I have a large outdoor compost bin and a small indoor vermicompost bin. I throw all the leaves I collect from my garden into the vermicompost and let the worms catch a buzz. I chop up the stems and break up the root mass and I bury them at the bottom of my compost bin at night when no one can tell what I'm really doing. I don't put the leaves in the outdoor compost because I would hate for one to resurface after I give it a good mix, and then blow into my neighbors yard or something. This method is safe and environmentally friendly. Flushing that shit down the toilet might clog it up. You want a plumber pulling you weed stems out of your pipes? If you don't compost, and I'm guessing you don't or you would have naturally thrown your plants in there, cut it, shred it, grind it, to a point that it is unrecognizable and throw it in someones dumpster down the street. Don't bury it if digging a hole is an odd thing to do where you are.