Bee-friendly Lawns: Mowing Less is a Big Win for Bees (Ep. 28)

Lawns are often dismissed as inhospitable environments for bees, but today we’re challenging this notion. Beyond the grass, lawns harbor various species of flowers such as dandelions, clovers, violets, and more. These small flowers are treasure troves of nectar and pollen, essential resources for bees. 

Dr. Susannah Lerman studied the impact of mowing frequency on bee populations. We discuss her findings, which highlight the tremendous potential of residential yards in creating habitat for bees and promoting biodiversity.

She recommends embracing a low mow approach throughout the entire growing season to provide a more consistent habitat for bees. Adjusting mowing frequency to every two weeks aligns with bee abundance and adheres to various city ordinances.

Susannah is a research ecologist with the United States Department of Agriculture Forest Service. She’s a wonderful advocate for pollinator habitats, and sharing the science-backed solutions we can all put into practice. 

Susannah and her team found that less mowing did not increase the occurrence of ticks. You can learn more in their report of the tick drags. If you’d like to read the study Susannah and I discussed, you can find that here. 

Good to know

Susannah talked about this marvelous concept she calls Humanity for Habitat. It promotes the ideas we discussed in the episode, that practical yard management promotes biodiversity. Conservation efforts shouldn’t be limited to protected areas, parks, forests, etc. Help for bees and other pollinators is right there in our own backyards.  

Transcript

[00:00:00] Welcome to The Bee’s Knees. I’m your host, Jacy Meyer. The Bee’s Knees is a podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity.
Thanks for being here.

If you have a lawn, how often do you mow it? Do you look at mowing as an enjoyable outdoor activity or a dreaded chore? If you fall in the latter category, what if I told you mowing less is a good way to support bees and pollinators? That’s right. Instead of working in your garden to create food and homes for bees, you can take a lazy lawn owner approach and achieve almost the same results.

But don’t take my word for it. [00:01:00] We’re going to talk to Dr. Susannah Lerman, a research ecologist at the United States Department of Agriculture Forest Service. Her work has found that mowing less can be a simple and cost effective way to support bee populations without the need for replacing lawns or creating separate pollinator gardens.

Thank you Susannah for being with us today. Lawns are green and beautiful, but they can be a bit lacking when it comes to supporting bees. Your study found that lawns can offer resources to pollinators. Can you share what they are? Sure. So, in addition to the grass that’s growing in our lawns, there’s a lot of different types of flowers.

And these little flowers like dandelion and clover and violets and a whole bunch of other species. They actually have a lot of resources for bees, like nectar and pollen. And so when we think about our lawns, we need to think beyond just the actual blades of grass. What made you curious about lawn mowing habits [00:02:00] and if changing them up might support bees?

So it all started in my own backyard. This was about 12 years ago. My husband and I just moved into our first house that we had owned, that we bought, and we were now in charge of mowing our lawn and we took turns doing it. And I remember there was one, um, the first year when my husband did the first mow and when I went out afterwards, I noticed that he had left a lot of different patches in the lawn.

And I thought. That’s a little strange. He’s British. So I thought maybe it was a British thing. And then I went out, I was doing some more investigation and thought, well, maybe our son had left some toys out in the yard and he was mowing around the toys. But then when I got closer to the patches that he didn’t mow, what I realized was that there were a lot of flowers growing in the lawn. And so he had left these flower patches growing because we just couldn’t be bothered to grow our own flowers in these flower gardens. And then the next thing I did was I actually looked down even closer and I started [00:03:00] seeing some movement and I was watching these bumblebees buzzing around on these flowers that were left after the mowing.

And it was at that moment that I had this aha moment where I thought, wow, if we can mow our lawns less. And we can provide these flowers, maybe that could be something good for bees. And just to put it also into a little bit more of a context, it was around this time when everybody’s newsfeed was just filled with the plight of bees.

And everybody was talking about what can we do to save mostly honeybees, but I was more interested in native bees. And to me, I thought, oh, well, this is something simple that people could do. And so I wanted to actually look at the science behind it. So you found that different mowing timeframes had a kind of different results.

Can you tell me about the ones you looked at, one week, two week, three week intervals? So when I was designing the study, I wanted to make sure that we were mimicking what people were actually doing and what people could be doing. And so from that perspective, [00:04:00] I designed the study to look at lawn mowing frequencies of mowing the lawn every week.

That was more of the, kind of the typical way every two weeks would be something that would be a bit more, you know, something to strive for. And then every three weeks, just to see what would happen both from a lawn perspective and from a people perspective. But one of the things that’s really challenging about doing some sort of manipulative study.

In science and research is that you want to try to control as much as possible so that you can get at the specific question that you’re getting at. And here it was lawn mowing frequency. And so, because of that, we offered free lawn mowing service for the entire course of the study for 2 years. So that was one way of trying to give back to people for letting us use their yards for science.

So that was kind of a, a fun component. And so we got to know the people that we were working on their, their yards over the course of two years. So that was kind of fun. So let’s go into that real quick. The different mowing frequencies [00:05:00] supported differences in the abundance and diversity. Can you break that down for us?

Sure. So over the course of two growing seasons, so from May to September, we would go into these yards and we would mow them either every week, every two weeks, or every three weeks, depending on the different regiment the yard was assigned to. And each time we went to mow, we would also count the number of flowers and then over the course of the growing season, six times we went and we collected bees to see which bees were, were present.

So we were able to match the number of flowers with the number of bees and then the type of bees that we had. And so what we found is that for the yards that were mowed every week and every three weeks they had the highest species diversity. So meaning the They had the most different types of bees, whereas the yards that were mowed every two weeks had the most bees, regardless of species.

And so it’s a somewhat typical relationship that you see in ecology so that, you know, you have [00:06:00] a kind of this opposite effect. And so one of the things that we noted in terms of the yards that were mowed every two weeks that had the most abundant number of bees was that it was mostly these workhorse species, so very common species.

But then what we found was that in the yards that were mowed every three weeks, a lot of the species richness, the species diversity, the individual types of bee species were species that we only had like one or two individuals. And so these, these, um, yards that were mowed every three weeks and every one week, these tended to be more of these rarer species.

And so I think both really kind of tell us this larger story. And so if we’re thinking about the diversity overall. One of the things that was really exceptional that I’m still in awe about even though this is 10 years since we finished up the study is that we identified 111 different species of bees in 16 yards in Springfield, Massachusetts.

So let me put that into context because [00:07:00] I still think that’s pretty incredible. Springfield, Massachusetts is the third largest city in the state of Massachusetts. It’s your kind of typical urban area. Uh, we only collected and focused on bees in backyards, in residential yards. We were not looking in prairies.

We were not looking in forests, we were not looking in these more natural areas, we were only looking in yards, so just one type of land use…So a lot of different species of bees that have been recorded in the state of Massachusetts. And we’re only in one section of the state, so it was a pretty limited area. And the 111 species, that’s roughly about a quarter of all different types of bees that have been recorded in the state of Massachusetts.

So when we think about, first of all, just yards in general, They really have a lot more biodiversity than we expect. And then when we focus in on lawns, they’re not as bad as we thought. And it also depends on how we’re managing our lawns. So I think that’s a key component. So, one other thing to mention in [00:08:00] terms of the study.

So, in addition to providing free lawn mowing service. All of the yards, the householders had to agree not to irrigate or fertilize or apply any sorts of pesticides. So again, we wanted to just focus on that one component of lawn mowing. Because we know, there’s other research that has shown that, you know, not everybody is going to be irrigating, not everybody is going to be fertilizing, but most people who have a lawn are going to be mowing.

So we really wanted to highlight and focus on that component. The other thing that we were able to do to again, focus specifically on the lawn flowers was we also counted all the other types of flowers that were blooming at the time when we were observing our bees. So this way we were able to tease apart that it wasn’t just the, you know, the floral resources, the flower gardens that were growing in most of these yards.

didn’t have much else going on except for the lawns. But again, we really wanted to focus in on what was going on in these lawns. So we could figure out some of these opportunities to making lawns less [00:09:00] bad. So one other question though, that I had when I was designing the study was if we were going to mow our lawns less frequently, we’d have taller grass.

What about the ticks? And so that was a big concern. And so this was something that’s, you know, a big concern in the Northeast, especially when we think about Lyme disease. And so in addition to looking at the number and types of flowers and bees, we also investigated whether or not tick presence was increased by having taller grass.

Like, so whenever we went out to collect our data, we also did these tick drags, which is basically you have a white cloth and you drag it across the lawn to see how many ticks and the ticks will jump onto the cloth. And so over the course of five months, throughout the entire growing season, over two years, we collected zero ticks.

And so that was pretty surprising because ticks are definitely prevalent in these areas. So one of the things, though, that [00:10:00] was really informative, I think, for me, is that we keep hearing about one of these opportunities to, you know, make, like, tick proof your yard is to mow your lawn really short. However, I think the context matters.

And so in certain areas, so if you live in an area where Your yard is surrounded by other yards, chances are the tick prevalence is not as high as if you were to live in an area that’s like closer to forested patches or, you know, forested areas. The other thing is that in general ticks don’t really like lawns.

Like when they’re in our yards, they tend to be on the, either on like stone walls or the scraggly bits, the parts that are unmanaged, not so much in our actual lawn. And so this was an important component to Again, try to appease how people might be feeling about their lawn and having it too high is that if they’re making it good for the bees, was it also making it good for ticks?
And so again, with our study, we were able to demonstrate that that was not the case. So that yes, you can have these lawns that are good for bees, [00:11:00] and it’s not going to increase your encounters with ticks. Again, within this certain types of types of yards in this certain context. Did you go into it thinking, Oh, we need to check this.

So this was one of those things where, yes, like, it was one of those things on, like, fortunately, because again, you know, the way that research usually works is you, you pitch an idea to a funding agency, and then you wait for a while for them to decide. Then they say, yes, you have the money. And then. You kind of scramble to put this study together because, you know, you, you kind of had it figured out.

And so when I found out that I got the funding from the National Science Foundation, you know, I started sharing the study with, with friends and colleagues and everybody was really excited about it, but I kept hearing over and over and over again. Oh, but what about the ticks? And so then when we were able to design the study, we were able to put that in.

So, yeah, because usually it’s one of those things like afterwards you think, Oh, what about the ticks? And you’ve already collected your data. And so this was the one instance where [00:12:00] I thought about something, like before it was a, it was an issue. So that we just, we got lucky there, I think. So let’s talk about that first spring mow.

It’s been recommended to delay it. Why should we wait? How does it support bees? And when do you believe it should happen? So the whole idea, you’re talking about this no mow May, which has really taken off. And I think it’s really exciting because one of the things that I’m noticing is that people are noticing their lawns and they’re noticing bees in their lawns and these opportunities.
And this is not just this small group of people, you know, I’m seeing this everywhere and, you know, really kind of seeing, well, is this, this new way of thinking about our, our lawns. The one thing though, that I’d like to highlight though, is the month of May is just one month of the growing season. And so when we delay our mowing just in May, and then we go back to like a weekly mowing regime for the rest of the season.

That might not have as many [00:13:00] benefits as if we were to have reduced mowing throughout the entire growing season. And so we want to be careful about when we’re mowing, because if we let our lawns grow way too high, and then all of a sudden we go in and we cut, you know, a big proportion of the blade of grass that has the possibility of having some damage and some causing some stress to the actual plants growing there.

And so one of the things that I’m really trying to Encourage people to think about is this new idea of this low mow summer and so it’s really kind of looking throughout the entire growing season. And then also May makes the month of May make sense in certain parts of the United States, but not others.

And so really trying to be less prescriptive about this lower lawn mowing frequency. The other thing that I’ve seen too, and I’ve been in touch with some cities, because a lot of cities have these different ordinances that have specific grass heights that you have to adhere to. And so some of these, these no mow May [00:14:00] programs

they extend beyond the limit. And so there’s kind of this, you know, this policy barrier that is in place. And so again, it’s really trying to find some of these ways that are really good for bees. And this two, mowing every two weeks in terms of providing the abundance of bees seems to be a really good solution.

And it adheres to many of these city ordinances as well. So what would you say is your best lawn mowing recommendation then? So I like the idea of every two weeks, if you can get away with every three weeks, that’s fine. One of the things that we realized with the lawns that were mowed every three weeks, one other, like a big part of the study that we found, was that the lawns that were mowed every week had the fewest amounts of flowers, and then every two weeks they had a little bit more, and then every three weeks they had the most flowers.

So we really wanted to, again, really test this relationship between The number of flowers and the number of bees and the types of bees. And so we were actually [00:15:00] surprised when we saw that it was the two weeks that had the most bees and that the, you know, in terms of the diversity that it didn’t follow exactly how the flowers, the flower abundance.

But one of the things to keep in mind is that many of the bees that we identified in these yards are super small. So they’re about the size of a grain of rice. And so When you have a lot of flowers in the lawns, you also have taller grass. And so what we think might be happening is that there still might be a lot of bees flying around.

However, the taller grass might make it a little bit more difficult for the bees to access some of these lawn flowers. So that might explain why there’s just not as many bees that we identified in these yards that were mowed every three weeks. So there are some of these trade offs here, but I think in terms of.

You know, what I would recommend, I think, you know, one of the things if we want to create pollinator habitat, there’s a whole bunch of different ways that people can [00:16:00] get involved. I think there’s planting pollinator gardens and we know that has these really great effects on bees and bee populations. The other thing for those of us who don’t have the time, don’t have the money, don’t have a green thumb.

We can just mow our lawns less. And so by mowing less and embracing the flowers that can grow these spontaneous species, these like these conservation champions that are growing in these lawns, I think is also another opportunity for everybody to contribute to bee habitat. So why do you do what you do?

Why bees? Why bees? So I’m actually a trained ornithologist. So my big thing, so I studied birds, but now bees too. So now I study the birds and the bees, but I was really interested in addressing this question of how do we make our lawns less bad? Because as somebody who’s dedicated my career towards conservation and conserving habitat.

especially for wildlife, for bees and birds and other critters as well, mostly birds. I recognize that [00:17:00] lawns cover a huge amount of area in the United States. And so I mostly focus my research in backyard habitats. And so one of the things that my research has already demonstrated was that native plants are really good for native birds.

Particular and also other species as well. And so there’s this opportunity to plant these native plants. But when we think about our yards, one of the things that covers most of the yards are these lawns. And so for me, I was hearing a lot from my colleagues of just really dismissing lawns as not habitat and vilifying lawns as being.

You know, horrible for wildlife, relatively useless for birds and for bees and other species. And part of me sort of agreed with that, but I kept going back to, there’s a lot of lawn. It’s like 163, 800 square kilometers. And that was a figure that was estimated back in 2005. So that’s a lot, but what does that mean?

So that’s roughly the size of Maine. New [00:18:00] Hampshire, Vermont, and Massachusetts, and so calling for, like, getting rid of all of our lawns, like, that’s great, but I don’t think that’s realistic. And so in addition to reducing the amount of lawn, I think really trying to find these other opportunities to making our lawns less bad is really a positive way to move forward.

And I felt like I couldn’t answer that specific question, looking at how birds were responding to lawn mowings, because they’re using a much larger area and were not specifically related to it. And so that’s when I got really excited about looking at bees. And ever since now I have, um, maybe three or four other projects, research projects that are focused on bees.

So I’m now really excited to figure out ways to Provide habitat for birds and bees and everything else. In terms of the work that I do, and I have a recent paper that just came out, this whole idea that we all have a role to play in supporting wildlife and habitat. And we’re calling this, this humanity for habitat approach [00:19:00] to saving nature.

Because when we think about all of the different areas where we’re doing conservation for wildlife, for bees, for birds, for other species, a lot of times it’s focused in these wild places. However, we, um, in this recent paper, what we discovered was that our yards cover roughly about 30%. of the United States.

So that’s a huge amount of area and a huge amount of potential for us to create habitat for us and for bees and for birds and for all these other species so that we can share these spaces together. And so I think that’s another important component is that there’s these opportunities that when we mow our lawns less, when we plant native plants, when we have more types of flowers and trees and shrubs in our yard.

We’re creating these spaces that are really good for us. They’re cooler, they’re storing more carbon, and they’re also providing habitat. Some of those numbers Susannah shared were really eye opening. The number of [00:20:00] species of bees they found in such a relatively small area shows that we really can create a backyard bee bonanza.

Thinking about the sheer amount of green space in residential yards, We can put our lawns to good use by helping reduce the negative effects of urban development and providing habitat for bees. I’d like to ask you to do two things, please. Visit thebeesknees. website to learn more about Susannah’s Humanity for Habitat work.

And sign up for The Hive, our twice a month newsletter. Thanks so much for joining me today. And until next time, choose to go low mow..