How to protect your garden from jumping worms

NINA MOINI: This warmer week we've had has gardeners across the state getting their beds ready, planting seedlings. That also means, thought, keeping those plants protected from critters that might snack on them, like bunnies or deer or bugs. There's a newer threat in town, too. They're an invasive species that have become common in the state. They're called jumping worms, and they're causing quite a stir with soil and plants. Here to explain is Erin Buccholz. She's an integrated pest management specialist at the Minnesota Landscape Arboretum. Erin, thanks for being with us today.

ERIN BUCCHOLZ: Thank you for having me.

NINA MOINI: Hey, Erin. For starters, would you just explain, for folks who don't know what the Minnesota Landscape Arboretum is? Because it's a pretty special place.

ERIN BUCCHOLZ: It's a wonderful place. I love working here. The Minnesota Landscape Arboretum is actually a department within the University of Minnesota. We are about 40 minutes of a drive west of the main Twin Cities campus, but we host a lot of the same researchers out here when they want to do something to explore nature, something plant-based or human and plant interactions-based, different nature-based therapy programming, and of course, our gorgeous gardens and plant collections.

NINA MOINI: Yeah. It's a fun place to visit, for sure. And you're really at the forefront of horticulture and studying all these things. So when trying to keep plants safe, when everyone's starting up their gardens this spring-- but I do want to talk about what these jumping worms are. When were they discovered?

ERIN BUCCHOLZ: Yes. When I went to the college, I went to the Department of Horticultural Science at the University of Minnesota back in the late '90s. And back then, all of my professors would say, earthworms are good. They're great for gardens. If you see worms in your soil, you've got healthy soil. It wasn't until decades later that I realized there are no native earthworms to Minnesota. Any of ours would have died out in the last Ice Age. So any earthworms that you see in Minnesota were introduced first from Europe.

And now, with these jumping worms, they are from Asia. And so it's difficult, because our environment has not evolved for the last 10,000 years with earthworms present. Our plant communities were free to just grow and grow without any interference. Jumping worms do interfere with a few processes in our forests, especially. And so we're still trying to study that and gauge it and measure it. And we're also working on ways to potentially control them so that they don't harm our plant communities.

NINA MOINI: Do they jump? I don't know if that's a silly question.

[LAUGHTER]

ERIN BUCCHOLZ: They do give that [INAUDIBLE].

NINA MOINI: Yeah How would you differentiate, oh, that's a jumping worm in my garden?

ERIN BUCCHOLZ: That is the best way to tell them apart. Now, the thing is that jumping worms are not active right now. In Minnesota, they are considered an annual species, so they only overwinter in the cocoon stage, tiny, tiny little eggs that are somewhere between a poppy seed and a peppercorn in size. And they blend right in with the soil, so you don't really see them very well. It's actually very difficult to find the cocoons sometimes. But once the soil warms up, they will hatch, usually in May, and then by the end of July, they will be full size.

And they can be maybe three inches long, but we have some that are like six inches long. They're the size of big old nightcrawlers. And yes, the main difference, like you said, is that they jump. They thrash around. They won't jump like 10 feet off the ground. But if you're holding one, and it gets agitated, it could very easily just kind of skitter right out of your hand, because it thrashes around so quickly, whereas a nightcrawler is a little more lazy, a little more subdued in its movements, crawls around very slowly.

NINA MOINI: OK. That might be fun for kids to get in there and see these giant worms. But is it a prevention thing? Or what are you kind of cautioning people to do to try to get ahead of some of that, maybe?

ERIN BUCCHOLZ: Yeah. Well, I mean, some of the things that we do, speaking of children, is we do host camps here. And every summer, I'm lucky enough that I get to talk to children about worms. Now, they'll learn that worm composting is actually a really good thing. But then when I talk to them about how worms interact with our plant communities and how they might cause erosion, or they might eat the plant roots, those are ways that worms actually are not that good. So it's important for the kids to realize there are good things about them, and there are not so good things about them.

As far as how they are in the gardens, we discovered them here. We only confirmed jumping worms, really, in most of the Twin Cities, and certainly at the Arboretum, only as far back as six to eight years ago. They were first detected in Minnesota by Dr. Lee Freilich, who is with the University of Minnesota. He gardens at Loring Park, and he saw them back then and thought, that's kind of weird. And so that was really the first time that we had confirmed jumping worms in our state.

But since then, more and more places, especially in the southern half of the state, have found them. And so certainly, there's a huge fear with gardeners. Am I going to lose all of my plants? What is it going to do to it? Am I spreading them around? We still have beautiful gardens here at the Arboretum, even with their presence. Our biggest thing is, yes, we want to teach people how not to spread them from one area to the other.

And we also want to study, are there safe ways that we can get rid of them without hurting anything else? We don't want to hurt people. We don't want to hurt other wildlife. And of course, we don't want to hurt our plants. So those are all different research topics that we're working on right now. And we're still early in the process, but we're also very, very hopeful that we will find ways to find a way to live in harmony with them.

NINA MOINI: OK. What are some of the other more common pests and issues that people might be running into this time of year?

ERIN BUCCHOLZ: Well, with gardens, certainly, we have 40,000 tulips that are just a few more weeks away from blooming, so deer. We worry about the deer. Before any of our flowering plants bloom, there's a lot of sugars in the leaves, and that's what they want to eat. But as soon as that flower bud comes up-- it's called bolting-- that's when the leaves start to become more bitter tasting, and they might leave them alone.

So for right now, we are applying some very friendly repellents, mostly scent and taste-based repellents, to our tulips to keep them off of there. Certainly, rabbits are going to become an issue as well. And then there are newer insects that were just detected by the Minnesota Department of Agriculture. Like the viburnum leaf beetle. It was first found in Minnesota in the year 2020 in Minneapolis-- or I'm sorry. In Eden Prairie, just down the road from us. We knew it was coming, but we were able to hold off for three years before we finally saw it here.

And those little critters like to eat the leaves off of our viburnum, which is kind of a bummer, but we're also working on ways to figure out how to hold them off so we don't lose our plants. But we also want to be very, very careful and not just spray any insect we see, because there are a lot of good insects that we still need in the world.

NINA MOINI: Yeah. And so much of what you're talking about is prevention through just coverage, it sounds like. And this is a time of year where temperatures are all over the place, notoriously. So what are your tips there for folks who might not know when to protect everything?

ERIN BUCCHOLZ: Sure. It really just depends on what you're seeing, so keep an eye out. What I do as a main part of my job is called scouting. I'm out there looking. I'm talking to the horticulturists and gardeners in the areas. What are you seeing? What are you noticing? And that way, as soon as we see that there's a potential problem, we can act. We might just handpick off the certain critters.

Or like you said, for weather, we might throw a little bit of protection on a plant to try and make sure that the frost doesn't harm it once it's already come up. We bring things in. We take things out. It's really just observation and then knowing what your options are and making sure that you have as many options available to you as possible. Sometimes, we do have to use pesticides, but we try to do that as a last resort.

If we can handpick them off, or even if we can knock them off with a garden hose, we're going to do that first, certainly. Maybe there's a particular rose that just keeps getting black spot all over it and loses its leaves every year. Well, maybe we won't grow that rose variety anymore. Maybe we'll grow a rose variety that has better resistance.

NINA MOINI: A lot of trial and error, it sounds like, Erin. Thank you so much for stopping by and filling us in about this. I loved learning about jumping worms.

ERIN BUCCHOLZ: You're very welcome. Be sure to come to the Arboretum soon, OK?

NINA MOINI: Yeah, it's a beautiful place. Thank you, Erin.

ERIN BUCCHOLZ: You bet. Bye bye.

NINA MOINI: That's Erin Buccholz, an integrated pest management specialist at the Minnesota Landscape Arboretum.