When Michiganders think about invasive plants, a white speckled field of garlic mustard (Alliaria petiolata) or the tall flower clusters of purple loosestrife (Lythrum salicaria) may come to mind.
But some of the most harmful invaders are hiding in plain sight along streets, in yards, and especially, at local garden centers.
Across the state, efforts are underway to fight them, and the work sometimes comes with four hooves and a healthy appetite.
On a hot July morning at the City of Rochester training center, six goats chewed through tall grasses and tangled vines. Their owner, Jessica Scavo, pointed them out,
“This is Chew-Chew, we call him Frank Sinatra for his blue eyes, this is vera, and then we have Prima and Moe over there, and then Lorenzo and Vincenzo.”
Scavo is the owner of MichiGoat, a personal project turned into a business.
Her original herd of 5 grew to 25 as word about her goats spread, “The interest was so great from just everywhere, people, friends, you know, as soon as I said, I have goats clear land, I instantly had a bunch of people say, can you come over and do my yard, or I have a few acres, or can you come do my horse pastures.”
They’re a food-motivated breed of goat called Kiko goats and “they’re very aggressive foragers. So, this is exactly what they were built to do,” said Scavo.
Her goats had been previously hired by DTE Energy to clear hazardous vegetation under power lines and now they’re hired to clear invasive plants.
On that day in July, the diet was phragmites (Phragmites australis subsp. australis), an invasive grass, or reed that has aggressively spread across the Great Lakes.
But there were other invasive plants the goats also cleared that day.
“This spot right here that they’ve gone into is the oriental bittersweet which is growing as a vine. And we were noticing here, when you’re in a forest situation, it’s starting to choke out the mature trees,” Scavo said pointing to some of them at the base of an oak tree.
Goats may be an unconventional tool, but they provide many benefits. They can navigate rough terrain, which may not be safe for humans. They’re a natural alternative to pesticides and herbicides, which means less harmful chemicals leaching into the environment.
And most of all, their digestive system and their teeth can render invasive plant seeds unviable. So, unlike other animals, there’s no risk they’ll spread those plants.
Scavo’s goats are one of many statewide responses to invasive plants.
Michigan has 22 regional groups called cooperative invasive species management areas, or CISMA’s.
Their goal is to prevent and eradicate invasive plants.
Shikha Singh coordinates the Jackson, Lenawee and Washtenaw County CISMA.
She says not all greenery is good and many people don’t realize the damage invasive plants can cause, “I think it's a fundamental understanding of the environment and you know, ecosystem services and how different you know organisms, you know, kind of interact with each other.”
Invasive species can grow quickly, and a lot of them will emerge in the spring before native plants. Since they catch all the sunlight first, they will create shade and prevent native plants from getting that sunlight.
That matters because native plants are the food base for Michigan’s native wildlife. And they’re vital towards a balanced ecosystem.
Singh says invasives might look nice, but for wildlife they are the equivalent of junk food.
Bill Schneider is a restoration ecologist and he says the impact can go beyond nutrition.
Studies have shown the berries from two invasive species of honeysuckle changed the feather color of cedar waxwings, northern flickers and many others. This phenomenon is called “plumage erythrism” and has been studied for over a decade.
“And when you change the color the plumage, it would change their breeding behavior, he said, “and we're just scratching the surface. We're not even talking about the soil microbiota and how we're changing the soil ecology. We’re just looking at what we can see.”
Some invasives like autumn olive (Elaeagnus umbellata) are nitrogen fixing and can change the nitrogen cycle in the soil while others like phragmites and garlic mustard are allelopathic, meaning their roots can secrete chemicals into the soil around them that will change the soil’s chemistry.
While this is perfect for the invasive plant, it renders the area uninhabitable for others, especially native plants.
Despite the risks, many invasive plants are still sold in nurseries and garden centers. A 2021 study at the University of Massachusetts Amherst found that more than half of the known invasive plants in the U.S. are available for sale as ornamentals. That includes some landscape favorites in Michigan like burning bush (Euonymus alatus), common periwinkle (Vinca minor) and Japanese barberry (Berberis thunbergii).
Audrey Menninga is the director of the northwest Michigan invasive species network, a CISMA covering the northern lower peninsula. She says west Michigan is one of the biggest producers of Japanese barberry.
Her CISMA created the Go Beyond Beauty program to fight invasive plants sold as popular ornamentals, specifically Japanese barberry.
Menninga said, “There’s oftentimes still landowners we talk to that have no idea it’s invasive. So that was one of those big species that started pushing us into this. And then the more we looked at it, the more we realized that a lot of our invasive species, a lot of our priority invasive species, were actually ornamental invasive species.”
Japanese barberry also poses a public health concern. Singh says the structure of the plant provides the perfect habitat for ticks.
“It's very tight, you know, like the branches are very tight and they do create a nice humid microclimate. And ticks, they do not like dry, hot, dry weather. They need a little bit of humidity. They need a little bit of moisture and so they're able to thrive,” she said.
Also, mice love this plant because the thorns provide an extra layer of protection. And now the ticks have an animal host - and the first meal for baby ticks - to spread their range.
So, while some invasives like autumn olive are already regulated, most popular ornamentals are not. Until that changes, programs like go beyond beauty are offering alternatives and hoping Michiganders will make the switch.
In the meantime, Singh says everyone can play a role, by cleaning their shoes and camping gear to stop the spread, and reporting invasives when they see them.
But when in your yard, Schneider says there needs to be a change in the landscape ethic which begins with investing less in a manicured lawn.
And if pulling out a thorny shrub infested with ticks feels daunting, Scavo says her goats are ready.
