They don’t have the cartoonish presence of a round goby, or the menacing, low slung eyes of an Asian carp. No, they often look dainty or even charming, but these are the botanical equivalent of the wolf in sheep’s clothing.
Invasive plants — mean green — are a more insidious brand of intruder. They seek to dominate the landscape once they get established, choking out native vegetation, and frequently offer little in the way of food or habitat for wildlife.
“The difference is that the native plants play well in the environment, while the non-natives have this tendency to take over,” said Sue Tangora, the invasive species program coordinator for the Michigan Department of Natural Resources.
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Some invasive plants reached North America as seeds hidden in ballast water, while most were brought here as landscaping enhancements. What many of them have done is alter the landscape in a very negative manner. Phragmites (frag-my-tees) is one of the biggest offenders in the botanical horde, quickly overwhelming what were once stands of native cat tails.
“We have thousands and thousands of acres in Saginaw Bay infested with non-native phragmites,” Ms. Tangora said. “It has just taken over.”
This tall, reed-like plant prefers wet, marshy areas, and although there is a native version, the invasive strain chokes that, and everything else, out. It has a dense root structure, with 80 percent of the plant mass below ground level.
Herbicides, mechanical removal, and prescribed burns are the only weapons available to tame phragmites and most of the other invasive plants, but this war is never won.
“Those methods only work to keep it down,” Ms. Tangora said. “It’s pretty much impossible to eradicate from the environment once it is established.”
There are numerous aquatics in the mean green club, and many other members with such innocent sounding names. There’s purple loosestrife, autumn olive, Japanese honeysuckle, multiflora rose, tree of heaven, and kudzu. And while a biological control — a beetle — has slowed purple loosestrife’s spread, the others are aggressive, highly adaptive, and able to thrive in marginal environments.
While it is not as prevalent in Ohio and Michigan, kudzu has become a menace in the South. This climbing vine, that was brought to the United States as an ornamental plant used in erosion control, blocks sunlight or chokes off stems to kill native plants, growing one foot per day once established.
Kudzu is believed to cover some 2 million acres of southern forest at this time, following the pattern of other invasives by choking out the competition and creating massive monoclutures — stands where only one species of plant survives.
“In general, less biodiversity is less healthy for the environment,” said Doug Kane, a biology professor at Defiance College. “These non-native plants create monocultures and cause a lot of problems that way.”