Purple loosetrife may look pretty but it is a noxious and invasive weed. The plants thrive in our wetlands and it chokes out native species that provide food for native species.
According to the Minnesota DNR there are about 2000 loosestrife infestations in Minnesota. I found some growing along the side of my house and removed it.
It is illegal to possess, plant, transport, or sell purple loosestrife in Minnesota. [MN DNR webiste]
Here is a clump of the stuff growing near Chestnut Plaza, along the Mississippi River across the river from Harriet Island