Invasive Species: How to Maintain a Happy, Healthy Landscape

Jacob Ryg from Davey's South St. Paul office shares a list of some invasive species, how to get rid of them and what species to plant in your garden and landscape instead. 

In this episode we cover:

• What makes a species invasive? (0:41)
• Invasive European buckthorn in South St. Paul (1:32)
• Did you know that garlic mustard is invasive? (6:41)
• Invasive species differ depending on where you are (8:26)
• Other kinds of invasive species (9:10)
• Is continual top cutting effective for getting rid of invasive species? (10:22) 
• Replace your invasive species by planting native species (11:19)
• Try and stay away from planting "gimmick plants" (12:52)
• It can be dangerous to plant unknown species in your garden (13:28)
• Which plants are positives to put in your garden? (14:13) (19:05)
• Kentucky coffee tree (15:31)
• Plants labeled "sterile" aren't always sterile (17:28)
• Dawn redwoods (20:12)
• Jacob's love for working with people, plants and trees (21:42)

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Transcript

Doug Oster: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much more. Tune in every Thursday to learn more because here at the Talking Trees podcast, we know, "Trees are the answer."

This week, I'm joined by Jacob Ryg. He's a district manager in the South St. Paul, Minnesota office for the Davie Tree Expert Company. Today we're talking all about invasive species. Jacob, welcome to the show. Good to see you.

Jacob Ryg: Thank you for inviting me. I appreciate it.

Doug: What is your definition of invasive?

Jacob: It's not precise, but it's mostly when trees or plants are not appropriate in that area or they spread significantly. Native species can be invasive. Exotic species can be invasive. It's just a plant that can take over an area.

Doug: I was trying to explain this myself the other day. I was running myself around in circles trying to define invasive plants. I think you just nailed it there because we don't think of a native being an invasive. We don't think of something that we love and grow being an invasive, but it certainly can be. In your area, when we're talking about trees, is there one on the top of the list that's an invasive or are there a bunch?

Jacob: There's a bunch. The most prolific one would be European buckthorn in our area.

Doug: School me on that. I have no idea about that tree from out here in Pittsburgh.

Jacob: Sure. Buckthorn arrived in the 1800s from Europe. The special characteristic of it is that birds eat it readily, but they also get diarrhea from it. It's non-nutritional for the birds and any other animals, and it spreads like wildfire by the seed.

Doug: Is there anything that can be done? When you see it, cut it out, or it's always going to be there, I'm sure, the way you're explaining it. What kind of things are you guys doing when you get on a property to deal with buckthorn?

Jacob: Sure. It's a double-edged sword for folks. Some people just love it because it's green, it makes a nice hedge, it blocks other houses, but ecologically speaking, it's a pretty rough customer. They have male and female buckthorn. The female buckthorn have the berries. How we manage that is typically removing the females off the property. That's just to keep the seed level to a light roar. Otherwise, buckthorn will grow in any bed, any location as long as there's soil. We've done everything from many hundreds of acres of control. We've tried to use a brush hog, brush mowers that take larger trees.

After we're done brush mowing or we use an herbicide on the stumps, that will allow it not to come back. If you don't use an herbicide, the buckthorn will just come back with a vengeance. It sprouts a lot worse than the original plant. That component, there's other ways to do it besides herbicides, but they're very challenging, covering them with plastic, things of that nature. Buckthorn is really a challenge for most forest managers in this area.

Doug: I think what's interesting about what you said there was that some people love it, and hence, the problem. Again, hey, we want this shrub to be a way to block the neighbors or whatever it might be. That just adds insult to injury when people actually like the plant. Some invasives, people, we're all on board. Japanese knotweed. We all hate Japanese knotweed, we know that, but when you've got a plant like that where it does have some positives when you're not thinking of the negatives, that's a problem.

Jacob: Absolutely. I was involved right out of college in what's called the buckthorn buster program where we take kids, basically, or students fresh out of college and do ecological restoration work pulling buckthorn by hand. They make special tools for that. Cutting plants up. Like we talked about, people will love it because it does have nesting capability. It does screen away from neighbors, but ecologically speaking, it's really hard on native plants and native species.

Doug: That's something I think most people would agree with, that that's something we want to perpetuate. We want to have our natives. We don't want to have something crowding out our natives. In the case of a buckthorn, the way you're explaining it, it seems like a tough battle. [chuckles]

Jacob: It's impossible. It's gotten so out of control. There's a lot of people fighting it all the time. There's a lot of reasons to fight it, I should say, in native areas because a lot of plants that birds, mammals, different types of insects, they key in on. When buckthorn replaces it, it creates a monoculture, which means there's nothing else left. It's super important, especially for critical habitat, to remove buckthorn and let the natives grow. There's some really great alternatives out there.

Doug: Is buckthorn something that people can actually still plant? Is it something you could buy at a nursery and plant?

Jacob: No. I believe in all 50 States, it's not allowed. I know that probably late '90s, you could still buy a different type of buckthorn, which is just as invasive, but they've stopped the sale of that as well. It's very slow in learning our lessons. Unfortunately, nature takes its course. Unfortunately, buckthorn is just the tip of the iceberg. There's so much more out there that is just as bad.

There's some very interesting plants like garlic mustard, for instance, that you and I can eat. We can make it into food, but it's highly invasive. Like buckthorn, it has what's called allelopathic properties, which restrict other plants from growing around it chemically. There's a lot of unusual stuff out there that the average person doesn't know about. If you go into the woods, can you smell garlic? You've got garlic mustard. It's very unique.

Doug: As someone who has had garlic mustard pesto and made it, I do know how invasive it is. I've got four acres of property. That's pretty easy to take care of garlic mustard for me. As long as I can get out there as soon as I see it and pull it immediately, don't let it go to seed, I can keep it under control. When garlic mustard escapes and goes out into the forest where no one's there, that's another problem right off the bat. It's funny. Again, we're talking about a plant that, hey, the pesto was great, but I don't want to perpetuate garlic mustard. It's another one of those invasives.

Another good point you made was that, in many cases, we've done this to ourselves where we've tried to put something in place that will stop erosion or whatever the case may be. As you said, we don't learn our lesson, do we?

Jacob: Exactly The interesting thing to me, too, is I spent a significant amount of time in Europe. Some of their most invasive stuff is stuff that we like, like black cherry, for instance, or black locust. They're native to the US, but in Europe, it's just like buckthorn. Same for Siberian elm. There's a ton of Siberian elm all over the place in the US. It's interesting how that whole philosophy of trying to find plants to bring here, and some of them escape, causing huge economic losses. It's very fascinating that our world is that way.

Doug: Going back to trees, what else is on your list there that is of a relative pain?

Jacob: Right alongside buckthorn is European honeysuckle. That's one that, like other invasives, look beautiful to the untrained eye. You go in the woods and, wow, these are beautiful pink or white flowers. I'd love to have this in my yard, but it does escape. There's a bunch of those types of plants that the intentions were great to have a hedge or a beautiful plant from overseas, but this escaped into the wild. Barberry is another one that escaped in the wild. There's actually a significant amount of plants out there and trees that affect the ecosystem negatively, even some of the trees that we cultivate.

Another one that is significant is called amur corktree. It has a female and a male variety. Quite often when people buy a plant like amur corktree at the nursery, it's a beautiful tree. It grows really fast, but then it escapes into the wild. Norway maple is another one. People love maples, and they love beautiful colored plants, but when they go into the wild, it's very challenging for people to manage those.

Doug: Well, I want to go back to the honeysuckle, and I want to ask your opinion on this. In a small space like I have, in these four acres, a plant like that, what I would try to do is just continual top-cutting and try to keep hacking the top off until the bottom is exhausted. Do you think that is an effective technique for a small space for a homeowner, or am I just wasting my time?

Jacob: It's a preference. If you like working outside and that's your forte, that's a great way to minimize the impact. For those that don't have as much time, typically removing it and replacing with a native that actually has benefits for birds, like viburnum species just off the top of my head, there's so many other plants out there that insects and birds and wildlife love. It's a philosophy. Again, if that's your cup of tea to work in your yard nonstop, have at it.

Doug: What you're saying is I somehow get that honeysuckle or whatever the invasive is out, and then I'm putting in something cool, something good, something positive, right?

Jacob: Absolutely. One of my old houses when I first moved to Minnesota, there was a burning bush there. I found out that it's invasive. It's beautiful in the fall. It's great. I plucked it out and I planted some hazelnuts, so the squirrels-- I love eating hazelnuts as well. There's more benefits to planting that native hazelnut. I typically enjoy that so much more. If I don't get a chance to harvest them, the squirrels will clean them up in a day.

Doug: Well, that's what I'm trying to do in my forest. As I lose my oaks, I'm trying to replace them with good natives and more diversity in the forest. Let's go that direction. You already mentioned viburnum. I love viburnum. It's funny. I planted a viburnum called Chicago Luster because it's deer-resistant, and I wanted the purple berries for the birds, but I found that the deer, they don't care about the leaves, but they love the purple berries. [chuckles]

Jacob: It's fun when you have a plant like that. Another one is serviceberry or amelanchier. That is like a gold mine to the birds if you've never seen that. There's some spectacular plants. Again, non-invasive that have been tested for quite some time. Just trying to stay away from the gimmick plants. There's a lot of them. You buy a seed catalog or something and you're getting something that was grown in Louisiana. It doesn't really fit very well in our ecosystem.

In fact, I got a load of trees a couple years back that had some invasive weeds in the bald and burlap soil. You got to be careful. Even if you go to your home store or Walmart, those types of nurseries, you could be getting plants from a serious distance away.

Doug: It's always dangerous to bring anything into your garden unless you know what it is. A lot of times here, they'll grind up our leaves and turn them into compost, but it's all stuff that people have been throwing out to the curb. In the corners of those compost piles, you can see some pretty nasty stuff growing there that you would not want in your garden. Just a warning, which is a great warning from you about looking at what's coming into your garden before you put it in. You want to make sure you're not adding anything invasive to your garden.

What are some other positives? Because I have a beautiful multi-stemmed serviceberry, and I always say I'm going to get to those berries just to give them a little nibble, but the birds are always getting there first, which is fine with me. What else is on your list? What else are things that you love? Now, we always know, right tree, right place. We go over that over and over again on this podcast, but I love to hear from guys like you about things that you love to put in, replacing an invasive.

Jacob: In Minnesota here, we have pretty severe winters, so we're pretty limited on what we can plant. There's a lot of exciting plants out there for me. Going to the more exotic side, for instance, a ginkgo tree, been around forever, beautiful leaves. That's one where it's a great tree to plant because it doesn't seed, it doesn't typically spread anywhere. Trees like the Kentucky coffeetree, it's native to Minnesota, but few people even know what that means.

Looking at different species and including them in your landscape, it's a lesson that we've learned from a different invasive species, emerald ash borer, that we need to plant diversity. I can absolutely share my list of special plants with you if you'd like, but there's a lot of more, like yellowwood. Yes, go ahead.

Doug: I want to go back to that Kentucky coffeetree because that is a cool tree that, again, it's off the radar of a lot of people, but a nursery that I go to all the time, they've got them planted out around their lake. When you see that tree-- Explain to people what a Kentucky coffeetree is and why you like it so much.

Jacob: It's a gorgeous tree. I was friends with a nurseryman years ago, and he said, "That's how I tell if I have a good salesman on my hands, if they can sell a coffeetree to someone." It looks like a stick growing in the ground, and it has recessed buds that really don't open up until later in the season. It's a nitrogen fixer. It's a very significant plant to the Native American community. There's a lot of history there. It has enormous leaves, like, tiny little leaflets, but one leaf can be the size of a piece of paper or larger. They're just very cool trees, and they're being a little bit over-planted in some cities, but that's what I always watch out for, just having a diversity.

The female Kentucky coffeetree has pods. The cool thing about these pods, unlike honey locust that can blow in the wind, these things just flop down. You can actually, when the seeds drop, just grab the pods and recycle them. I've also grown them from seed. They're really easy to grow if you scarify the seed. They sprout very well. It's just a really cool, more unusual tree for people that are tired of planting maples.

Doug: What made you want to grow that from seed? That's pretty cool.

Jacob: A long story, but my brother went to Brown University, and Brown University campus had a coffeetree. I grabbed some seeds off the pod, and I germinated them in my living room, and then planted them in my yard.

Doug: That's pretty cool. I wanted to ask you about some of these invasives that now I see them coming out where they're supposed to be sterile. There's Rose of Sharon that's supposed to be sterile. There's barberry that's supposed to be sterile. Now, I'm afraid, especially with the barberry, we have such a terrible problem here with ticks. Barberry is a tick-magnet. I wouldn't ever want to plant one, but people, like you said, even with barberry, as much as they've been warned, people like barberry. It's got the thorns. It keeps people out of the yard, et cetera. What do you think about a plant where they release it and say it's sterile? Can I trust that?

Jacob: I would not. There's lots of examples out there. I'll give you an example off the top of my head. Honey locust. It's a native tree. The actual wild honey locust has thorns that will go through your body if you're not careful. They're very sharp. What they do is they take the rootstock of a wild honey locust, and they put the cultivar onto that. I'm just using basic terms here, but onto the root system, and it grows. If you were to cut that down below the graft union, you'll have a wild honey locust. Same for barberry. I've seen so much good intentions become really bad problems. I'd rather look for the native alternatives or something that better fits and doesn't become more invasive.

Doug: Before I let you go, I want another one of your favorites because I'm liking this path you're walking down with us here.

Jacob: Yes. Some of the ones that I really enjoy are dawn redwood, metasequoia glyptostroboides. There's a lot of really cool little stuff that I could put in microclimates. I'm a geek when it comes to that. In my backyard, I have a hill and a ravine. Back in that ravine, I put things like Katsura trees. Stuff that maybe you're familiar with, but people in Minnesota don't know much about. I was big into agroforestry, the hazelnuts. The American chestnut is just spectacular if you can get those to grow.

There's a ton of really good stuff out there that's not mass marketed. It might have some detrimental things. The American chestnut has this bur that if you grab onto it with your skin, it'll leave little tiny pieces in your skin. Tolerating some of that stuff. Again, there's some really good, interesting plants out there that everyone should give it a shot if you have land and a will to try.

Doug: All right. We're going to geek out right now on dawn redwoods because that's one of my favorites. I just got back from a trip to London, and I was in Kew Garden. I had never seen all these different cultivars of dawn redwood. I knew there was a chartreuse one. They were growing seedlings out in the forest area of all sorts of ones I'd never heard of before. We've talked about dawn redwood before here, but you tell me why you love it. I've got a giant one in my yard. It's my number one tree on the property. I love it so much. Everything about it. What is it for you about dawn redwood?

Jacob: I had a really good friend when I was an arborist in Madison, Wisconsin, that had a giant one as well. I think it was 30 inches in diameter. Just the texture of the bark. It's a deciduous conifer. I'm a fan of those older trees. I remember looking up dawn redwood originally, and I found that on eBay they had petrified cones for sale. I bought those. Just looking through the historical record of some of those plants is just amazing. Living fossils. Dawn redwood to me, I love giant sequoia. I love dawn redwoods. Just to have something that I can grow near me, I love it.

Doug: One more question before we end this talk. How did you get into this, and why is it for you?

Jacob: I was one of those lucky kids that when I was 13, 14, I knew I wanted to be working with native plants, with trees, and finding a career, and getting a master's degree eventually, it was just a love of education and a love of knowledge. I love plants, and I love working outside with them. Urban forestry is just a great way to make a good living and do what I like. Overall, I think working with people and plants together, that's where I get excited. I can have a really miserable day, and then I go and talk to a client that is in love with their plants, and I'm happy.

Doug: All right, Jacob, I'm going to leave it right there. I sure appreciate all the information and the time. It was great to meet you. Great to talk to you. I've got a feeling you and I might talk again here in the future.

Jacob: I would love to. I'm a fanatic when it comes to some of this stuff.

Doug: I get that feeling.

Jacob: It was nice to meet you.

Doug: All right, Jacob. Thanks.

Jacob: Thank you. Bye-bye.

Doug: Well, that was nice having a talk with Jacob. We could have gone on for, I bet, another half hour at least. All right, you tree lovers, do me a big favor, tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. I'd love it if you'd subscribe to the podcast so you'll never miss the show. What do you think of this podcast? What should we be covering? Let us know. You can send us an email to podcasts@davey.com. That's P-O-D-C-A-S-T-S @ D-A-V-E-Y.com. You can also click the link at the end of our show notes to text us a fan mail message. Your ideas might be on a future podcast. We'd love to hear from you.

As always, we like to remind you on the Talking Trees podcast, "Trees are the answer."

[00:23:45] [END OF AUDIO]