Can you compost weeds, even if they’ve gone to seed? The answer is yes, but there’s a few things to consider:
1) If you have a compost bin that’s 1 cubic yard or greater, your pile should have no issues heating up to the temperatures needed to kill weed seeds (131F for 3 days). I add to one bin for a year before letting it sit for a year…plenty of time.
2) If you’re working with a smaller compost system such as a trash can shown in this video, it will not be able to generate the necessary heat to kill weed seeds.
Try letting them sit for a few days to dry out. Once they’re dry, add all the thin brown stuff to your compost pile. Put your thicker stems off to the side for now.
Weeds are organic material, therefore they will compost- the key is just knowing how to add them, depending on your setup.
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. 🙂