This weed is very common in western Idaho, but I have yet to find out what it is. I haven't seen it online in any weed database I've searched. Yes, as large as it is, it's growing in a crack in the cement patio. It's been in the area for as long as I can remember (probably since at least the 80's). It can get a lot taller than this (maybe 7 feet tall or so). If you break any part of it, white latex leaks out. It's an annual. I think the seeds are cottony. It's one of the first weeds to grow in the spring, and it's around up until at least the first frost. The stems are spiny. The edges and veins of the leaves are spiny.