There's an invasive plant in Missouri that is hard to spot during the growing season, but easy to see right now and it can be real trouble if it literally takes root.
It's always nice when the place you live ends up at the top of an internet best of list unless it's one that ranks states with the most invasive plants and that's exactly where Illinois is near the top.
If you've driven down a Wisconsin highway and noticed some very pretty purple plants along the roadside, there are several possibilities as to what you're seeing. One in particular can be a real problem if a stray cat would happen to get near them though.