NOT SO MANY years in the past, relative to the historical past of horticulture, even a now-ubiquitous phrase like “pollinator plant” wasn’t a part of our on a regular basis gardening language and mindset the way in which it’s at the moment. Our collective consciousness in regards to the significance of native vegetation has grown quick, and with it have come extra new phrases for our vocabulary.
One phrase that I’ve heard rather a lot these days is “keystone plant”—an expression I most likely didn’t even know 5 years in the past—describing native species which might be disproportionately essential to native ecosystems, the form of powerhouse vegetation of all.
I needed to study extra about simply what keystone vegetation are, and which of them belong in my backyard and why, and Uli Lorimer, director of horticulture at Native Plant Belief, helped clarify all that to me.
Uli, who has devoted his profession to native vegetation, additionally writes the “Ask the Gardener” column for “The Boston Globe.”
Learn alongside as you hearken to the Dec. 15, 2025 version of my public-radio present and podcast utilizing the participant beneath. You’ll be able to subscribe to all future editions on Apple Podcasts (iTunes) or Spotify (and browse my archive of podcasts right here).
keystone vegetation with uli lorimer
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Margaret Roach: How are you over there throughout Massachusetts from me?
Uli Lorimer: Making an attempt to remain heat [laughter], however delighted to be right here.
Margaret: Good luck with that. In order I mentioned within the introduction, I believe the phrase keystone vegetation—it’s one which’s spoken rather a lot these days. Do you bear in mind the primary time you heard it?
Uli: I most likely put myself in your camp, perhaps about 5 to seven years in the past, and would additionally actually credit score Doug Tallamy for bringing this to form of extra of the general public’s consciousness.
In researching the idea itself, it dates again fairly a methods, a number of many years in the past, when it was first coined, and it got here out of oceanographic analysis. And I believe it’s considered one of these ideas that I believe has generated numerous dialogue, no less than within the ecology world, generated a lot of related phrases like indicator species and flagship species and purposeful teams and all these types of issues that I believe have actually helped transfer the needle in how we take into consideration the function of gardens and the surroundings and the way they work together with one another.
Margaret: So even earlier than it had this identify keystone vegetation that, as you mentioned, Doug Tallamy of the College of Delaware and the Homegrown Nationwide Park nonprofit, has helped popularize in more moderen years, it was form of on the market. I forgot it got here from the ocean [laughter]; I forgot that.
Uli: A Dr. [Robert] Paine coined it, and had found that whenever you take away one specific species on this system that he was finding out, it had a form of cascade of unfavourable results. And he thought, wow, that is form of akin to that keystone that sits on the middle of an arch and retains the entire thing collectively. And if you happen to take away it, then these ecosystems collapse.
Margaret: And so initially, I assume as native vegetation have develop into increasingly the topic of analysis and extra broadly used and so forth, numerous the analysis initially was most likely evaluating the influence on the ecosystems of native versus non-native vegetation, I’d think about; that’s most likely the place it started. After which extra like natives in comparison with each other. And from there we discovered the keystones, those that have been probably the most impactful.
Uli: Yeah, I believe that’s typically the-
Margaret: I’m oversimplifying; excuse me [laughter].
Uli: Nicely, however I believe that what I’ve come to acknowledge these days is that ecological horticulture is admittedly multidisciplinary, by which you need to draw from information units and swimming pools of data and experience from the entomology world, from the ornithology world, from those that examine fungi, and that the interactions of specific insect group with vegetation has most likely lengthy been well-known, however unknown to the horticultural world till we began placing collectively these items and connecting the dots as you simply did.
Margaret: And as soon as these analysis research occurred, together with by Doug Tallamy’s staff and different colleagues within the native plant world, I imply, a few of the statistics, a few of the numbers, are fairly astonishing. I bear in mind the one, as a result of he has targeted us rather a lot on the significance of caterpillars—of the Lepidoptera—and the caterpillars and the way they assist the meals webs so critically. And I believe it was like 14 p.c of native plant species assist 90 p.c of the caterpillars, that then in flip assist the terrestrial meals net. It’s this small quantity. And once more, these form of “keystones.”
Uli: Yeah. I imply, if we may outline this within the trendy sense as one thing that has a disproportionate influence on biodiversity far past its abundance on the panorama. And I believe that drawing the connections with butterflies and moths and the sooner levels of their lives, and the truth that I learn 96 p.c of all songbirds want bugs to be reproductively profitable. And I used to be actually astonished to listen to that.
After which a pal of mine, Dr. Desiree Narango, printed a examine a number of years again form of quantifying this for Carolina chickadees. And I typically cite this analysis {that a} pair of chickadees requires greater than 5,000 caterpillars to boost a brood of chicks in a season, which is only a stupefying quantity of caterpillars, if you consider it. And the place are they going to search out it?
Margaret: I at all times say that caterpillars are the infant meals of the songbird set; that’s my widespread manner of claiming it [laughter]. As a result of actually that’s even fowl species, songbird species, who should not as adults as predominantly insectivorous, at the moment of their life cycle, of their life historical past, once they’re elevating a brood, that’s the child meals, that’s the go-to stuff. Even when they use seeds way more or different creatures, different issues, different sources of meals, way more, particularly seeds.
Uli: It stands to purpose that seeds and fruit are sources which might be extra ample within the later components of the 12 months. And there’s this form of stunning convergence of not solely vegetation rising and flowering, but in addition all that insect life and biodiversity and biomass that’s so properly timed with the vegetation, all coming collectively on the similar time. And I used to be simply considering that although a pair of chickadees would possibly clear out 5,000 caterpillars within the rapid neighborhood, there’s nonetheless extra for all of these moths and butterflies to finish their life cycle. So I imply, there have to be actually tens of 1000’s hiding within the forest, if no more, that we by no means see as a result of they’re all up excessive within the cover.
Margaret: And apparently the caterpillars are protein-packed, I assume. They’re a very dense type of diet. In order that’s vital for these little infants, too, I believe.
Uli: However I believe one of many massive shifts right here, I believe, is that we could have assumed that adjoining, close by pure areas have been intact sufficient to assist all of those organisms, and that we may actually focus our gardens on simply being fairly. And I believe that there’s a rising realization that the well being of forests and meadows and so forth isn’t perhaps not as nice as we thought, and that gardeners who actually want to make a optimistic influence are considering, what sort of intentional decisions can I make in my gardens to assist? To assist create wildlife corridors or present sources that simply aren’t reliably within the surroundings anymore? I believe numerous that is what drives this motion ahead.
Margaret: So at Native Plant Belief, after which dot dot dot (if we are able to translate a few of the classes of how you employ and the way you consider deciding what vegetation to make use of whenever you and your staff go in regards to the work that you just do). You might have propagation operations, you could have numerous various things happening in addition to two properties and extra I assume that you just’re additionally conserving, however the two major areas. How do you resolve what the function of keystone vegetation is—how typically does this come up in your work, and the way ought to we gardeners be desirous about keystone vegetation? As a result of I imply, can we even record the keystone vegetation? It’s not the identical in each area.
Uli: I take into consideration considered one of our core missions can also be to coach the general public about all of the tales round native vegetation. And so we do various analysis within the winter to attempt to uncover what these relationships are between a selected species and perhaps an insect herbivore or a specialist bee or specialist pollinator, or if it’s a number for a selected butterfly or moth. And I believe that we attempt to search out methods to include these vegetation into our shows with the assumption that we’re offering not simply one thing stunning for people to get pleasure from and a way of place, but in addition a lacking useful resource for these organisms.
The problem I believe, in any backyard, is how do you discover the steadiness between species range and biodiversity? And you could possibly make the argument that a lot of various things is a web profit for the wild, versus a design that’s legible to us that we are able to make sense of, and that there’s form of a steadiness and a center floor between what we get out of gardens and what we’re offering for the native wildlife. And so I believe that’s at all times somewhat little bit of a push and pull the place we love vegetation, we wish to develop all the pieces we presumably can, however typically the positioning situations don’t permit us to develop all the pieces. And so you need to make arduous decisions typically.
Margaret: And discovering out which of them although are the keystones of our space—I imply, it seems like that’s a very good instructional first step. Understanding that, understanding what they’re, each the woody vegetation and the herbaceous vegetation. I imply, I do know that Doug Tallamy, he wrote a complete e-book about oaks, and oaks are in numerous habitats powerhouses, particular powerhouses, and all of it is sensible. After which there’s different woody vegetation, but in addition once more, herbaceous perennials and so forth.
Uli: Quite a lot of herbaceous perennials, too [above, Monarda fistulosa visited by Hemaris thysbe]. And there’s some good sources. The Nationwide Wildlife Federation has some nice lists which might be based mostly on his work. I’ll say that there’s not like a one-stop store to determine all the pieces that there’s. And numerous the analysis now’s skewed in direction of caterpillars, which we’ve related rather well with fowl life. However there’s nonetheless a complete lot we don’t learn about insect herbivores, different stem-cavity nesters—organisms that use vegetation as habitat, not essentially simply as meals.
All of this, if I take a step again, I believe that we’re all trending in direction of this better consciousness as a result of there’s a realization that our decisions have actual optimistic impacts for the surroundings. I believe that’s actually what this boils all the way down to. And that welcoming native vegetation is a welcome step, however you don’t should be a purist about it in your gardens.
Horticulture has launched numerous actually stunning vegetation from different components of the world. A few of them, we’ll say, have turned out to be dangerous as they’ve escaped, however the actuality is that wildlife interacts with all of them in a technique or one other. And I believe that Doug Tallamy’s message of aiming for 70 p.c native is a very good one, as a result of it’s a purpose; it’s a journey upon which every particular person gardener can resolve how briskly and the way rapidly they work in direction of it. So long as you don’t lose that intention of attempting to make a forward-thinking alternative, that’s going to assist shield what stays.
Margaret: I believe one factor that I’m listening to you say is that the keystone vegetation for caterpillars could be somewhat bit completely different than the record of keystone vegetation for say, bees—like for pollinators. So if I needed to consider pollinators, as an illustration, and I needed to consider perennials, herbaceous perennials, flowering perennials, would I be wanting most likely—and I’m going to guess—within the Aster household, the form of daisy-like flowers, and likewise perhaps the mint household, as a result of that’s the place I see numerous the motion in my backyard?
Uli: I’d throw within the carrot household too, the Apiaceae. [Above, pollinator on Cicuta maculata (Apiaceae)]
Margaret: Oh, proper. The umbels.
Uli: The umbels are actually fantastic. However what numerous these, significantly the Aster household, what they share is a basic flower form that accepts all comers. It doesn’t matter if you happen to’re a giant muscular bumblebee or a small sweat bee or one thing.
Margaret: Accessibility [laughter].
Uli: Accessibility. And now due to this lengthy relationship that flower form and bug form have pushed specialization, it’s good to have the generalists in there. And also you additionally want to offer for are specialists that needn’t simply flower form. I used to be simply desirous about spring beauties [Claytonia virginica] and the spring magnificence mining bee, and right here’s a very shut little relationship that bee wants the actual nectar and pollen of that plant to be reproductively profitable, and nothing else—there’s no substitute for it. And so I believe that is the place favoring a local species to assist these specialists is admittedly good; there’s a robust argument to made for that. [Below, spring beauty mining bee on Claytonia caroliniana.]
Margaret: As a result of the generalists may use that in addition to many different issues.
Uli: Completely. You might have a garden filled with crocuses and spring beauties and also you get each the assist for the specialist and perhaps somewhat bit extra design decisions with the crocuses, however we all know crocuses aren’t going to take over the world, and even when they did, that wouldn’t be so dangerous.
Margaret: Proper. However what we’re saying is we’re going to look within the case of perennials, as an illustration—and actually regardless of the place we’re, as a result of morphologically structurally, these three teams of vegetation that we simply named as households are, there’s structurally there, once more, accessible—we’re going to look most likely in these households. And I may give the hyperlinks; you alluded to a few of the web sites which will have lists by bioregion of keystone vegetation and so forth the place individuals can perform a little homework. However once more, you need to know what your keystone vegetation for what you’re searching for, which is a bit more sophisticated.
Uli: Nicely, for pollinators, I believe there’s one other actually implausible useful resource, that’s by a person named Jarrod Fowler.
Margaret: Oh, sure.
Uli: And he has these actually fantastic lists of native perennials and the entire bee species that they assist or that they’ve identified to affiliate with. And there’s loads of choices in Composite household and mint and carrot household after which a great deal of others. And that provides you, once more, that form of research-based, data-based background to tell your decisions in a backyard of which perennials you’ll be able to embody to assist not solely the generalists, but in addition with a watch to the specialists.
Margaret: And in woody vegetation, I imply, I discussed that Doug has taught us a lot in regards to the oaks, however in woody vegetation, are there some… I imply, as an illustration, in your work at Native Plant Belief, are there some genera of woody vegetation that you just really feel like are actual powerhouses that you just see their contribution as outsize, form of?
Uli: Yeah. I consider the primary one involves thoughts are viburnums, and viburnums I believe are… there’s a great deal of range. The flowers assist numerous pollinators. There are a selection of Lepidoptera that host on viburnums, after which you could have the additional benefit of actually nutritious fruit that birds depend on within the fall. And so you actually get a complete completely different units of interactions because the season goes by. After which I believe from the human perspective, they’re stunning shrubs. They’ve obtained fantastic fall shade. If you need a substitute for your burning bush, like put in a Viburnum nudum and also you received’t be dissatisfied. In order that involves thoughts. [Above, Viburnum dentatum in fruit.]
Quite a lot of the Vaccinium–
Margaret: I used to be going to say loopy about blueberries; I’m loopy about blueberries, yeah.
Uli: Sure. And for all the identical causes that the flower assist quite a lot of pollinators; the birds love the fruit. It’s a must to compete with them somewhat bit to get the fruit, however fall shade is outstanding. I imply, there’s all these items that form of converge and I believe make them actual keystone species in a backyard.
Margaret: And with the blueberries, I’ve by no means actually picked any. I’ve had a few of them for the shrubs for 30-plus years, however I form of tucked all of them in these form of what I name biohedges, on the borders of the property, all these woody plant mixtures; they’re in all places. There’s a number of right here and some there and some in all places. And the bugs and the birds love them. They’re not for me. And what’s for me is that attractive purple fall shade, and so they’re stunning. They’re stunning vegetation, however they don’t want actually a lot consideration, but they attract all of the wildlife.
Uli: Yeah. I believe it is a good segue, too, to the concept of the appropriate steadiness between what I’d name essential upkeep in gardens—so ensuring that there aren’t leaves in your stone patio which might be going to trigger you to slide and fall—and that steadiness with what I’d consider as actually ecologically ahead practices. Like leaving stems, leaving the leaves, the concept of making mushy landings, your intentional hedges that aren’t so that you can harvest from, however are for the wildlife, or intentional brush piles. Or my pal Edwina von Gal and her snake habitat that she created. I really like that. I completely like it.
So I believe that’s form of one other perspective to deliver into this dialog, that you would be able to actually maximize the influence of keystone species by pairing these vegetation with a balanced method of the way you preserve your backyard. As a result of there’s not a lot level in planting a viburnum if you happen to’re going to then blow all of the leaves away within the fall and rake it up after which exchange it with wooden chip mulch.
Margaret: Not to mention an oak tree, the place goodness is aware of what number of creatures are going to be within the leaf litter of that tree that’s going to be pretty persistent.
Uli: Completely.
Margaret: You wish to attempt to let that be, as you say, like a mushy touchdown, a spot that may perpetuate and be largely untouched.
Uli: Yeah. And I believe you begin to put collectively this idea of an actual workhorse species. That concept, and the truth that gardens aren’t only for us anymore, and mixed with some actually conscientious and ecologically delicate upkeep practices, and the result’s a backyard that bursts with life, that gives all of those fantastic alternatives so that you can observe, to be impressed, to realize the entire advantages of gardening, which we all know is much less stress and extra happiness.
Margaret: Yet another tree or shrub as an illustration, that you just wish to shout out, as a result of I simply suppose the woody vegetation are so essential and so they’re everlasting fixtures within the backyard.
Uli: I’m going to name out dogwoods.
Margaret: Yay. Good, good.
Uli: As a result of I believe you could have each the attractive small-flowered Cornus florida [above] and its purple fruit once more, and the interactions. After which the entire fantastic shrubby ones that exist in our wetland margins which have, just like the viburnums, the power to attract completely different teams of organisms all through the season. So my high two are going to be dogwoods and viburnums.
Margaret: O.Okay. Nicely, Uli Lorimer it’s at all times enjoyable to speak to you. And yeah, keystone plant: I believe it’s been one of many phrases of the 12 months for positive. I’ve heard it increasingly and extra on a regular basis. Thanks for making time at the moment. Keep heat over there.
Uli: Will do. You do the identical.
(Pictures from Uli Lorimer; used with permission.)
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