read along as you listen to the May 3, 2021 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).
all about trillium, with uli lorimer
Margaret Roach: Welcome back, Uli, and happy Trillium Week. Mine are opening up by the second over here, too.
Uli Lorimer: Thank you. I’m really thrilled to be here, and I’m thrilled to have another chance to discuss trillium. It’s one of my favorite groups of wildflowers.
Margaret: Yeah, and so Trillium Week includes in-person events in Framingham, at Garden in the Woods, but also I was so excited that you’re having some virtual ones, including some free ones where people can really learn about growing them and so forth on their computers, from wherever they are.
Uli: Yeah. So every year, usually right around the 1st of May, which is when most of our trilliums begin to open up, to flower, we celebrate Trillium Week. So this year it runs from May 1st to May 8th. And we have a full slate of programs, from sort of daily workshops, and education classes. If you are fortunate enough to live near the garden, you can come and take advantage of a trillium tour that we do, which is led by our very knowledgeable garden guides.
And this year we also have a new phone app. So if you go into your Apple or Google Play and look for Native Plant Trust, you will find our new app there. And you can do a self-guided tour, which features both a general tour of the garden, but also a specific one, featuring our trilliums, for those folks who prefer a self-paced tour through the garden. So we’re really happy to be able to launch that in time for Trillium Week.
Margaret: Great. I will include the links to all of the information, again, as well as some of the virtual events that people anywhere can look at.
So I believe that most species of trilliums on the planet are in North America. I’ve seen different numbers on how many and so forth, but we kind of have most of them here, don’t we?
Uli: Yes, we do. There are sort of globally about 50 species right now, the current taxonomy. And I’d say with the exception of one or two that exist in Eastern Asia, they’re almost all entirely in North America, and the bulk of them in the Eastern part of North America. There’s a few that are in Western North America as well. But by far they’re Eastern North American plants, and the sort of center of diversity for them is in the Southeast.
And despite their growing in the Southeast, they’re actually all fully hardy to be grown all the way up in New England. And in fact, one of the best reference books for trilliums was one written by Fred and Roberta Case titled “Trilliums” [affiliate link]. And they grew all the possible trilliums you could imagine in their garden in Michigan, and everything was fully hardy there.
Margaret: Right. I have Trillium luteum, a yellow-flowered one, which I see always referred to as Southeastern, but it’s Zone 4-hardy. And that’s true of a lot of native plants that are hardier are much farther north than their current range on the earth. [Above, T. luteum from Uli Lorimer.]
Uli: Yes, this is very true.
Margaret: So there’s a few species in Japan, yeah? Is that where they are?
Uli: Yes. There’s some in Japan and far Eastern Russia. And then a few that are in Alaska, and some around the sort of Pacific Northwest coast, in some of the mountainous regions there.
Margaret: So trillium, the name, it gives us a clue: tri-. Tell us about their sort of biology, so to speak.
Uli: Yeah, so they are, when they’re fully mature, the leaves—there are three leaves, and then all of the reproductive parts are also in multiples of three. So the sepals, the petals, the anthers the numbers of ovules within the ovary are all multiples of three.
And this is another hallmark of monocots, which is another sort of bigger group of plants. And trilliums belong to that since they have floral parts in multiples of threes, as opposed to multiples of four or five or more.
Margaret: What’s interesting, you said when they’re mature or when they’re grown up sort of, they have these three parts. First of all, they don’t germinate very fast at all from seed. And when they do, I don’t know, a year or two or however many later, you may see one little leaf, not three. And then I think, depending on the species, in like year three or four, you may see the first true-looking arrangement of three. I mean, it’s a slow process, isn’t it?
Uli: Yes. Yeah. They are very slow to grow. And I think that’s one of the reasons why they’re not more widely available in the nursery trade, is because they take a long time to grow from seed. And you’re correct that the first year that they do germinate, they only produce a single leaf. And then maybe year two or three, they’ll produce two leaves. And then usually by third or fourth year, depending if you’ve got good growing conditions, you’ll begin to see the characteristic three leaves.
And then from there, it may take them up to five years before they actually produce a flower. And so a lot of it also has to do with the fact that this is a plant that will go dormant once the summer heat and drought arrives. It retreats back into a thick rhizome, and it takes a while for the plant to store up energy and thicken that rhizome in order to be able to make flowers every year. So if you see a particularly old clump that may have multiple, multiple flowering stems, you’re probably looking at something that’s 20, 30, maybe even 40 years old.
Margaret: Amazing. So I want to delve more into sort of how they grow and propagation and so forth. But first I want to ask you, because I know part of what Native Plant Trust does is also it has a whole operation, Nasami Farm, that propagates, ethically propagates, and grows and sells plants. So I want to ask more about that.
But first: the collection. If we come to virtual or in-person Trillium Week, the collection at Garden in the Woods in Framingham, now how diverse is it? How many different kinds of trilliums would we see there?
Uli: So we are a nationally accredited collection holder. This is an accreditation that we received through the American Public Gardens Association. I believe with our sister garden, the Mt. Cuba Center in the mid-Atlantic, we are the only collection holders for the genus Trillium.
And so what that means is that we have, right now, I think we’ve got 28 or 30 different taxa. And so these are a different species and varieties and forms of the species represented in our garden. And so if you want to see them all in one place, there’s no better place to come and see them than us if you’re in New England. And if you happen to be in the mid-Atlantic region, then be sure to check out the Mt. Cuba Center, because their collection is also spectacular.
Margaret: Now you have them in a collection there at the garden, but I was fascinated to learn when I first came to where I garden, which is sort of adjacent to the Berkshires of Massachusetts, in New York State in the Hudson Valley. I thought, “Oh, there must be lots of different kinds of trilliums,” because I knew them as a gardener, you know what I mean? I had seen pictures of them in garden books and so forth, different species.
And what I’ve learned over the years, living here and doing projects with my local flora sort of nonprofit—the nonprofit doing the flora of my county, sort of telling what grows here, and what’s native here, and what’s existing here—is that there are three in my county [laughter]; three species in my county. And that the most popular ones among gardeners, that might have larger flowers or be a little more showy, are not necessarily here. [Above, T. grandiflorum from Uli Lorimer.]
So those taxa that you just spoke of having, they’re not all literally native to Framingham, Massachusetts, are they?
Uli: No. So we recognize four taxa, four species of trillium that are native to the ecoregions of New England. And so those are Trillium grandiflorum, the white wake robin; Trillium erectum, which is a red trillium, which also has lots of colorful names like stinking Benjamin or the wet dog trillium. Trillium cernuum [photo, top of page], which is a nodding trillium, and it’s sort of a little bit of a bashful species because it holds its flower underneath the leaves.
And then what many people consider one of the most beautiful trilliums of all of the species is the painted trillium, Trillium undulatum [below, photo from Uli Lorimer]. It features sort of wavy pedals and this really beautiful splotch of pink-maroon in the center and that kind of bleeds out along the veins of the petals. It’s quite a remarkable plant if you ever come across it.
It is, however, one of the ones that is nearly impossible to cultivate, because it has specific relationships with fungi in the soil. And so it’s one that is probably one of the only local species that we don’t cultivate here, because we can’t.
And I have heard from many, many other native plant experts that if you ever see it for sale in a nursery, it’s probably been dug out of the wild, and that you shouldn’t waste your money or your time trying to cultivate it because without the fungi present, it will be not a successful venture.
Margaret: Right. Plus by buying it, you’d be supporting theft from the wild.
Margaret: Yes, so we don’t want to do that.
Uli: That’s something that faces a lot of trillium species in general. Because they are so slow to grow from seed or from divisions, folks think it’s a lot easier just to go up in the woods and dig them up and sell them for a quick buck. And so it just really pays to make sure that whatever nursery you patronize, that you ask them how they were sourced and if they were done so ethically and morally.
And if you know that places like Garden in the Woods and our nursery out in Western Massachusetts, the Nasami Farm, we do grow all of ours from seed or from stock beds, where we make divisions. And so there’s never any chance of us digging them up from the wild, because that’s against our whole mission. We’d like to keep wild things wild.
Margaret: Right. And so the key phrase is “nursery-propagated,” not “nursery-grown.” Nursery-grown may mean, “Oh, we dug them up and now we’re growing them in pots and going to sell them to you.” Whereas nursery-propagated is the direction we want to look, I think.
Uli: Yes, absolutely. Correct. And there’s other plants too. I think perhaps as a separate discussion sometime, ramps is another one that I think could be nursery -propagated, but is oftentimes ripped out of the woods because it’s cheaper and faster than waiting.
Margaret: If I see one more social-media posting everybody digging up ramps in the wild—I mean, I could just scream. I shouldn’t probably even say that out loud because people will now yell at me on social media. But honestly, I mean, it’s a plant… It’s a wild, native plant and it’s unethical and probably illegal to dig it up. You know what I mean?
Margaret: O.K. Oh boy, now my blood is boiling [laughter].
Uli: But I mean, people want to have these beautiful plants in their gardens and for good reason, because they’re charismatic, they’re gorgeous. It’s a real sign that spring has arrived. And to meet the demand that people have for these plants, we are not patient enough oftentimes, and so people do turn to unethical methods to supply the demand, unfortunately.
Margaret: Right. But they are available, usually bare-root, early in the season, you can buy these plants from an ethical supplier and then have them in your garden in a way that supports an ethical supplier, and everyone wins, I mean. So, yeah.
Margaret: So we were talking about from seed, how slow they are. And again, I think it depends. I was reading, for a “New York Times” story I did for last week, I was reading a book by Carol Gracie about spring wildflowers of the Northeast. Yeah, and looking at pictures of the rhizomes. You were talking about how if you see a lot of flower stems coming up it’s a really old clump and so forth. That if you lift them to divide them, if you lifted an old clump like that and you saw the many different rhizomes or even just one, they have like little ridges on them. [Photo of rhizome above from Uli Lorimer.]
Margaret: Yeah. And how you can approximate their age. Of course, just like with rattlesnake’s rattle, some may have fallen off on an old one. The end may have fallen off. It’s not precise, but that they’ve found ones that are approximated to be as old as 70 years. Rhizomes as old as 70 years. Quite amazing.
Uli: Yeah. I mean, they’re slow and steady, and those ridges are what are called terminal bud scars. So every year at one end of the rhizome, the plant will make a new bud, which will contain the leaves and the flower. And it leaves a little ring. So you can count back from the growing tip, and you can see approximately how many years. I know we’ve had ones that maybe are as long as my finger and can be 20 years old.
Uli: So you know, patience is rewarded in this genus. And I think as any gardener understands, delayed gratification is the best thing about gardening. It’s not immediate gratification. And watching this plant come back every year and get bigger every year is really satisfying. You know, they grow with you. That’s the best way I could put it.
Margaret: So let’s talk about, I mean, my first ones—and I’ve told this story many times on the show, so I’ll tell the very short version. When I first came to this house 35 years ago, I was crawling around out front by the front porch, and I spied three little green things just tucked under the edge of the wooden front porch floor. I grabbed them out of the soil and they turned out to be trilliums—what did I know? And I put them somewhere else in a bet I was making, and now I have—it’s Trillium erectum, the wake robin, or all those other funny names you said.–and now I have many, many, many [laughter]. [Above, T. erectum at Margaret’s.]
So that was how I learned to propagate really, not the most elegant or professional manner, just curiosity-driven. But it was at bloom time and over the years I’ve always done. So if I have a big clump and I want to continue to move them around, that’s when I do it because I can see them then. I can see where the clumps are, because as you said, they behave as ephemerals. They can go dormant in the heat of summer, especially in more Southern areas, I think.
Uli: Yeah. And again, with patience they can spread with a little help of our friends, the ants.
Uli: Oftentimes, when you come across bigger patches in the woods, they just seem to be kind of randomly dotted here and there. It’s because ants plant the seeds, and it’s not by mistake that they’re attracted to the trilliums. The seeds that the trilliums produce have a tasty little ant snack attached to the seed [laughter]. It’s called an elaiosome, but it’s really sort of fat and lipid and protein. [Above, seeds with elaiosomes attached, from Uli Lorimer.]
The ants love it. And as soon as the capsule opens, they’ll come and collect all the seeds and then take them away. And after they’ve eaten the little snack, they’ll deposit the seed into the leaf litter and then two, three years later, there’s another trillium. It’s wonderful. Again, if you’re fortunate enough to garden the same space over a long period of time, you begin to notice how there’s one that popped up over there. I never planted one there. How did it get there? Thank you, ants. You know, they’re industrious and wonderful, and over time they will help plant your own garden for you.
Margaret: So I’ve read that this plant-ant mutualism that you just described, where they go to get the lipid-rich snack and in the process walk away and move it to a different place away from the parent plant and “plant it,” quote unquote. That as many as 35 percent of Eastern woodland wildflowers depend on that mutualism—that many species do. So it’s pretty fascinating.
Uli: Yeah. I mean things like bloodroot, and your Dutchman’s breeches and squirrel corn—dicentras. They all need the help from the ants to get things around.
Margaret: Yeah. So if we want to grow them, and we buy ethically—whether bare-root or potted up—we buy ethically, nursery-propagated trilliums, many of them are woodland species. So anything else about making them happy—and especially I’m fascinated in what do you… At Garden in the Woods, do they grow just among themselves, or do you have them ever with other things?
Uli: Yes. I mean, so for most of them, and I’ll come to two specific examples that are sort of don’t follow this trend. But for many of them, they like rich soils. So, good organic-matter content, but not too wet. That’s one of the things that is, just as a quick tangent, a challenge for nursery people to grow them in pots, because oftentimes the soil media stays too wet, especially early in the spring, and then the rhizomes rot.
So a certain amount of drainage is important for them to keep the rhizomes from rotting. Because they have sort of a strong growing point, and they can push up through things, we planted them into big clumps of, let’s say, like oak sedge, different kinds of sedges.
Uli: We have them with woodland phlox, or barren strawberry. Any kind of like low groundcover kind of a plant that you could think of, they are really wonderful components because they’ll just kind of push up through that.
Then one of my favorite combinations that we have going here at Garden in the Woods is with what’s called long beech fern, Phegopteris connectilis. It’s a fern that spreads slowly through rhizomes, and we’ve paired that with the white wake robin, Trillium grandiflorum. So the new fronds are emerging just as the trilliums are blooming, and it’s just a delightful combination.
Margaret: Wow. See, this is a whole new thing for me. I’m in trouble now. Now I’m going to start pairing them with groundcover-y kind of things. That’s a good idea. That’s a great idea.
Uli: Yeah. You can also feature them as a clump, or sort of as an accent. But we tend to like to have as much of the beds full of plants, sort of akin to a green mulch, if you’d like, and then having other things emerge out of them, because that’s the way you see them in the wild. Plants grow intimately with one another and not so far away that they can’t touch each other. And so I think groundcovers and trilliums are really wonderful partners together.
Margaret: Yeah. I like if I just have a little of something special among these sort of ephemerals or early woodland spring bloomers, I tend to put it along the edge of a path when it’s just getting started, even if it’s not a mass and it isn’t going to be for many, many years. Do you know what I mean? Where it’s a little treasure right along the edge of the path where even in the early spring, I might be walking.
Uli: Yeah. That’s very good. I mean, you, you really want to enjoy them while they’re there because they don’t stay much later into the summer. Like I said, once things get too hot, or too dry, then they’ll just retreat back to that rhizome and you have to wait a whole other year.
Margaret: [Laughter.] Right. If you do want to fall dig, if you do have a big clump and you do want to fall dig, it’s good to mark them while they’re up though and awake, right, so that you don’t dig in the wrong place.
Uli: Well, in fact, this actually raises another good point. The best time to dig and divide them is actually right after they’re done flowering, rather than in the fall, because you’ll see them obviously; you’ll know. And then they’ll still have a little bit more of the growing season to kind of get established once they’ve been divided up.
And then for many of the ephemerals, actually they will continue to quote unquote “grow.” Even when they’re not above-ground, they’ll be busy making that next year’s bud already. And they kind of slowly grow all the way through the winter so that when the cues for spring arrive, the bud is already ready to go. It just has to push out of the ground. [How Margaret divides trilliums.]
Margaret: Well, Uli, happy Trillium Week. I mean, we’re going to tell people. Just as we wind down here, tell people again, all the links to how they can virtually or in-person participate. And what’s your favorite? Just real quick as we finish up, what’s your favorite? Do you have one?
Uli: It’s like being asked to pick a favorite child. That’s really hard. You know, I would say Trillium erectum, I think would be one of my favorites.
Margaret: Yeah, the one I started with.
Uli: Yeah. Just because it’s a great example of a flower that doesn’t… You know, not all flowers have to have really nice smells. And I like that this one sort of turns the tables a little bit and it doesn’t smell entirely fantastic. But it’s because it wants fungus gnats and things to come and pollinate it. I think they have really beautiful, attractive foliage, and that dark maroon color is not an easy one to find in garden plants.
And it just has great sort of cultural connections. You know, I mentioned stinking Benjamin and wet dog trillium. Stinking Willy is another name for it that I think is great. Bloody butchers.
Margaret: Oh my goodness!
Uli: There’s all sorts of fantastic, very colorful names for these plants. And I think we probably don’t have time to get into it, but there’s a whole other sort of human connection with these plants which spans long periods of time. They’ve been used medicinally. And I think it also really sort of underpins why people connect with them so very much, and why they’re such treasured members of the spring flora.
Margaret: Well, thank you for making the time today. And I hope I’ll talk to you again soon, if not about trilliums, about something else. Thanks, Uli.
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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 May 3, 2021 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).