John, that's porterweed. I usually try to ID my plants when posting but sometimes I get tired of typing Porterweed over and over. The butterflies (and the bees and the hummingbirds) really like it. To those who want some, make sure you get the native. There is an invasive species, as well. Here's a good PDF about it from UF.
http://lee.ifas.ufl.edu/Hort/G... By the way, I'm pretty sure I have the hybrid. I tried the invasive one back when I was young and naive and that stuff springs up everywhere. The one I have now reseeds itself, but not so much I can't just pull it out.
