Adam Baker, technical advisor for the Davey Institute, talks all about pollinators, such as how trees support them, why it's beneficial to plant trees and plants for pollinators and which trees and plants he recommends based off his scientific research.
In this episode we cover:
To find your local Davey office, check out our find a local office page to search by zip code.
To read Adam's research on monarch butterflies mentioned in the podcast, you can find it linked here in the Frontiers in Ecology and Evolution scientific journal.
To learn more about bees and trees, read our blog, Do Bees Like Trees? Trees for Bees Guide.
To learn more about creating a pollinator garden, read our blog, Creating a Pollinator Garden (Steps and a Pollinator Plant List).
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Doug: Welcome to the Davey Tree Expert Company's Podcast, Talking Trees. I'm your host, Doug Oster. Each episode showcases one of Davey’s certified arborist, sharing advice with everyone about caring for your trees and landscapes. We'll talk about everything from introduce pests, seasonal tree care, zero damage, how to make your trees thrive, and much, much more. Tune in every Thursday to learn more because here's at the Talking Trees podcast, we know trees are the answer.
Well, I'm excited this week to be joined by Adam Baker. He's a technical advisor for the Davey Tree Expert Company. We're going to talk all about how trees help butterflies and pollinators. Adam, I have to tell you, I planted a stewartia tree two years ago and it is covered in flowers right now and I can see the bees enjoying that tree and I'm just overjoyed.
Adam: That's awesome, Doug. I'm glad you're experiencing some pollinators on your own landscape. A stewartia seem to be a pretty attractive ones.
Doug: Underused in the landscape but I'm still wondering about its hardiness but I had to give it a shot. I put it in a protected spot. I think I got it in the right spots but we'll see as we get down the road when we get a hard winter or a tough summer. Let's talk a little bit about pollinators and butterflies in general. How do trees work for them? When we think about pollinators, a lot of times we were thinking flowers in the garden but trees do a lot for pollinators, right?
Adam: Right, most of the trees that we're familiar with are going to be in that same group. The angiosperms are going to be creating nectar and pollen sources that can support a lot of different pollinators. There's this fine relationship between the types and the forms of the flowers as well as what types of bees and what types of pollinators are able to utilize them so different types of flowers will attract different types of bees.
What's great about trees if you think about one single tree with thousands and thousands of blooms on it, if you were to lay that canopy out onto the ground, you would get almost the entire meadow whereas it would take hundreds of plants to create that same floral resource that you get with just the blooms from one tree.
Doug: What is that term that you used at the beginning of the answer?
Adam: Angiosperm. Just the flowering. What we typically think of a plant with flowers. We have the conifer groups and the endosperm groups which is essentially just flowering plants.
Doug: Do you have any specific trees that you like to recommend for people that want to help pollinators?
Adam: Yes. As far as the floral resources are concerned, I think the ideal goal for the landscape is to create a landscape that has floral resources, that nectar, and that pollen from early spring to late fall. That way, there's always something there for pollinators to forage on. Some of the plants that I like a lot, I really like redbuds early in the year. They're very important for a specific type of bee called the andrenids. They're known as the mining bees or the ground-dwelling bees.
If you go out in early spring, you see a bunch of things that look like little anthills. You see a bunch of insects hovering over the ground. Those are those really early season andrenids and things like the redbud are going to be very important for that group because they're going to fade off somewhere around mid-June. That's kind of the time span that they're going to be active in the environment. Beyond that, I really like things like the winged sumac. Winged sumac was one of the plants that I surveyed that had one of the greatest visitations of any of the plants we looked at.
I guess I should preface this. Anyways, when I was an undergraduate student at University of Kentucky, I was involved in a project where we were trying to quantify the communities of bees on common and lots of common landscape, trees, and shrubs. What we did was we found 75 species of trees and shrubs, went out to five different locations, and sampled bees off of all of these different plants so we could build these community lists and we could also look at the overall attractiveness of these. One of the ones that stood out in that was that winged sumac.
Doug: The winged sumac, is that the sumac that I know that just grows wild and has the red flowers on there or is that a cultivated variety?
Adam: Potentially, it could be one of those that you see growing out there but there are many different species from the staghorn and others. I like the winged sumac because it has that very, I think its Rhus glabra as the species and it's got a very shiny leaf and it has that wing connecting between all of those little leaflets. It's a little bit smaller than some of the ones like the staghorns can get rather big and unruly and that's probably what you're seeing on the side of the highway and such.
As I'd mentioned during this survey of 75 landscape woody trees, and shrubs, the winged sumac was one of the most impressive that I saw throughout the entire investigation. There were so many bees on it. They were almost carrying away this planting of winged sumac. They can be a little bit unruly so if you do plant it, put it in a place where it's not going to be able to spread underground and you can be able to control it a little bit. Other plants that turned out to be really attractive were, let me think, let me pull it out. The things like, if you like more of a sprawling understory type tree/shrub, the bottlebrush buckeye was one of my favorites.
Got these really great, tall, white, panicle flowers. That's very, very attractive to not only bees but also a bunch of butterflies as well. Then one that's really great for the late-season that we noticed was the Seven-sons flower. That one's going to be a non-native tree but I think it's okay to sprinkle in a little bit on non-native trees as long as it fulfills an ecological niche that's not fulfilled by our native plants. This particular tree blooms in very late summer, early fall and there's not a whole lot blooming. It's great for bees at the end of the season as well as is great for migrating monarch butterflies and all those other pollinators holding on at the end of the season.
Doug: Let's talk about that end of the season for something like a monarch butterfly. We'll get into host plants and that sort of thing and gardeners are planting host plants for pollinators but that food source at the end of the season is important too, right?
Adam: Yes. If we use the monarch butterfly, in particular, as an example here, they really need two important things throughout the year. They need to have their host plants available when they're in the reproductive stage. They also need to have rich nectar sources available for them in early spring and in that fall migration because they use that nectar to fuel all of their flight. Those carbohydrates and the nectar are going to be very important for sustaining flight. It's also really good for things like social bees that really need to finish the season strong. Stocking up their stores so they can remain strong and over winter successfully.
Doug: I'm really excited because I have a Heptacodium Seven-son flower and a bottlebrush buckeye in my landscape. That bottlebrush buckeye actually will lay down on the ground and route and sometimes make another shrub. I've been making more that way but that one gets pretty big, right?
Adam: Yes, it can get pretty big but it generally, it likes to hang out in the understory area. I think it's a great alternative for a screening. People generally use a lot of like arbor body and things that like things like bagworms love to eat. Whereas something like the bottlebrush buckeye can add interest in the shape of the foliage as well as that sprawling form. Then like I said those flowers during the heat of the summer are really, really attractive and they draw in a lot of swallowtails and things like that to feed on.
Doug: When you did that research, were you surprised by the results, or was this what you thought would be the plants that were preferred by pollinators?
Adam: Well, when we started this research, there's tons and tons of different lists online. We call it the list mania. You can find them everywhere where people can create their own anecdotal-based lists. Things change throughout the landscape just because you see a lot of things on your storage or in your backyard, in particular, that may not be the rule across the landscape. Our aim was to create the first science-based list. Like I said, we had five sites for all the different trees. We checked the visitation as well as the communities of bees on them. Coming into this, there are some that you would think that would be highly attractive. Things like the tulip poplar, has a lot of nectar, but for whatever reason in that Ohio River Valley region, that one was not very attractive, that may be because there's other sources that are more attractive at the time, maybe they have different metabolites or different proteins in there that the bees are after. Then some of the ones that really impressed us were the bottlebrush buckeye, things like St John's-wort, the frondosum cultivar especially was just extremely attractive to bumblebees.
One of the ones that was really interesting was the Philadelphus, the Mock Orange. When we started sampling that, we were almost getting collections of bees all from the exact same gene and species, which is genus or species is actually Philadelphus. The Mock Orange Megachile bee. It's a specialist resin that scrapes the resin from Mock Orange flowers, and almost every single bee about 95% of the bees we collected off of all the Mock Oranges were all of that same species. What's pretty interesting is we'll find a Mock Orange, there may not be another one within a mile yet, we still find this specialist be on there. There's a very intrinsic relationship between these two species.
Doug: Oh, that is really cool. I have Mock Orange too in my garden. This is good stuff. Let's talk a little bit just about bees in general, and people should not be afraid of bees. They're just, they're doing their work and they help us garden.
Adam: Right. Bees, in general, they get a bad rap and that's mainly from one guy out in the field. That's the yellowjacket. The yellowjacket is generally mistaked as a bee. That one is going to be much more aggressive than any of the bees. Generally, when bees are pollinating, they are very docile, fuzzy bumblebees have been known to even, give them a little pet when they're on their flowers. They don't mind at all. Unless you're inside their nest, unless you're causing trouble to their colony, they are not going to sting you.
Now, that being said, most bees that are in the landscape are actually solitary bees as far as the numbers of species. When we think about bees, we think about things like honey bees and bumblebees, which are the big social groups of bees. They have the greatest number, but the actually the greatest number of species are all solitary bees. That includes the leafcutter bees, the mason bees, the digger bees, the masked bees, and the small little metallic grain, sweat bees that we see in the summer. Bees are really interesting. They're basically pollinating machines. They have all sorts of different morphological traits that help and facilitate that pollination.
One of the things that they use are these hooked hairs that grab onto pollen, for instance, the Megachile group or the leafcutter bee group, they have almost a set of bristles on the bottom side of their abdomen that just comb right over the top of the flowers and pick up a lot of pollen, things like the bumblebees and the honey bees have what they corbiculum or pollen baskets. There are these flattened spaces on their back hind legs, which they can store pollen and carry back to the nest. Then bees also, they come in all different shapes, sizes, and colors.
Then one of the things that's really cool with them is their mouthpart informs the type of flowers that they can visit. Generally, there's bees with really, really long tongues and there's bees with short tongues, and they can only use certain types of flowers. Now, of course, not all bees agree with this. Things like bumblebees, if they go into a flower, their mouth part is just too big. Think of like a long, skinny trumpet flower. They'll actually just go in, cut the nectary open with their mandibles and engage in what we call nectar robbing, which is good for them but provides no pollination services for the plants.
Doug: Well, let's just talk about the importance of attracting pollinators. In general, gardeners, and people that love nature, love trees should want to encourage pollinators, right?
Adam: Certainly. Generally, the more biodiversity on your landscape, the more healthy that landscape is going to be. Sterile environments should be left for places like operating rooms, whereas the outdoors should be filled with insects and pollinators. Those pollinators are going to be just an indicator of that health of that ecosystem. Maybe we can step away from the traditional American landscape with the manicured monoculture turf systems and maybe the same species of trees especially get away from things like the Bradford pears and some of those non-natives that we're planting along the streets and maybe think about getting a little more biodiversity in our landscapes.
We can do that through trees and shrubs. We can do that through perennials and annuals and then just mix that landscape to make it both aesthetically pleasing for yourself and for your mental state and your stress and all that kind stuff, as well as making it an attractive buffet for our pollinators.
Doug: Oh, Adam, we've talked so much on this podcast about Bradford pears. Oh, and I think every arborist and every scientist that I've talked to, they just, they hate that tree and that tree is so problematic, but let's talk a little bit about in the landscape, how about host plants for pollinators?
Adam: Certainly. Generally, when we think about host plants, the one that comes to mind first is the milkweed for the Monarch butterflies, but lots of different trees can act as host plants for particular species here. For instance, Hackberry, although not the most desirable species for some is the host plant for a lot of things like question marks, mourning cloaks, the Hackberry emperor, the Tawny emperor. Another great one, I think is the pawpaw tree, which creates delicious fruits for one, as long as you can get to them before the squirrels do.
They are host plants to the zebra swallowtail, which is one of the most charismatic butterflies we got around. Things like the black cherry and tulip tree are great for the Eastern tiger swallowtails. Spicebush is another one of my favorites, it's got that very fragrant, lemony foliage. That's going to be a host plant for our spicebush swallowtails. If you like the little tiny blue and silver butterflies that you see fluttering usually close to the ground, things like dogwoods and black cherries are also going to provide habitat for them but not only just the foliage as a host food source, the architecture of the tree itself creates habitat for things like birds and insects and other creatures that can use that space inside the architecture of the tree.
Doug: Well, we've talked on the show before about pawpaws and listeners couldn't see, but when you mentioned pawpaw and we can see each other, I'm raising my hands up in the air and shaking it. Yes, yes, pawpaws. That's a tree that is underused in the landscape, but that is a wonderful, wonderful tree. When you get two of them and they pollinate and that fruit is to die for, and it's a native too.
Adam: Yes. What I love about those two, it creates all sorts of interest. It's got a very interesting, like oblong leaf shape. If you crumple up the leaf, it smells like green pepper, which is great. When you're walking around with your kids or grandkids, you can take off a little piece of foliage and let them experience that same thing with like the spicebush, and then a lot of these caterpillars too that I'd mentioned that's on the spicebush, and pawpaw, have these really cool caterpillars that look like little snake mimics. They're almost like little anime cartoon characters. They're quite beautiful as well.
Doug: Let's talk about how you got into this. Does this go back to childhood, or does this become something later in your life?
Adam: Well, as a child, I grew up in Southwest Michigan and we lived in an interesting habitat, between the dunes and the forest systems of Michigan. We had a bog that was right behind our house. I spent lots of time hanging out in the bog precariously climbing through the weaved button Bush roots over the sphagnum moss mats. Yes, I've always had an interest in nature and insects.
I really was into turtles and snakes and the herpetology stuff back in the day. I actually went to University of Kentucky to pursue a degree in Environmental Journalism and Environmental Literature. At that point, I started working in entomology lab. The first one I worked in was looking at a project that was looking at the impacts of the Hemlock woolly adelgid on the stream systems of Eastern Kentucky.
We were comparing deciduous, dominated streams with the Hemlock dominator stream. We were looking at what they call the [unintelligible 00:19:38] invertebrates or the larval stages of insects that are living and interacting in that environment. We were comparing the numbers of feeding guilds. From there, I got a job in Dan Potter's lab looking at that bee issue, looking at the communities of bees, on the plants, as well as looking at the way that insecticides translocate from the Woody tissues into the pollen and nectar. Then from there, he received a grant to look into monarch butterfly conservation on places like golf courses and other urban environments. At that point, I was graduating out and I accepted a position as a graduate student in his lab. This is a perfect place for me to be because it mixes in the science as well as the storytelling. The monarch butterfly, of course, has a very attractive and interesting story and it also connects people with nature. We use it to inform our scientific literacy early on. We've all had them monarch caterpillar and our elementary classrooms go from the hungry caterpillar to the Chrysalis and then emerge.
Still today, we continue that education at all sorts of our arboreta and zoos and places where they have installments where they create the monarch habitats or monarch waste station habitats that generally have some educational signage with that. What I was really looking at is how we can use the ecology of the monarch butterfly to inform our conservation practices. Essentially, I was investigating how the monarch butterfly actually finds and utilizes its milkweed and then incorporating that into our monarch conservation garden design.
Doug: As we finish up and we're talking about pollinators, for homeowners, talk about the importance of creating this environment for pollinators, and for the most part, that should be chemical-free if you're trying to help a pollinator.
Adam: When you're building your landscape for pollinators, you want to choose plants that are going to be attractive but not inherently buggy or covered in pests so you won't ever have to have the need to treat or to apply any insecticides for these habitats. The fact that you're seeing leaves shoot up, the fact that you're seeing frass and some of the foliage torn up is a good thing. That's what you want to happen in the environment.
I said if you want that pristine aesthetic, choose plants that are not going to be attracting things that use foliage. If you want to have that more interesting ecological experience, you want to get out and be a observer in the garden and see some of the really interesting relationships between the plants and the animals, choose those ones that are going to act as host plants as well as those floral resources. We definitely want to minimize those pesticides in our pollinator habitats.
Then beyond just the value for the insects themselves, there's a body of literature out there that looks at how more biodiverse landscapes influence our human health and wellness. There's lots of studies looking at measuring stress hormones compared to being in landscapes with high biodiversity versus low biodiversity. It's helps lower stress and just overall affects our mental wellness.
Doug: Adam, that is great stuff. Appreciate your time-
Doug: -learned a lot and I'm sure that our listeners did too. Thanks so much for sharing your information with us.
Adam: Hey, thanks for having me, Doug.
Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. I'm excited for next week's show as we discover a great list of drought-tolerant trees, very important these days, that's for sure. As always, we'd like to remind you on the Talking Trees podcast, trees are the answer.
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