Area fields filled with purple flowers may look pretty, but those familiar with this particular specimen think otherwise.
“I think most people think it’s just a wildflower,” Lisa Neuenfeldt, district conservationist in the U.S. Department of Agriculture’s (USDA’s) Waupaca office, said about spotted knapweed.
The short-lived perennial grows three to four feet in height and has single thistlelike pinkish-purple flowers.
Neuenfeldt said it prefers sandy soil, where it has less competition, but grows everywhere.
She said it is allelopathic, which means it is a natural herbicide as it prevents other seeds and plants around it from growing. “If you chop it above the root, it will still flower,” she said.
It is believed that the plant was introduced into the U.S. in the 1890s as a contaminant in alfalfa or hay seed from Europe and Asia. Spotted knapweed has become a problem in the rangelands in the northwestern U.S. In recent years, the plant has invaded relatively undisturbed natural areas in Wisconsin, as well as heavily disturbed sites.
Spotted knapweed produces 1,000 seeds per plant per year and lives at least seven years in soil.
“There are ways of controlling it. It takes years to tackle it,” Neuenfeldt said.
Several weeks ago, Lynn Craig, Jane Haasch and Pat Timm began to work on doing a survey for the Wisconsin Department of Natural Resources as to where the plant is located in the towns of Dayton, Farmington and St. Lawrence.
When they see the plant, they mark it on a map. The maps will be sent to the DNR.
All three women have prairies, and Timm is a member of the Prairie Enthusiasts. Timm learned through the Prairie Enthusiasts chapter that she is a member of that the DNR was looking for volunteers to survey spotted knapweed.
“People aren’t aware of what it is,” Haasch said. “If you see one plant in your yard, get rid of it now.”
Neuenfeldt said wildlife relies on plant diversity and when other plants cannot grow because of an invasive species, it can have a snowball effect.
There are different ways to control spotted knapweed.
She said if the plant is in a backyard, it can be pulled. This method works well when there is a small amount of the plant.
The entire root has to be removed, and it is easiest to do so when the soil is moist.
Timm recommends wearing gloves when pulling the plant. “If I pull it, I notice my hands tingle,” she said.
After the plants are pulled, put them in a pile and burn them.
Neuenfeldt said in cases when there is an entire field of spotted knapweed, biological control, including weevils, and chemicals are measures that can be used.
“But, there are some sites where there can be other plants,” she said.
Therefore, property owners will first want to make sure there are not other species of plants worth saving in fields. “If not, hire someone to apply chemicals,” she said.
Neuenfeldt said that when applying chemicals, always read the labels, because misusing them can be very toxic.
She also said that for both farmers and nonfarmers, the USDA does offer cost sharing in the county for invasive species control. The local office can be reached at 715-258-7162.