Compost bin

Dandelion flowers can still open and set seed even when they've been pulled up - so that's one reason. Also I guess the plant could regrow from the root if your compost is exposed to light. HOWEVER! I've been putting Dandys in my compo bin for years and never had a problem. I would suggest not putting seed heads/open flowers in, but otherwise they're fine!

It is the roots which really may cause problems, there is nothing wrong with the leaves. One should really avoid adding any flowers,seed heads to your heap. The heat generated in a domestic heap is not really high enough to kill off the seeds.