Daphne Richards has a nice video here explaining why it’s OK to put weeds in your compost pile if it’s one that’s really cooking. Once you get into the 130 and up range, the weed seeds die off in a matter of hours…she mentions 150 degrees, but in my experience it doesn’t need to get THAT hot…although it’s cool if you do.
I would simplify the video by saying that if you’re working with a large compost bin, you can definitely compost weeds with no problem. However, in smaller volumes there’s just not enough heat generated for a sustained period of time to kill the weed seeds.
Personally I like to put a big stack of weeds on top of my compost as an insulating layer, because I simply have so many I have to pull…the one that comes to mind is that darn Virginia Creeper (aka five finger).
My neighbors leave their backyards run rampant with the stuff to the point that it starts climbing up the walls, so I pull it down and add it to my own compost pile…helps us both out. 🙂