Growing Greener Podcast – Microenvironments with Tom Wessels

Creating Microenvironments to Boost Your Garden’s Biodiversity and Resilience

Tom Wessels, professor emeritus at Antioch University New England and a celebrated ecologist, author, and educator explains how gardeners can enrich their landscapes with microenvironments to hugely boost their biodiversity and resilience. Listen and read the transcript.

September 2, 2026

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Transcript

Growing Greener host Tom Christopher

Welcome to Growing Greener, your guide to environmentally informed gardening. Produced in partnership with the Perfect Earth Project, this program brings you each week some expert who puts you in touch with a different aspect of gardening and partnership with nature. Our goal is to make your personal landscape healthier, more beautiful, more sustainable, and more fun.

This is your host, Tom Christopher, and today I will be talking to Tom Wessels, a distinguished terrestrial ecologist, who is a professor emeritus at Antioch New England University and the author of a series of popular, knowledge-rich books. He’ll be discussing with me the role that microclimates and the more inclusive category of microenvironments can play in enhancing the biodiversity of your landscape. Microenvironment is a very technical-sounding term, but creating one in your own garden may be as simple as pruning a dead tree to remain standing as a snag, or placing a large rock in the landscape. And the result can boost the biodiversity of your garden by tens of thousands of species of wildlife and generally enhance its resilience in the face of environmental challenges such as pollution or climate change.

Before we go to the conversation, though, I want to thank Growing Greener’s sponsor, the Garden Conservancy, a national nonprofit dedicated to preserving, sharing, and celebrating America’s gardens and diverse gardening traditions. Through preservation, education, and public access, the Conservancy helps protect these living works of art for future generations. Learn more and discover gardens near you at GardenConservancy.org.

Welcome back to Growing Greener, Tom.

Tom Wessels

Oh, I’m glad to be here. Thank you, Tom.

Tom Christopher

I always learn a lot and enjoy learning a lot when I speak to you. I first became aware of your work, I think, 15 years ago when I was introduced to your book, Reading the Forested Landscape, A Natural History of New England. That’s a guide to observing and understanding the various details of a woodland, ranging from the character of the stone walls to why beech and birch trees have smooth bark while other trees have rough bark.

Anyway, when you put these things together, you can read the ecology and history of those landscapes. And then I gradually learned about the succession of other books you’ve written, including Forest Forensics, which is a field guide to reconstructing the history of a forest, and Guide to the Roadside Ecology of New England.

Tom Wessels

New England’s Roadside Ecology.

Tom Christopher

Anyway, I want to add that most of your books are focused on the landscapes and ecology of New England, where you’ve lived and taught as a professor of terrestrial ecology and conservation biology at Antioch, New England. But I think the methodology you share for understanding the forested landscapes of that region would also, with adjustments, provide insights into those of other regions of North America.

Tom Wessels

Yeah, I think that they, throughout North America, would apply pretty well. I mean, it’s interesting, after Reading The Forested Landscape came out, my publisher said, well, this is really great. Why don’t you do one for each section of the United States? You know, one from the southeast, the lake states, the Rocky Mountains, the Sierra. And I said, you know, it’d be a pretty redundant project and would be better done by someone living in that area. There’s about, I’d say, 80 percent of the materials quite transferable to pretty much anywhere in North America.

Tom Christopher

And the approach it teaches readers, I think, is really transferable. In other words, you know, looking at these details and interpreting what they say about the place.

Tom Wessels

Yeah, very true.

Tom Christopher

So today I want to discuss with you a subject that has an impact on gardens as well as natural ecosystems. And that is the localized variations within a landscape that provide islands of conditions different from the regional norm and which have a big impact on a landscape’s biodiversity. So I want to start with microclimates, which is how this concept is usually presented to gardeners. As a young and aspiring gardener, I was taught to look for features such as a south facing wall. Now, a south facing wall, I was told, would get lots of direct exposure to sunlight and so absorb extra solar radiation, which would warm it and it would re-radiate that at night and during cooler periods to provide an area at its base with warmth and keep it warmer than the surrounding landscape. And the difference could be significant with such a microclimate remaining, say, 10 to 15 degrees Fahrenheit warmer than the surrounding landscape on a sunny winter afternoon. Similarly, a north facing wall or slope would receive less sunshine than its surroundings and so remain cooler during hot summer afternoons. Such microclimates, I was taught, could be exploited to grow plants that wouldn’t normally flourish in your landscape so that you could, for example, nurture plants from more southern regions at the foot of that south facing wall or perhaps grow alpine plants on that north facing slope.

Such feats are a very common source of pride and prestige among gardeners. Gardeners love to have rarities to show off to visitors. But they’re also an expansion of the biodiversity within the garden, although they often feature exotic plants that have little relationship to the local ecology. But I wanted to start with microclimates because that’s something I think gardeners would know about. What sort of role do they play in natural ecosystem?

Tom Wessels

Well, they’re pretty big. And actually, it’s not just microclimates, it’s microenvironments, which gets into physical aspects that might not be climate related. But what they do is they dramatically increase the ability for more specialized species to be present. So, when we’re looking at plants or any type of organisms in ecology, there’s a continuum from generalists, which can tolerate an incredibly wide array of conditions. So, for example, around here, white pine trees are a generalist species. They can grow in wetlands. They can grow in really dry outcrop communities. They can grow in rich sites, poor sites in terms of nutrients. They can grow just about anywhere. But then on the other extreme of that spectrum, you get the specialists. And these are species that have very tight, narrow tolerances for various conditions, whether it might be moisture or nutrient level or things like that. So, for example, there are trees like bitternut hickory up around here that are very specific to soils that are circumneutral like pH 7 to 7.5 and are moist and only grow in sites like that. So, when we create microenvironments or microclimates, let’s say in a landscape situation, we’re creating sites that specialists can move into and boost the biodiversity because they need very, very specific conditions.

Tom Christopher

Now, you said in a communication with me that microenvironment is a category which includes not only microclimates, as you’ve said, but also a host of other local variations from the regional norm. Could you define for us what sorts of conditions a microenvironment might include?

Tom Wessels

All right. Well, let me give you an example, which was probably, you know, I’ve known about this intellectually, taught about it for years. But when my daughter was 17, she wanted to learn to scuba dive and I didn’t scuba dive. So, I thought, all right, we’ll do this together. We’ll become diving buddies. And after we were certified, we made a trip down to Florida so we could scuba dive in coral reefs, something neither one of us had ever done.

And during our first dive, we started off in a lagoon setting, which was, you know, maybe a 15-foot depth of ocean water to a sandy bottom. So, Kelsey and I, my daughter, we went down and we’re right along the bottom, moving along over the sand, just looking at what we could see. And, you know, we saw some species of fish. But when we entered the coral reef, because of the structures the coral created, it created all these microenvironments where the fish numbers just escalated dramatically because different fish were specialized to different cavity sizes in the corals or to different textures of the corals or to different sort of zonations within the coral. So, we had all these specialists that could come in there while out in the lagoon, and it was very generalized species that we could see some of those species also in the reef, but a lot of the specialists were just excluded. So, that’s an example of just physical structure and displacements based on size, capacity and stuff that’s not really climate related, because the climate throughout that water column was pretty much the same.

Tom Christopher

Uh-huh. So in a terrestrial setting, the differences might be nutrients in the soil or soil pH, as you alluded to with the bitternut hickory, or it could be exposure to sunlight, full sun versus shade, and even moisture versus…

Tom Wessels

Yes, because microenvironment includes microclimates, but it also adds the physical features that might not be climate related, like soil pH, soil textures, for example, a rock substrate which will grow lichens that can’t grow on bare soil. So, it includes physical aspects like that as well.

Tom Christopher

So, it creates essentially niches for species and often for specialist species, but it’s not only plants, right? It’s, I mean, the biodiversity includes a host of other organisms.

Tom Wessels

Yeah. So right now up here, I live up in coastal Maine and live in an area where we have a lot of glacially scoured granite domes. And it’s one of my favorite environments because of the outcrop communities there, these incredible moss, lichen communities. But right at this time of year, to give an idea of a specialist, is this grasshopper. It’s called the bandwing grasshopper, also the clicking grasshopper. And I only find it up on exposed granite bedrock. And it’s colored to look just like lichen on the bedrock. So, it’s really cryptically colored. But when it flies, it makes this very loud clicking noise and has the bright yellow underwing. So, what you do is you focus on that color. It’s sort of really changing your whole search image.

And this grasshopper lands on the lichen-covered granite, closes the wings, and hops a little bit to the side and completely vanishes from view. So, it’s very specialized to those outcrop conditions because of its cryptic coloration. So, there’s an example of just an animal that is commonly seen up here at this time of year.

Tom Christopher

So I would imagine these specialist species would be much less abundant in general than the generalist species. And that, okay, so it would be very hard to recreate a granite outcrop with lichens in your gardens. But in the cases where you could create an appropriate niche for them, it might be a real benefit to biodiversity in your area.

Tom Wessels

It’s huge. I mean, when we look at most of our ran endangered species, they’re pretty much all specialists because they need these very, very specific sites. And if they decline for any reason, then those species numbers decline. But if a species is generalist, it can grow anywhere or exist anywhere. It’s not a big deal.

Tom Christopher

So, the organisms, and again, they could be soil organisms, for instance, as well. Even fungi, for instance, that live in the soil, I mean, would require certain conditions. And you could be benefiting them. Gardeners are just beginning to understand the importance of fungi in the garden ecosystem.

Tom Wessels

Yeah, fungi are certainly an area we’re starting to learn a lot about. I remember when I was doing my work as an undergraduate at the University of New Hampshire back in the late 60s, early 70s, we were out in woodlands and I was being taught that trees were individuals. And because of that, they only competed with each other. Well, we know that’s not the case now. Starting with Suzanne Simard’s work back in the mid 90s, looking at mycorrhizal fungal communities in forests, these mycorrhizae associate with the roots of photosynthetic plants. So, what they do is that’s where they get their energy resource. They extract the plant sugars from the roots of that plant. But any plant that has a mycorrhizal partner gets a benefit because of the extensive mycelium of the mycorrhizae in the soil. Any plant that has a mycorrhizal partner can increase water and nutrient uptake by about tenfold. So, it’s really a mutualistic relationship where both parties benefit. But not only that, these mycorrhizal fungi are stitching together the roots of all these plants. So, actually nutrient and energy transfer is going back and forth between plants, even a different species, creating a very integrated network.

And we’re beginning to realize it’s part of the great resiliency of forest ecosystems. If everything just simply competed, and I think about this in a human context, if we had, let’s say, communities where everyone just competed with each other, they wouldn’t be as thriving. They wouldn’t be as resilient as a community where they’re in mutually beneficial relationships with each other and supporting each other and helping each other out. So, ecology is teaching us some important lessons. And that’s why I think life has thrived on this planet. You know, it’s been around for 3.8 billion years. That is an incredible amount of time. Just a huge amount of time. And during that time, life has not only sustained itself, it’s thrived, because what we’re learning now is at its core, it’s developing these mutually beneficial, dense networks that have been relationships, which create these very resilient, thriving systems. So I don’t know. I think I got off on a tangent there. I can’t remember what the original question was.

Tom Christopher

Well, we started talking about fungi. And I’ve also spoken to grassland ecologists. And the mycorrhizal connections and the mycorrhizal fungi are really important in terms of their thriving and their resilience, too. So it’s not just forests, although forests are a great example.

Tom Wessels

You know, another good example is we have a number of groups of plants that are so highly co-evolved, they need a mycorrhizal partner. They cannot exist without them. So, for example, all the members of the orchid family, every single orchid has to have a mycorrhizal partner. You can’t get orchids without, if they don’t have mycorrhizae. The same with all the members in the Ericaceae, the heath family, like blueberries and huckleberries and cranberries.

And so near me is this bog up in Orono, it’s called the Orono Bog, which if anybody gets the chance to go there, I highly recommend it. They have a beautiful boardwalk with, I think, the best interpretive trail signage I’ve seen on any interpretive nature trail. But if you get out in that bog, every single woody plant you see out there is a plant that needs a mycorrhizal partner, like all the cranberries, the leatherleaf, the black spruce, all these woody plants that stitch that bog ecosystem together into an integrated unit. And if mycorrhizae wasn’t there, none of them would be there and you wouldn’t have a bog ecosystem. So, mycorrhizae in that case are the keystone species of that whole ecosystem, which is now a wetland ecosystem.

Tom Christopher

That’s amazing to think of them as a keystone species. When we’re talking about these organisms that are going to thrive in the microenvironments, do they typically find those microenvironments on their own? Or do you have to introduce them if you’re doing a restoration or a garden?

Tom Wessels

Well, that’s a good question. I think that really relates to dispersal mechanisms of the individual species. So in some cases, like with lichens that can disperse their seridia hundreds, thousands of miles, it may not be an issue. But other species that may have seed dispersal mechanisms that are rather restricted and don’t travel that far, it may be necessary to actually, if there are new microenvironments opening up and you want them present, to actually move them in.

Tom Christopher

So, it would really pay somebody who’s doing a restoration or hoping to enrich the biodiversity of their garden to understand these microenvironments so that they can recognize them and benefit by them.

Tom Wessels

Yeah, that’s true. And, you know, just one thing that I’ll mention that will work for any person doing landscape design of any sort is that in any ecosystem, when its physical structure increases, when its physical complexity gets more complex, like the corals in the coral reef, right alongside biodiversity goes up because you’re creating all these microenvironments. So, people just think about if they’re making a garden, like probably a rock garden that has boulders or whatever else in it, are going to create a lot of microenvironments compared to just a regular bed of soil that’s smooth and even. So, anytime you can increase structure, you’re automatically going to increase biodiversity.

Tom Christopher

And not being too tidy. If you have a woodland part of your landscape, there’s a movement to leave fallen trees, for instance, and leave snags. And that would increase the structure.

Tom Wessels

It’s huge. It’s really huge. So, you know, we call it in ecology coarse woody debris, anything that’s like four inches in diameter or more. I think it was the first year the Oak Spring Foundation opened to do courses. This is down at the Bunny Melon Estate down in Virginia. And I was brought down to teach a week-long ecology class. And two of the participants were arborists from England. And over dinner one night, we got talking and they said, you know, we’re quite specialized in what we do. And I say, oh, really? What’s that? And they say, well, we’re paid to go around England to prune large standing dead trees to keep them standing. And I said, really? Why are you doing that? And they said, well, our forests don’t have the coarse woody debris your forests have. And research has shown these large dead snags are the refugia for a wood decomposing community. And studies of England have shown a really dead, large ochre chestnut throughout its whole tenure, before it completely decays away, will host about 20,000 different species of wood decomposers.

That is a huge amount of biodiversity. And so an example of the impact of removing coarse woody debris to make your forests look nice and neat and tidy is that this was a practice that happened in Germany in the Black Forest. People thought all this down woody material looked unsightly and was picked out to make the forest look nice and neat and tidy.

And they didn’t realize that they’re compromising their ecosystem, because when air pollution started to impact the Black Forest, the areas picked clean and coarse woody debris underwent canopy collapse. While areas that retained it did not, because it had a much fuller complement of the biota, and therefore was a more resilient ecosystem.

Tom Christopher

Fascinating. Tom, I need to pause here for a moment to remind listeners that this radio station is WESU 88.1 FM, and this program is Growing Greener, a weekly conversation about gardening in partnership with nature. This is your host Tom Christopher, and today I am speaking with ecologist and author Tom Wessels about the role of microenvironments in increasing the biodiversity of your landscape. So, I wonder if we could get back to gardens, and this is a little bit outside of your purview, but you seem to be able to shift gears pretty easily. What other things could gardeners do to increase the microenvironments within their garden?

Tom Wessels

Well, like I said, any structure you can add in any way, shape or form will create these microenvironments. And I don’t know how to go into specifics because I’m not really in landscape design, but just thinking about it, how can I make the structure of the environment more complex, automatically you’ll do that. And something else I’ll mention that doesn’t relate to microenvironments, but use native species whenever you can, because our native species have co-evolved together and created a lot of these mutualistic relationships we’re not even aware of. And so right away, if you’re working with native plant species, automatically your system is going to be more resilient than if you’re working with exotic species that have not co-evolved with our natives.

Now, I should mention, given enough time, thousands of years, exotic species do co-evolve and become functional members of our ecosystems, but it takes a long time, a lot longer than any of us are going to be around if we’re doing landscape design. So, I’d say, yeah, whatever you can do, adding structure and think about working with native species because they have this huge array of these mutually beneficial interactions, many of which we don’t even know about, that will create more resilient systems.

Tom Christopher

I suppose it’d be easy to create new microenvironments if your landscape consists largely of lawn. If nothing else, planting woody plants so that you’ll create some shade underneath them, that creates a cooler microenvironment with less intense sunlight that’s going to invite in species that won’t flourish just out in the middle of the lawn.

Tom Wessels

Yeah, absolutely. And not only that, the structure itself, not just the shade, but the structure itself will create conditions where other things can move in. So, for example, on the coast of Maine here we get quite a bit of ocean fog, and so any of our woody plants start getting lichen growth on their twigs and branches and things. And that actually will not only boost the biodiversity, it’ll also, at least up here, brings in a lot of nutrients into the system because lichens pretty much get all their nutrients out of the air. A lot of it absorbed in rainwater or fog, and fog carries a huge amount of nutrient because a raindrop forms around one nuclei, which will have some nutrient material in it. But each fog droplet forms around a nuclei, and it takes about a thousand fog droplets to equal a rain droplet, so fog can bring in a lot of nutrients. So the lichens absorb it, eventually those nutrients will come out into the soil, and right away you can start enriching sites.

So, yeah, any structure, like any plant structure, is going to automatically start boosting microenvironments.

Tom Christopher

Another instance that occurs to me is that traditionally wet spots in the landscape were, well, they wouldn’t grow lawn properly for starters, but the impulse was to figure out a way to drain them or fill them in. And if you want to work with microenvironments, that would seem to me a great place to maybe strip off the lawn that isn’t doing very well and create, well, a rain garden, but also a moist microenvironment.

Tom Wessels

Yeah, absolutely. I’ve often thought you get into moist soils here in New England, and in forest settings you often find skunk cabbage growing in there, which is a dramatic plant, and I’m thinking, well, maybe you could do that in landscape design or something, but it would naturally grow. And, again, being this very coarse plant is creating, again, a lot of microenvironments, all in just its presence being there. So, yeah, I’d say, yeah, if you’ve got areas that are wet, utilize them and bring in the specialists that do well there, and you’ll have a much more diverse landscape system.

Tom Christopher

I want to put in a particular plug for skunk cabbage, which is one of my favorite plants. It’s a very early bloomer, and perhaps you can check me on this, but my understanding is that what we find, the unpleasant odor of the flowers actually helps to attract flies, which are active at that time, and early pollinators. And the plant actually will, I think, warm inside the flowers, partly by consuming starch from its storage in its roots. Is that correct?

Tom Wessels

Yeah, it’s very correct. And if you look at the space of a skunk cabbage flower, you’ll see it’s sort of banded red and green. It’s actually trying to mimic gangrenous flesh, like rotting flesh, because it blooms so early, we really don’t have bees and a lot of flies around. So, it’s attracting carrion beetles and carrion flies, who are looking for dead meat to lay their eggs in. So, it also emits an odor that’s sort of like that to them. So, they see it, they smell it, they climb in there, and you’re correct, the red of those space is anthocyanin, and they’re not only producing heat from starch, but anthocyanin absorbs heat. In other words, it’s absorbing in the light spectrum, that heat area of the light spectrum. So, those flowers can heat up, yeah, a good 15 degrees above air temperature. So, these carrion flies or carrion beetles get in there, and of course, they find no meat, and that’s a big problem for them. But we’re finding out it’s again a mutualism, because they go in there, and it’s like a little warming hut for them. They get warmed up, which means they can travel out again further to look for dead carrion.

So, here again, a mutual beneficial interaction where these carrion flies and carrion beetles are pollinators, but are being warmed by the plant so that they can go out and actually continue their lifestyle.

Tom Christopher

So, you could call those skunk cabbage flowers actually microenvironments.

Tom Wessels

They are.

Tom Christopher

This is great. Well, Tom, we’ve run out of time, but I want to close by recommending again that listeners explore your books. They offer an entree into landscape ecology that I find intriguing, but they’re also written in language that a layperson such as myself can easily understand. And I love the fact that many of them are interactive, too. You involve the reader in the narrative. It’s not just, here’s information, absorb it. It’s, well, if you go out in the woods, you’ll see this, and what will that tell you kind of thing.

Tom Wessels

I think that problem solving, which I do a lot of in my teaching, I ask students I’m working with to try to figure things out, actually engages people in material in a way that they can connect to it better than just hearing about it. And, you know, if people don’t want to get books, they can watch my YouTube videos for free. They’ll learn a lot about what I do, and then if that intrigues them, they can get the books after that.

Tom Christopher

Yeah, I should have mentioned the videos, because I really enjoy the videos, too. Well, thank you for making time for this.

Tom Wessels

My pleasure, Tom.

Tom Christopher

That brings us to the end of this week’s Growing Greener. Please join us again at the same time next week on this radio station, WESU 88.1 FM for another episode, or listen to Growing Greener as a podcast at www.thomaschristophergardens.com. If you have comments or suggestions, please share them with me, Tom Christopher, via the same website, www.thomaschristophergardens.com. Growing Greener is produced as a community service in partnership with the Perfect Earth Project, a nonprofit dedicated to educating, engaging, and inspiring individuals, land care professionals and decision makers to adopt toxic-free, nature-based, and climate-responsible landscaping practices.

 Transcribed by TurboScribe.

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