Did you ever plant a perennial and then wish you hadn't?
If so, what did you plant, and why did you regret it?
I'll go first... saponaria oficinalis "bouncing bet". I saw it growing along a roadside near the Finger Lakes area of NY... and dug up a bit for my garden. It grows well, but too well; it takes over, and can creep underground for several feet. I should move it all to the "wild fringes of the yard".