Best non-organic winter insulation?
I want to try leaving all my Crocosmia plants in the ground this winter. Several cultivars were labelled Zone 5 or 6, so I am wondering what winter mulch might be the most likely to help them survive. I've been told to use a large bag of oak leaves on each plant, but since I'm willing to get pretty extreme with this experiment I keep thinking about what might be even better. Styrofoam panels in a protective case? Styrofoam peanuts in a bag? Attic insulation in a bag? Some kind of quilt with thick batting? Old sleeping bags? A pile of Polartec blankets (we happen to have a lot of old ones)? Wouldn't using something like these be better than oak leaves? Has anyone used any of these ideas or found something even better?