‘pollinators of native plants,’ with heather holm
BEES HAVE BEEN increasingly making the headlines–but often the conversation is specifically about honey bees, an imported European species that settlers brought over to help with pollination of agricultural crops, harnessing them like a farm animal, if you will.
Native bees species (like the mining bee above on the wildflower boneset) don’t get as much attention, and other insect pollinators even less, but without our wild pollinators we’d enjoy far less biodiversity, both in plants and animals—because they’re key to the food web, which would otherwise break down.
To get to know some of these unsung heroes and the critical roles they play, I spoke with Heather Holm, author of the book “Pollinators of Native Plants,” which teaches us how to identify and attract and appreciate them in our gardens and beyond. (Enter to win a copy at the very bottom of the page.)
Regular readers and listeners know that I love learning great words from science, and Heather writes that her book is about entomophily. Entomophily is very much like another word that I love: anemophily, which means wind-pollinated, but this one means insect-pollinated.
“It’s the relationship between insects and plants in particular, which I find absolutely fascinating,” says Heather, the principal of a native plant consulting and design firm in Minnesota and frequent lecturer and environmental educator. “As a horticulture person I’ve always been looking at plants. And then about 10 years ago I finally started to notice that it’s not just the plants that form the basis of our food web and ecosystem, it’s all this interaction that’s going on between the plants and insects.”
We talked about different kinds of bees, about bee-lookalikes, about powerhouse pollinator plants and more, on my public-radio show and podcast. Read along as you listen to the Aug. 10, 2015 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).
my q&a on pollinators, with heather holm
Q. If I had to sum it up in a phrase, I’d say that your book is about the connection between wild bees, or wild pollinators and native plants. Not the honey bees, which is a big subject that you make clear you’re not covering in this book.
A. Honey bees have been well-covered in other books, plus with my passion for native plants I wanted to look at all of these insects that have that close co-evolutionary relationship between the plant and the insect pollinator.
The book includes many types of wild bees, but it also includes butterflies and moths, and the other secondary insect pollinators that people don’t realize are doing a little pollination, like flies and beetles.
I tried to pick up some of those species to show the common ones that people would find in their garden, but with more emphasis on the native bees.
Q. Native plants because, again with the honey bees, the agricultural relationships between bees and crops have been covered; how hives are kept and moved around to pollinate certain crops. But this is a different subject.
A. This is more of what’s going on in your garden, especially if you’re not keeping honey bees or there are not honey bees nearby. You’re likely to see all this other insect diversity—all these insects that are not related at all to honey bees.
Q. If I asked most people to name a bee besides a honey bee, including lots of keen gardeners with a lot of experience, I suspect they might say “bumble bee,” which is a vague word; it’s not just one species of bees. Or maybe people like myself who have holes in the side of their old houses would say, “carpenter bee.” [Laughter.] But there is quite a diversity of wild bees–can we talk about the range a little? [Above: Lemon cuckoo bumble bee, Bombus citrinus, on sweet Joe-pye weed.]
A. You’re exactly right. When I give talks to people being introduced to bees, their model is the honey bee; they’re the basis of their model. They think of many bees nesting socially, in a colony, and what’s interesting is that most of our wild bees are so radically different. People don’t realize that.
So for example, the majority of them nest in the ground. The females are building these nests alone for the most part, so they’re solitary nests.
And then the minority are nesting in cavities. That can include hollow plant stems from last year’s growth, for example, or holes in standing dead trees, or perhaps rotting logs on the ground. They’re basically nesting above-ground in some kind of natural cavity.
Q. In the book you say about 70 percent of wild bee species nest in the ground. That’s a dramatic number.
A. It’s a staggering number. The other thing people think of when you say bees nest in the ground: They immediately think of ground-nesting social wasps, which are the insects most of the time that people are stung by.
Q. Like yellow jackets, people say.
A. Yes, and those yellow jackets are building this large paper colony, similar to what we see hanging in a tree, but below ground. It’s typically the social insects—the insects that nest together in a colony—that are more apt to do nest defense, and sting.
Most of our wild bees are nesting by themselves. They have a very short lifespan as adults, so it’s very unlikely to be stung by one of these solitary bees that nest in the ground.
It’s a bit of a hurdle for me to get gardeners past the notion that it’s OK to allow bees to nest in their gardens and landscapes, because people have a memory that they dredge up, and they have a hard time differentiating.
Q. I had my first bee sting in maybe 15 years yesterday, and I think it was because I knew I was going to speak to you. I’m blaming you, Heather. [Laughter.]
Years ago I was less observant, and occasionally when push-mowing I’d mow over an area where the yellow jackets were in the ground. Now I’m much more observant.
But I went to deadhead in a very dense area of flowering tobaccos—annual Nicotiana—and I leaned in and somebody just got me in the arm. I thought, “Oh, it’s been such a long time.” I’m around bees all the time—like bumble bees of various sizes, and they couldn’t care less about me.
A. When they’re at the floral buffet feeding, most insects couldn’t care less if you walk by or brush by them. Usually stinging is when there is a direct threat: for example, if an insect flies into your clothing and can’t get out. It’s a defensive thing, and most of the time it’s when we get too close to a nest, that we get stung.
A. That common name can be used for a number of different ground-nesting bees, but I like to use it for the genus Andrena. They’re one of the most diverse genus that we have; in Minnesota alone we have over 90 species of Andrena.
Q. I saw a big one not long ago that I think was in that genus. It was making a hole in the ground.
A. What’s interesting about that genus, is that the majority of mining bees are active in the spring, so they’re the bees that pollinate a lot of woodland wildflowers and flowering shrubs. In the middle of the summer we don’t see that many species active.
Then in the fall a subset of species emerge as adults, and many of those are specialists. Often people don’t realize we do have specialist relationships between bees and plants–much like the monarch butterfly caterpillars who will only eat milkweed, we have bees that the females will only collect pollen from a narrow range of plants. That could be a particular plant family, or more narrowly a plant genus.
These mining bees that emerge in the fall: Many of them are specialists in the goldenrods, or asters, so that’s likely what you saw, what I call one of the fall specialists.
Q. You just talked about those close relationships, perhaps to a plant family, for example. Is that how we choose better plants to add to our garden, to cultivate more of these helper species?
A. It can be. The most important thing from a garden standpoint—because we have this large diversity of bees with short adult lifespans and that are out at different times throughout the season—the first rule of thumb is to have something flowering throughout the season–so you are providing something for all bees. Then if you’re really interested, you can come up with more customized planting lists, especially if you know what kind of bees you’re observing in your garden. You could start to plant more specific things that you know that particular genus of bees likes.
For example, the long-horned bees (genus Melissodes), which are common in midsummer through fall, they tend to like plants in the Aster family—the sunflowers, the asters, the goldenrods. If you plant anything in that family, you are likely to attract that particular genus of bees.
Q. The long-horned bees?
A. They’re called long-horned bees because the males have extremely long antennae; the females do not.
Q. I have to look around now more closely. That’s not a characteristic that I have observed.
A. It’s pretty telltale when you see the males; you think, “Wow, that bee has such long antennae.” You can almost immediately throw it into that genus.
A. It’s a family of bees (Halictidae), as well as the genus Halictus—which has the common name sweat bee. They get that common name from the behavior where they like to land on human skin on a hot summer’s day that’s sweaty, because they’re attracted to the salt in our sweat. So they can be quite persistent, if you have a sweaty crevice in your elbow, or that they’ve discovered behind your knee. That is one bee people will get stung by because they unknowingly swat at this insect that keeps land on their arm or leg.
What’s interesting about sweat bees: I talked about solitary nesters. Sweat bees nest in the ground, but many in that family nest between what we’d call solitary and social. So they’d have multiple females sharing a nest entrance, but building their own nests inside the ground. Or some of them might be sort of sharing duties, and there might be multiple generations existing in one nest. They not a succinct group—they’re in between; depending on what kind of sweat bee they are, they could be anywhere on that spectrum.
Q. I loved that your book “Pollinators of Native Plants” is divided into sections, according to the habitat that particular pollinators and plants favor–like prairie, woodland edge, wetland edge. It’s so understandable, and helpful, instead of organizing it by genus of bee, for instance.
By prairie, you don’t mean just Midwestern prairie, correct?
A. It could be, but prairie means any upland dry site—so in the East it would be more of a meadow. Any open, sunny area where those native plants would occur. I tried to come up with those three sections at least as a starting point for a gardener or someone doing a restoration.
They can base their planting on the different categories in the book. So it’s not only a pollinator guide, but as you said, providing information as a planting guide.
Q. It helped me to make connections with insects that I see in certain spots. You have photos of pollinators in certain flowers I was familiar with, and I thought, “Oh, right, and this is in the Woodland Edge section, and that’s a woodland wildflower—I get it.” I know it sounds like I’m an idiot [laughter] but when a person like myself, a gardener, is learning the science and the connections, it doesn’t hurt to be reminded very clearly like that. It was very helpful.
And the wetland edge area—you do see different insects there.
A. A lot of the wetland-edge plants I feature in the book are big wasp plants—solitary wasp plants. That may scare some people, but the solitary wasps like the solitary bees have no interest in stinging. The solitary wasps seem to be more attracted to those wetland edge plants—now whether their nesting habitat is closer to some kind of riparian area, or the wasps tend to like white-flowering plants. They tend to show a preference for white flowers, and there are a lot of white flowers in the wetland edge section.
Q. I didn’t consciously take that in—the white connection.
A. And then along the wet areas, sometimes slightly upland from there the soils can be slightly sandy if it’s a river. Looser soils tend to be preferred for the ground-nesting insects. They’re easier to excavate; you find more types of ground nests in well-drained soils. Not pure sand, obviously, but you’ll find more nests in middle-of-the-road soils than in heavy clay.
Q. They’re no dummies; they know not to bother with a bad site. [Laughter.]
A. It’s a lot more work.
Q. There are so many insects out in my yard that look like bees—but are not. Technically they’re called bee mimics. I was looking at snowberry clearwing moths the other day, which look like a hummingbird crossed with a bee. And there are these syrphid flies… [Photo above of Spilomyia longicornis, a syrphid that mimics a yellow jacket.]
A. It’s an interesting strategy. Most of the mimics tend to be flies, and will often look like honey bees or bumble bees or even wasps. They are all mimicking looking like a stinging insect. A lot of insects who are flower visitors are preyed on by birds, so if you look like a stinging insect, a bird is less likely to consider trying to eat you. It’s just a mimicry that has provided some defense for these insects.
Q. Defense against predation: Disguise yourself as a bee!
Are there plant families that you find yourself really so wanting more, more, more of in your own garden and landscapes you create—sort of powerhouse plants on the top of your list right now?
A. For attracting a pollinator diversity, starting with the fall plants, you can’t go wrong with goldenrods—and I know some people shy away from goldenrods. But we have many native goldenrod species and some are more clump-forming and much better-behaved than the Canada goldenrod.
Q. Which is on the move through my upper meadow right now. [Laughter.]
A. Those rhizomes!
Q. But it’s OK; I’ll pull some out and edit it a little bit.
A. Goldenrods are just starting to bloom here in the Midwest.
Q. Here, too.
A. I encourage people just to go out and stand by a patch of goldenrod and you’ll be amazed at the number and types of insects that will visit the flowers.
That’s a powerhouse fall plant—and you also can’t go wrong with any of the asters, because they tend to flower a little bit later than goldenrods. So those insects that are migratory, like the butterflies; it’s a really high nectar reward for them to get energy to make their migration. Asters are really important.
Q. Two really good ones that are coming up.
A. And also Joe-pye weed if you have the space. They’re super for many bumble bee species, as well as butterflies. And boneset as well; its former cousin (the taxonomists keep changing things).
Q. It’s a Eupatorium, too (Eupatorium perfoliatum)?
A. Also because it’s white [photo, top of page] it will attract some of those solitary wasps, and it’s a great plant for a wetland-edge site, too.
Q. Thank you, Heather.
more from heather holm
- Heather’s Facebook page, Restoring the Landscape
- Heather’s website, including bee-related reference materials, plus downloadable posters, and more
- On the Houzz website, Heather has posted columns about small carpenter bees, and mining bees, and sweat bees, for example
enter to win ‘pollinators of native plants’
HEATHER HOLM has generously shared two extra copies of “Pollinators of Native Plants” with me, to share with you. All you have to do to enter to win is answer this question in the comments box below, way below the last reader comment:
What’s your garden’s powerhouse plant or plants, in terms of appeal to beneficial insects like bees?
I agree with Heather that the late-season stars like goldenrod, aster and Eupatorium create a stir in my garden, and I work hard to have very early blooming shrubs, trees and perennials for the first pollinators who awaken, too. So basically: I think about the extremes of the season, from when the snow melts, to when frost comes back in autumn.
No answer, or feeling shy? Just say something like, “Count me in,” and I will–but an answer’s even better. I’ll pick two winners at random after entries close at midnight Monday, August 16. Good luck to all. U.S. and Canada only.
prefer the podcast version of the show?
MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. 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 Aug. 10, 2015 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).
(All photos copyright Heather Holm.)