The western suburbs, their forests already clogged by buckthorn plants, face invasion by an equally nasty invasive plant species.
The plant, going by the flavorful name "garlic mustard," could cause an "ecological disaster," according to one local expert.
"The problem is most people don't have a clue what it is," said Mike Osterholm, a University of Minnesota professor who lives in Greenwood and has studied the plant.
Many west suburban cities and counties don't recognize the threat from garlic mustard, Osterholm said, and may even be making the garlic mustard problem worse.
Public works crews and private lawn services who can't identify the weed apparently are mowing it and then carrying seeds inside their mowers to sites far and wide, he said.
Garlic mustard and buckthorn are both called "invasive" because they are not native to North America and have no natural predators that can slow their spread.
Garlic mustard came from Europe as a plant grown in vegetable gardens.
It can have small white flowers and releases capsules of seeds in its second year. The plant out-competes native plants -- the primary victims are native wildflowers -- both by growing taller and denying them sunlight and by releasing a toxin that makes other plants' growth difficult. The result can be a dense carpet of the weed on forest floors where native wildflowers once flourished.
Buckthorn was a popular hedge plant that came from Europe. But in the wild, it can form impenetrable walls of vegetation in forests, wetlands and other habitats, and its strong roots make it hard to pull out of the ground.
Minnetonka's natural resources manager, Jo Colleran, says residents are becoming much more adept at identifying buckthorn and more enthusiastic about fighting its spread.
But she said garlic mustard is often popping up in areas that have just been cleared of buckthorn.
Osterholm is director of the University of Minnesota's Center for Infectious Disease Research and Policy and a widely known expert on flu pandemics and other public health threats. But his sideline is prairie restoration, and he has spent many hours studying garlic mustard, which he says has spread quickly through the western suburbs during the past two years.
City and county experts agree with Osterholm that the problem from garlic mustard has gotten much worse.
Roel Ronken, a Hennepin County environmentalist, keeps a close eye on valuable natural areas in the county. "This spring when I went there I was shocked by the amount of garlic mustard we found," Ronken said. There also is still an "astonishing" amount of buckthorn on public and private lands, he said.
The only way to combat garlic mustard on a large scale would be to develop some sort of biological agent to contain it, Ronken said. University of Minnesota researchers are exploring the idea that a weevil, an insect, could control garlic mustard and leave other plants untouched.
Plants like buckthorn and garlic mustard crowd out native species and forever alter local ecosystems, including insect and animal life, Ronken said.
"We're trying to preserve the character of whatever natural communities that are left in the county," Ronken said.
Land that may look like a healthy forest to the untrained eye ends up largely dominated by one type of plant with no natural predators. "It's choking out anything else that could possibly grow," Colleran said of buckthorn's effect.Minneapolis Star Tribune
