Hello Linda, 

Thanks for reaching out! There is a helpful UMN Extension article with lots of information about managing weeds in your lawn: https://extension.umn.edu/lawn-care/lawn-weeds

Identifying the weeds is most helpful in knowing how to effectively control them. This link shows common weeds in MN lawns and gardens: https://extension.umn.edu/find-plants/weeds If you need further help with identification, feel free to send us a few photos of the weed, with as many details as you can provide. We can do our best to assist. 

You may wish to consider trying a few more cultural control methods, such as changing how often you mow, or raising/lowering your mower height. The article also lists recommendations for using herbicides (scroll down to the "Using Herbicides" section), but again, knowing the weed would be most helpful in determining the best protocol. 

If you decide to use an herbicide, make sure to always follow the label directions attached to the container you are using. Be sure that the area you wish to treat is listed on the label of the herbicide you intend to use. Remember, the label is the law.

Good luck!