Teasel

I noticed these plants down where the Snells do their boating.  After some research, I've learned it's an invasive species and on the noxious weed list for Iowa.  So basically not welcome.  And now that I've paid attention when driving around, I see it more and more.

The name of the plant is teasel.  It can grow to nine feet.  What caught my eye were the seedheads.