I uploaded this weed once before but the best guess was a member of the mustard family, Brassicaceae. I still haven't been able to narrow it down more specifically so thought I'd try again.
I think that's a reasonable and interesting thought. I'm not finding anything in the many varieties that quite look like what I have. Most have much lusher flowers but the leaves on some do look quite similar. I'm glad you mentioned fireweed because it's not something I'm familiar with and I found that at least 2 different plants with that name grow in my county.
Marc
Marc - have you considered taking your pics and plant samples to your university botanical department? I know you like weeds and that may be a good source of info. I enjoy your pics and look forward to any identification that you get.
Elizabeth - or Your Majesty
Living and growing in Lafayette, La.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown