Thanks for the question.

White snakeroot (Ageratina altissima) is a native North American plant that can be found in Minnesota and other parts of the United States. While it is a valuable plant for wildlife, it can become a problem in certain situations, such as when it invades gardens or pastures. I suspect that this may describe your situation. Here are some remedial steps for you to consider:

1). Manually pull the plants from the ground. You could also use a shovel. However, be sure to wear gloves as the plant can be toxic. Dispose of the plants in the trash. Do not compost. Be sure to remove as much of the root system as possible to prevent regrowth.

2). Herbicides can be effective for controlling white snakeroot. The most effective herbicide would be one containing glyphosate.

3) If possible, do regular mowing. The most effective time to do this would be before the plant goes to seed.

Here is some further information on these and related points:

https://www.minnesotawildflowers.info/flower/white-snakeroot

http://www.minnesotaseasons.com/Plants/white_snakeroot.html

https://www.inaturalist.org/taxa/119048-Ageratina-altissima

https://ag.purdue.edu/department/btny/ppdl/potw-dept-folder/2023/white-snakeroot.html - :~:text=Control of white snakeroot can,may be a viable option.

https://ask2.extension.org/kb/faq.php?id=811897

Good luck. Thanks for the question.