Over the last 15 years, a shrub has been spreading throughout Petoskey and sending down roots — strong roots.
The shrub, the invasive knotweed, comes in two varieties: Japanese and giant. Growing mostly throughout Petoskey is Japanese knotweed. But both are prohibited in Michigan, which means it is illegal to possess or introduce this species without a permit from the Michigan Department of Natural Resources.
Still, Jackie Pilette, wetland specialist with the Natural Resources Department of the Little Traverse Bay Bands of Odawa Indians, says the plant seems attractive to people who want to landscape their yards. With its hollow, sectioned stems, the plant looks like bamboo.
"But it's not a true bamboo, which is a grass. This is a different plant entirely," said Pilette. "It can seem appealing for people for gardening or landscaping because it grows fast and can seem attractive. But it's too easy to grow."
The plant is a "pioneers species" from Japan, said Vern Stephens, wildlife assistant in the wildlife division of the Natural Resources Department. The plant was brought to the United States as an erosion control.
"It comes in after a volcanic event, and breaks that volcanic material up," he said. "It's pretty aggressive, and it's not a nice plant."
In 2009, the DNR added knotweed to a section of the Natural Resources and Environmental Protection Act, which prohibits a person from knowingly owning, planting, selling or transporting knotweed, said Kevin Walters, aquatic invasive species coordinator for the wildlife division of the DNR.
Though people can apply for permits to have a cutting of the plant for educational purposes, Walters said violations of the law can carry fines ranging from $100-$250,000.
Where it grows, knotweed push roots into the cracks of house foundations and muscle through concrete. Pilette has seen photos of the plant growing on either side of a roadway and ripping up the concrete between.
Separately, Japanese and giant knotweed, she said, do not produce viable seeds, so the plant reproduces by sending up shoots from its roots or the nodules at the stalks' joints.
That's the reason one of the worst ways to control the weed is to mow it, says Stephens. Along roadways, for example, county road commissions can unknowingly spread the weed in the direction of traffic.
"Every segment on the plant starts a new plant," said Stephens. "Every nodule that touches the ground is going to be a new plant."
In Emmet County, the road commission has agreed to stop mowing a stand of knotweed alongside Van Road, between U.S. 31 and Pleasantview Road.
Though some county employees say the stand has been growing alongside the road for "30, 40 years," said Brian Gutowski, the engineer manager for Emmet County Road Commission, the stand hasn't gotten any larger.
"But we've had to mow it because it actually grows so large, it drops over the road," said Gutowski. "We definitely want to get rid of that stand because it is definitely a pain in our side."
Gutowski also said the commission has noticed other stands popping up across Emmet County, though he doesn't know where they're coming from.
Ultimately, that the plant spreads by clippings is somewhat of a saving grace for the DNR and the tribe. If they can keep Japanese knotweed separate from giant knotweed, they can more easily control it. That's because apart, Japanese and giant knotweed seeds aren't viable. But when the knotweeds cross pollinate the seeds are fertile. That can become a problem, said Stephens.
"When the two cross pollinate, it then becomes 'bohemian knotweed,' and that bohemian knotweed produces a viable seed. That's why we're trying to find all the giant knotweed populations. There aren't that many of them. If we can go in and eradicate those, at least we'll have time to deal with the Japanese knotweed," he said. "It's just one of those things that's innocuous until it becomes a problem."
For more information, visit www.michigan.gov/invasivespecies.
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Controlling invasive knotweed
Because the invasive species Japanese and giant knotweed spread through clippings and through its roots, the Little Traverse Bay Bands of Odawa Indians Natural Resources Department and the Michigan Department of Natural Resources say mowing the shrub is the worst way to control it. Instead, people should treat it with an herbicide called imazapyr, though they should take caution because the pesticide is strong.
Pesticides such as glyphosphate — RoundUp, to the layperson — are ineffective. They might look like they work, but the herbicide is really just killing the foliage you can see and actually seems to stimulate the knotweed to grow more, said Jackie Pilette and Vern Stephens, wetland specialist with the Natural Resources Department of the Little Traverse Bay Bands of Odawa Indians and wildlife assistant with the wildlife division of the Michigan Natural Resources Department, respectively.
"RoundUp is ineffective over time at really attacking the roots and making sure the stand gets killed," said Pilette.
Imazapyr is a strong herbicide, depending on its concentration, said Pilette. A brand called "Habitat" resides longer in soil, and can kill nearby trees or non-target vegetation. But a brand called "Clearcast," while more expensive, should not harm non-target plants and does not stay as long in the soil.
Stephens recommends buying the herbicide through a chemical company to ensure you are getting the correct kind and concentration. He recommends the website www.cwc-chemical.com.
Residents do not need a permit to apply the herbicide on private property, unless they are applying in a wet area, though they should pay special attention to the herbicide's instructions.
