the wages of sin

About 30 years ago I dug a plant like this up (or collected its seed, I can't remember which) outside a Connecticut restaurant. It was growing in a neglected area, and I didn't think I was stealing, but I must have been, because I've been punished by this plant ever since! It's one of my worst weeds. Can't remember its name (something that begins with a C?), but if you see it, do NOT move it into your garden. Pretty is as pretty does, and this pretty-looking  plant spreads like wildfire. The round thing in the photo is a spool of wooden "ribbon"some arrangers unfurl to embellish arrangements. I left it coiled and added it to the windowsill just because it was handy and I thought it added interest.