Most people equate the color green with health and natural living, but the inconvenient truth is that some green plants in natural areas cause serious harm to the ecosystem in which they’ve established themselves.
Invasives, as they’re non-affectionately categorized, are defined by two strict criteria: being non-native to the area in which they’ve become established, and causing environmental, economic, or human harm.
Most invasive species were brought to the United States intentionally as ornamentals or for soil erosion and wildlife habitat. The most prominent accidental examples involve insects, such as the emerald ash borer and the Asian long-horned beetle arriving as stowaways on wood packaging material.
Today, I’m focusing on the invasive plants of the prairies and forests, because that’s my area of expertise and there are ample opportunities for everyone to help invasive plant-control efforts.
Common Invasive Plants
The invasive plants most often found in the timbers of Iowa include Asian honeysuckles, multiflora rose, autumn olive, white mulberry, and black locust. Some that are not as common but just as problematic are oriental bittersweet, Japanese barberry, Callery/Bradford pear, tree of heaven (ailanthus), trumpet creeper, privet, garlic mustard, and buckthorn.
The prairie invasives include many of the same species described for the forest, but some that are unique to prairies include sericea lespedeza, reed canary grass, Canada thistle, purple loosestrife, and teasel.
If you own property with prairie or forested acres and want to know if you have some of these invasives, you have free professional resources that can help you, which even include a site visit from private lands biologist Kevin Andersen of the Iowa DNR (kevin.andersen@dnr .iowa.gov). The DNR Invasive Species Guide found online is a good resource to learn how to identify these plants.
What’s the Harm?
All of the invasive plants I’ve listed cause environmental harm to the ecosystem in which they have become established. How bad is the specific environmental harm caused by invasives?
According to the U.S. Forest Service, “Invasive species have contributed to the decline of 42 percent of U.S. endangered and threatened species, and for 18 percent of U.S. endangered or threatened species, invasives are the main cause of their decline.”
Invasive species can lower the quality of habitat for wildlife by reducing native plants necessary for food and nesting. They can also affect the ability of certain trees to regenerate by shading them out.
Landowners Can Help
It is optimistic to imagine that if we just leave nature alone, it will take care of itself. But the truth is that humans, by attempting to utilize the land, have introduced these invasive species, and being a part of the natural ecosystem ourselves, we couldn’t “leave it alone” if we tried. And if we can’t leave it alone, the more constructive option is to be stewards and take proper, educated care of it. Controlling invasive species is a very important part of that stewardship.
So, how do we control these invasive plants that are threats to our natural areas? We have multiple tools available, and it almost always takes at least two of these tools to be successful. Success is often defined by 10 percent or less of the ground being occupied by invasive species.
Stewardship Tools
Prescribed fire is a fantastic way to help control invasives while also encouraging native species to thrive. Prairies and oak timbers greatly benefit from fire rotations. Fire also reduces the need for herbicide.
Herbicide application in the form of foliar spraying, cut-stump, hack-and-squirt, or basal barking is often an essential tool to use in severe cases.
Other tools are mulching or mowing, hand pulling on small-scale projects, prescribed grazing by goats and other ruminants, and weed torching—a creative way to reduce the need for herbicide. It’s definitely more time-consuming and requires trial and error.