HOUGHTON - Some are a good complement to a meal. Some are nice to look at.
But left unchecked, invasive plant species can cause economic hardship, push out native vegetation and block access to water.
Frequent monitoring and early action is recommended to minimize the effect of the usurpers, said Mike Jensen, director of MSU Extension in Baraga County.
"When the populations are small, they're much easier to try to reduce and manage, and the costs are much less to reduce a small population as compared to a large population," he said. "It's really important to get a handle on where these invasives are, and to reduce the introduction of invasives by people who are planting them."
When introduced into an environment free of their natural checks, the plants reproduce quickly, crowding out native species.
Emblematic of the pernicious problem is purple loosestrife, a perennial, square-stemmed plant with magenta flowers. It's even occasionally listed in some flower and seed catalogs, Jensen said.
"It's actually a pretty showy flower, but it outcompetes local vegetation and spreads quickly, crowds out vegetation and then makes it difficult to have access to ponds, lakes and streams," he said.
Another culprit is Japanese knotweed, which flourishes in high-light areas such as by roadways.
"A large patch is definitely more than most people want to see," he said. "It can be a very difficult plant to control once it's established."
Garlic mustard is a biennial that grows to a height of about three feet. It's generally found upland in flood plain forestries.
While it's more prevalent in the Marquette area, it's also popped up in some spots of the Keweenaw, Jensen said.
"That's one that's monitored and best removed before seed development," he said. "That's one that can definitely be difficult to control once it's established."
Buck thorn hasn't made it to Houghton or Keweenaw counties, but it has shown up in Baraga County. Popular as an ornamental plant in hedgerows, it, along with its close relative, glossy buck thorn, can slip the bonds of domesticity to spread in forests.
One more poster boy for the law of unintended consequences is Norway maple, a popular ornamental tree that grows densely and outcompetes other plants.
"It's one that if allowed to grow unchecked, it can be an invasive species," Jensen said.
While they can be treated with herbicides, they may need multiple treatments if too far along, Jensen said.
The negative effects can be far-reaching, Jensen said: crop production, aesthetics and timber production can all suffer.
"We all pretty much have a stake in it," he said. "We all can do our part with organized efforts, or even locally on our own property."
Garrett Neese can be reached at gneese@mininggazette.com.